Sleep Disturbance
Sleep disturbance is a broad term encompassing any alteration in normal sleep patterns, including difficulty initiating or maintaining sleep, excessive sleepiness, or abnormal behaviors during sleep, that impairs daytime functioning and overall health.
Sleep Disturbance
Sleep disturbance is an umbrella term encompassing any condition in which the quality, timing, or amount of sleep is altered, leading to daytime distress or functional impairment. It includes:
- Insomnia (difficulty initiating or maintaining sleep, or early-morning awakening)
- Sleep-disordered breathing (obstructive sleep apnoea, central sleep apnoea, obesity-hypoventilation syndrome)
- Hypersomnolence disorders (narcolepsy, idiopathic hypersomnia)
- Circadian rhythm sleep-wake disorders (delayed/advanced sleep phase, shift-work disorder, jet lag)
- Parasomnias (sleepwalking, night terrors, REM sleep behaviour disorder)
- Sleep-related movement disorders (restless legs syndrome, periodic limb movement disorder)
The word "insomnia" derives from Latin: in- (not) + somnus (sleep) — literally "not sleeping." "Parasomnia" = para- (beside/abnormal) + somnus (sleep) — abnormal events during sleep.
Clinical Terminology
In Hong Kong clinical practice, "sleep disturbance" is the most commonly used presenting-complaint term. It is NOT a diagnosis — your job is to find the underlying cause and classify it according to the International Classification of Sleep Disorders (ICSD-3, revised 2023) or DSM-5-TR.
2. Epidemiology
- Insomnia is the most common sleep disturbance worldwide:
- Prevalence 22.1% under DSM-IV (1-month criterion) and 10.8% under DSM-5 (3-month criterion) [1]
- Hong Kong community surveys show ~30–40% of adults report at least one insomnia symptom; ~10% meet criteria for chronic insomnia disorder
- Hong Kong has a uniquely high burden linked to long working hours, small living spaces (noise, light pollution), high population density, and high academic/occupational stress
- Obstructive Sleep Apnoea (OSA):
- OSA syndrome (AHI ≥5/h + sleepiness): 4% in males, 2% in females in middle age [2]
- OSA (AHI ≥5/h alone) is much higher (~2× prevalence) [2]
- In Hong Kong, prevalence mirrors Western data; may be underdiagnosed in the Chinese population because craniofacial features (e.g. relative retrognathia, shorter maxillary length) predispose even at lower BMI
- Restless Legs Syndrome (RLS): 2–5% worldwide, slightly lower in East Asian populations (~1–2%)
- Narcolepsy: rare (~0.02–0.05%), but important differential for excessive daytime sleepiness
| Factor | Effect on Sleep Disturbance |
|---|---|
| Age | Insomnia prevalence ↑ with age (physiological ↓ in slow-wave sleep); OSA peaks in middle age (40–65y); parasomnias peak in children |
| Sex | Insomnia ↑ in females (2:1), likely hormonal + psychosocial; OSA ↑ in males (2–3:1, equalises post-menopause) |
| Psychiatric comorbidity | Depression, anxiety, somatisation strongly associated with insomnia [1] |
| Obesity | Respiratory: obesity-hypoventilation syndrome, dyspnoea, OSA [3] |
| Shift work | Very common in HK (healthcare workers, transport industry) — circadian disruption |
3. Risk Factors
Understanding risk factors requires the 3P Model (Spielman's Model), which is the dominant framework for chronic insomnia — but the logic applies to all sleep disturbances:
Multifactorial: generally a result of a combination of bio-, psycho-, social factors → 3P model [1]
| Factor | Examples | Explanation |
|---|---|---|
| Predisposing (trait-level vulnerability) | Genetic tendency to hyperarousal; female sex; anxious temperament; family history of insomnia | These raise your baseline "sleep vulnerability" — you are closer to the threshold even before a stressor hits |
| Precipitating (acute triggers) | Life stressors (bereavement, exams, job loss); acute medical illness; pain; jet lag; new medication | These push you over the threshold — acute insomnia begins |
| Perpetuating (maladaptive behaviours that maintain insomnia) | Excessive time in bed; napping; clock-watching; caffeine/alcohol use; irregular sleep schedule; conditioned arousal in the bedroom | Even after the precipitant resolves, these keep insomnia going — Chronic insomnia is more due to perpetuating factors [1] |
High Yield – 3P Model
The 3P model explains why acute insomnia (e.g. exam stress) becomes chronic: the original stressor resolves, but the patient has developed maladaptive sleep behaviours (perpetuating factors) that sustain the problem. This is exactly why CBT-I (Cognitive Behavioural Therapy for Insomnia) targets perpetuating factors and is first-line.
Demographic:
- Older age, female sex, lower socioeconomic status, divorced/widowed
Medical:
- Pain, night sweating, hot flushes, cancer, COPD, PD (Parkinson's Disease) [1]
- GERD — nocturnal acid reflux causes micro-arousals and is an independent risk factor for sleep disturbance [4]
- Heart failure (paroxysmal nocturnal dyspnoea, orthopnoea)
- Nocturia (prostatic disease, diabetes, UTI)
- Pruritus (eczema, liver disease, uraemia)
Psychiatric:
- Depression, anxiety, schizophrenia [1]
- Substance use disorders
Pharmacological / Drugs:**
- Stimulants, alcohol, beta-blockers, SSRIs, steroids [5]
- Caffeine, nicotine
- Diuretics (nocturia)
- Theophylline, decongestants (sympathomimetic)
- Chronic opioid use (central sleep apnoea)
Sleep-specific:
- Circadian sleep-wake disorder, OSA, periodic limb movement disorder [1]
- Poor sleep hygiene
Masquerades checklist [5]:
- Depression
- Diabetes
- Drugs: stimulants, alcohol, beta blockers, SSRIs, steroids
- Thyroid/other endocrine: hyperthyroid
- Spinal dysfunction
- Urinary tract infection: nocturia
4. Normal Sleep: Anatomy, Physiology and Function
You cannot understand sleep disturbance without understanding normal sleep architecture.
Sleep is regulated by two independent but interacting processes:
| Process | Name | Mechanism |
|---|---|---|
| Process S (Homeostatic) | Sleep pressure | Adenosine accumulates in the basal forebrain during wakefulness → the longer you are awake, the stronger the drive to sleep. Caffeine blocks adenosine A₁/A₂A receptors — that's why it keeps you awake. |
| Process C (Circadian) | Circadian alerting signal | The suprachiasmatic nucleus (SCN) in the anterior hypothalamus acts as the master clock, entrained by light via the retinohypothalamic tract → SCN drives alerting signals during the day. Melatonin (from pineal gland, peaks ~2–4 AM) reinforces the circadian night signal. |
Sleep occurs when Process S (high sleep pressure) coincides with Process C (low circadian alerting signal, i.e. nighttime).
Factors affecting sleep patterns [2]:
- Age
- Prior sleep history
- Circadian rhythms
- Drug ingestion
- Pathological states
| Structure | Role |
|---|---|
| Suprachiasmatic nucleus (SCN) | Master circadian clock; receives photic input from retinal ganglion cells |
| Ventrolateral preoptic nucleus (VLPO) | "Sleep switch" — GABAergic/galanin neurons that inhibit arousal centres to promote sleep |
| Ascending reticular activating system (ARAS) | Brainstem nuclei (locus coeruleus [noradrenaline], raphe nuclei [serotonin], tuberomammillary nucleus [histamine], pedunculopontine/laterodorsal tegmental nuclei [acetylcholine]) that promote wakefulness |
| Lateral hypothalamus (orexin/hypocretin neurons) | Stabilise the wake state — loss of these neurons → narcolepsy (a flip-flop switch without a stabiliser) |
| Pineal gland | Secretes melatonin under SCN control (inhibited by light) |
The Flip-Flop Switch Model (Saper, 2005): VLPO and ARAS mutually inhibit each other. This creates a bistable switch — you are either awake or asleep, with rapid transitions. Orexin/hypocretin stabilises the switch in the "wake" position. Without orexin (narcolepsy), the switch is unstable → sudden intrusions of sleep into wakefulness (sleep attacks, cataplexy).
Normal adult sleep cycles through stages in ~90-minute cycles (4–6 cycles/night):
| Stage | % of Total Sleep | EEG Features | Characteristics |
|---|---|---|---|
| N1 (NREM Stage 1) | 5% | Low-amplitude, mixed-frequency; vertex sharp waves | Light sleep, easily aroused; hypnic jerks may occur |
| N2 (NREM Stage 2) | 45–55% | Sleep spindles (12–14 Hz) and K-complexes | Moderate depth; memory consolidation begins |
| N3 (NREM Stage 3 / Slow-Wave Sleep) | 15–20% | High-amplitude delta waves (0.5–2 Hz, ≥75 μV) | Deep/restorative sleep; GH secretion peaks; parasomnias (sleepwalking, night terrors) arise from this stage; ↓ with age |
| REM | 20–25% | Low-amplitude, mixed-frequency (resembles wakefulness); sawtooth waves | Dreaming; skeletal muscle atonia (mediated by glycinergic inhibition of spinal motor neurons); autonomic instability; REM behaviour disorder occurs when atonia fails |
Why this matters clinically:
- Insomnia → ↓ N3 and/or ↓ total sleep time → fatigue, impaired cognitive function
- OSA → repeated arousals fragment sleep architecture → ↓ N3 and REM → excessive daytime sleepiness despite "adequate" hours in bed
- Depression → characteristically ↓ REM latency (REM starts earlier), ↑ REM density, ↓ N3 (why depressed patients often have non-restorative sleep and early-morning awakening)
- Age → progressive ↓ N3, ↑ N1/N2, ↑ awakenings → elderly naturally have lighter, more fragmented sleep (this is physiological, not pathological)
| Function | Evidence |
|---|---|
| Memory consolidation | N2 spindles and N3 slow waves facilitate hippocampal-neocortical transfer; REM consolidates procedural memory |
| Metabolic restoration | GH secretion peaks in N3; protein synthesis ↑ during sleep |
| Glymphatic clearance | During sleep, glymphatic system clears β-amyloid and tau from the brain — chronic sleep deprivation → ↑ dementia risk |
| Immune regulation | Sleep deprivation → ↑ IL-6, TNF-α, ↓ NK cell activity |
| Cardiovascular regulation | Normal sleep → nocturnal BP dipping (10–20%); loss of dipping in OSA → sustained hypertension |
Control of breathing during sleep depends on [2]:
- Respiratory centre
- Chemical, mechanical and CNS information
- Respiratory muscles (upper airways, diaphragm and others)
Why is this important? During sleep, wakefulness drive to breathe is lost. Breathing becomes entirely dependent on chemical (PaCO₂, PaO₂, pH) and mechanical feedback. If these feedback loops are blunted (e.g. central hypoventilation, obesity) or the mechanical response is impaired (e.g. upper airway collapse in OSA), apnoea results.
5. Aetiology (Hong Kong Focus) and Pathophysiology
The aetiological approach to sleep disturbance should be systematic. I organise it by the ICSD-3 classification framework, emphasising conditions relevant in Hong Kong.
5.1 Insomnia Disorders
Classification: based on ICSD-3 (2014) [1]:
- Defined as symptoms lasting < 3 months [1]
- Generally occur in response to an identifiable stressor, e.g. physical, psychosocial [1]
- Usually resolve when stressor is eliminated or resolved or with adaptation [1]
- Pathophysiology: Acute stress → hypothalamic-pituitary-adrenal (HPA) axis activation → ↑ cortisol and noradrenaline → hyperarousal → difficulty initiating/maintaining sleep. Normally self-limiting.
- Defined as symptoms occurring ≥3×/week persisting for ≥3 months [1]
- Generally lasts for years but may be triggered by initial stressful event [1]
- Vary between nights and with psychosocial stressors and medical/psychiatric comorbidities [1]
Pathophysiology of chronic insomnia — the Hyperarousal Model: Chronic insomnia patients demonstrate 24-hour hyperarousal (not just at night):
- ↑ cortisol secretion (especially evening)
- ↑ sympathetic nervous system activity (↑ heart rate, ↑ metabolic rate)
- ↑ beta EEG activity during NREM sleep (objective evidence of hyperarousal)
- ↑ whole-brain glucose metabolism on FDG-PET during sleep (the brain is "too active" to sleep)
This hyperarousal becomes conditioned: the bed/bedroom becomes a conditioned stimulus for wakefulness (classical conditioning) → perpetuating factor. This is why stimulus control (a component of CBT-I) works: by re-associating the bed only with sleep.
Previously divided into subtypes but now eliminated as not reliably reproducible in practice [1]:
- Idiopathic insomnia: begins in childhood, lifelong, cannot be explained by other causes [1]
- Secondary insomnia: result from drug, substance, medical condition, mental disorder [1]
- Paradoxical insomnia: complaint of severe insomnia despite no objective evidence of sleep disturbance — previously sleep state misperception — ?due to misinterpretation of sleep as wakefulness [1]
- Psychophysiological insomnia: insomnia plus excessive amount of anxiety/worry regarding sleep/insomnia [1]
Paradigm shift: from "secondary" to "comorbid" insomnia [1]:
- Some cases previously conceptualised as "secondary" to other conditions
- Nowadays this was abandoned in favour of "comorbid" insomnia as insomnia can play a role precipitating these psychiatric/medical conditions as well → difficulty to ascertain causality
- In general, now insomnia can be diagnosed together with axis I/II diagnoses, e.g. depression
Concept: Bidirectionality of Insomnia and Psychiatric Disorders
The paradigm shift from "secondary" to "comorbid" is exam-relevant. Depression causes insomnia (↑ HPA axis → hyperarousal), but insomnia also predicts the development of new-onset depression (OR 2.1). They co-perpetuate. Treat both simultaneously.
Aetiology of primary insomnia exists in a continuum [1]:
- "Organic" on one end (i.e. idiopathic) as determined by genetic and biological abnormalities in sleep regulation
- "Lifestyle" on the other end (i.e. sleep hygiene insomnia) due to behaviour that exceed natural automaticity and plasticity of sleep system
- Psychophysiologic insomnia represents the middle of the continuum
Common comorbid conditions [1]:
- Medical disorders, e.g. pain, night sweating, hot flushes, cancer, COPD, PD…
- Psychiatric disorders, e.g. depression, anxiety, schizophrenia
- Sleep disorders, e.g. circadian sleep-wake disorder, OSA, periodic limb movement disorder
5.2 Sleep-Disordered Breathing
This is the big one — extremely high yield for exams and clinically important in Hong Kong.
Definition [2]:
- Apnoea: complete cessation of airflow at nose/mouth lasting ≥10 seconds
- Hypopnoea: ↓airflow with ≥3–4% ↓SaO₂ and > 10 seconds/episode
- Apnoea-hypopnoea index (AHI): number of apnoeic/hypopnoeic episodes per sleep hour
- Normal = < 5; Mild OSA = 5–15; Moderate OSA = 15–30; Severe OSA = > 30
- In children, the cut-off is > 1
Pathophysiology — Understanding this from first principles [2]:
During sleep, ventilatory drive drops → ↓responsiveness to blood gas changes [2] Inspiration → negative pressure in upper airway → ↑collapsibility [2] ↓neuromuscular tone of upper airway during sleep (or other factors e.g. alcohol) [2] ↑weight of soft tissue in neck due to obesity [2]
Result: upper airway collapses during inspiration → snoring (mild) and apnoea (severe) → arousal response to re-dilate airway and regain wakefulness drive [2]
Let me walk through this step by step:
- Normal wakefulness: The pharynx is a collapsible tube (no cartilage, unlike the trachea). It stays open because dilator muscles (genioglossus, tensor palatini) are tonically active under wakefulness neural drive.
- Sleep onset: Wakefulness neural drive is lost → dilator muscle tone ↓ → pharyngeal cross-sectional area ↓
- Inspiration during sleep: Diaphragm contracts → intrathoracic pressure becomes negative → this negative pressure is transmitted to the upper airway → collapsing force on the pharyngeal walls
- In a normal person: The remaining muscle tone is sufficient to keep the airway patent
- In an OSA patient: Predisposing anatomical factors (fat deposition, large tongue, small jaw) + ↓ muscle tone = the collapsing force exceeds the dilator force → airway occlusion → apnoea
- Consequences of apnoea: No airflow → PaO₂ falls, PaCO₂ rises → chemoreceptors detect this → brainstem triggers an arousal → sympathetic surge → pharyngeal muscles reactivate → airway opens with a gasp/snore → patient briefly wakes (often unaware) → falls asleep again → cycle repeats
- Each cycle = ~20–40 seconds. In severe OSA, this can happen > 30 times per hour → massive sleep fragmentation
Anatomical abnormalities may predispose to functional obstruction [2]:
- Micrognathia (undersized jaw) — "micro" = small, "gnathia" = jaw
- Macroglossia may fall back on supine posture — Macroglossia/tonsillar hypertrophy [5]
- Enlarged tonsils or adenoids: important factor in children (∵ small airway) [2]
- Redundant pharyngeal tissues due to fatty infiltration [2]
Risk factors for OSA [2]:
- Obesity (BMI > 30): strongest modifiable risk factor. Fat deposits in parapharyngeal space and tongue → ↓ airway lumen. Also ↑ weight on the chest wall → ↓ FRC → ↓ traction on trachea → ↓ pharyngeal patency
- Male sex: males have more central fat distribution, longer pharynx
- Age: ↑ prevalence with age (loss of muscle tone, ↑ tissue laxity)
- Craniofacial abnormalities: retrognathia, micrognathia — important in the Chinese population where BMI may be normal but craniofacial features predispose
- Alcohol / sedatives: ↓ dilator muscle tone → ↑ collapsibility
- Smoking: mucosal oedema → ↑ upper airway resistance
- Nasal obstruction: allergic rhinitis, nasal polyps, deviated septum → ↑ negative pressure needed to inhale → ↑ collapsibility
- Endocrine: Acromegaly (macroglossia → OSA ~50%) [6], Hypothyroidism (myxoedema of upper airway soft tissues, ↓ ventilatory drive) [5]
- Post-menopausal women (loss of progesterone, which has respiratory stimulant and upper-airway dilator properties)
- Family history (genetic craniofacial structure + obesity tendency)
Central: apnoea due to abnormalities of ventilatory drive [2] No arousal response [2] Defect in central (↓ventilatory drive) or peripheral (↓muscle contraction) [2] Causes: central neurological lesions, neuropathies, NMJ disease, muscle diseases [2]
Pathophysiology: During sleep, respiratory drive is entirely chemoreceptor-dependent. If the brainstem respiratory centres or their peripheral effectors malfunction, breathing effort ceases altogether (unlike OSA, where effort continues against a closed airway).
Key cause in clinical practice: Cheyne-Stokes respiration in heart failure → the ↑ circulation time from heart to chemoreceptors creates a delay in feedback → oscillatory ventilation → periodic apnoea.
