Learning objectives
- Explain normal sleep physiology, architecture and circadian regulation.
- Classify insomnia, sleep-related breathing, hypersomnolence, movement, parasomnia and circadian-rhythm disorders.
- Take a complete sleep history and choose targeted investigations.
- Recognise obstructive sleep apnoea, narcolepsy, restless legs, parasomnias and medical causes of sleep disruption.
- Apply behavioural treatment, CPAP principles, safety advice and cautious medicine use.
1. Physiology of normal sleep
Sleep is an active, reversible state regulated by the interaction of homeostatic sleep pressure and the circadian clock in the suprachiasmatic nucleus. Light, meal timing, activity, illness, age and social schedules influence the clock. Melatonin rises in dim evening light and helps signal biological night.
| Stage | Physiology | Clinical relevance |
|---|---|---|
| N1 | Transition from wakefulness; light sleep, slow eye movements and easy arousal. | May be confused with poor sleep; brief awakenings are normal. |
| N2 | Sleep spindles and K-complexes; reduced heart rate and temperature. | Largest proportion of adult sleep; fragmented by pain, noise and sleep apnoea. |
| N3 | Deep slow-wave sleep with high arousal threshold and restorative functions. | Sleepwalking, night terrors and enuresis often arise here. |
| REM | Rapid eye movements, vivid dreaming, variable autonomic activity and skeletal-muscle atonia. | REM intrusion causes cataplexy and sleep paralysis; REM behaviour disorder involves loss of atonia. |
Sleep cycles recur approximately every 90–110 minutes, with more N3 earlier and more REM later in the night. Infants, adolescents, adults and older people have different sleep duration and architecture; ask about function rather than enforcing one number.
2. Classification of sleep disorders
| Group | Examples | Typical clue |
|---|---|---|
| Insomnia disorders | Chronic insomnia, short-term insomnia, comorbid insomnia. | Difficulty initiating/maintaining sleep or early waking plus daytime impairment. |
| Sleep-related breathing | Obstructive sleep apnoea (OSA), central sleep apnoea, hypoventilation. | Loud snoring, witnessed apnoeas, choking, morning headache and daytime sleepiness. |
| Central disorders of hypersomnolence | Narcolepsy, idiopathic hypersomnia. | Irresistible sleep attacks, cataplexy, sleep paralysis or prolonged unrefreshing sleep. |
| Circadian rhythm disorders | Delayed sleep-wake phase, advanced phase, shift-work and jet lag. | Sleep is normal when allowed at the person’s preferred time but impossible at required times. |
| Parasomnias | Sleepwalking, night terrors, nightmares, REM sleep behaviour disorder, sleep paralysis. | Unwanted behaviours or experiences during sleep transitions. |
| Sleep-related movement | Restless legs syndrome, periodic limb movements, bruxism. | Urge to move, unpleasant sensations or repetitive movements. |
3. Sleep history and examination
Ask the patient and bed partner
- Bedtime, sleep-onset latency, awakenings, wake time, naps, total sleep opportunity and variability.
- Snoring, witnessed pauses, gasping, choking, mouth breathing and morning dry mouth/headache.
- Daytime sleepiness, unplanned dozing, microsleeps, cataplexy, sleep paralysis and vivid dream-like experiences.
- Nightmares, sleepwalking, dream enactment, bruxism, leg discomfort and nocturnal seizures.
- Caffeine, nicotine, alcohol, cannabis, stimulants, sedatives, shift work, screens, pain, mood and stress.
- Medical conditions: obesity, hypertension, diabetes, heart failure, stroke, COPD/asthma, thyroid disease, anaemia, pregnancy, menopause, Parkinson disease and epilepsy.
Use a two-week sleep diary and, when helpful, the Epworth Sleepiness Scale, Insomnia Severity Index and STOP-BANG. Examine BMI/neck circumference, nasal/oropharyngeal obstruction, blood pressure, cardiopulmonary and neurological status, mood and medicines.
4. Insomnia
Insomnia is persistent difficulty falling asleep, staying asleep or waking too early despite adequate opportunity, with daytime fatigue, mood, concentration or functioning problems. It may be acute or chronic and frequently coexists with depression, anxiety, PTSD, pain, substance use, menopause, reflux or another sleep disorder.
Red flags and differential
- Mania: reduced need for sleep with increased energy, grandiosity or risky behaviour.
- Suicidal depression, psychosis, delirium, alcohol/benzodiazepine withdrawal or stimulant use.