- BMI ≥ 30 + chronic daytime hypercapnia (PaCO₂ > 45 mmHg) + no other cause of hypoventilation
- Respiratory: obesity-hypoventilation syndrome, dyspnoea, OSA [3]
- Pathophysiology: massive obesity → ↓ chest wall compliance + ↓ diaphragmatic excursion → chronic hypoventilation → ↓ chemosensitivity to CO₂ (reset of the "CO₂ thermostat") → worsening hypoventilation → cor pulmonale
5.3 Hypersomnolence Disorders
Narcolepsy: predominantly presents with excessive daytime sleepiness, but may also have cataplexy (intense emotions precipitate drop attack), sleep paralysis, sleep-related hallucinations [1]
Pathophysiology:
- Narcolepsy Type 1 (with cataplexy): Autoimmune destruction of orexin/hypocretin-producing neurons in the lateral hypothalamus (strong HLA-DQB1*06:02 association). Without orexin to stabilise the wake-sleep flip-flop switch → sudden intrusions of REM phenomena into wakefulness:
- Cataplexy = sudden loss of muscle tone (REM atonia intruding into wakefulness), triggered by strong emotions (laughter, surprise)
- Sleep paralysis = inability to move on waking (persistence of REM atonia)
- Hypnagogic/hypnopompic hallucinations = REM dream imagery intruding into wake-sleep/sleep-wake transitions
- Narcolepsy Type 2 (without cataplexy): Normal CSF orexin levels; mechanism less clear
- Excessive daytime sleepiness without REM intrusion phenomena
- Normal or ↑ total sleep time with severe sleep inertia ("sleep drunkenness")
- Diagnosis of exclusion
The SCN "master clock" has an intrinsic period of ~24.2 hours and is entrained to exactly 24 hours by light exposure. When this entrainment is disrupted, the circadian signal and the actual desired sleep time become misaligned.
| Disorder | Mechanism | HK Relevance |
|---|---|---|
| Delayed Sleep-Wake Phase Disorder | SCN clock phase-delayed → cannot fall asleep until 2–6 AM, cannot wake until late morning | Very common in HK adolescents/young adults (screen time, late-night studying) |
| Advanced Sleep-Wake Phase Disorder | SCN clock phase-advanced → sleepy by 6–8 PM, awake by 2–4 AM | More common in elderly |
| Shift-Work Disorder | Work schedule conflicts with circadian rhythm | Extremely common in HK (healthcare, transport, F&B industry) |
| Jet Lag Disorder | Rapid transmeridian travel | HK as international travel hub |
| Non-24-Hour Sleep-Wake Disorder | Free-running circadian rhythm (> 24h) not entrained to external cues | Almost exclusively in totally blind individuals (no light input to SCN) |
| Irregular Sleep-Wake Rhythm | Fragmented circadian rhythm | Associated with dementia, brain injury |
Parasomnias: characterised by unusual behaviour/events during sleep. May lead to intermittent wakening and difficulty resuming sleep. [1]
Parasomnias e.g. night terrors [5]
| Category | Examples | Stage of Sleep | Pathophysiology |
|---|---|---|---|
| NREM Parasomnias | Sleepwalking (somnambulism), night terrors (pavor nocturnus), confusional arousals | N3 (slow-wave sleep) | Incomplete arousal from deep sleep → dissociated state where motor activity is activated but consciousness is not. More common in children because they have proportionally more N3 sleep. |
| REM Parasomnias | REM sleep behaviour disorder (RBD), nightmare disorder | REM | RBD: failure of normal REM atonia (brainstem lesion/degeneration) → patients "act out" their dreams. Strong association with α-synucleinopathies (Parkinson's, Lewy body dementia, MSA) — RBD may precede motor symptoms by years. |
| Other | Sleep-related eating disorder, exploding head syndrome | Various | Variable mechanisms |
5.6 Sleep-Related Movement Disorders
- Irresistible urge to move the legs, worse at rest, worse in the evening/night, relieved by movement
- Pathophysiology: Central dopaminergic dysfunction (likely in the A11 diencephalospinal pathway) + brain iron deficiency (iron is a cofactor for tyrosine hydroxylase, the rate-limiting enzyme in dopamine synthesis). Low brain iron → ↓ dopamine → RLS symptoms.
- Associations: Iron deficiency (most important secondary cause — always check ferritin), uraemia, pregnancy, peripheral neuropathy, medications (antidopaminergics, SSRIs/SNRIs, antihistamines)
- Repetitive, stereotyped limb movements during sleep (typically dorsiflexion of the ankle/toe, every 20–40 seconds)
- Often co-occurs with RLS but can exist independently
- Causes sleep fragmentation → excessive daytime sleepiness
- Pathophysiology: Likely related to the same dopaminergic dysfunction as RLS
| Category | Conditions | HK-Specific Notes |
|---|---|---|
| Psychiatric | Depression (terminal insomnia), anxiety (initial insomnia), PTSD, substance abuse | Very common; depression prevalence 2.9% in HK [7] |
| Medical | Chronic pain, GERD, HF, COPD, asthma, nocturia, pruritus, hyperthyroidism | Thyroid/other endocrine: hyperthyroid [5]; GERD a/w sleep disturbance [4] |
| Drugs | Stimulants, alcohol, beta-blockers, SSRIs, steroids [5]; caffeine, theophylline | High caffeine culture; alcohol use in business/social settings |
| Sleep-disordered breathing | OSA, CSA, OHS | Craniofacial predisposition in Chinese; obesity epidemic |
| Circadian | Delayed phase, shift-work | Student/young adult screen use; shift workers |
| Movement | RLS, PLMD | Iron deficiency common in young females |
| Parasomnias | Night terrors, sleepwalking, RBD | RBD: consider neurodegenerative prodrome in elderly |
| Narcolepsy | Type 1 and 2 | Rare but must not miss |
6. Classification
The standard nosological framework:
- Insomnia Disorders (short-term insomnia; chronic insomnia disorder)
- Sleep-Related Breathing Disorders (OSA, CSA, sleep-related hypoventilation)
- Central Disorders of Hypersomnolence (narcolepsy type 1/2, idiopathic hypersomnia, Kleine-Levin syndrome)
- Circadian Rhythm Sleep-Wake Disorders (delayed/advanced phase, shift-work, jet lag, irregular, non-24h, free-running)
- Parasomnias (NREM-related, REM-related, other)
- Sleep-Related Movement Disorders (RLS, PLMD, sleep-related bruxism, sleep-related leg cramps)
- Other Sleep Disorders
| Type | Description | Classical Associations |
|---|---|---|
| Initial (predormitional) insomnia: difficulty falling asleep [1] | Cannot fall asleep for > 30 min after getting into bed | Anxiety, conditioned arousal, delayed circadian phase, RLS |
| Middle insomnia: sleep broken, choppy, intermittent or lacunary [1] | Frequent awakenings during the night | OSA, pain, PLMD, nocturia, alcohol |
| Terminal (postdormitional) insomnia: early wakening with inability to fall asleep again [1] | Waking > 30 min before desired time | Depression (classic!), advanced circadian phase |
Pattern Recognition for Exams
Initial insomnia → think anxiety. The anxious mind cannot "switch off." Terminal insomnia → think depression. Early morning awakening is a hallmark biological symptom of melancholic depression (HPA axis hyperactivity → cortisol peaks earlier). Middle insomnia → think medical causes (pain, OSA, nocturia).
| Severity | AHI (events/hour) |
|---|---|
| Normal | < 5 |
| Mild | 5–15 |
| Moderate | 15–30 |
| Severe | > 30 |
7. Clinical Features
A careful history is required because some patients have unrealistic expectations about the required amount of sleep they need or have misperceptions of how long they have slept. Explore lifestyle factors esp. psychosocial reasons, painful conditions, drug use and abuse, appetite, energy, sexual issues and physical factors. Examine past medical history including diabetes, hypertension and cerebrovascular disease, as well as drug history, esp. alcohol. Check thyroid status, esp. hyperthyroidism. [5]
7.1 History Taking Framework
Key history [5]:
The approach to a patient with sleep disturbance should be structured:
- What is the problem?
- Difficulty falling asleep? (initial insomnia → anxiety, RLS, delayed circadian phase)
- Difficulty staying asleep? (middle insomnia → OSA, pain, nocturia, PLMD)
- Early morning awakening? (terminal insomnia → depression, advanced phase)
- Non-restorative sleep? (OSA, PLMD — patient may sleep "enough" hours but the quality is poor)
- Excessive daytime sleepiness? (OSA, narcolepsy, insufficient sleep, circadian disorder)
Clarify symptom: sleepiness is different from fatigue [2]:
- Sleepiness tends to manifest during sedentary activities [2]
- Fatigue tends to manifest during exertion [2]
This distinction is crucial! A patient who falls asleep watching TV, reading, or at traffic lights is sleepy (think OSA, narcolepsy). A patient who feels tired climbing stairs but cannot nap is fatigued (think anaemia, hypothyroidism, depression, CFS).
Prefer sleep diary over 2-week period [1]:
- HPI: nature of complaint, number of awakenings, duration, timing, exacerbating/relieving [1]
- Sleep history: bedtime, duration until sleep onset, final awakening, nap times and length, self-rated sleep quality [1]
- Nighttime symptoms: abnormal movement, parasomnia, snoring, breathing problems [1]
- Try to include history from bed partner [1]
- Daytime symptoms: sleepiness, impact on functioning and mood [1]
- Sleep hygiene: exercise, smoking, drinking, caffeine, light/noises in bedroom [1]
- Comorbidities: anxiety, depression, other sleep disorders (e.g. OSA, RLS), drug use [1]
What are the night-time symptoms? [2]:
- Sleep choking, unusual body/limb movements → arousals following apnoeic episodes [2]
- D/dx: distinguish between restless sleep (no specific pattern) and restless leg syndrome (only one leg) [2]
- Snoring → obstructed airflow [2]
- Witnessed apnoeic episodes: witnessed pausing of breathing [2]
| Symptom | Pathophysiological Basis | Points Towards |
|---|---|---|
| Loud snoring | Vibration of narrowed pharyngeal soft tissues during turbulent airflow | OSA |
| Witnessed apnoeas | Complete pharyngeal collapse → cessation of airflow, observed by bed partner → followed by gasp/choking | OSA (highly specific) |
| Gasping/choking arousals | Hypoxia → chemoreceptor stimulation → arousal from sleep → airway reopens with gasp | OSA |
| Restless legs / urge to move | Central dopaminergic dysfunction → dysaesthesia worse at rest/evening | RLS |
| Periodic limb jerking | Rhythmic dorsiflexion movements every 20–40 sec during sleep | PLMD |
| Dream-enacting behaviour | Loss of normal REM atonia → patient moves/punches/kicks during dreams | RBD (think α-synucleinopathy) |
| Sleepwalking/night terrors | Incomplete arousal from N3 deep sleep | NREM parasomnia |
| Nocturia | BPH, diabetes, HF (nocturnal fluid redistribution), diuretics, UTI | Multiple medical causes |
| Orthopnoea / PND | Recumbent position → ↑ venous return → pulmonary congestion in HF | Heart failure |
| Nocturnal heartburn | Recumbent → loss of gravity → gastric acid reflux into oesophagus | GERD |
| Nocturnal cough / wheeze | Airway inflammation + vagal tone ↑ at night; also GERD-related | Asthma, GERD |
What are the day-time symptoms? [2]:
| Daytime Symptom | Pathophysiological Basis |
|---|---|
| Excessive daytime sleepiness | Sleep fragmentation (OSA, PLMD) → ↓ restorative N3/REM → unrefreshed → sleep pressure accumulates |
| Morning headache | Nocturnal hypercapnia (CO₂ is a cerebral vasodilator → AM headache); seen in OSA and OHS |
| Poor concentration / memory | ↓ N3 and REM → impaired memory consolidation; chronic sleep deprivation → prefrontal cortex dysfunction |
| Irritability / mood changes | Sleep deprivation → amygdala hyperreactivity (↓ prefrontal control) |
| Impaired libido / erectile dysfunction | OSA → chronic intermittent hypoxia → ↓ testosterone; also sympathetic overactivation |
| Cataplexy (if narcolepsy) | Orexin deficiency → REM atonia intrusion triggered by emotions |
Are there any complications? [2]:
- Risk assessment: driving, operation of heavy machinery, any previous accidents [2]
- Complications: HTN, ischaemic heart disease, DM [2]
Medicolegal Point
In Hong Kong (and globally), you MUST assess driving risk in any patient with suspected OSA or excessive daytime sleepiness. Untreated OSA with excessive sleepiness = unfit to drive. Failure to ask about this and document it is a medicolegal risk.
7.2 Symptoms Organised by Condition
| Symptom | Pathophysiology |
|---|---|
| Difficulty falling asleep (initial insomnia) | Conditioned hyperarousal (bed = stimulus for wakefulness) + ruminating thoughts → ↑ cortical arousal at bedtime |
| Frequent awakenings (middle insomnia) | Hyperarousal → ↓ threshold for environmental stimuli to cause cortical arousals |
| Early morning awakening (terminal insomnia) | In depression: ↑ HPA axis → cortisol peaks earlier → premature arousal |
| Daytime fatigue / irritability / poor concentration | ↓ total sleep + ↓ sleep quality → inadequate restorative function |
| Anxiety about sleep | Psychophysiological component — worrying about sleep makes it harder to sleep (perpetuating factor) |
| Symptom | Pathophysiology |
|---|---|
| Loud snoring | Turbulent airflow through narrowed pharynx → soft tissue vibration |
| Witnessed apnoeas | Complete pharyngeal collapse → absent airflow |
| Gasping/choking arousals | Hypoxaemia/hypercapnia → chemoreceptor-triggered arousal |
| Excessive daytime sleepiness | Repeated arousals → sleep fragmentation → ↓ N3/REM |
| Morning headache | Nocturnal hypercapnia → cerebral vasodilation |
| Nocturia | Intermittent hypoxia → ↑ atrial pressure (right heart strain) → ↑ ANP release → diuresis |
| Impotence / ↓ libido | Chronic intermittent hypoxia → ↓ testosterone + sympathetic overdrive |
| Unrefreshing sleep | Despite adequate hours in bed, architecture is fragmented |
| Symptom | Pathophysiology |
|---|---|
| Excessive daytime sleepiness | Orexin deficiency → unstable flip-flop switch → intrusion of sleep into wakefulness |
| Cataplexy | Orexin deficiency → REM atonia mechanism activated by emotional stimulation during wakefulness → sudden bilateral muscle weakness |
| Sleep paralysis | Persistence of REM atonia into the wake transition |
| Hypnagogic/hypnopompic hallucinations | REM dreaming intrudes into wake-sleep (hypnagogic) or sleep-wake (hypnopompic) transition |
| Fragmented nocturnal sleep | Paradoxically, narcolepsy patients also have poor nighttime sleep because the flip-flop switch is unstable in BOTH directions |
| Symptom | Pathophysiology |
|---|---|
| Urge to move legs, worse at rest | Central dopaminergic dysfunction → abnormal sensory processing; worse at rest because movement activates dopaminergic pathways |
| Worse in the evening/night | Circadian variation in dopamine levels (nadir in the evening) + iron availability ↓ at night |
| Relief with movement | Movement activates dopaminergic and sensory pathways that suppress the dysaesthesia |
| Secondary insomnia (initial) | Cannot lie still → cannot fall asleep |
Key examination [5]:
- General features: appearance of patient, vital signs including BMI, inspection of the nasal passages, throat and neck (goitre) [5]
- General respiratory and cardiovascular examination [5]
| Sign | What to Look For | Significance |
|---|---|---|
| BMI / obesity | BMI > 30; waist circumference; neck circumference > 40 cm (M) or > 38 cm (F) | OSA risk; OHS |
| Oropharyngeal examination | Mallampati score (I–IV); macroglossia/tonsillar hypertrophy [5]; elongated uvula; high-arched palate | Anatomical predisposition to OSA. Friedmann tongue position and tonsil grading (Grade I–IV) [2] |
| Nasal examination | Deviated septum; polyps; mucosal oedema | Nasal obstruction → ↑ OSA severity |
| Neck | Goitre [5]; neck circumference | Hypothyroidism → myxoedematous infiltration of URT; large neck → OSA risk |
| Jaw | Retrognathia / micrognathia | Craniofacial risk for OSA |
| Facial features | Coarsened features, prognathism, large hands/feet | Acromegaly (OSA in ~50%) [6] |
| Cardiovascular | BP (HTN secondary to OSA); signs of RHF (elevated JVP, peripheral oedema — cor pulmonale); AF | Complications of untreated OSA; also HF as a cause of CSA |
| Respiratory | Wheeze/crackles; barrel chest (COPD) | Comorbid respiratory disease |
| Thyroid | Goitre, tremor, tachycardia, lid lag | Hyperthyroidism → hyperarousal → insomnia [5]; or hypothyroidism → OSA |
| Neurological | Parkinsonian features (bradykinesia, rigidity, tremor) | RBD as prodrome of Parkinson's/Lewy body disease |
| Peripheral | Peripheral neuropathy signs | Secondary RLS |
| Mood/affect | Flat affect, psychomotor retardation or agitation | Depression as cause of insomnia |
Clinical Pearl: The Bed Partner History
Many sleep disorders are diagnosed by the bed partner, not the patient. The patient with OSA is asleep during the apnoeas — they don't know they stop breathing. The patient with RBD is asleep during dream-enacting behaviour. The patient with PLMD is asleep during limb movements. Always ask the bed partner.
Untreated OSA is a/w a variety of consequences and confers extra mortality! [2]:
- Sleep fragmentation → sleepiness → car accidents, neurocognitive impairments [2]
- Sympathetic activation → ↑BP → secondary hypertension [2]
- Oxidative stress + release of mediators (hormones, cytokines, adipokines) → ↑atherosclerosis + metabolic disturbances → cardiovascular diseases, e.g. CAD, HF, arrhythmia, stroke [2]
- Chronic hypoxaemia → chronic respiratory failure → cor pulmonale (rare except in presence of other conditions, e.g. OHS, COPD) [2]
For insomnia:
- ↑ risk of depression (bidirectional)
- ↑ cardiovascular risk (chronic sympathetic activation)
- ↑ workplace accidents and motor vehicle accidents
- ↓ quality of life, ↓ productivity
- ↑ healthcare utilisation
Note: ↑ morbidity and mortality with ↑ body weight [3] — obesity ties many of these together.
Is the patient trying to tell me something? A consideration if nil findings. Some cases are normal variant or idiopathic. [5]
8. Differential Diagnosis of Specific Presentations
(Brief overview here; detailed DDx will follow in Part 2)
Differential diagnosis [2]:
- ↓ sleep duration: sleep deprivation, disturbance of sleep-wake cycle
- ↓ sleep quality:
- Respiratory: sleep apnoea (central, obstructive), obesity-hypoventilation syndrome
- Neurological: periodic limb movement syndrome
- Normal sleep:
- Neurological: narcolepsy, fibromyalgia, neurological lesions
- Others: drugs, idiopathic hypersomnolence (rare)
- Others: depression, other medical conditions
| Category | Examples |
|---|---|
| Primary sleep disorders | Chronic insomnia disorder, circadian rhythm disorders, RLS, PLMD |
| Psychiatric | Depression, anxiety (GAD, PTSD), bipolar disorder, substance use |
| Medical | Pain (any cause), GERD, HF, COPD, asthma, hyperthyroidism, nocturia (BPH, DM, UTI), pruritus (eczema, liver disease), menopause |
| Pharmacological | Caffeine, stimulants, SSRIs, steroids, beta-blockers, theophylline, diuretics |
| Behavioural | Poor sleep hygiene, jet lag, shift work |
Key investigations [5]: Nil for most cases. Others according to history and findings.
Consider [5]:
- FBE
- ESR/CRP
- LFTs (γGT)
Additional targeted investigations:
| Investigation | Indication | What It Shows |
|---|---|---|
| Sleep diary (2 weeks) | All sleep disturbance | Subjective sleep-wake pattern; ± mismatch with objective data |
| Actigraphy | As adjunct to sleep diary when suspecting circadian sleep-wake disorder [1] | Wrist-worn device measuring movement as proxy for sleep-wake; useful for circadian disorders |
| Polysomnography (PSG) | Only when suspect another sleep disorder, e.g. OSA [1]; also for narcolepsy, PLMD, parasomnias | Gold standard; measures EEG, EOG, EMG, airflow, chest/abdominal effort, SpO₂, body position, snoring |
| Multiple Sleep Latency Test (MSLT) | Suspected narcolepsy | Measures time to fall asleep in 5 daytime nap opportunities; mean latency < 8 min + ≥2 sleep-onset REM periods (SOREMPs) = narcolepsy |
| Screening questionnaires | Pittsburgh Sleep Quality Index (significant sleep disturbance = > 5/21 points [1]); Epworth Sleepiness Scale (≥10 = EDS); STOP-BANG (OSA screening); Sleep Problems Questionnaire (significant sleep disturbance = ≥4 on any single item) [1] | |
| Blood tests | As guided by clinical suspicion: TFTs (hypothyroid/hyperthyroid), ferritin (iron deficiency → RLS; target ferritin > 75 μg/L in RLS), FBE (anaemia), HbA1c (diabetes), LFTs (alcohol, liver disease), renal function (uraemic RLS) | |
| Oximetry (overnight) | Screening for OSA | Desaturation index; limited sensitivity but useful if PSG unavailable |
| Lateral cephalometry / nasopharyngoscopy | OSA with suspected craniofacial abnormality | Anatomical assessment for surgical planning |
High Yield Summary
Key Points:
-
Sleep disturbance is a symptom, not a diagnosis — always search for the underlying cause using a systematic approach (psychiatric, medical, pharmacological, primary sleep disorder).
-
Normal sleep architecture (N1 → N2 → N3 → REM in 90-min cycles) is disrupted differently by different conditions: OSA fragments architecture via arousals; depression alters REM latency; aging reduces N3.
-
The 3P model (Predisposing, Precipitating, Perpetuating) explains why acute insomnia becomes chronic — perpetuating factors (maladaptive behaviours) are the key target for CBT-I.
-
Insomnia pattern matters: Initial → anxiety/RLS; Terminal → depression; Middle → medical/OSA.
-
OSA pathophysiology: Loss of wakefulness drive → ↓ pharyngeal dilator tone → negative inspiratory pressure → upper airway collapse → apnoea → hypoxaemia/hypercapnia → arousal → cycle repeats.
-
OSA is undertreated and confers real mortality: HTN, arrhythmia, stroke, CAD, car accidents, neurocognitive decline.
-
Narcolepsy: Orexin/hypocretin deficiency → unstable flip-flop switch → cataplexy, sleep paralysis, hypnagogic hallucinations.
-
RLS: Central dopaminergic dysfunction + brain iron deficiency → always check ferritin.
-
Always take a bed partner history — many sleep disorders are observed, not self-reported.
-
Always assess driving risk in any patient with excessive daytime sleepiness.
-
Masquerades: Depression, Diabetes, Drugs (stimulants, alcohol, beta-blockers, SSRIs, steroids), Thyroid (hyperthyroid), Spinal dysfunction, UTI (nocturia).
Active Recall - Sleep Disturbance (Definition to Clinical Features)
[1] Senior notes: Ryan Ho Psychiatry.pdf (Section 9.2.3 Insomnia, pp. 222–224) [2] Senior notes: Ryan Ho Respiratory.pdf (Section 3.8 Sleep-Associated Disorders, pp. 155–161) [3] Senior notes: Ryan Ho Endocrine.pdf (Section on Complications of Obesity, p. 117) [4] Senior notes: Ryan Ho GI.pdf (Section on GERD, p. 57) [5] Lecture slides: murtagh merge.pdf (p. 62 — Insomnia) [6] Senior notes: Ryan Ho Endocrine.pdf (Section 5.2.3 Acromegaly, p. 111) [7] Senior notes: Ryan Ho Psychiatry.pdf (Section 7.2 Depressive Disorders, p. 155)
Differential Diagnosis of Sleep Disturbance
The approach to differential diagnosis of sleep disturbance follows the Murtagh diagnostic strategy framework — a structured, probability-based method that prevents you from anchoring on the most common cause and missing something dangerous. Let me walk you through this systematically.
The core clinical question is: Why is this patient not sleeping well? — which really breaks down into three sub-questions:
- Is the patient not getting enough sleep? (insufficient sleep opportunity or inability to initiate/maintain sleep → insomnia and circadian disorders)
- Is the patient sleeping but the sleep quality is poor? (something disrupts sleep architecture → OSA, PLMD, parasomnias)
- Is the patient sleeping adequately but still excessively sleepy? (intrinsic hypersomnolence → narcolepsy, idiopathic hypersomnia)
These are not mutually exclusive — a patient with OSA may have insomnia (frequent arousals) AND excessive daytime sleepiness.
Murtagh's Diagnostic Strategy for Insomnia / Sleep Disturbance
This is the high-yield lecture framework. Every item matters.
These are the common causes — what you should think of first in any patient presenting with sleep disturbance:
| Diagnosis | Why It Causes Sleep Disturbance |
|---|---|
| Stress and anxiety | Psychological hyperarousal → ↑ cortisol, ↑ sympathetic tone → the brain cannot "switch off" → initial insomnia (difficulty falling asleep). Anxious rumination at bedtime creates a conditioned arousal response to the bed itself. |
| Depression | HPA axis dysregulation → cortisol secretion peaks earlier in the night → terminal insomnia (early morning awakening). Also ↓ serotonin → disrupted sleep architecture (↓ REM latency, ↑ REM density, ↓ N3). Depression is the single most important psychiatric cause to exclude. |
| Inappropriate sleep hygiene or lifestyle | Caffeine late in the day (blocks adenosine → ↓ sleep pressure), screen use at night (blue light suppresses melatonin secretion from the pineal gland via the retinohypothalamic tract → delays circadian phase), irregular sleep-wake schedule (desynchronises the SCN clock), exercising too close to bedtime (↑ core body temperature and sympathetic tone). |
| Environmental e.g. noisy household | External stimuli cause cortical arousals → sleep fragmentation. This is particularly relevant in Hong Kong given small flats, thin walls, and high population density. |
| Drug withdrawal inc. alcohol, hypnotics | Alcohol is a GABA-A receptor agonist → acutely sedating, but as blood levels fall in the second half of the night, there is rebound CNS excitability → middle/terminal insomnia + vivid dreams. Chronic alcohol → GABA-A receptor downregulation → withdrawal causes severe insomnia, anxiety, and even seizures. Benzodiazepine/Z-drug withdrawal → rebound insomnia (same GABA mechanism). |
| Biorhythm disruption e.g. shift work, travel | Misalignment between the endogenous circadian clock (SCN) and the desired sleep time → the circadian alerting signal is active when the patient is trying to sleep. Shift workers in Hong Kong (healthcare, transport, hospitality) are particularly affected. |
Most Common Causes — Think of These First
In clinical practice and exams, the top 3 causes of sleep disturbance presenting to primary care are: (1) Anxiety/stress, (2) Depression, (3) Poor sleep hygiene. Always screen for these before ordering investigations.
These are conditions where missing the diagnosis causes significant morbidity or mortality:
| Diagnosis | Why It Causes Sleep Disturbance | Why It's Serious |
|---|---|---|
| Peripheral vascular disease | Nocturnal limb ischaemia → rest pain (worse at night when legs are horizontal → loss of gravity-assisted perfusion) → awakens the patient | Critical limb ischaemia; amputation risk |
| Congestive cardiac failure | Orthopnoea (recumbent → ↑ venous return → pulmonary congestion → dyspnoea) and PND (nocturnal fluid redistribution → pulmonary oedema → wakes patient gasping) → middle insomnia. Also Cheyne-Stokes respiration → central sleep apnoea. | Life-threatening decompensation |
| Pharyngeal tumours | Mass effect → upper airway obstruction → OSA-like presentation or stridor. Can also cause dysphagia, odynophagia. | Malignancy — delay in diagnosis worsens prognosis |
| Pain syndromes e.g. back, arthritis, CTS, cancer | Pain activates ascending nociceptive pathways → cortical arousal → multiple awakenings (middle insomnia). Inflammatory arthritis characteristically worse in early morning (cytokine levels peak at night → morning stiffness). Cancer pain may be constant. CTS is classically worse at night because wrist flexion during sleep compresses the median nerve. | Underlying malignancy; progressive joint destruction; nerve damage |
| Respiratory e.g. asthma, COPD, nasal obstruction | Asthma: circadian ↑ in airway resistance + ↑ vagal tone at night → nocturnal bronchoconstriction → awakens with wheeze/cough. COPD: ↓ FRC in supine position + ↓ accessory muscle use during sleep → hypoventilation → hypoxaemia → arousals. Nasal obstruction: ↑ negative inspiratory pressure → ↑ pharyngeal collapsibility → OSA. | Acute severe asthma; respiratory failure; may worsen OSA |
| Post-traumatic stress disorder (PTSD) | Hyperarousal (↑ noradrenaline) + re-experiencing symptoms (nightmares, flashbacks during sleep-wake transition) → initial insomnia + middle insomnia. Nightmares cause avoidance of sleep. | Psychiatric emergency if suicidal; severe functional impairment |
| Psychosis | Disrupted dopaminergic and serotonergic circuits → severe circadian disorganisation. Paranoid ideation may prevent the patient from sleeping (fear of vulnerability). Mania → ↓ need for sleep (NOT insomnia — the patient does not feel tired). | Risk to self and others |
| Restless legs / nocturnal myoclonus | RLS: central dopaminergic dysfunction → compelling urge to move legs at rest → cannot initiate sleep (initial insomnia). PLMD: repetitive limb movements every 20–40 seconds during sleep → cortical arousals → sleep fragmentation → excessive daytime sleepiness. | Iron deficiency may be the underlying cause (treatable); uraemia may be undiagnosed |
These are diagnoses that clinicians frequently overlook:
| Diagnosis | Why It's Missed | Key Distinguishing Features |
|---|---|---|
| Sleep apnoea | The patient is unaware of the apnoeas (they are asleep!). They present with "insomnia" or "tiredness" and the clinician doesn't ask about snoring or obtain a bed-partner history. | Loud snoring, witnessed apnoeas, excessive daytime sleepiness, unrefreshing sleep, morning headache, nocturia. Obese middle-aged male is the classic patient but normal-weight individuals with craniofacial features also get it. |
| GORD | Nocturnal acid reflux causes micro-arousals without the patient being aware. They may not have classic heartburn — in Asians, atypical presentations are more common [4]. | Posturally aggravated symptoms; acid taste; chronic cough; throat tightness. May improve with PPI trial. |
| Dementia | Altered sleep-wake cycle: another hallmark of delirium [8] — but early dementia also disrupts the SCN and circadian rhythms. Sundowning (↑ confusion/agitation in the evening) mimics insomnia. Families may attribute the sleep disturbance to "old age." | Progressive cognitive decline; behavioural changes; sundowning; should screen with cognitive assessment (MMSE/MoCA). |
| Menopausal symptoms | Hot flushes and night sweats cause frequent arousals → middle insomnia. Women may not volunteer these symptoms unless asked directly. | Perimenopausal age, vasomotor symptoms, irregular menses, mood changes. |
Don't Miss Sleep Apnoea
OSA is the most commonly missed cause of sleep disturbance. It affects 4% of middle-aged men and 2% of middle-aged women. Untreated OSA causes secondary hypertension, cardiovascular disease, and road traffic accidents. Always ask about snoring and witnessed apnoeas — get a bed-partner history!
| Diagnosis | Explanation |
|---|---|
| Macroglossia / tonsillar hypertrophy | Enlargement of the tongue or tonsils narrows the pharyngeal airway → OSA. Causes of macroglossia include acromegaly (GH excess → soft tissue overgrowth → OSA in ~50%) [6], hypothyroidism (myxoedematous infiltration), amyloidosis, Down syndrome. Tonsillar hypertrophy is a particularly important cause in children [2]. |
| Malnutrition | Protein-calorie malnutrition → ↓ tryptophan (precursor to serotonin → melatonin pathway) → disrupted sleep. Also micronutrient deficiencies (iron → RLS; magnesium → muscle cramps at night; B12/folate → neuropathy → RLS-like symptoms). |
| Parasomnias e.g. night terrors | NREM parasomnias (sleepwalking, night terrors) are caused by incomplete arousal from N3 deep sleep → dissociated state with motor activity but without consciousness. More common in children (who have proportionally more N3). In adults, new-onset parasomnias (especially REM sleep behaviour disorder) should prompt investigation for neurodegenerative disease [9]. |
These are common medical conditions that "masquerade" as other things — always run through this list:
| Masquerade | Mechanism of Sleep Disturbance |
|---|---|
| Depression | HPA axis dysregulation → early cortisol peak → terminal insomnia. ↓ serotonin → ↓ melatonin. Also psychomotor agitation or excessive rumination. Most important masquerade. |
| Diabetes | Polyuria/nocturia (osmotic diuresis from hyperglycaemia) → middle insomnia. Peripheral neuropathy → neuropathic pain/RLS-like symptoms at night. Also ↑ OSA risk (obesity). |
| Drugs: stimulants, alcohol, beta blockers, SSRIs, steroids | Stimulants/caffeine → adenosine receptor blockade → ↓ sleep pressure. Alcohol → rebound excitability. Beta-blockers → ↓ melatonin secretion (β₁-receptors on pinealocytes mediate melatonin release; blocking them → ↓ melatonin → insomnia + vivid dreams). SSRIs → ↑ serotonin → suppresses REM sleep → vivid dreams, insomnia, PLMD. Steroids → ↑ cortisol → hyperarousal. |
| Thyroid/other endocrine: hyperthyroid | Excess thyroid hormone → ↑ metabolic rate → ↑ sympathetic tone → hyperarousal → initial insomnia, anxiety, tremor, palpitations. Also consider hypothyroidism → myxoedema of upper airway → OSA; ↓ ventilatory drive. |
| Spinal dysfunction | Chronic back/neck pain → nocturnal pain exacerbated by recumbent position → middle insomnia. Radiculopathy → limb pain/paraesthesia at night. |
| Urinary tract infection: nocturia | Cystitis → bladder irritation → frequency, urgency, nocturia → middle insomnia. Also consider BPH, diabetes, CCF, OSA (↑ ANP → nocturia) as causes of nocturia [10]. |
A consideration if nil findings. Some cases are normal variant or idiopathic. [5]
This is Murtagh's reminder to consider:
- Psychosocial stressors the patient is not disclosing (domestic violence, financial distress, relationship problems, work stress)
- Normal variant: some people are natural "short sleepers" (genetically determined, require < 6 hours and are not impaired) — they present because they think something is wrong, but they have no daytime symptoms
- Unrealistic expectations: elderly patients who expect 8 hours of unbroken sleep but physiologically only need 6–7 hours with more awakenings
Differential diagnoses from the DSM-5 framework [1]:
| D/dx | Salient differentiating features |
|---|---|
| Normal sleep variations | Short sleepers: some individuals require little sleep and do not feel difficulty falling/staying asleep or daytime sleepiness. These individuals may mimic insomnia if they try to stay in bed for a longer time. Inadequate opportunity of sleep due to e.g. shift work, other disturbances [1] |
| Situational insomnia | Lasts days to weeks and a/w life events or with changes in sleep schedules. Classified under other specified insomnia disorder under DSM-5 if < 3 months but otherwise meets criteria. [1] |
| Delayed sleep-wake phase disorder | Classified under delayed sleep phase type of circadian rhythm sleep-wake disorder. Usually report sleep-onset insomnia when try to sleep at socially normal times, but do not complain of insomnia when follow endogenous circadian rhythm. [1] — Key differentiator: if the patient is allowed to sleep at their preferred time (e.g. 3 AM–11 AM), they sleep perfectly normally. |
| Restless leg syndrome | Often produces difficulties initiating and maintaining sleep. Should have urge to move legs, unpleasant leg sensation when sitting/lying down. Partner may report Hx of restless sleep or even limb movement/muscle twitches during sleep. [1] |
| Breathing-related sleep disorders | Majority have Hx of loud snoring, breathing pauses during sleep. May report interrupted sleep (frequent arousal due to apnoea) and daytime sleepiness. [1] |
Additional differentials to consider:
| D/dx | Differentiating Features |
|---|---|
| Substance/medication-induced insomnia | Temporal relationship with drug initiation/dose change. Common culprits: caffeine, stimulants, SSRIs, steroids, beta-blockers, theophylline. Resolves with drug withdrawal/dose adjustment. |
| Insomnia due to medical condition | Sleep disturbance clearly temporally related to and adequately explained by the medical condition (pain, dyspnoea, GERD, nocturia, pruritus). |
| Psychiatric comorbid insomnia | Insomnia co-occurs with depression, anxiety, PTSD, psychosis. Now diagnosed as comorbid rather than secondary — treat both. |
| Paradoxical insomnia | Patient complains of severe insomnia but PSG shows normal sleep. The discrepancy is due to misperception of sleep as wakefulness. Rare. |
Differential diagnosis [2]:
| Category | Conditions | Mechanism |
|---|---|---|
| ↓ Sleep duration | Sleep deprivation, disturbance of sleep-wake cycle | Simply not enough hours of sleep → accumulated sleep debt → ↑ adenosine → overwhelming sleep pressure during the day |
| ↓ Sleep quality (Respiratory) | Sleep apnoea (central, obstructive), obesity-hypoventilation syndrome | Repeated apnoeas → arousals → sleep fragmentation → ↓ restorative N3/REM despite adequate time in bed |
| ↓ Sleep quality (Neurological) | Periodic limb movement syndrome | Repetitive limb movements → cortical arousals every 20–40 seconds → sleep fragmentation |
| Normal sleep (Neurological) | Narcolepsy, fibromyalgia, neurological lesions | Narcolepsy: orexin deficiency → unstable flip-flop switch → irresistible sleep intrusions. Fibromyalgia: alpha-wave intrusion into NREM sleep → non-restorative sleep. Lesions (e.g. hypothalamic tumours, encephalitis): damage to arousal centres. |
| Normal sleep (Others) | Drugs, idiopathic hypersomnolence (rare) | Sedating drugs (benzodiazepines, antihistamines, opioids) → ↑ GABAergic or ↓ histaminergic/noradrenergic tone → sleepiness. Idiopathic hypersomnia: unknown mechanism; diagnosis of exclusion. |
| Others | Depression, other medical conditions | Depression: psychomotor retardation, hypersomnia variant (atypical depression), fatigue misinterpreted as sleepiness. Medical conditions: hypothyroidism (↓ metabolic rate → lethargy), anaemia (↓ O₂ delivery → fatigue), chronic kidney disease, liver failure. |
D/dx for sudden episodic awakening with breathing difficulty during sleep [2]:
- OSA – "choking" sensation [2]
- PND – may be a/w orthopnoea, does not resolve immediately upon awakening, relieved by sleeping with several pillows [2]
- Asthma – a/w wheezes, Hx of atopy [2]
- Rhinitis with severe nasal blockade [2]
Key Distinction: Waking Up Short of Breath at Night
This is a classic exam question. OSA choking resolves almost immediately upon waking (because the arousal opens the airway). PND from heart failure takes several minutes to resolve (because pulmonary oedema needs time to redistribute). Asthma has audible wheeze and Hx of atopy. Rhinitis has nasal congestion. The timing and associated features differentiate them.
Nocturia is a common but under-recognised cause of middle insomnia. A structured approach [10]:
| System | Cause | Mechanism |
|---|---|---|
| Respiratory | Obstructive sleep apnoea | Difficulty with sleep maintenance and loss of diurnal variation in release of vasopressin (ADH) [10]. Also: intermittent hypoxia → ↑ right atrial pressure → ↑ ANP release → natriuresis → nocturia |
| Cardiovascular | Hypertension, congestive heart failure, peripheral oedema | CHF: daytime fluid accumulates in dependent tissues → at night, recumbent position → fluid redistributes centrally → ↑ renal perfusion → nocturia |
| Urological | UTI, BPH, prostatic cancer | UTI: bladder mucosal inflammation → irritative symptoms (frequency, urgency). BPH: bladder outlet obstruction → incomplete emptying → frequent voiding |
| Endocrine | Diabetes mellitus, diabetes insipidus | DM: osmotic diuresis from glycosuria. DI: nocturnal polyuria — loss of diurnal variation or deficiency for vasopressin (ADH) [10] |
Altered sleep-wake cycle: another hallmark of delirium [8]
Delirium must always be considered in the differential of acute sleep disturbance, especially in hospitalised and elderly patients. The key differentiating feature is impaired consciousness and attention — insomnia alone does NOT impair consciousness.
| Feature | Delirium | Insomnia | Dementia with Sundowning |
|---|---|---|---|
| Onset | Acute (hours–days) | Gradual or acute (linked to stressor) | Chronic (months–years) |
| Consciousness | Impaired [8] | Normal | Normal until late stages |
| Attention | Impaired (hallmark) [8] | Normal (may have poor concentration from fatigue, but attention itself is intact) | Impaired in later stages |
| Fluctuation | Acute onset with diurnal fluctuation (usu worse at night) [8] | Consistent sleep difficulty, stable during waking hours | Evening worsening ("sundowning") |
| Hallucinations | Common (esp visual) | Absent | May occur (esp in DLB — visual hallucinations 67%) [11] |
| Reversibility | Reversible if cause treated | Variable | Progressive |
| Condition | Insomnia Type | Key Night Symptoms | Key Day Symptoms | Key Clues |
|---|---|---|---|---|
| Anxiety | Initial | Rumination, difficulty switching off | Worry, tension, irritability | Persistent worry; somatic symptoms |
| Depression | Terminal | Early morning wakening | Low mood, anhedonia, fatigue | 2-week Hx of low mood [7]; weight/appetite change |
| OSA | Middle | Snoring, witnessed apnoeas, choking | EDS, morning headache, poor concentration | Obese male; large neck; macroglossia/tonsillar hypertrophy [5] |
| RLS | Initial | Urge to move legs, worse at rest | Fatigue | Low ferritin; worsened by SSRIs |
| PLMD | Middle | Repetitive limb jerks (bed partner reports) | EDS | Often co-occurs with RLS |
| Circadian disorder | Initial (delayed) or Terminal (advanced) | Sleeps well at "wrong" time | Sleepy at socially required times | Shift worker; adolescent with delayed phase |
| GERD | Middle | Nocturnal heartburn, acid taste, cough | May have no daytime GI symptoms | Postural aggravation; responds to PPI |
| Heart failure | Middle | PND, orthopnoea | Exertional dyspnoea, oedema | Bilateral ankle oedema; ↑ JVP; displaced apex |
| Narcolepsy | — | Fragmented nocturnal sleep paradoxically | EDS + cataplexy + sleep paralysis + hallucinations | Young onset; irresistible sleep attacks |
| Delirium | Reversed cycle | Agitation, confusion, hallucinations | Drowsy, inattentive | Acute onset; fluctuating; impaired attention |
| RBD | Middle | Dream enactment, vocalisation, violence | May have mild Parkinsonian signs | M > F = 9:1; a/w synucleinopathies (PD, MSA, DLB) [9] |
| Menopausal | Middle | Hot flushes, night sweats | Mood changes, fatigue | Perimenopausal age; vasomotor symptoms |
High Yield DDx Points for Exams:
- Always use the Murtagh framework: Probability → Serious → Pitfalls → Rarities → Masquerades → "Trying to tell me something?"