- Snoring/apnoea, restless legs, nocturnal seizures, hyperthyroidism, pain, reflux, pregnancy or medication effects.
First-line treatment: CBT-I
- Stimulus control: bed only for sleep/intimacy; leave bed for a quiet activity if unable to sleep and return when sleepy.
- Sleep restriction/compression: limit time in bed to actual sleep initially, then expand as efficiency improves; avoid in untreated bipolar disorder, epilepsy risk or severe sleepiness without supervision.
- Cognitive work: challenge catastrophic beliefs about sleep and reduce clock-watching.
- Relaxation: breathing, muscle relaxation, mindfulness and a wind-down routine.
- Sleep scheduling: consistent wake time, morning light and daytime activity.
Sleep hygiene alone is usually insufficient for chronic insomnia but supports CBT-I: reduce evening caffeine/nicotine/alcohol, manage pain/reflux, keep the room dark and cool, and avoid late heavy meals or stimulating screens.
Medicines
Short-term medication may be considered after assessment and shared decision-making. Melatonin may help selected circadian or older-adult patients; product strength and regulation vary. Benzodiazepines and “Z-drugs” can cause dependence, falls, confusion, respiratory depression, parasomnias and next-day impairment—avoid routine long-term use, alcohol combinations and use in untreated OSA. Sedating antihistamines are not a benign chronic solution.
5. Obstructive sleep apnoea
OSA results from recurrent upper-airway collapse during sleep, causing intermittent hypoxaemia and arousals. Risk increases with obesity, large neck circumference, craniofacial narrowing, male sex, age, alcohol/sedatives, nasal obstruction and family history. It also occurs in children, where enlarged tonsils/adenoids and learning or behaviour problems may predominate.
Clinical features
- Loud habitual snoring, witnessed pauses, gasping/choking, restless sleep, nocturia and morning headache.
- Daytime sleepiness, poor concentration, irritability, resistant hypertension, atrial fibrillation, diabetes or road crashes.
- Children: mouth breathing, enuresis, growth problems, morning headache, hyperactivity or poor school performance.
Diagnosis and management
Arrange home sleep-apnoea testing or polysomnography according to local availability and comorbidity. Polysomnography records brain waves, breathing, heart rate and oxygenation; a normal single-night test may need clinical correlation. Treat weight, nasal disease, alcohol/sedative use and smoking. Continuous positive airway pressure (CPAP) is highly effective when used consistently; provide mask fitting, humidification, education and adherence follow-up. Oral appliances or surgery may suit selected patients after specialist assessment. Avoid sedatives and driving when sleepy.
6. Central hypersomnolence and narcolepsy
Narcolepsy causes excessive daytime sleepiness with sleep attacks, and may include cataplexy (sudden loss of muscle tone triggered by emotion), sleep paralysis and vivid hypnagogic/hypnopompic hallucinations. Idiopathic hypersomnia causes severe sleepiness and prolonged unrefreshing sleep without typical cataplexy.
- Exclude insufficient sleep, OSA, depression, sedative/substance use, anaemia, hypothyroidism and neurological disease.
- Sleep specialist testing may include overnight polysomnography followed by a multiple sleep latency test.
- Use planned naps, regular sleep, safety restrictions and psychosocial support. Wake-promoting medicines such as modafinil require specialist prescribing and interaction/pregnancy review; stimulants require cardiovascular, psychiatric and misuse monitoring.
7. Circadian-rhythm sleep-wake disorders
In delayed sleep-wake phase disorder, the patient cannot sleep early or wake for school/work but sleeps normally on a preferred late schedule. Shift-work disorder follows work-time misalignment; jet lag follows rapid time-zone change.
- Keep a sleep diary/actigraphy, set gradual schedule shifts, use bright morning light for delayed phase and reduce evening light.
- Timed melatonin may be used under professional guidance; correct timing is more important than high dose.
- Support night-shift workers with planned naps, strategic light/caffeine, protected daytime darkness and fatigue-risk policies.
8. Parasomnias
NREM parasomnias
Sleepwalking, confusional arousals and night terrors arise from deep sleep, often in children and with sleep deprivation, fever, stress or OSA. Protect the environment, avoid waking abruptly, improve sleep regularity and assess triggers. Recurrent injurious episodes, adult onset or atypical events warrant sleep/neurology evaluation.
Nightmares and REM sleep behaviour disorder
Nightmares may follow trauma, medication, fever or stress; imagery rehearsal therapy can help. REM sleep behaviour disorder involves dream enactment and loss of normal REM atonia, often in older adults and associated with neurological disease. Remove weapons and sharp objects, pad the environment and refer for assessment; clonazepam or melatonin is specialist-led because clonazepam can worsen falls and breathing disorders.