- The three patterns of insomnia (initial/middle/terminal) immediately narrow your differential.
- OSA is the most commonly missed diagnosis — always ask about snoring and obtain a bed-partner history.
- Depression is the most important psychiatric cause — terminal insomnia + low mood + anhedonia = screen for MDD.
- Beta-blockers cause insomnia by blocking pinealocyte β₁-receptors → ↓ melatonin. This is a favourite exam question.
- Delirium must be excluded in any acute sleep-wake disturbance in a hospitalised/elderly patient — check attention.
- RBD in an elderly patient = prodrome of Parkinson's / DLB until proven otherwise.
High Yield Summary
Differential Diagnosis of Sleep Disturbance — Key Takeaways:
-
Probability diagnoses: Stress/anxiety, depression, poor sleep hygiene, environment, drug/alcohol withdrawal, biorhythm disruption.
-
Serious not to miss: PVD, CCF, pharyngeal tumour, pain syndromes (back/arthritis/CTS/cancer), respiratory (asthma/COPD/nasal obstruction), PTSD, psychosis, RLS/PLMD.
-
Pitfalls (often missed): Sleep apnoea, GORD, dementia, menopausal symptoms.
-
Rarities: Macroglossia/tonsillar hypertrophy, malnutrition, parasomnias.
-
Masquerades: Depression, diabetes, drugs (stimulants, alcohol, beta-blockers, SSRIs, steroids), thyroid (hyperthyroid), spinal dysfunction, UTI (nocturia).
-
Pattern-based approach: Initial insomnia → anxiety/RLS/delayed phase. Middle insomnia → OSA/pain/nocturia/GERD. Terminal insomnia → depression/advanced phase.
-
Always exclude delirium in acute sleep-wake disturbance in hospitalised/elderly patients.
-
Always get a bed-partner history — OSA, PLMD, and RBD are observed conditions.
-
Nocturnal dyspnoea DDx: OSA (resolves immediately) vs PND (takes minutes) vs asthma (wheeze) vs rhinitis (nasal blockage).
-
RBD in the elderly → investigate for α-synucleinopathy (PD, DLB, MSA).
Active Recall - Differential Diagnosis of Sleep Disturbance
References
[1] Senior notes: Ryan Ho Psychiatry.pdf (Section 9.2.3 Insomnia, pp. 222–224) [2] Senior notes: Ryan Ho Respiratory.pdf (Section 3.8 Sleep-Associated Disorders, pp. 155–161) [4] Senior notes: Ryan Ho GI.pdf (Section on GERD, p. 57) [5] Lecture slides: murtagh merge.pdf (pp. 61–62 — Insomnia) [6] Senior notes: Ryan Ho Endocrine.pdf (Section 5.2.3 Acromegaly, p. 111) [7] Senior notes: Ryan Ho Psychiatry.pdf (Section 7.2 Depressive Disorders, p. 155) [8] Senior notes: Ryan Ho Neurology.pdf (Section 4.1.3 Delirium, p. 95) [9] Senior notes: Ryan Ho Psychiatry.pdf (Section 9.2.5 REM Sleep Behaviour Disorder, p. 229) [10] Senior notes: felixlai.md (Differential diagnosis of nocturia) [11] Senior notes: Ryan Ho Neurology.pdf (Section 5.4.5 Dementia with Lewy Bodies, p. 134)
Diagnostic Criteria, Diagnostic Algorithm and Investigations for Sleep Disturbance
The diagnosis of sleep disturbance is overwhelmingly clinical — it is built on a thorough history (including a bed-partner history) and targeted physical examination. Investigations are reserved for specific situations where you suspect an underlying sleep disorder (e.g. OSA, narcolepsy, circadian disorder) or a medical/psychiatric comorbidity driving the insomnia. Let me walk you through this systematically.
1. Diagnostic Criteria
1.1 Chronic Insomnia Disorder
This is the condition you will encounter most frequently. Two classification systems exist side by side — ICD-10 and DSM-5. You should know both for exams.
Clinical features: remember the number '3' = ≥30min delay/awake/early wakening for 3×/w × 3mo [1]
| Criterion | Detail |
|---|---|
| A | A predominant complaint of dissatisfaction with sleep quantity or quality, associated with ≥1 of: [1] |
| (1) Difficulty initiating sleep. (In children, this may manifest as difficulty initiating sleep without caregiver intervention.) [1] | |
| (2) Difficulty maintaining sleep, characterised by frequent awakenings or problems returning to sleep after awakenings. (In children, this may manifest as difficulty returning to sleep without caregiver intervention.) [1] | |
| (3) Early-morning awakening with inability to return to sleep. [1] | |
| B | Clinically significant distress or functional impairment. [1] — This criterion prevents over-diagnosis in people who sleep "little" but function perfectly well (i.e. natural short sleepers). If there is no daytime consequence, it is not insomnia disorder. |
| C | The sleep difficulty occurs ≥3 nights per week. [1] — Why 3? This threshold separates the normal occasional bad night from a clinically significant pattern. |
| D | The sleep difficulty is present for ≥3 months. [1] — This distinguishes chronic insomnia from short-term/adjustment insomnia ( < 3 months). |
| E | The sleep difficulty occurs despite adequate opportunity for sleep. [1] — This is crucial: a shift worker who only has 4 hours in bed does not have insomnia — they have insufficient sleep opportunity. The patient must have a reasonable window for sleep. |
| F | The insomnia is not better explained by and does not occur exclusively during the course of another sleep-wake disorder (e.g. narcolepsy, a breathing-related sleep disorder, a circadian rhythm sleep-wake disorder, a parasomnia). [1] — However, insomnia can be diagnosed comorbidly with these if the insomnia is out of proportion to what the other disorder would explain. |
| G | The insomnia is not attributable to the physiological effects of a substance (e.g. a drug of abuse, a medication). [1] |
| H | Coexisting mental disorders and medical conditions do not adequately explain the predominant complaint of insomnia. [1] — Again, comorbid diagnosis is allowed; this criterion only excludes cases where the insomnia is entirely explained by the other condition. |
| Specify | Episodic (≥1 month, < 3 months), persistent (≥3 months), recurrent (≥2 episodes/year) [1] |
The 3-3-3 Rule for Chronic Insomnia
A useful mnemonic: ≥30 min sleep onset latency or wake time, ≥3 nights per week, for ≥3 months. If a patient meets all three 3s plus has daytime impairment and adequate sleep opportunity, they have chronic insomnia disorder.
Requires ALL of the following:
| Criterion | Detail |
|---|---|
| (a) | Complaint of difficulty falling asleep or maintaining sleep or of poor quality of sleep [1] |
| (b) | Sleep disturbance occurred ≥3×/week for ≥1 week [1] — Note: ICD-10 requires only 1 week (vs DSM-5's 3 months). This is a much lower threshold, meaning ICD-10 captures both acute and chronic insomnia under one code. |
| (c) | Preoccupation with sleeplessness and excessive concern over its consequences at night and during the day [1] — This reflects the psychophysiological component (conditioned arousal, worry about sleep). |
| (d) | Causes marked distress or interferes with ordinary ADL [1] |
ICD-10 vs DSM-5: Key Differences
The ICD-10 requires only 1 week of symptoms; DSM-5 requires 3 months. This means a patient with 2 weeks of insomnia meets ICD-10 criteria but not DSM-5 criteria (they would be classified as "short-term insomnia" or "other specified insomnia disorder" in DSM-5). In Hong Kong clinical practice, both systems are used — HA coding uses ICD-10; psychiatric research often uses DSM-5.
The ICSD-3 criteria are essentially harmonised with DSM-5:
- Difficulty initiating/maintaining sleep or early morning awakening
- Adequate opportunity and circumstances for sleep
- Daytime consequences (fatigue, mood disturbance, cognitive impairment, social/occupational dysfunction)
- ≥3 nights per week for ≥3 months
- Not better explained by another sleep disorder
The ICSD-3 also defines Short-Term Insomnia Disorder (same criteria but < 3 months duration, often situational).
Suspect OSA if snoring at night plus either one of [2]:
Formal diagnosis requires polysomnography (PSG):
Apnoea-hypopnoea index (AHI): number of apnoeic/hypopnoeic episodes per sleep hour [2]:
- Normal = < 5 [2]
- Mild OSA = 5–15 [2]
- Moderate OSA = 15–30 [2]
- Severe OSA = > 30 [2]
- In children, the cut-off is > 1 [2]
The AASM (American Academy of Sleep Medicine) diagnostic criteria for OSA syndrome require:
- AHI ≥ 5 events/hour AND symptoms (EDS, unrefreshing sleep, fatigue, insomnia, nocturnal gasping/choking/snoring, witnessed apnoeas)
- OR AHI ≥ 15 events/hour regardless of symptoms (because even asymptomatic moderate-severe OSA confers cardiovascular risk)
Why the dual criteria? Because some patients with significant OSA are not subjectively sleepy (possibly due to chronic adaptation or individual variation in arousal threshold), but they still have the cardiovascular and metabolic consequences of repetitive hypoxaemia and sympathetic surges.
Narcolepsy: predominantly presents with excessive daytime sleepiness, but may also have cataplexy, sleep paralysis, sleep-related hallucinations [1]
ICSD-3 Criteria for Narcolepsy Type 1:
- A. Daily periods of irrepressible need to sleep or daytime lapses into sleep for ≥3 months
- B. One or both of:
- Cataplexy AND mean sleep latency ≤8 min with ≥2 SOREMPs on MSLT (a SOREMP on the preceding nocturnal PSG may replace one MSLT SOREMP)
- CSF hypocretin-1 (orexin-A) ≤110 pg/mL or < 1/3 of mean normal values
ICSD-3 Criteria for Narcolepsy Type 2:
- Meets criterion A + MSLT findings (mean latency ≤8 min, ≥2 SOREMPs) BUT no cataplexy AND CSF orexin is normal or not measured
Multiple sleep latency test (MSLT): multiple trials of naps spaced throughout the day → monitor mean sleep latency + number of REM periods → ≥2 trials with +ve REM sleep indicates narcolepsy [12]
Why SOREMP (Sleep-Onset REM Period) is diagnostic: normally, REM sleep does not occur until ~90 minutes into sleep (you go through N1 → N2 → N3 first). In narcolepsy, orexin deficiency destabilises the flip-flop switch → REM intrudes abnormally early → the patient enters REM within 15 minutes of falling asleep. Finding this in ≥2 out of 5 nap opportunities is pathological.
IRLSSG (International RLS Study Group) / ICSD-3 Criteria — ALL 5 required:
- Urge to move the legs, usually accompanied by uncomfortable/unpleasant sensations in the legs
- Symptoms begin or worsen during periods of rest or inactivity (sitting, lying down) — because movement activates dopaminergic pathways that suppress the dysaesthesia
- Symptoms are partially or totally relieved by movement (walking, stretching) — at least as long as the activity continues
- Symptoms occur exclusively or predominantly in the evening/night — because of the circadian nadir of dopamine in the evening
- The above features are not solely accounted for by another condition (leg cramps, positional discomfort, habitual foot tapping, myalgia, venous stasis, arthritis, peripheral neuropathy)
Supportive features: family history, response to dopaminergic therapy, periodic limb movements during sleep on PSG.
Because altered sleep-wake cycle is a hallmark of delirium [8], you must exclude delirium in any acute sleep disturbance, especially in hospitalised/elderly patients.
DSM-5 Diagnostic Criteria for Delirium [8]
| Criterion | Detail |
|---|---|
| A | A disturbance in attention and awareness. [8] |
| B | The disturbance develops over a short period of time (usually hours to a few days), represents a change from baseline attention and awareness and tends to fluctuate in severity during the course of a day. [8] |
| C | An additional disturbance in cognition (e.g. memory deficit, disorientation, language…). [8] |
| D | Not better explained by another pre-existing, established or evolving neurocognitive disorder and does not occur in the context of a severely reduced level of arousal (e.g. coma). [8] |
| E | Evidence from Hx, P/E, Ix that the disturbance is a direct physiological consequence of another medical condition, substance intoxication or withdrawal, or exposure to toxin or is due to multiple aetiologies. [8] |
The following algorithm provides a systematic clinical approach to any patient presenting with sleep disturbance, integrating the history-taking framework, screening tools, and targeted investigations.
3. Investigation Modalities
The approach to investigation in sleep disturbance follows a tiered logic:
- Most cases of insomnia require no investigations — the diagnosis is clinical
- Targeted blood tests exclude masquerade conditions
- Sleep-specific investigations (diary, actigraphy, PSG, MSLT) are reserved for when a specific sleep disorder is suspected
Key investigations [5]: Nil for most cases. Others according to history and findings.
These are your first-line "investigations" — they are cheap, quick, and help quantify the problem and guide further workup.
| Tool | What It Measures | Scoring & Interpretation | When to Use |
|---|---|---|---|
| Pittsburgh Sleep Quality Index (PSQI) | Global sleep quality over the past month across 7 domains (subjective quality, latency, duration, efficiency, disturbances, medication use, daytime dysfunction) | 0–21 scale; significant sleep disturbance = > 5/21 points [1] | Any patient with sleep complaint — good for baseline assessment and monitoring treatment response |
| Sleep Problems Questionnaire | Specific sleep complaints | Significant sleep disturbance = ≥4 on any single item [1] | Alternative to PSQI |
| Insomnia Severity Index (ISI) | Insomnia severity and impact | 0–28; 0–7 = no insomnia, 8–14 = subthreshold, 15–21 = moderate, 22–28 = severe | Preferred by AASM guidelines for tracking insomnia treatment outcomes |
| Epworth Sleepiness Scale (ESS) | Daytime sleepiness — rates likelihood of dozing in 8 situations | 0–24; ≥10 = excessive daytime sleepiness [2] | Any patient with EDS; essential for OSA workup |
| STOP-BANG Questionnaire | OSA risk screening | Snoring, Tiredness, Observed apnoeas, Pressure (HTN), BMI > 35, Age > 50, Neck > 40cm, Gender male; ≥3 = intermediate-high risk | Screening before sleep study referral; pre-operative screening |
| PHQ-9 | Depression screening | 0–27; ≥10 = moderate depression | When terminal insomnia or low mood is present |
| GAD-7 | Anxiety screening | 0–21; ≥10 = moderate anxiety | When initial insomnia with excessive worry is present |
| Confusion Assessment Method (CAM) / 4AT | Delirium screening | CAM: 4 features (acute onset, inattention, disorganised thinking, altered consciousness); 4AT: 0–12 score, ≥4 = possible delirium | Any acute sleep-wake disturbance in hospitalised/elderly patient |
STOP-BANG Mnemonic for OSA Screening
S = Snoring (loud enough to be heard through closed doors?) T = Tired (daytime sleepiness/fatigue?) O = Observed apnoeas (has anyone witnessed you stop breathing?) P = Pressure (treated for hypertension?) B = BMI > 35 A = Age > 50 N = Neck circumference > 40 cm (16 inches) G = Gender = male
Score ≥3 → intermediate-to-high risk → consider sleep study.
Sleep diary: as above, to document sleep and wake habit over a period of time [12]
Prefer sleep diary over 2-week period [1]
What it records (typically over 14 consecutive days):
- Time got into bed
- Time attempted to fall asleep (sleep onset time)
- Estimated sleep onset latency (how long to fall asleep)
- Number of awakenings and duration of each
- Final wake time and time out of bed
- Naps (timing and duration)
- Caffeine, alcohol, medication use
- Subjective sleep quality rating
What you derive from it:
| Parameter | Calculation | Clinical Significance |
|---|---|---|
| Total Time in Bed (TIB) | Time out of bed − time into bed | Often excessive in insomnia patients (perpetuating factor) |
| Total Sleep Time (TST) | TIB − (sleep onset latency + wake after sleep onset + terminal wakefulness) | Actual amount of sleep obtained |
| Sleep Efficiency (SE) | TST / TIB × 100% | Normal ≥ 85%. In insomnia, often 50–70%. A key target in sleep restriction therapy. |
| Sleep Onset Latency (SOL) | Time to fall asleep after attempting | ≥30 min = clinically significant (initial insomnia) |
| Wake After Sleep Onset (WASO) | Total time awake during the night after initially falling asleep | ≥30 min = clinically significant (middle insomnia) |
Why it matters: The sleep diary is the foundation of CBT-I. It identifies perpetuating factors (e.g. spending 10 hours in bed but only sleeping 5 → SE 50% → needs sleep restriction). It also reveals circadian patterns (delayed phase: consistently falling asleep at 3 AM and waking at 11 AM).
Actigraphy: watch-like device to assess rest-activity/sleep-wakefulness for days/weeks [12] Measures activity through light and movement [12] Useful in assessing circadian rhythm disorder and insomnia [12]
How it works: A wrist-worn accelerometer detects movement. Movement = wakefulness; stillness = sleep (inferred). Modern actigraphs also include a light sensor (detecting ambient light exposure, which is useful for circadian assessment).
Advantages over sleep diary: Objective (no recall bias); continuous monitoring for weeks; less burdensome for patients.
Limitations: Cannot distinguish sleep stages (no EEG); cannot detect apnoeas; overestimates sleep in quiet wakefulness (patient lying still but awake is counted as sleep).
When to use:
- As adjunct to sleep diary when suspecting circadian sleep-wake disorder [1] — confirms the phase relationship between sleep and the light-dark cycle
- Monitoring treatment response in insomnia
- When patient reliability with sleep diary is questionable (e.g. cognitive impairment)
- Not as a standalone diagnostic tool for OSA or narcolepsy
Overnight sleep study (polysomnography): measures multiple physiological parameters overnight [12]
PSG is the gold standard for diagnosing sleep-disordered breathing, narcolepsy, PLMD, and parasomnias. It is NOT routinely indicated for insomnia (insomnia is a clinical diagnosis).
Only when suspect another sleep disorder, e.g. OSA [1]
What it measures (and why):
| Channel | Parameters | Clinical Significance |
|---|---|---|
| EEG (electroencephalogram) | Brain electrical activity; multiple leads (typically F3, F4, C3, C4, O1, O2) | Sleep staging (N1, N2, N3, REM, Wake). Identifies sleep architecture disruption, sleep onset latency, WASO, and SOREMPs in narcolepsy. |
| EOG (electro-oculogram) | Eye movements | REM detection (rapid conjugate eye movements). Distinguishes REM from NREM. |
| EMG (electromyogram) — chin and legs | Muscle tone (submental) and limb movements (anterior tibialis) | Chin EMG: loss of tone during REM → if tone persists = RBD. Leg EMG: periodic limb movements (≥0.5–10s duration, every 5–90s, amplitude ≥8μV above baseline → PLM index ≥15/h = PLMD). |
| Nasal airflow | Thermistor (qualitative, detects apnoea) + nasal pressure transducer (quantitative, detects hypopnoea) | Apnoea = complete cessation ≥10s. Hypopnoea = ≥30% reduction in airflow with ≥3–4% desaturation or arousal. These two channels together generate the AHI. |
| Thoracoabdominal effort | Respiratory inductance plethysmography (RIP) bands on chest and abdomen | Distinguishes obstructive apnoea (effort continues but no airflow → chest/abdomen move out of phase, "paradoxical" breathing) from central apnoea (no effort AND no airflow → both channels flat). |
| Pulse oximetry (SpO₂) | Oxygen saturation | Desaturation index; nadir SpO₂; % time spent < 90%. Quantifies the hypoxaemic burden of apnoeas. |
| ECG | Heart rhythm | Detects arrhythmias associated with apnoeas (sinus bradycardia during apnoea → tachycardia on arousal; AF; heart block). |
| Body position | Supine/lateral/prone | Positional OSA: AHI significantly worse in supine (because gravity pulls tongue/palate posteriorly) → may guide treatment (positional therapy). |
| Snoring sensor | Microphone or vibration sensor | Quantifies snoring intensity. |
| Video (video-PSG) | Infrared camera | Essential for diagnosing parasomnias (see the behaviour), epilepsy (seizure semiology), RBD (dream enactment). |
Key PSG findings by condition:
| Condition | PSG Findings | Interpretation |
|---|---|---|
| OSA | AHI ≥5/h; obstructive apnoeas/hypopnoeas (effort present, no/reduced airflow); desaturations; arousals terminating events; cyclical pattern | Upper airway collapse during sleep → hypoxaemia → arousal → re-opening → repeat |
| Central Sleep Apnoea | Central apnoeas (absent airflow AND absent effort); may show Cheyne-Stokes pattern (crescendo-decrescendo in tidal volume) | Loss of ventilatory drive during sleep; oscillatory control instability (e.g. in HF) |
| PLMD | PLM index ≥15/h in adults (≥5/h in children); stereotyped dorsiflexion of ankle/toe, 0.5–10s duration, 5–90s intervals | Repetitive movements → cortical arousals → sleep fragmentation |
| Narcolepsy | Short sleep latency; SOREMP on overnight PSG (< 15 min into sleep); fragmented sleep architecture | Flip-flop switch instability → rapid REM intrusion |
| RBD | REM sleep without atonia (RSWA) on chin/limb EMG; increased phasic EMG activity during REM; dream-enactment behaviour on video | Loss of normal glycinergic inhibition of spinal motor neurons during REM → motor activity during dreams |
| Insomnia (when performed) | Prolonged sleep onset latency; frequent arousals; ↓ sleep efficiency; ↑ N1, ↓ N3; ↓ total sleep time | Objective confirmation of poor sleep; may reveal paradoxical insomnia (normal PSG despite subjective complaint) |
When NOT to Order PSG
PSG is not indicated for routine insomnia evaluation. It is expensive, labour-intensive, and the insomnia patient often sleeps even worse in the unfamiliar sleep lab environment ("first-night effect"). Reserve PSG for: (1) suspected OSA, (2) suspected narcolepsy (followed by MSLT), (3) suspected parasomnia (video-PSG), (4) suspected PLMD, (5) treatment-refractory insomnia where an occult sleep disorder is suspected.
A simplified alternative to in-lab PSG for uncomplicated suspected OSA in patients with a high pre-test probability. Measures airflow, respiratory effort, and SpO₂ (minimum 4 channels), but does NOT include EEG (so cannot stage sleep).
Advantages: Cheaper, more accessible, patient sleeps in own bed (more representative). Limitations: Underestimates AHI (because it divides events by recording time, not actual sleep time — if the patient is awake for 2 hours, those hours dilute the index). Cannot diagnose central sleep apnoea, PLMD, or parasomnias. Not suitable for patients with significant comorbidities (HF, COPD, neuromuscular disease) where central apnoea or hypoventilation may coexist.
Current guideline (AASM 2017): HSAT is acceptable for diagnosing OSA in patients with high pre-test probability (STOP-BANG ≥5, or clinician assessment) without significant comorbidities. A negative HSAT does not exclude OSA — if clinical suspicion remains, proceed to in-lab PSG.
Daytime sleep study: usually follows overnight study, similar monitoring during daytime [12] Multiple sleep latency test (MSLT): multiple trials of naps spaced throughout the day → monitor mean sleep latency + number of REM periods [12]
Protocol:
- Performed the day after an overnight PSG (to document adequate prior-night sleep of ≥6 hours)
- Patient given 5 nap opportunities at 2-hour intervals (e.g. 9 AM, 11 AM, 1 PM, 3 PM, 5 PM)
- In each trial, the patient lies in a dark, quiet room and is told to try to fall asleep
- If they fall asleep, they are allowed to sleep for 15 minutes, then woken
- If they don't fall asleep within 20 minutes, the trial ends
- Measures: Sleep onset latency for each trial and presence/absence of REM sleep (SOREMP = REM onset within 15 minutes of sleep onset)
Interpretation:
| Finding | Meaning |
|---|---|
| Mean sleep latency < 8 min | Pathological sleepiness |
| Mean sleep latency 8–10 min | Borderline |
| Mean sleep latency > 10 min | Normal (no objective excessive sleepiness) |
| ≥2 SOREMPs | Indicates narcolepsy [12] (a SOREMP on the preceding night's PSG may count as one) |
| < 2 SOREMPs with short latency | Excessive sleepiness from another cause (sleep deprivation, OSA, drugs); or narcolepsy type 2 if all other causes excluded |
Why SOREMPs are significant: Normal individuals do NOT enter REM during short naps because the NREM → REM sequence takes ~60–90 minutes. Entering REM within 15 minutes of sleep onset means the REM-generating circuitry is disinhibited — this is the hallmark of orexin/hypocretin deficiency in narcolepsy.
Important caveats:
- Must discontinue REM-suppressing medications (SSRIs, SNRIs, TCAs, MAOIs) ≥14 days before the test (these drugs suppress REM and can cause false-negative SOREMPs)
- Must have adequate prior-night sleep (documented by PSG) — sleep deprivation itself can cause short sleep latency and SOREMPs
- Must exclude OSA on the prior-night PSG (OSA → sleep fragmentation → short sleep latency on MSLT, which would be a false positive for narcolepsy)
Maintenance of wakefulness test (MWT): multiple trials of staying awake under sleep-inducing stimuli [12]
Protocol: Patient sits in a dimly lit room and is asked to try to stay awake (opposite of MSLT). Four 40-minute trials at 2-hour intervals.
Interpretation: Mean sleep latency < 8 min = pathologically unable to maintain wakefulness; < 40 min = impaired ability. Used primarily to assess fitness to drive or operate machinery after treatment of sleep disorders (e.g. after starting CPAP for OSA). Not a diagnostic test for a specific disorder.
Key investigations [5]: Nil for most cases. Others according to history and findings.
Consider [5]:
The rationale for each:
| Investigation | Indication | What You're Looking For | Why |
|---|---|---|---|
| FBE (Full Blood Examination) [5] | Fatigue, RLS | Anaemia (↓ Hb); microcytic (iron deficiency → RLS); macrocytic (B12/folate deficiency, alcohol) | Iron deficiency is the most important secondary cause of RLS. Anaemia causes fatigue that may be misinterpreted as sleepiness. |
| ESR/CRP [5] | Suspected inflammatory/malignant cause of pain, fatigue | ↑ ESR/CRP → chronic inflammation, infection, malignancy | Screens for occult serious disease presenting with sleep disturbance (e.g. cancer pain, rheumatological disease). |
| LFTs (γGT) [5] | Suspected alcohol excess | γGT is a sensitive marker of chronic alcohol intake (induced by alcohol via CYP enzymes) | Alcohol is a major cause of sleep disruption. ↑ γGT without ↑ other LFTs (ALP, ALT) suggests chronic alcohol use. |
| Ferritin | RLS | Low ferritin ( < 75 μg/L in RLS guidelines, < 30 μg/L is definitely deficient) | Iron is a cofactor for tyrosine hydroxylase (rate-limiting enzyme for dopamine synthesis). Low brain iron → ↓ dopamine → RLS. Target ferritin > 75 μg/L. |
| Iron studies (serum iron, transferrin, TIBC, transferrin saturation) | RLS, fatigue | Iron deficiency pattern (↓ serum iron, ↓ transferrin saturation, ↑ TIBC) | Complements ferritin (ferritin is an acute-phase reactant — can be falsely normal in inflammation) |
| TFTs (Thyroid Function Tests) | Thyroid/other endocrine: hyperthyroid [5]; also hypothyroidism → OSA | Hyperthyroidism: ↓ TSH, ↑ free T4 → hyperarousal → insomnia. Hypothyroidism: ↑ TSH, ↓ free T4 → myxoedema of URT → OSA; ↓ ventilatory drive; fatigue. | Always check in sleep disturbance — thyroid disease is common and treatable. |
| Renal function (Cr, eGFR, urea) | RLS, nocturia, fatigue | Uraemia → secondary RLS (uraemic toxins impair dopaminergic function); polyuria from CKD | |
| HbA1c / Fasting glucose | Diabetes [5]; nocturia, neuropathy | Undiagnosed DM → osmotic diuresis → nocturia; peripheral neuropathy → neuropathic pain / RLS-like symptoms | |
| Calcium, Phosphate, Magnesium | Muscle cramps, arrhythmia | Hypocalcaemia/hypomagnesaemia → muscle cramps/spasms at night → middle insomnia | |
| CSF orexin/hypocretin-1 | Suspected narcolepsy type 1 (when MSLT equivocal or unavailable) | ≤110 pg/mL or < 1/3 of mean normal = diagnostic of narcolepsy type 1 | Reflects loss of orexin-producing neurons; very specific (~99%) |
| Investigation | Indication | What It Shows |
|---|---|---|
| Lateral cephalometry | OSA with suspected craniofacial abnormality; surgical planning | X-ray measurement of mandible, maxilla, hyoid bone position, posterior airway space. Identifies retrognathia, micrognathia, low hyoid. |
| Nasopharyngoscopy / Müller's manoeuvre | OSA surgical planning | Direct visualisation of upper airway. Müller's manoeuvre (forced inspiration against closed mouth/nose during nasopharyngoscopy) assesses dynamic collapsibility of oropharyngeal tissues [2]. |
| MRI Brain | Suspected narcolepsy (exclude structural lesion), RBD (brainstem pathology), neurodegeneration | May show hypothalamic/brainstem lesions; usually normal in idiopathic narcolepsy; brainstem changes in MSA/DLB. |
| Drug-induced sleep endoscopy (DISE) | OSA surgical planning | Under propofol sedation, nasopharyngoscopy identifies site and pattern of upper airway collapse — guides surgical intervention. |
| Overnight pulse oximetry | OSA screening where PSG unavailable | Oxygen desaturation index (ODI ≥5/h with sawtooth pattern suggests OSA); limited sensitivity (misses events without significant desaturation). |
| ECG / Echocardiography | OSA with suspected cardiac complications; PND → HF evaluation | ECG: AF, LVH, bradycardia-tachycardia pattern. Echo: LV function, diastolic dysfunction, pulmonary hypertension (cor pulmonale from chronic hypoxaemia). |
| ABG | Suspected OHS or chronic respiratory failure | PaCO₂ > 45 mmHg with obesity → OHS. PaO₂ < 60 mmHg → chronic hypoxaemia. Daytime hypercapnia in an obese patient with OSA = OHS until proven otherwise. |
| Clinical Scenario | First-Line Investigation | Second-Line / Confirmatory |
|---|---|---|
| Simple insomnia (no red flags) | Sleep diary × 2 weeks; PSQI or ISI; screen for depression (PHQ-9) and anxiety (GAD-7) | Nil further if clinical diagnosis is clear |
| Suspected OSA | STOP-BANG; Epworth Sleepiness Scale; sleep diary | PSG (gold standard) or HSAT (if uncomplicated, high pre-test probability) |
| Suspected narcolepsy | Clinical assessment; ESS | Overnight PSG followed by MSLT the next day; ± CSF orexin-1 |
| Suspected RLS | Clinical diagnosis (IRLSSG criteria); ferritin + iron studies; renal function | PSG with anterior tibialis EMG (if PLMD suspected or diagnosis uncertain) |
| Suspected circadian disorder | Sleep diary × 2–4 weeks; actigraphy ± light sensor | Dim-light melatonin onset (DLMO) measurement (research/specialist only) |
| Suspected parasomnia | Clinical history + bed-partner history | Video-PSG (to visualise behaviour and correlate with sleep stage/EMG) |
| Acute sleep-wake disturbance in hospital | CAM or 4AT for delirium screening; targeted medical workup (FBE, CMP, UEC, CXR, urinalysis, drug levels, blood cultures) | As guided by delirium evaluation |
| Masquerade screen [5] | FBE, ESR/CRP, LFTs (γGT) [5]; add TFTs, HbA1c, ferritin, renal function based on clinical suspicion | As guided by results |
Key Diagnostic Principles:
- Insomnia is a clinical diagnosis — sleep diary + screening tools are sufficient. PSG is NOT routine.
- The DSM-5 "3-3-3" rule for chronic insomnia: ≥30 min SOL/WASO, ≥3 nights/week, ≥3 months.
- OSA requires PSG (or HSAT) for formal diagnosis and severity grading (AHI).
- Narcolepsy requires PSG + MSLT — look for ≥2 SOREMPs with mean sleep latency ≤8 min.
- Always screen for masquerades: FBE, TFTs, ferritin, HbA1c, renal function, LFTs, ESR/CRP.
- Always screen for delirium in acute hospital settings — CAM or 4AT.
- Actigraphy is the investigation of choice for circadian rhythm disorders.
High Yield Summary
Diagnostic Criteria & Investigations — Key Takeaways:
-
Chronic insomnia (DSM-5): Difficulty initiating/maintaining sleep OR early awakening + daytime impairment + ≥3 nights/week + ≥3 months + adequate sleep opportunity + not explained by another sleep/medical/psychiatric/substance disorder. Remember the 3-3-3 rule.
-
ICD-10 has a lower threshold (≥1 week vs ≥3 months).
-
OSA diagnosis: AHI ≥5/h with symptoms OR AHI ≥15/h regardless. Severity: Mild 5–15, Moderate 15–30, Severe > 30.
-
Narcolepsy: MSLT showing mean sleep latency ≤8 min + ≥2 SOREMPs, OR CSF orexin ≤110 pg/mL.
-
RLS: Purely clinical diagnosis — 5 IRLSSG criteria. Check ferritin (target > 75 μg/L) and renal function.
-
PSG is NOT for insomnia — it is for OSA, narcolepsy, PLMD, and parasomnias.
-
Sleep diary is the most important first-line tool — derives sleep efficiency, SOL, WASO, and reveals circadian patterns.
-
HSAT is acceptable for uncomplicated OSA but negative HSAT does not exclude OSA.
-
Masquerade screen bloods: FBE, ESR/CRP, LFTs (γGT), TFTs, ferritin, HbA1c, renal function.
-
Delirium screening (CAM/4AT) is mandatory for any acute sleep-wake disturbance in hospitalised/elderly patients.
Active Recall - Diagnostic Criteria, Algorithm and Investigations
References
[1] Senior notes: Ryan Ho Psychiatry.pdf (Section 9.2.3 Insomnia, pp. 221–224) [2] Senior notes: Ryan Ho Respiratory.pdf (Section 3.8 Sleep-Associated Disorders, pp. 155–161) [5] Lecture slides: murtagh merge.pdf (pp. 61–62 — Insomnia) [8] Senior notes: Ryan Ho Psychiatry.pdf (Section on Delirium, p. 75); Ryan Ho Fundamentals.pdf (Section 3.4.5 Delirium, p. 325) [12] Senior notes: Ryan Ho Psychiatry.pdf (Section on Sleep investigations, p. 221)
Management of Sleep Disturbance
The management of sleep disturbance follows a logical, stepwise approach: treat the cause first, then optimise sleep habits, then consider specific therapies. The single most important principle is that management must be targeted to the underlying diagnosis — there is no one-size-fits-all sleeping tablet. Let me walk you through this systematically.
Treatment principles [1]:
- Goals: (1) ↑ sleep quality and quantity (2) ↓ insomnia-related daytime impairment [1]
- Optimise treatment of comorbid sleep, medical, psychiatric disorder first [1]
- Address underlying factors esp drugs, e.g. stimulants, SSRI/SNRI, steroids, chronic opioid use [1]
- Ensure good sleep hygiene [1]
- CBT for insomnia (CBT-I): 1st line but not readily available [1]
These principles can be distilled into a hierarchy:
- Identify and treat the underlying cause (medical, psychiatric, pharmacological, another sleep disorder)
- Sleep hygiene education (for every patient, regardless of cause)
- CBT-I (first-line for chronic insomnia disorder)
- Pharmacotherapy (second-line, or adjunctive to CBT-I when needed)
- Device/surgical therapy (for specific conditions like OSA)
The Cardinal Rule of Sleep Medicine
Never prescribe a hypnotic without first asking: "Why is this patient not sleeping?" A sleeping tablet treats the symptom, not the cause. If the patient has OSA, a hypnotic will worsen it (↓ muscle tone → ↑ airway collapse). If they have depression, the insomnia will not resolve until the depression is treated. Always diagnose first, then treat appropriately.
Ensure good sleep hygiene [1]
Sleep hygiene is a set of behavioural and environmental recommendations that promote normal sleep. It is necessary but not sufficient as standalone treatment for chronic insomnia — think of it as the foundation upon which everything else is built.
| Recommendation | Rationale (From First Principles) |
|---|---|
| Maintain a regular sleep-wake schedule (same bedtime and wake time every day, including weekends) | Entrains the SCN circadian clock → Process C and Process S become synchronised → predictable sleep onset |
| Get up at the same time every morning regardless of how you slept | This is more important than bedtime. The wake time anchors the circadian rhythm. Sleeping in after a bad night delays the circadian phase → makes the next night's insomnia worse. |
| Avoid daytime naps (or limit to < 20 min before 3 PM) | Napping discharges homeostatic sleep pressure (Process S — adenosine clearance) → less sleep drive at night → harder to fall asleep |
| Use the bed only for sleep and sex (not reading, TV, phone, working) | Stimulus control principle: if the bed is associated with wakeful activities, it becomes a conditioned stimulus for wakefulness. Restricting bed use to sleep re-associates it with sleep. |
| If unable to sleep after ~20 min, get up and do a quiet activity, then return when sleepy | Prevents the bed from becoming a cue for frustration and wakefulness. This is the "quarter-of-an-hour rule." |
| Avoid caffeine after midday | Caffeine blocks adenosine receptors → ↓ Process S sleep pressure. Half-life of caffeine is 5–7 hours, so afternoon coffee is still active at bedtime. |
| Avoid alcohol | Alcohol is a GABA-A agonist → sedating initially, but as blood levels fall → rebound glutamatergic excitation → fragmented second-half sleep, vivid dreams, early awakening. Also ↓ pharyngeal muscle tone → worsens OSA. |
| Avoid heavy meals close to bedtime | Large meals → ↑ GI motility, potential GERD → arousals. Light snack is acceptable. |
| Regular exercise (but not within 4 hours of bedtime) | Exercise ↑ adenosine production (↑ sleep pressure) and ↑ core body temperature; the subsequent temperature drop promotes sleep onset. But exercising too close to bedtime → ↑ sympathetic tone and core temperature → delays sleep. |
| Optimise the sleep environment (dark, quiet, cool ~18–20°C) | Darkness promotes melatonin secretion. Noise causes cortical arousals. Core body temperature needs to drop for sleep initiation (a cool room facilitates this). |
| Avoid screens for ≥30–60 min before bed | Blue light (460 nm) from screens stimulates melanopsin-containing retinal ganglion cells → suppresses melatonin secretion → delays circadian phase |
| Avoid clock-watching | Clock-watching → time monitoring → frustration → arousal → perpetuates insomnia. Turn clocks away from the bed. |
Treatment for sleepiness in general [9]:
- Sleep hygiene: regular and adequate sleep, caffeine not later than 4 PM [9]
- Short naps 15 min [9]
- Bright light: esp for shift work, jet lag, seasonal affective disorder [9]
- Adjust shift work, e.g. forward shift, regular night shift, 12-hour 2-shift [9]
4. Management of Chronic Insomnia
CBT for insomnia (CBT-I): 1st line but not readily available [1] Techniques: sleep education, stimulus control, sleep restriction, relaxation training, cognitive therapy [1] Form: self-help, individual, group, face-to-face [1]
CBT-I is the gold standard first-line treatment for chronic insomnia disorder (AASM 2021, European Sleep Research Society 2023). It is superior to pharmacotherapy in long-term outcomes because it targets the perpetuating factors (the "3rd P" in Spielman's model) that maintain insomnia, rather than just inducing sleep chemically.
Components of CBT-I:
| Component | What It Involves | Mechanism (Why It Works) |
|---|---|---|
| Sleep Education | Teaching normal sleep architecture, age-related changes, the 3P model, and debunking sleep myths (e.g. "everyone needs 8 hours") | ↓ Catastrophic beliefs about sleep → ↓ performance anxiety about sleeping → ↓ hyperarousal |
| Stimulus Control | (1) Go to bed only when sleepy; (2) Use bed only for sleep and sex; (3) If awake > 15–20 min, get up and do a quiet activity; (4) Wake at the same time daily; (5) No daytime naps | Based on classical conditioning: the bed has become a conditioned stimulus for wakefulness. By removing wakeful activities from bed and leaving bed when not sleeping, the bed is re-associated with sleep (extinction and reconditioning). |
| Sleep Restriction Therapy | Restrict time in bed to match actual sleep time (from sleep diary). E.g. if TST = 5h, prescribe TIB = 5h only (e.g. 1 AM–6 AM). Gradually increase TIB by 15–30 min/week as sleep efficiency improves to ≥85%. | ↓ TIB → mild sleep deprivation → ↑ homeostatic sleep pressure (↑ adenosine) → consolidated sleep → ↑ sleep efficiency. Counter-intuitive but highly effective. Minimum TIB should not go below 5 hours for safety. |
| Relaxation Training | Progressive muscle relaxation, diaphragmatic breathing, guided imagery, mindfulness | ↓ Somatic and cognitive arousal → ↓ sympathetic nervous system activity → ↓ cortisol → facilitates sleep onset |
| Cognitive Therapy | Identifying and challenging dysfunctional beliefs about sleep (e.g. "If I don't sleep 8 hours I'll collapse," "I haven't slept at all" when they actually slept 5 hours) | ↓ Catastrophic cognitions → ↓ anticipatory anxiety → breaks the worry-arousal-insomnia cycle |
Evidence:
- Meta-analyses show CBT-I improves sleep onset latency, WASO, sleep efficiency, and total sleep time with effect sizes comparable to or exceeding hypnotics in the short term and superior in the long term
- Effects are durable (persist ≥12 months after treatment) unlike hypnotics (effects stop when drugs stop)
- Can be delivered digitally (e.g. Sleepio, CBT-I Coach app) — increasingly relevant given limited access to trained therapists in Hong Kong
Contraindications/Cautions for sleep restriction:
- Untreated bipolar disorder (sleep deprivation can trigger mania)
- Seizure disorders (sleep deprivation lowers seizure threshold)
- Parasomnias (sleep deprivation ↑ slow-wave sleep → may trigger NREM parasomnias)
- Occupations requiring high vigilance (during the initial restriction phase, patients may be sleepier during the day)
Why CBT-I Works Better Than Pills Long-Term
Hypnotics work while you take them. The moment you stop, insomnia often returns (or worsens — rebound insomnia). CBT-I changes the underlying conditioned hyperarousal and maladaptive behaviours that perpetuate insomnia. Once the patient has learned the techniques, they have them for life. This is why every guideline recommends CBT-I as first-line.