Sleep paralysis
Brief inability to move at sleep onset or awakening can be frightening and is associated with sleep deprivation, irregular schedules and narcolepsy. Reassure, regularise sleep and investigate narcolepsy or other causes when frequent.
9. Restless legs syndrome and movement disorders
Restless legs syndrome is an urge to move the legs with uncomfortable sensations, worse at rest and evening, and relieved temporarily by movement. Ask about iron deficiency, pregnancy, renal disease, neuropathy and medicines such as antihistamines or dopamine-blocking agents. Check ferritin and iron studies when indicated; correct deficiency and review triggers. Specialist options include gabapentin/pregabalin or dopamine agents, but augmentation and sedation require monitoring.
10. Sleep in children and adolescents
- Establish age-appropriate sleep opportunity, routines, school start time, screens, caffeine, anxiety, ADHD, autism, pain and family stress.
- Bedtime resistance and night waking often respond to consistent routines, graduated settling and caregiver coaching.
- Snoring, pauses, restless sleep, mouth breathing, daytime hyperactivity or growth problems suggest OSA assessment.
- Adolescents commonly have delayed circadian phase; combine school accommodations, morning light, reduced late screens and specialist melatonin advice when appropriate.
11. Medicines, substances and sleep
| Can worsen sleep | Can cause sleepiness | Clinical action |
|---|---|---|
| Caffeine, nicotine, stimulants, corticosteroids, some antidepressants, decongestants and levothyroxine excess. | Alcohol, opioids, benzodiazepines, sedating antihistamines, antipsychotics, gabapentinoids and some antiseizure medicines. | Review timing, dose, interactions and indication; never stop essential medicines abruptly. |
Alcohol may shorten sleep onset but fragments REM/NREM sleep and worsens OSA. Opioids can cause central apnoea and dangerous sedation. Combining alcohol, opioids and benzodiazepines can be fatal.
12. When to refer urgently
- Sleepiness causing crashes, repeated syncope, hypoxaemia, severe apnoea or suspected narcolepsy affecting safety.
- New nocturnal seizure, status epilepticus, violent REM behaviour with injury, sudden neurological deficit or severe headache.
- Mania, psychosis, suicidal thinking, delirium, alcohol/benzodiazepine withdrawal or overdose.
- Child abuse concerns, severe failure to thrive, dangerous sleepwalking or suspected airway obstruction.
Clinical cases
Quick self-test
- What are the main differences between insomnia and delayed sleep-wake phase disorder?
- List four symptoms or consequences that should prompt OSA assessment.
- What is cataplexy?
- Why can chronic benzodiazepine or alcohol use worsen sleep despite sedation?
- Name three environmental measures for dangerous parasomnias.
Answers
- Insomnia persists despite adequate opportunity and is not solved by changing schedule; delayed phase has normal sleep when the person follows a late preferred schedule but difficulty at conventional times.
- Habitual snoring, witnessed apnoeas, gasping, morning headache, daytime sleepiness, resistant hypertension, atrial fibrillation, crashes or childhood learning/behaviour problems.
- Sudden emotion-triggered loss of muscle tone while consciousness is usually preserved, commonly associated with narcolepsy.
- They fragment sleep architecture, cause tolerance/rebound insomnia, suppress breathing and create dependence/withdrawal.
- Remove weapons/sharp objects, lock windows/doors, pad hazards, protect stairs and use a safe sleep environment.
Key take-home messages
- Sleep disorders are common, clinically important and often treatable.
- Take a two-week sleep history/diary and screen for medical, psychiatric, substance and medication causes.
- CBT-I is the foundation for chronic insomnia; sedatives require restraint and monitoring.
- OSA, narcolepsy, dangerous parasomnias and withdrawal require targeted investigation and referral.
- Always address driving, work, school, pregnancy, child safety and respiratory-depressant combinations.
References and further reading
- National Heart, Lung, and Blood Institute (NIH). Sleep science and sleep disorders: NHLBI resource.
- NHLBI. Sleep disorder treatments: NHLBI treatment overview.
- NHLBI. Sleep studies: NHLBI diagnostic resource.
- American Academy of Sleep Medicine. Behavioral and psychological treatments for chronic insomnia: AASM guideline.
- American Academy of Sleep Medicine. Pharmacologic treatment of chronic insomnia: AASM guideline.