4.2 Pharmacotherapy for Insomnia — Second-Line
Pharmacotherapy is indicated when:
- CBT-I is unavailable, refused, or insufficient
- Short-term relief is needed while CBT-I takes effect (typically 4–8 weeks)
- Acute/short-term insomnia with significant distress
Address underlying factors esp drugs, e.g. stimulants, SSRI/SNRI, steroids, chronic opioid use [1]
General principles of pharmacotherapy:
- Use the lowest effective dose for the shortest duration necessary
- Prefer intermittent dosing (e.g. 2–3 nights/week) over nightly use for chronic insomnia
- Always combine with sleep hygiene ± CBT-I
- Plan an exit strategy (taper schedule) from the outset
- Avoid in the elderly where possible (↑ falls, ↑ confusion, ↑ next-day sedation)
| Feature | Detail |
|---|---|
| Examples | Temazepam (short-intermediate acting), lorazepam, nitrazepam, triazolam, diazepam |
| MoA | Bind to the benzodiazepine site on the GABA-A receptor → allosteric positive modulation → ↑ frequency of Cl⁻ channel opening → neuronal hyperpolarisation → ↑ inhibition → sedation, anxiolysis, muscle relaxation, anticonvulsant effect |
| Indications | Short-term insomnia ( < 2–4 weeks); acute anxiety; alcohol withdrawal (chlordiazepoxide, diazepam) |
| Advantages | Effective for both sleep-onset and sleep-maintenance insomnia; anxiolytic properties helpful when anxiety co-exists |
| Disadvantages | Tolerance develops within 2–4 weeks → dose escalation → dependence. Rebound insomnia on withdrawal (often worse than baseline). ↓ N3 (slow-wave sleep) and ↓ REM → non-physiological sleep. Hangover effects (next-day sedation). ↑ Risk of falls in elderly. Cognitive impairment. Respiratory depression (especially in OSA — contraindicated). Dependence and withdrawal syndrome. |
| Contraindications | OSA (↓ muscle tone → worsens airway collapse), severe hepatic insufficiency, myasthenia gravis, respiratory failure, acute alcohol intoxication, pregnancy (teratogenic — category D) |
BZDs and OSA — A Dangerous Combination
Benzodiazepines are contraindicated in untreated OSA. They reduce pharyngeal muscle tone AND blunt the arousal response to hypoxaemia. This means the patient's airway collapses AND they don't wake up to re-open it → prolonged apnoeas → severe desaturations → potentially fatal. If you must sedate an OSA patient (e.g. for a procedure), ensure CPAP is available and monitoring is in place.
Z drugs, e.g. zolpidem (Stilnox), zopiclone (Imovane), zaleplon (Sonata) [13]
| Feature | Detail |
|---|---|
| MoA | Non-BZD drugs acting as specific agonists at BZD receptors (ω₁ receptors) [13] — They selectively bind the α₁ subunit-containing GABA-A receptors (which mediate sedation) rather than all BZD-binding subtypes → more selective hypnotic effect with less anxiolytic, muscle relaxant, and anticonvulsant activity compared to BZDs |
| Effect | Produces ↓ changes in sleep architecture and has ↓ duration of action cf BZDs [13] — They preserve more normal N3 and REM compared to BZDs |
| Use | Usually for sleep onset insomnia but Stilnox CR can be used for sleep maintenance insomnia [13] |
| S/E | Bitter aftertaste (Imovane), residual effects (slow, drowsiness, ↓ daytime performance, ↑ risk of falls), rarely behavioural disturbances (confusion, amnesia, ↓ mood) [13]. Complex sleep behaviours (sleep-eating, sleep-driving) — particularly with zolpidem. |
| Choice | Stilnox has a shorter half-life (↓ propensity for hangover) and less bitter, but may be less effective in sleep maintenance and may be more expensive [13] |
| Comparison |
| Drug | Half-Life | Best For | Notes |
|---|---|---|---|
| Zaleplon (Sonata) | ~1 hour | Sleep-onset insomnia only | Ultra-short acting; can be taken if patient wakes in the middle of the night (if ≥4 hours of sleep time remain) |
| Zolpidem (Stilnox) | ~2.5 hours | Sleep-onset insomnia | Most commonly prescribed; CR formulation available for sleep maintenance |
| Zopiclone (Imovane) | ~5 hours | Sleep onset + maintenance | Bitter metallic aftertaste; slightly longer duration |
| Eszopiclone (Lunesta) | ~6 hours | Sleep onset + maintenance | S-enantiomer of zopiclone; approved for long-term use in some guidelines |
Advantages over BZDs: Fewer effects on sleep architecture; shorter duration of action (less hangover); somewhat lower abuse potential (though still present); less rebound insomnia.
Disadvantages: Still cause tolerance and dependence (though less than BZDs); complex sleep behaviours; residual sedation (especially zopiclone); still ↓ pharyngeal muscle tone (caution in OSA).
Contraindications: Similar to BZDs — severe hepatic impairment, OSA (relative CI — use with caution and only with CPAP), myasthenia gravis, severe respiratory insufficiency, pregnancy.
| Feature | Detail |
|---|---|
| Examples | Melatonin (Circadin — prolonged-release 2 mg); Ramelteon; Tasimelteon |
| MoA | Melatonin binds MT₁ and MT₂ receptors in the SCN → MT₁ activation ↓ SCN neuronal firing (promotes sleepiness); MT₂ activation shifts the circadian clock phase. Ramelteon is a selective MT₁/MT₂ agonist with higher affinity than endogenous melatonin. |
| Indications | Insomnia in patients ≥55 years (Circadin — licensed in many jurisdictions for this age group); circadian rhythm disorders (jet lag, delayed sleep phase); insomnia in children with neurodevelopmental disorders |
| Advantages | No dependence, no tolerance, no rebound insomnia, no abuse potential; does not suppress N3 or REM; safe in elderly; does not worsen OSA |
| Disadvantages | Modest effect size (smaller than BZDs/Z-drugs for insomnia); mainly improves sleep onset latency rather than total sleep time; not effective for all insomnia subtypes |
| S/E | Headache, dizziness, drowsiness (mild); generally very well tolerated |
| Contraindications | Autoimmune conditions (theoretical — melatonin is immunomodulatory); severe hepatic impairment (melatonin is hepatically metabolised); fluvoxamine co-administration (CYP1A2 inhibitor → massive ↑ melatonin levels) |
This is a newer drug class representing a paradigm shift in insomnia pharmacotherapy.
| Feature | Detail |
|---|---|
| Examples | Suvorexant (Belsomra); Lemborexant (Dayvigo) |
| MoA | Block orexin/hypocretin receptors (OX₁R and OX₂R) → attenuate the wake-promoting signal from the lateral hypothalamus → allows the VLPO sleep switch to activate. Rather than artificially "forcing" sleep (like BZDs), DORAs "turn down" wakefulness — a more physiological approach. |
| Indications | Chronic insomnia disorder (both sleep-onset and sleep-maintenance); approved for long-term use (unlike BZDs/Z-drugs) |
| Advantages | Preserve normal sleep architecture (N3 and REM maintained); low abuse potential; no respiratory depression (safe in mild-moderate OSA); effective for both sleep onset and maintenance |
| Disadvantages | May cause sleep paralysis, hypnagogic hallucinations (logically — they are blocking the same orexin system that is deficient in narcolepsy); next-day somnolence (especially suvorexant 20 mg) |
| S/E | Somnolence, headache, abnormal dreams, sleep paralysis (uncommon), suicidal ideation (rare — black box warning in some jurisdictions) |
| Contraindications | Narcolepsy (already orexin-deficient — would worsen symptoms); severe hepatic impairment; concomitant strong CYP3A4 inhibitors (suvorexant) |
DORAs — The Conceptual Leap
Traditional hypnotics (BZDs, Z-drugs) amplify the "sleep signal" by enhancing GABA-A inhibition — they push the brain into sedation. DORAs take the opposite approach: they block the "wake signal" (orexin) so that the brain's intrinsic sleep-promoting mechanisms can take over. This is why DORAs preserve normal sleep architecture and have less abuse potential. Think of it as removing a "wake brake" rather than pressing a "sleep accelerator."
| Drug | MoA | Dose for Insomnia | Notes |
|---|---|---|---|
| Trazodone | 5-HT₂A antagonist + weak SARI (serotonin antagonist and reuptake inhibitor) at low doses; H₁ antagonist | 25–100 mg at night | Very commonly used off-label for insomnia, especially with comorbid depression. At low doses, the antihistaminic and 5-HT₂A antagonist effects predominate (sedation) without significant serotonergic reuptake inhibition. Does not cause dependence. S/E: orthostatic hypotension, priapism (rare). |
| Mirtazapine | NaSSA (noradrenergic and specific serotonergic antidepressant); potent H₁ antagonist at low doses | 7.5–15 mg at night | Paradoxically more sedating at lower doses (H₁ antagonism predominates) and less sedating at higher doses (noradrenergic stimulation overcomes sedation). Useful for insomnia with comorbid depression and poor appetite (↑ appetite/weight gain). |
| Amitriptyline | TCA; H₁ antagonist + anticholinergic | 10–25 mg at night | Useful for insomnia with comorbid pain (neuropathic pain, fibromyalgia). Anticholinergic S/E: dry mouth, constipation, urinary retention, tachycardia. Caution in elderly (anticholinergic burden → delirium, falls). |
| Doxepin | TCA; highly selective H₁ antagonist at ultra-low doses | 3–6 mg at night | At ultra-low doses (3–6 mg, marketed as Silenor), doxepin is a highly selective H₁ antagonist with minimal anticholinergic effects. FDA-approved for insomnia (sleep maintenance). |
| Agent | MoA | Notes |
|---|---|---|
| Antihistamines (diphenhydramine, doxylamine, hydroxyzine) | H₁ receptor antagonism → sedation | OTC sleep aids. Tolerance develops rapidly (within days). Anticholinergic S/E (dry mouth, urinary retention, constipation, delirium in elderly). NOT recommended for chronic insomnia by any guideline. |
| Gabapentin / Pregabalin | Binds α₂δ subunit of presynaptic voltage-dependent Ca²⁺ channels → blocks release of excitatory neurotransmitters, e.g. glutamate [13] | Useful when insomnia is comorbid with chronic pain, RLS, or anxiety. Improves slow-wave sleep. S/E: somnolence, dizziness, ↑ appetite, mood changes, confusion, ataxia, tremor, memory impairment [13]. Discontinuation symptoms: insomnia, headache, nausea, diarrhoea, anxiety, sweating, dizziness [13]. |
| Quetiapine (low-dose) | D₂ antagonist + H₁ antagonist + α₁ antagonist at low doses | Sometimes used off-label for insomnia, especially with comorbid psychosis or agitation. NOT recommended for primary insomnia due to metabolic S/E (weight gain, diabetes, dyslipidaemia) even at low doses. |
| Clinical Scenario | Preferred Agent | Rationale |
|---|---|---|
| Chronic insomnia, no comorbidity | CBT-I first; if Rx needed → melatonin (≥55y) or DORA or short-course Z-drug | Melatonin: safe, no dependence. DORA: physiological, long-term approved. Z-drug: short-course only. |
| Insomnia + anxiety | CBT-I + SSRI/SNRI for anxiety; adjunct low-dose trazodone or BZD (short-term) | Treating the anxiety treats the insomnia. Trazodone for sleep without dependence risk. |
| Insomnia + depression | SSRI/SNRI + CBT-I; consider mirtazapine (if poor appetite/weight loss) or trazodone adjunct | Mirtazapine: sedating + appetite stimulation. Note SSRIs themselves can worsen insomnia initially. |
| Insomnia + chronic pain | Gabapentin/pregabalin or amitriptyline (low-dose) | Dual benefit: analgesic + sedating. |
| Insomnia in elderly | Melatonin (Circadin) or DORA; avoid BZDs/Z-drugs | Elderly: ↑ sensitivity to sedative S/E, ↑ falls, ↑ hip fracture, ↑ cognitive impairment. Melatonin and DORAs are safer. |
| Insomnia + mild OSA | Melatonin or DORA; avoid BZDs/Z-drugs | DORAs do not suppress respiratory drive or muscle tone. BZDs/Z-drugs worsen OSA. |
| Acute/short-term insomnia | Short-course Z-drug (3–7 days) or BZD | Self-limiting; brief pharmacotherapy to prevent perpetuating factor development. |
5. Management of Obstructive Sleep Apnoea
Tx [2]:
General [2]:
- Weight reduction if overweight [2] — Even 10% weight loss can ↓ AHI by 26–50%. Fat loss in the parapharyngeal space and tongue directly ↑ airway calibre. Weight loss also ↓ the mechanical load on the chest wall → ↑ FRC → ↑ tracheal traction → ↑ pharyngeal patency.
- Avoid alcohol and hypnotics [2] — Alcohol ↓ pharyngeal dilator muscle tone AND blunts the arousal response → longer, deeper apnoeas with worse desaturations. Hypnotics (BZDs, Z-drugs) have the same effect.
- Sleep hygiene and posture, e.g. lying laterally [2] — Supine position → tongue falls posteriorly under gravity → ↑ airway obstruction. Lateral position ↓ AHI in positional OSA. Positional therapy devices (e.g. tennis ball technique, positional vibration devices) can enforce lateral sleeping.
- AVOID CAR-DRIVING if not adequately treated [2] — This is both a clinical and medicolegal point. Untreated OSA with EDS → ↑ risk of RTA (2–3× general population).
- Mx of predisposing factors, e.g. rhinitis, acromegaly, care after sedation/anaesthesia [2]
- Monitor for obesity-related conditions, e.g. metabolic syndrome, DM, HTN [2]
Nocturnal nasal cPAP: application of positive pressure through nasal mask during sleep [2] Most consistently effective treatment of OSA, but effect depends on compliance (usually poor) [2]
How CPAP works (from first principles): During inspiration, negative intraluminal pressure causes the pharynx to collapse (as discussed in pathophysiology). CPAP delivers a constant stream of pressurised air (typically 4–20 cmH₂O) through a nasal or oronasal mask. This positive pressure acts as a pneumatic splint — it stents the airway open from inside, preventing collapse regardless of muscle tone. Think of it like inflating a balloon from the inside to keep it from caving in.
Indications:
- Moderate-to-severe OSA (AHI ≥15/h)
- Mild OSA (AHI 5–15/h) with significant symptoms (EDS, impaired quality of life) or cardiovascular comorbidities
- Indications for urgent arrangement of nCPAP [2]:
Benefits:
- ↓ AHI (often to < 5/h — essentially normalisation)
- ↓ Daytime sleepiness (ESS typically drops by 3–5 points)
- ↓ Blood pressure (2–3 mmHg on average; greater in drug-resistant HTN)
- ↓ Cardiovascular events (observational data; RCT data mixed but trending positive)
- ↓ Road traffic accidents
- ↑ Quality of life, mood, cognitive function
Compliance challenge:
- Only ~50–60% of patients use CPAP adequately (≥4 hours/night on ≥70% of nights)
- Common barriers: mask discomfort, claustrophobia, nasal dryness/congestion, aerophagia (swallowing air), noise, partner disturbance
- Solutions: proper mask fitting, heated humidification, ramp function (starts at low pressure and gradually increases), desensitisation training, ENT review for nasal obstruction, auto-titrating CPAP (APAP — adjusts pressure breath-by-breath)
Mandibular advancement device [2]: Device worn during sleep to advance mandible to enlarge URT and modify muscle collapsibility [2] Variable efficacy, usually cannot completely control severe OSA [2]
How it works: A custom-fitted oral appliance pushes the mandible (and attached tongue base/genioglossus) forward → ↑ retrolingual and retropalatal airway space → ↓ collapsibility.
Indications:
- Mild-to-moderate OSA where CPAP is declined, not tolerated, or not indicated
- Primary snoring
- Adjunct to CPAP in severe OSA (combined therapy)
Contraindications: Insufficient teeth for retention, severe TMJ disorder, central sleep apnoea (no upper airway obstruction to splint), periodontal disease.
S/E: TMJ discomfort, dental misalignment with long-term use, excessive salivation, dry mouth.
Surgery: useful in selective patients with predisposing anatomical abnormalities [2]
| Procedure | Indication | Mechanism |
|---|---|---|
| Removal of hypertrophic tonsils/adenoids in children [2] | Adenotonsillar hypertrophy (most common cause of paediatric OSA) | Removes the obstructing tissue → ↑ airway lumen. Curative in majority of children. |
| Uvulopalatopharyngoplasty (UPPP): removal/remodelling of uvula, soft palate and pharynx [2] | Adults with palatal-level obstruction | Removes redundant soft tissue. Variable efficacy, not favoured [2] — success rate only ~50% because OSA is often multilevel. |
| Faciomaxillary/mandibular surgery [2] | Significant maxillofacial anomalies (retrognathia, micrognathia) | Maxillomandibular advancement (MMA) moves both jaws forward → dramatically enlarges posterior airway space. Needs more evidence of long-term efficacy. Useful in those with significant maxillofacial anomalies [2]. Most effective surgical option for OSA (success rate ~85–90%). |
| Bariatric surgery [2] | Morbid obesity (BMI ≥40, or ≥35 with comorbidities) with OSA | Useful to ↓ obesity-related medical problems [2]. Massive weight loss → ↓ parapharyngeal fat, ↓ tongue volume, ↓ chest wall load → ↓ AHI. May cure OSA in some cases. |
| Surgical correction of snoring/nasal obstruction [2] | Deviated septum, nasal polyps, turbinate hypertrophy | ↓ Nasal resistance → ↓ negative oropharyngeal pressure during inspiration → ↓ collapsibility. May not cure OSA alone but improves CPAP tolerance. |
| Hypoglossal nerve stimulation (Inspire) | Moderate-severe OSA intolerant of CPAP; BMI < 32; predominantly tongue-base collapse on DISE | Implanted device stimulates CN XII → genioglossus contracts during inspiration → tongue protrudes → airway opens. Newer therapy with growing evidence. |
| Treatment | MoA | Indication |
|---|---|---|
| Modafinil / Armodafinil | Wake-promoting agent; exact MoA unclear but involves dopamine reuptake inhibition + orexin/histamine pathway activation | First-line for EDS in narcolepsy. Does not treat cataplexy. Lower abuse potential than amphetamines. |
| Solriamfetol | Dual dopamine and noradrenaline reuptake inhibitor | EDS in narcolepsy and OSA (adjunct to CPAP) |
| Pitolisant | H₃ receptor inverse agonist → ↑ histamine release from tuberomammillary nucleus → ↑ wakefulness | EDS and cataplexy in narcolepsy |
| Sodium oxybate (GHB) | GABA-B agonist → consolidates nocturnal sleep (↑ N3) → ↓ daytime sleepiness; also ↓ cataplexy | EDS + cataplexy (addresses both). Given at bedtime and again 2.5–4 hours later. Narrow therapeutic window; respiratory depressant. |
| Methylphenidate / Amphetamines | Dopamine/noradrenaline reuptake inhibition + release | Second-line for EDS (higher abuse potential) |
| Venlafaxine / Fluoxetine / Clomipramine | SNRI/SSRI/TCA → ↑ noradrenaline/serotonin → suppresses REM → ↓ cataplexy | Cataplexy (REM atonia intrusion suppressed by REM-suppressing drugs) |
| Scheduled naps | Discharge sleep pressure during the day | Adjunctive: strategic 15–20 min naps can refresh for 1–3 hours |
Step 1: Correct reversible causes
- Iron supplementation if ferritin < 75 μg/L (IV iron if ferritin < 30 or oral iron not tolerated/ineffective; target ferritin > 75) — iron is a cofactor for tyrosine hydroxylase → ↑ dopamine synthesis
- Treat uraemia (dialysis, erythropoietin)
- Discontinue exacerbating drugs (antidopaminergics, SSRIs, SNRIs, antihistamines)
Step 2: Non-pharmacological
- Sleep hygiene, regular exercise, avoidance of caffeine/alcohol
- Leg massage, hot/cold baths, pneumatic compression
Step 3: Pharmacotherapy
| Drug Class | Examples | MoA | Notes |
|---|---|---|---|
| α₂δ ligands (first-line per 2024 IRLSSG guidelines) | Pregabalin, gabapentin | Bind α₂δ subunit of presynaptic voltage-dependent Ca²⁺ channels → block excitatory neurotransmitter release [13] | Now preferred over dopamine agonists as first-line because they do not cause augmentation. Also improve sleep quality (↑ slow-wave sleep). S/E: sedation, dizziness, weight gain. |
| Dopamine agonists (second-line) | Pramipexole, ropinirole, rotigotine (patch) | D₂/D₃ receptor agonism in the central nervous system → ↑ dopaminergic transmission | Previously first-line but now second-line due to augmentation (paradoxical worsening: symptoms become more severe, start earlier in the day, spread to arms). Also impulse control disorders (gambling, hypersexuality, compulsive shopping). |
| Opioids (severe refractory) | Low-dose oxycodone, tramadol | μ-opioid receptor agonism → modulates pain/sensory pathways; also interact with dopaminergic pathways | Reserved for severe, refractory RLS. Risk of dependence, respiratory depression. |
| Iron (IV or oral) | Ferric carboxymaltose (IV), ferrous sulphate (oral) | Replenishes iron stores → ↑ tyrosine hydroxylase activity → ↑ dopamine | Cornerstone of RLS management. IV iron produces faster and more reliable repletion. |
Augmentation — The Trap of Dopamine Agonists in RLS
Augmentation is the most important long-term complication of dopamine agonist therapy for RLS. It manifests as: (1) earlier onset of symptoms in the afternoon, (2) increased severity, (3) spread to upper limbs/trunk, (4) shorter latency to symptom onset at rest. Risk increases with higher doses, longer duration, and low ferritin. This is why the 2024 IRLSSG guidelines now recommend α₂δ ligands as first-line.
| Disorder | Treatment | Mechanism |
|---|---|---|
| Delayed Sleep-Wake Phase | Morning bright light therapy (10,000 lux, 30 min, within 1 hour of desired wake time) + low-dose melatonin (0.5–3 mg) 5–7 hours before desired bedtime (the "advance" dose) | Bright light in the morning advances the circadian phase (phase-response curve: light before the core body temperature minimum advances the clock). Melatonin in the evening also phase-advances. |
| Advanced Sleep-Wake Phase | Evening bright light therapy + avoidance of morning light; melatonin in the morning (to delay) | Evening light delays the circadian phase. |
| Shift-Work Disorder | Bright light: esp for shift work, jet lag, seasonal affective disorder [9]; strategic napping before shifts; melatonin for daytime sleep; Adjust shift work, e.g. forward shift, regular night shift, 12-hour 2-shift [9] | Forward rotation (morning → afternoon → night) is easier to adapt to than backward rotation (follows the natural > 24h tendency of the SCN clock). |
| Jet Lag | Timed light exposure and melatonin according to direction of travel; strategic napping | Eastward travel (phase advance needed): morning light at destination, melatonin at destination bedtime. Westward (phase delay): evening light, avoid morning light. |
| Non-24-Hour (Blind) | Tasimelteon (MT₁/MT₂ agonist) | Entrains the free-running circadian rhythm in totally blind individuals |
| Parasomnia | Management | Rationale |
|---|---|---|
| NREM parasomnias (sleepwalking, night terrors) | Safety measures (lock windows/doors, clear pathway, mattress on floor); avoid triggers (sleep deprivation, alcohol, stress); treat comorbid OSA (arousals trigger parasomnias); low-dose clonazepam at bedtime if frequent/dangerous | Clonazepam suppresses N3 (reduces the "launching pad" for NREM parasomnias) and raises the arousal threshold. |
| REM Sleep Behaviour Disorder | Safe sleeping environment, melatonin (augments REM sleep), clonazepam [9]. Screen and monitor for α-synucleinopathies (PD, DLB, MSA). | Melatonin (3–12 mg) may restore REM atonia (unclear mechanism; possibly via modulation of the sublaterodorsal nucleus). Clonazepam (0.25–2 mg) ↓ phasic motor activity during REM. Both are first-line. Sharp/dangerous objects should be removed from the bedroom. Bed partner may need to sleep separately. |
| Nightmare Disorder | Image rehearsal therapy (CBT technique: patient rewrites the nightmare script during the day → rehearses the new, non-threatening version); prazosin (α₁-blocker) can ↓ PTSD symptoms, nightmares, sleep disturbance [14] | Prazosin blocks noradrenergic hyperarousal during REM → ↓ nightmare intensity. Effective in PTSD-related nightmares. |
Mx [8]:
- Treat underlying causes and complications: often multifactorial [8]
- Supportive care [8]:
- Review medications and remove potentially harmful drugs [8]
- ABC + fluid/electrolyte balance + adequate nutrition and vitamins [8]
- Avoid restraint and Foley's catheters [8]
- Nurse in reassuring, supportive setting → well-illuminated, quiet place (prefer convalescent ward), try to normalise sleep-wake cycle, ask family to bring familiar objects [8]
- Avoid Cx: mobilisation (↓VTE), skin/bedsore care [8]
- Rx for behavioural S/S: ONLY to agitated patients at risk of harming others or own safety [8]:
- Prevention [8]:
- Orientation and therapeutic activities for cognitive impairment [8]
- Early mobilisation [8]
- Nonpharmacological approaches (minimise psychoactive drugs use) [8]
- Interventions to prevent sleep deprivation [8]
- Communication methods and adaptive equipment for vision and hearing impairment [8]
- Early intervention for volume depletion [8]
| Condition | First-Line | Second-Line | Key Points |
|---|---|---|---|
| Chronic Insomnia | CBT-I | Pharmacotherapy (melatonin ≥55y, DORA, Z-drug short course, trazodone) | CBT-I has durable effects; drugs are for short-term adjunct |
| Short-term Insomnia | Sleep hygiene + reassurance | Z-drug or BZD (≤2–4 weeks) | Self-limiting; avoid perpetuating factor development |
| OSA | CPAP (moderate-severe) | MAD (mild-moderate or CPAP intolerant); surgery (anatomical cause); weight loss | CPAP is the gold standard; compliance is the main barrier |
| Narcolepsy | Modafinil (EDS); sodium oxybate (EDS + cataplexy) | Amphetamines; venlafaxine/clomipramine (cataplexy) | Lifelong condition; scheduled naps are adjunctive |
| RLS | Iron repletion (ferritin > 75); α₂δ ligands | Dopamine agonists (watch for augmentation); opioids (refractory) | Always check and correct iron first |
| Circadian Disorders | Light therapy + melatonin (timed) | Chronotherapy; tasimelteon (non-24h) | Timing of light and melatonin is everything |
| NREM Parasomnias | Safety measures; treat triggers | Clonazepam | Safety is priority; avoid sleep deprivation |
| RBD | Safety; melatonin | Clonazepam | Screen for neurodegeneration |
| Delirium | Treat underlying cause; supportive | Haloperidol (agitation); lorazepam (2nd line) | Non-pharmacological measures first |
High Yield Summary
Management of Sleep Disturbance — Key Takeaways:
-
Always treat the underlying cause first — psychiatric, medical, pharmacological, or primary sleep disorder.
-
Sleep hygiene is necessary for ALL patients but NOT sufficient alone for chronic insomnia.
-
CBT-I is first-line for chronic insomnia — techniques include sleep education, stimulus control, sleep restriction, relaxation, and cognitive therapy. Effects are durable; hypnotics are not.
-
Pharmacotherapy for insomnia is second-line: melatonin (elderly), DORAs (physiological), Z-drugs (short-term), trazodone (comorbid depression/anxiety). Avoid BZDs long-term.
-
CPAP is the gold standard for moderate-severe OSA — it works as a pneumatic splint. Compliance is the main challenge. MAD for mild-moderate or CPAP-intolerant patients.
-
Urgent CPAP indications: Pickwickian syndrome, nocturnal arrhythmia, nocturnal angina, severe EDS with driving risk.
-
AVOID car-driving in untreated OSA with EDS — medicolegal obligation.
-
RLS: Correct iron (ferritin > 75) first; α₂δ ligands (pregabalin/gabapentin) are now first-line over dopamine agonists (augmentation risk).
-
DORAs (suvorexant, lemborexant) represent a paradigm shift — they block the wake signal rather than forcing the sleep signal, preserving normal sleep architecture.
-
BZDs are contraindicated in OSA — they reduce muscle tone and blunt the arousal response.
-
RBD management: Safety + melatonin/clonazepam + long-term monitoring for α-synucleinopathy.
-
Delirium: Treat cause + supportive care + normalise sleep-wake cycle. Haloperidol only for dangerous agitation.
Active Recall - Management of Sleep Disturbance
References
[1] Senior notes: Ryan Ho Psychiatry.pdf (Section 9.2.3 Insomnia — Treatment principles, p. 224) [2] Senior notes: Ryan Ho Respiratory.pdf (Section 3.8 Sleep-Associated Disorders — OSA Treatment, pp. 155–161) [5] Lecture slides: murtagh merge.pdf (pp. 61–62 — Insomnia) [8] Senior notes: Ryan Ho Fundamentals.pdf (Section 3.4.5 Delirium — Mx, p. 326); Ryan Ho Neurology.pdf (Section 4.1.3 Delirium — Mx, p. 96) [9] Senior notes: Ryan Ho Psychiatry.pdf (Section 9.2.6 Other Sleep Disorders — Treatment for sleepiness, p. 229) [13] Senior notes: Ryan Ho Psychiatry.pdf (Section 3.1.4.2 Non-benzodiazepine Anxiolytics and Hypnotics, p. 60) [14] Senior notes: Ryan Ho Psychiatry.pdf (Section on PTSD treatment, p. 197)
Complications of Sleep Disturbance
Sleep disturbance is not merely about feeling tired. Chronic, untreated sleep disorders carry a significant burden of morbidity and mortality that spans virtually every organ system. The complications arise from distinct pathophysiological mechanisms depending on the underlying sleep disorder. Understanding these mechanisms from first principles is essential — both for exams and for counselling patients about why treatment matters.
Complications of sleep disturbance can be grouped by the underlying pathophysiological insult:
| Mechanism | Primary Sleep Disorder | Downstream Complications |
|---|---|---|
| Chronic sleep fragmentation / deprivation | Insomnia, OSA, PLMD, any cause | Neurocognitive, psychiatric, immune, metabolic |
| Chronic intermittent hypoxaemia | OSA, OHS | Cardiovascular, metabolic, neurocognitive |
| Sympathetic overactivation | OSA, insomnia (hyperarousal) | Hypertension, cardiovascular events |
| Circadian disruption | Shift work, circadian disorders, chronic insomnia | Metabolic, cancer risk, psychiatric |
| Treatment-related | Hypnotics (BZDs, Z-drugs), CPAP | Falls, dependence, rebound insomnia, complex sleep behaviours |
2. Complications of Untreated Obstructive Sleep Apnoea
This is the highest-yield area. OSA is the sleep disorder with the most serious and well-documented complications.
Untreated OSA is a/w a variety of consequences and confers extra mortality! [2]
Sympathetic activation → ↑ BP → secondary hypertension [2] Oxidative stress + release of mediators (hormones, cytokines, adipokines) → ↑ atherosclerosis + metabolic disturbances → cardiovascular diseases, e.g. CAD, HF, arrhythmia, stroke [2]
| Complication | Pathophysiology (From First Principles) | Clinical Significance |
|---|---|---|
| Secondary hypertension | Each apnoea triggers a massive sympathetic surge (arousal response) → ↑ catecholamines → vasoconstriction → acute BP spike. Repeated hundreds of times per night → chronic sympathetic overactivation → sustained daytime HTN with loss of normal nocturnal dipping. Also: intermittent hypoxaemia → endothelin-1 release → vasoconstriction; ↓ nitric oxide (endothelial dysfunction) → ↑ peripheral resistance. | HTN is well-demonstrated to be a result of OSA [2]. OSA is the most common identifiable cause of secondary/resistant hypertension. Up to 80% of patients with drug-resistant HTN have undiagnosed OSA. CPAP ↓ BP by 2–3 mmHg on average (greater effect in drug-resistant HTN). |
| Coronary artery disease | Chronic intermittent hypoxaemia → ↑ reactive oxygen species (ROS) → oxidative stress → endothelial dysfunction → accelerated atherosclerosis. Also: ↑ systemic inflammation (↑ CRP, IL-6, TNF-α) → plaque instability. Sympathetic surges → ↑ myocardial O₂ demand against a background of ↓ O₂ supply (hypoxaemia) → myocardial ischaemia, especially during REM sleep (when apnoeas are longest and most severe). | CAD [2]. Severe OSA (AHI > 30) independently ↑ risk of fatal and non-fatal cardiovascular events. Nocturnal angina is an urgent indication for CPAP [2]. |
| Heart failure | Chronic hypertension → LVH → diastolic dysfunction → HF. Also: extreme negative intrathoracic pressure swings during obstructed inspiration → ↑ LV afterload (the heart has to pump against a greater transmural pressure gradient) AND ↑ venous return (↑ RV preload) → interventricular septal shift → ↓ LV filling. Chronic intermittent hypoxaemia → myocardial injury over time. | HF [2]. OSA prevalence in HF patients is 40–60%. Conversely, HF can cause central sleep apnoea (Cheyne-Stokes respiration). The two conditions co-perpetuate. |
| Arrhythmias | Vagal stimulation during apnoea → bradycardia; sympathetic surge on arousal → tachycardia → tachy-brady cycles (characteristic PSG finding). Atrial distension (from ↑ venous return against a closed airway) → atrial fibrillation. Hypoxaemia → ↑ arrhythmogenicity (↓ refractory period, ↑ ectopic activity). | Arrhythmia [2]. AF prevalence in OSA ~4× general population. Nocturnal malignant arrhythmia is an urgent CPAP indication [2]. Recurrent AF post-cardioversion is strongly associated with untreated OSA. |
| Stroke | Atherosclerosis (as above) + paradoxical emboli (patent foramen ovale + ↑ right atrial pressure during apnoea) + AF → cardioembolic stroke. Also: ↑ blood viscosity from polycythaemia (chronic hypoxaemia → ↑ EPO → ↑ RBC) + ↑ fibrinogen + ↑ platelet aggregability → prothrombotic state. | Stroke [2]. Severe OSA independently ↑ stroke risk 2–3×. |
| Complication | Pathophysiology |
|---|---|
| Type 2 Diabetes / Insulin Resistance | Intermittent hypoxaemia → ↑ sympathetic activation → ↑ cortisol and catecholamines → hepatic gluconeogenesis ↑, peripheral insulin resistance ↑. Also: sleep fragmentation → ↑ ghrelin, ↓ leptin → ↑ appetite → weight gain → further insulin resistance. Pro-inflammatory state (↑ TNF-α, IL-6) directly impairs insulin signalling. |
| Dyslipidaemia | Sympathetic overactivation + intermittent hypoxaemia → ↑ hepatic lipogenesis, ↑ triglycerides, ↓ HDL |
| Metabolic Syndrome | OSA is now considered an independent component and driver of metabolic syndrome (central obesity + HTN + dyslipidaemia + insulin resistance). |
Complications: HTN, DM, metabolic syndrome [2]
Sleep fragmentation → sleepiness → car accidents, neurocognitive impairments [2]
| Complication | Pathophysiology | Clinical Impact |
|---|---|---|
| Excessive daytime sleepiness | Repeated arousals → sleep fragmentation → ↓ restorative N3 and REM → unmet sleep pressure accumulates | Principal symptom; ↓ quality of life; ↓ productivity |
| Car accidents [2] | EDS → microsleeps at the wheel → loss of vehicle control | Risk assessment: driving, operation of heavy machinery, any previous accidents [2]. RTA risk ↑ 2–7× in untreated OSA. |
| Neurocognitive impairments [2] | Sleep fragmentation → ↓ hippocampal memory consolidation (N3-dependent); chronic intermittent hypoxaemia → hippocampal and prefrontal cortex neuronal injury; ↓ glymphatic clearance → ↑ amyloid-β accumulation | Irritability, ↓ cognitive function, ↓ concentration, ↓ work performance [2]. ↑ risk of dementia with long-term untreated severe OSA. |
| Mood disturbance | Sleep deprivation → amygdala hyperreactivity with ↓ prefrontal cortical regulation → emotional dysregulation; also chronic hypoxaemia → serotonergic pathway disruption | Depression (comorbid in ~30% of OSA patients); irritability; anxiety |
| ↓ Libido / erectile dysfunction [2] | Chronic intermittent hypoxaemia → ↓ nocturnal testosterone production (testosterone secretion peaks during REM, which is fragmented); sympathetic overdrive → endothelial dysfunction → erectile dysfunction |
Why You Must Ask About Driving
AVOID CAR-DRIVING if not adequately treated [2]. In Hong Kong, a driver with untreated OSA causing EDS is legally unfit to drive. If you diagnose OSA and fail to document that you counselled the patient about driving risk, you share medicolegal liability if they cause an accident. Always document this conversation.
Chronic hypoxaemia → chronic respiratory failure → cor pulmonale (rare except in presence of other conditions, e.g. OHS, COPD) [2]
| Complication | Pathophysiology |
|---|---|
| Pulmonary hypertension | Chronic intermittent (and in OHS, sustained) hypoxaemia → hypoxic pulmonary vasoconstriction (HPV, Euler-Liljestrand reflex: alveolar hypoxia → pulmonary arteriolar smooth muscle contraction to divert blood to better-ventilated areas) → if sustained/repeated → vascular remodelling (medial hypertrophy, intimal fibrosis) → fixed pulmonary arterial hypertension |
| Cor pulmonale | Pulmonary hypertension → ↑ RV afterload → RV hypertrophy → RV dilatation → RV failure → peripheral oedema, hepatomegaly, ↑ JVP. Rare except in presence of other conditions (OHS, COPD) [2] because OSA alone rarely causes sustained enough hypoxaemia to drive this; it requires a "second hit." |
| Complication | Mechanism |
|---|---|
| Nocturia / enuresis | Intermittent hypoxia → ↑ right atrial distension → ↑ ANP release → natriuresis/diuresis; also: loss of vasopressin diurnal rhythm. Enuresis or nocturia [2]. |
| Morning headache | Nocturnal hypercapnia → cerebral vasodilation → raised ICP → headache on waking |
| Polycythaemia | Chronic hypoxaemia → ↑ renal EPO production → ↑ erythropoiesis → ↑ Hb/Hct → ↑ blood viscosity → prothrombotic state |
| GERD exacerbation | Large negative intrathoracic pressure swings during obstructed inspiration → "suck" gastric contents into the oesophagus → nocturnal GERD worsens → further sleep disruption (vicious cycle) |
Natural history: chronic insomnia is notoriously persistent → Prognosis: lasts ≥1y in 74%, ≥3y in 46% [1]
| Complication | Pathophysiology | Evidence |
|---|---|---|
| Depression | Chronic insomnia → persistent HPA axis hyperactivation → ↑ cortisol → hippocampal neurotoxicity and serotonergic dysregulation. Also: sleep deprivation → amygdala hyperreactivity → emotional dysregulation. Bidirectional: depression causes insomnia AND insomnia predicts new-onset depression (OR 2.1). | Meta-analysis: insomnia ↑ risk of incident depression 2.1× |
| Anxiety disorders | Chronic hyperarousal (the core neurobiological feature of insomnia) overlaps with and feeds into generalised anxiety. Cycle of worry: worry lack of sleep will compromise daytime function → ↑ stress → ↑ difficulty to sleep [1] | Strong bidirectional relationship |
| Cardiovascular disease | Chronic sympathetic overactivation from insomnia-related hyperarousal → sustained ↑ HR, ↑ BP → endothelial dysfunction → atherosclerosis. Also: chronic inflammation (insomnia ↑ CRP, IL-6). | Short sleep duration ( < 6h) and insomnia independently associated with ↑ HTN, MI, and stroke risk |
| Impaired immune function | Sleep deprivation → ↓ NK cell activity, ↓ T-cell proliferative responses, ↑ pro-inflammatory cytokines. Also ↓ antibody response to vaccination. | ↑ susceptibility to infections; reduced vaccine efficacy |
| Metabolic disturbances | Sleep deprivation → ↑ ghrelin (hunger hormone from stomach), ↓ leptin (satiety hormone from adipose tissue) → ↑ appetite and caloric intake. Also: ↓ glucose tolerance, ↑ insulin resistance (via sympathetic overactivation and cortisol). | ↑ risk of obesity, T2DM with chronic short sleep |
| Neurocognitive decline | ↓ N3 → ↓ hippocampal-neocortical memory transfer; ↓ REM → ↓ procedural memory consolidation; ↓ glymphatic clearance → ↑ amyloid-β and tau accumulation | Compromised daytime function, e.g. fatigue, malaise, ↓ concentration, ↓ work performance [1]. Emerging evidence: chronic insomnia ↑ dementia risk |
| Accidents | ↓ Attention, ↓ reaction time, microsleeps → workplace accidents, road traffic accidents | Sleep-deprived drivers have similar accident rates to intoxicated drivers |
| ↓ Quality of life | Cumulative impact of fatigue, mood disturbance, impaired cognition, social withdrawal | Chronic insomnia patients report quality of life comparable to chronic medical conditions (CHF, diabetes) |
| Substance misuse | Self-medication with alcohol (GABA-A agonist → initial sedation) or illicit substances; escalating use of hypnotics | ↑ risk of alcohol use disorder; BZD dependence |
| Complication | Pathophysiology |
|---|---|
| Injury from cataplexy | Sudden loss of muscle tone triggered by emotions → falls, fractures, head injuries. Cataplexy while driving or operating machinery → accidents. |
| Psychosocial impact | Irresistible sleep attacks → embarrassment → social withdrawal; misdiagnosed as "lazy" → academic and occupational failure; depression (prevalence ~30% in narcolepsy) |
| Obesity | Orexin deficiency → ↓ metabolic rate (orexin normally promotes energy expenditure); also: ↓ physical activity due to sleepiness; disrupted eating patterns |
| Sleep fragmentation paradox | Despite irresistible daytime sleep, narcolepsy patients also have fragmented nocturnal sleep (unstable flip-flop switch in both directions) → double burden of poor day AND night sleep |
| Complication | Mechanism |
|---|---|
| Chronic insomnia | RLS prevents sleep initiation; PLMD causes repetitive arousals → chronic sleep deprivation |
| Depression / anxiety | Chronic sleep deprivation + discomfort + frustration → psychiatric comorbidity (depression in ~20–30% of RLS patients) |
| Cardiovascular risk | Chronic sympathetic activation from repeated limb-movement-associated arousals → ↑ BP, ↑ heart rate; emerging evidence of ↑ cardiovascular risk in severe PLMD |
| Iron deficiency consequences | If secondary to iron deficiency: anaemia, fatigue, impaired cognition, pica |
| Complication | Pathophysiology |
|---|---|
| Metabolic syndrome / obesity | Circadian misalignment → eating during the biological night → impaired glucose tolerance (the β-cell circadian clock normally downregulates insulin secretion at night); ↓ leptin, ↑ ghrelin → ↑ appetite |
| Cardiovascular disease | Chronic sympathetic activation from fragmented sleep; loss of nocturnal BP dipping; chronic inflammation |
| Cancer risk | IARC classifies night shift work as "probably carcinogenic" (Group 2A). Mechanism: melatonin suppression (melatonin is oncostatic — inhibits tumour growth, is antioxidant, promotes DNA repair). Light at night → ↓ melatonin → ↓ oncostatic protection. ↑ risk of breast, prostate, and colorectal cancer in shift workers. |
| Reproductive dysfunction | Circadian disruption → altered GnRH pulsatility → menstrual irregularity, ↓ fertility; ↑ adverse pregnancy outcomes in shift workers |
| Psychiatric disorders | Chronic circadian misalignment → ↑ depression, ↑ anxiety, ↑ substance use |
7. Treatment-Related Complications
These are iatrogenic complications that arise from the management of sleep disturbance itself. They are extremely important and frequently tested.
| Complication | Mechanism |
|---|---|
| Tolerance | GABA-A receptor downregulation with chronic use → the same dose produces ↓ effect → need for dose escalation. Typically develops within 2–4 weeks for hypnotic effect. |
| Dependence | Neuroadaptation to chronic GABA-A potentiation → withdrawal syndrome on cessation (anxiety, insomnia — often worse than baseline ["rebound insomnia"], tremor, seizures in severe cases). Physical AND psychological dependence. |
| Rebound insomnia | On abrupt withdrawal, the GABA-A system is downregulated → rebound CNS excitability → insomnia worse than before treatment. This convinces the patient they "need" the drug → reinforces dependence. |
| Falls and hip fractures | Sedation + muscle relaxation + ↓ postural reflexes + ↓ coordination → ↑ falls, especially in the elderly (nocturia + sedation = falls during nocturnal bathroom visits). Pooled OR for hip fracture ~1.5× with BZD use. |
| Cognitive impairment | GABA-A potentiation → ↓ hippocampal function → anterograde amnesia (especially with long-acting BZDs). Chronic use in elderly associated with ↑ dementia risk (controversial but consistently observed). |
| Complex sleep behaviours | Particularly with zolpidem: sleep-driving, sleep-eating, sleep-walking, sleep-texting — the patient performs complex activities with no recollection. Mechanism: incomplete arousal from sedated state. |
| Respiratory depression | BZDs/Z-drugs depress the medullary respiratory centre AND reduce pharyngeal muscle tone → worsens OSA, can precipitate respiratory failure in patients with COPD, OHS, or neuromuscular disease. |
| Morning hangover | Residual sedation from drugs with longer half-lives → ↓ daytime performance, ↓ driving ability |
| Drug interactions | BZDs + alcohol = synergistic CNS depression (both enhance GABA-A → additive respiratory depression). BZDs + opioids = lethal combination (FDA black box warning). |
The BZD Trap
The most insidious complication of BZDs/Z-drugs is the tolerance → rebound insomnia → dose escalation → dependence cycle. The patient starts a "short course" of sleeping tablets, develops tolerance in 2–4 weeks, tries to stop, experiences rebound insomnia worse than baseline, concludes they "need" the medication, and continues indefinitely. This is why guidelines mandate: lowest dose, shortest duration, and always combine with CBT-I so the patient has a non-pharmacological strategy when the drug is tapered.
| Complication | Mechanism | Management |
|---|---|---|
| Mask intolerance / discomfort | Pressure on nasal bridge → skin breakdown; claustrophobia | Proper fitting; try different mask types (nasal pillows, full-face); desensitisation |
| Nasal dryness / congestion | Continuous airflow dries nasal mucosa → mucosal inflammation → congestion | Heated humidification; nasal saline spray; topical nasal steroids |
| Aerophagia | Positive pressure air enters oesophagus → gastric distension → bloating, belching, flatulence | ↓ pressure if possible; APAP to reduce mean pressure; sleep position adjustment |
| Poor compliance | Multifactorial: discomfort, inconvenience, noise, partner disturbance, claustrophobia | Education; mask fitting; APAP; ramp function; regular follow-up |
| Skin pressure ulceration | Chronic pressure from mask straps, especially on nasal bridge | Properly fitted mask; cushion/gel pads; regular skin checks |
| Parasomnia | Complications |
|---|---|
| Sleepwalking | Injury (falling down stairs, walking into traffic, falling from windows); medicolegal issues (acts during sleepwalking: homicide cases exist in forensic literature) |
| Night terrors | Psychological distress to the family/bed partner; injury during thrashing; sleep disruption |
| RBD | Injury to self (falling out of bed, hitting furniture) and bed partner (punching, kicking during dream enactment). Progression to neurodegenerative disease: RBD may precede motor symptoms of Parkinson's disease, DLB, or MSA by years to decades — conversion rate ~6%/year, with > 80% eventually developing a synucleinopathy. This makes RBD a prodromal marker and an opportunity for neuroprotective trials. |
Non-motor symptoms [of PD]: may precede TRAP for many years — Other features: fatigue, pain, sleep disturbance (e.g. hypersomnolence), sexual problems [15]
Prognosis [16]:
- Mortality: independent predictor of mortality, esp for those with protracted delirium → Mortality data: 14% (1mo), 22% (6mo), 6× non-delirious patients [16]
- Outcome: most cases recover rapidly when underlying cause is treated [16]
| Complication | Mechanism |
|---|---|
| Prolonged hospital stay | Delirium → agitation, refusal to cooperate, inability to participate in rehabilitation → ↑ LOS |
| Mortality | Delirium is an independent predictor of mortality (reflects the severity of the underlying medical insult) |
| Accelerated cognitive decline | Neurotoxicity from the underlying metabolic insult + neuroinflammation during the delirious episode → permanent hippocampal and cortical neuronal injury → ↑ dementia risk |
| Falls and injuries | Disorientation + psychomotor agitation + sedating medications → falls → hip fracture → further immobility → further delirium (vicious cycle) |
| Iatrogenic harm | Inappropriate use of restraints → pressure injuries, aspiration. Inappropriate use of antipsychotics → QTc prolongation, neuroleptic malignant syndrome. Inappropriate BZDs → paradoxical disinhibition, respiratory depression. |
Modern sleep medicine increasingly recognises that sleep disturbance is not an isolated symptom but a systemic disease driver. The key pathways:
| Pathway | Mechanism | End-Organ Consequences |
|---|---|---|
| Sympathetic overactivation | ↑ Catecholamines 24/7 | HTN, arrhythmia, LVH, HF, sudden cardiac death |
| Chronic inflammation | ↑ CRP, IL-6, TNF-α from sleep deprivation and/or intermittent hypoxia | Atherosclerosis, insulin resistance, cancer promotion |
| HPA axis dysregulation | ↑ Cortisol (insomnia: evening peak; OSA: nocturnal surges) | Insulin resistance, visceral adiposity, hippocampal atrophy, depression |
| Impaired glymphatic clearance | ↓ N3 → ↓ clearance of amyloid-β and tau from brain interstitial fluid | Alzheimer's disease and vascular dementia |
| Melatonin suppression | Light at night, circadian disruption | ↓ Antioxidant defence, ↓ oncostatic protection → cancer risk |
| Immune dysregulation | ↓ NK cell activity, ↓ T-cell function | ↑ Infection susceptibility, ↓ vaccine response, ↑ cancer risk |
Key Points for Exams:
- OSA complications are driven by 3 mechanisms: intermittent hypoxaemia, sympathetic activation, and intrathoracic pressure swings.
- HTN is the most well-established cardiovascular consequence of OSA — always think of OSA in resistant hypertension.
- Chronic insomnia ↑ risk of depression (bidirectional), cardiovascular disease, metabolic syndrome, and dementia.
- RBD → synucleinopathy conversion rate is ~6%/year — one of the strongest prodromal markers for PD/DLB/MSA.
- BZD/Z-drug complications: tolerance, dependence, rebound insomnia, falls (elderly), cognitive impairment, complex sleep behaviours, respiratory depression (worsens OSA).
- Shift work is classified as "probably carcinogenic" (IARC Group 2A) due to melatonin suppression.
High Yield Summary
Complications of Sleep Disturbance — Key Takeaways:
-
Untreated OSA confers extra mortality via secondary hypertension, CAD, arrhythmia (AF), HF, stroke, and road traffic accidents.
-
OSA → HTN is the most robustly demonstrated cardiovascular consequence. OSA is the most common cause of resistant hypertension.
-
Metabolic complications of OSA and chronic insomnia: insulin resistance, T2DM, dyslipidaemia, obesity — chronic sleep deprivation disrupts ghrelin/leptin balance and cortisol regulation.
-
Neurocognitive impairment from sleep fragmentation and intermittent hypoxia: ↓ memory consolidation, ↓ concentration, ↑ dementia risk (impaired glymphatic clearance of amyloid-β).
-
RBD is a prodromal marker for α-synucleinopathies (PD, DLB, MSA) — conversion rate ~6%/year.
-
Delirium is an independent predictor of mortality and 5× ↑ incidence of dementia in 2 years.
-
BZD/Z-drug complications: tolerance → rebound insomnia → dependence cycle; falls in elderly; respiratory depression (contraindicated in OSA); complex sleep behaviours.
-
Shift work is probably carcinogenic (Group 2A, IARC) via melatonin suppression.
-
Depression and insomnia are bidirectional — each ↑ the risk of developing the other.
-
Always assess and document driving risk and occupational risk in patients with EDS — medicolegal obligation.
Active Recall - Complications of Sleep Disturbance
References
[1] Senior notes: Ryan Ho Psychiatry.pdf (Section 9.2.3 Insomnia — Clinical features and Natural history, p. 223) [2] Senior notes: Ryan Ho Respiratory.pdf (Section 3.8 Sleep-Associated Disorders — Complications of OSA, pp. 155–161) [5] Lecture slides: murtagh merge.pdf (pp. 61–62 — Insomnia) [8] Senior notes: Ryan Ho Fundamentals.pdf (Section 3.4.5 Delirium, pp. 325–326) [15] Senior notes: Ryan Ho Neurology.pdf (Section on Parkinson's Disease — Non-motor symptoms, p. 121) [16] Senior notes: Ryan Ho Psychiatry.pdf (Section on Delirium — Prognosis, p. 76)
High Yield Summary
Key Points:
-
Sleep disturbance is a symptom, not a diagnosis — always search for the underlying cause using a systematic approach (psychiatric, medical, pharmacological, primary sleep disorder).
-
Normal sleep architecture (N1 → N2 → N3 → REM in 90-min cycles) is disrupted differently by different conditions: OSA fragments architecture via arousals; depression alters REM latency; aging reduces N3.
-
The 3P model (Predisposing, Precipitating, Perpetuating) explains why acute insomnia becomes chronic — perpetuating factors (maladaptive behaviours) are the key target for CBT-I.
-
Insomnia pattern matters: Initial → anxiety/RLS; Terminal → depression; Middle → medical/OSA.
-
OSA pathophysiology: Loss of wakefulness drive → ↓ pharyngeal dilator tone → negative inspiratory pressure → upper airway collapse → apnoea → hypoxaemia/hypercapnia → arousal → cycle repeats.
-
OSA is undertreated and confers real mortality: HTN, arrhythmia, stroke, CAD, car accidents, neurocognitive decline.
-
Narcolepsy: Orexin/hypocretin deficiency → unstable flip-flop switch → cataplexy, sleep paralysis, hypnagogic hallucinations.
-
RLS: Central dopaminergic dysfunction + brain iron deficiency → always check ferritin.
-
Always take a bed partner history — many sleep disorders are observed, not self-reported.
-
Always assess driving risk in any patient with excessive daytime sleepiness.
-
Masquerades: Depression, Diabetes, Drugs (stimulants, alcohol, beta-blockers, SSRIs, steroids), Thyroid (hyperthyroid), Spinal dysfunction, UTI (nocturia).
High Yield Summary
Differential Diagnosis of Sleep Disturbance — Key Takeaways:
-
Probability diagnoses: Stress/anxiety, depression, poor sleep hygiene, environment, drug/alcohol withdrawal, biorhythm disruption.
-
Serious not to miss: PVD, CCF, pharyngeal tumour, pain syndromes (back/arthritis/CTS/cancer), respiratory (asthma/COPD/nasal obstruction), PTSD, psychosis, RLS/PLMD.
-
Pitfalls (often missed): Sleep apnoea, GORD, dementia, menopausal symptoms.
-
Rarities: Macroglossia/tonsillar hypertrophy, malnutrition, parasomnias.
-
Masquerades: Depression, diabetes, drugs (stimulants, alcohol, beta-blockers, SSRIs, steroids), thyroid (hyperthyroid), spinal dysfunction, UTI (nocturia).
-
Pattern-based approach: Initial insomnia → anxiety/RLS/delayed phase. Middle insomnia → OSA/pain/nocturia/GERD. Terminal insomnia → depression/advanced phase.
-
Always exclude delirium in acute sleep-wake disturbance in hospitalised/elderly patients.
-
Always get a bed-partner history — OSA, PLMD, and RBD are observed conditions.
-
Nocturnal dyspnoea DDx: OSA (resolves immediately) vs PND (takes minutes) vs asthma (wheeze) vs rhinitis (nasal blockage).
-
RBD in the elderly → investigate for α-synucleinopathy (PD, DLB, MSA).
High Yield Summary
Diagnostic Criteria & Investigations — Key Takeaways:
-
Chronic insomnia (DSM-5): Difficulty initiating/maintaining sleep OR early awakening + daytime impairment + ≥3 nights/week + ≥3 months + adequate sleep opportunity + not explained by another sleep/medical/psychiatric/substance disorder. Remember the 3-3-3 rule.
-
ICD-10 has a lower threshold (≥1 week vs ≥3 months).
-
OSA diagnosis: AHI ≥5/h with symptoms OR AHI ≥15/h regardless. Severity: Mild 5–15, Moderate 15–30, Severe > 30.
-
Narcolepsy: MSLT showing mean sleep latency ≤8 min + ≥2 SOREMPs, OR CSF orexin ≤110 pg/mL.
-
RLS: Purely clinical diagnosis — 5 IRLSSG criteria. Check ferritin (target > 75 μg/L) and renal function.
-
PSG is NOT for insomnia — it is for OSA, narcolepsy, PLMD, and parasomnias.
-
Sleep diary is the most important first-line tool — derives sleep efficiency, SOL, WASO, and reveals circadian patterns.
-
HSAT is acceptable for uncomplicated OSA but negative HSAT does not exclude OSA.
-
Masquerade screen bloods: FBE, ESR/CRP, LFTs (γGT), TFTs, ferritin, HbA1c, renal function.
-
Delirium screening (CAM/4AT) is mandatory for any acute sleep-wake disturbance in hospitalised/elderly patients.
High Yield Summary
Management of Sleep Disturbance — Key Takeaways:
-
Always treat the underlying cause first — psychiatric, medical, pharmacological, or primary sleep disorder.
-
Sleep hygiene is necessary for ALL patients but NOT sufficient alone for chronic insomnia.
-
CBT-I is first-line for chronic insomnia — techniques include sleep education, stimulus control, sleep restriction, relaxation, and cognitive therapy. Effects are durable; hypnotics are not.
-
Pharmacotherapy for insomnia is second-line: melatonin (elderly), DORAs (physiological), Z-drugs (short-term), trazodone (comorbid depression/anxiety). Avoid BZDs long-term.
-
CPAP is the gold standard for moderate-severe OSA — it works as a pneumatic splint. Compliance is the main challenge. MAD for mild-moderate or CPAP-intolerant patients.
-
Urgent CPAP indications: Pickwickian syndrome, nocturnal arrhythmia, nocturnal angina, severe EDS with driving risk.
-
AVOID car-driving in untreated OSA with EDS — medicolegal obligation.
-
RLS: Correct iron (ferritin > 75) first; α₂δ ligands (pregabalin/gabapentin) are now first-line over dopamine agonists (augmentation risk).
-
DORAs (suvorexant, lemborexant) represent a paradigm shift — they block the wake signal rather than forcing the sleep signal, preserving normal sleep architecture.
-
BZDs are contraindicated in OSA — they reduce muscle tone and blunt the arousal response.
-
RBD management: Safety + melatonin/clonazepam + long-term monitoring for α-synucleinopathy.
-
Delirium: Treat cause + supportive care + normalise sleep-wake cycle. Haloperidol only for dangerous agitation.
High Yield Summary
Complications of Sleep Disturbance — Key Takeaways:
-
Untreated OSA confers extra mortality via secondary hypertension, CAD, arrhythmia (AF), HF, stroke, and road traffic accidents.
-
OSA → HTN is the most robustly demonstrated cardiovascular consequence. OSA is the most common cause of resistant hypertension.
-
Metabolic complications of OSA and chronic insomnia: insulin resistance, T2DM, dyslipidaemia, obesity — chronic sleep deprivation disrupts ghrelin/leptin balance and cortisol regulation.
-
Neurocognitive impairment from sleep fragmentation and intermittent hypoxia: ↓ memory consolidation, ↓ concentration, ↑ dementia risk (impaired glymphatic clearance of amyloid-β).
-
RBD is a prodromal marker for α-synucleinopathies (PD, DLB, MSA) — conversion rate ~6%/year.
-
Delirium is an independent predictor of mortality and 5× ↑ incidence of dementia in 2 years.
-
BZD/Z-drug complications: tolerance → rebound insomnia → dependence cycle; falls in elderly; respiratory depression (contraindicated in OSA); complex sleep behaviours.
-
Shift work is probably carcinogenic (Group 2A, IARC) via melatonin suppression.
-
Depression and insomnia are bidirectional — each ↑ the risk of developing the other.
-
Always assess and document driving risk and occupational risk in patients with EDS — medicolegal obligation.
Shoulder Pain
Shoulder pain is a common musculoskeletal complaint arising from disorders of the rotator cuff, glenohumeral or acromioclavicular joints, bursae, or referred sources such as cervical spine or visceral pathology.
Sore Throat Complaints
Sore throat is a symptom of pharyngeal pain or irritation, commonly caused by viral or bacterial infections, allergies, or environmental irritants, prompting evaluation to distinguish benign from serious etiologies such as group A streptococcal pharyngitis or peritonsillar abscess.