• Sleep architecture:
o Cycles of non-REM (N1, N2, N3) and REM sleep.
o REM sleep first occurs ~90 minutes after sleep onset.
o Non-REM = restorative, slow-wave (N3 most deep).
• Age effects:
o ↓ Slow-wave sleep with age.
o ↑ Nocturnal awakenings.
• REM sleep in mood disorders:
o Reduced REM latency (enters REM earlier) in depression.
o Increased REM density.
• Definition: Difficulty initiating or maintaining sleep, early waking, non-restorative sleep.
• Classification:
o Short-term: <3 months; usually stress-related.
o Chronic: >3 months, ≥3 nights/week.
• Management:
o First-line: CBT for insomnia (CBT-i).
o Sleep hygiene: regular schedule, avoid caffeine/alcohol, reduce screen time.
o Avoid long-term benzodiazepines or Z-drugs (risk of dependence).
• Medications (only if severe, short-term use):
o Short-acting hypnotics (e.g., zopiclone).
o Melatonin in elderly (limited role).
• Features:
o Excessive daytime sleepiness ("sleep attacks").
o Cataplexy: sudden muscle weakness triggered by emotions (laughter, anger).
o Hypnagogic (on falling asleep) or hypnopompic (on waking) hallucinations.
o Sleep paralysis.
• Diagnosis:
o Multiple Sleep Latency Test (MSLT): mean sleep latency <8 min + ≥2 sleep-onset REM periods.
o CSF hypocretin (orexin) levels low in some cases.
• Treatment:
o Modafinil first-line for daytime sleepiness.
o Sodium oxybate or antidepressants may help cataplexy.
• Associations:
o Strong HLA-DQB1*0602 association.
• Obstructive Sleep Apnoea (OSA):
o Repeated upper airway obstruction → hypoxia, arousals.
o Risk factors: obesity, male, craniofacial abnormalities, alcohol/sedatives.
• Clinical features:
o Loud snoring.
o Witnessed apnoeas.
o Excessive daytime sleepiness (Epworth Sleepiness Scale often used).
• Diagnosis:
o Polysomnography (gold standard).
o Apnoea–hypopnoea index (AHI):
Mild: 5–15/hr.
Moderate: 15–30/hr.
Severe: >30/hr.
• Treatment:
o CPAP (continuous positive airway pressure).
o Weight loss, avoid alcohol/sedatives, positional therapy.
• Complications:
o Hypertension, arrhythmias, pulmonary hypertension, insulin resistance.
• NREM-related (arousal disorders):
o Sleepwalking (somnambulism).
o Sleep terrors: sudden arousals, screaming, autonomic signs.
o Common in children; amnesia for event.
• REM-related:
o REM sleep behaviour disorder (RBD):
Dream enactment, violent movements.
Strongly associated with synucleinopathies: Parkinson’s, Lewy body dementia, MSA.
o Nightmares: vivid, recalled upon waking.
• Treatment:
o Reassurance, safety precautions (e.g., safe environment).
o Clonazepam sometimes used in severe RBD.
Extra Revision Pearls
• RBD can precede Parkinsonism by years → important prodromal clue.
• OSA → secondary polycythaemia due to nocturnal hypoxia.
• In narcolepsy, cataplexy is pathognomonic but not always present.
• Hypnagogic hallucinations = “going to sleep”, hypnopompic = “popping out” of sleep.
• Insomnia is often secondary to mood disorders → always screen for depression/anxiety.
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Author & Educational Disclaimer
Author:
Dr Phillip Cockrell BM FRCP DipClinEd
Dr Phillip Cockrell is a UK Consultant Physician in Internal Medicine, currently working at Queen Alexandra Hospital, Portsmouth University Hospitals NHS Trust. He has previously worked as a registrar across Intensive Care Medicine, Gastroenterology, Cardiology, Stroke Medicine, Acute Medicine, and Respiratory Medicine.
He has held senior leadership roles including Associate Clinical Director of the Acute Medical Unit, Clinical Director of Internal Medicine, and Chief of Medicine. Dr Cockrell has over 15 years’ experience in postgraduate medical education, having lectured extensively across the MRCP syllabus and contributed to MRCP revision teaching and course development.
Dr Cockrell holds a Bachelor of Medicine (BM), Fellowship of the Royal College of Physicians (FRCP), and a Diploma in Clinical Education (DipClinEd). His teaching approach is based on structured consolidation of complex medical topics to support efficient and effective revision for postgraduate examinations.
Purpose of this content:
The material on this page is intended solely for educational purposes to support revision for the MRCP (UK) Part 1 examination. It reflects examination-relevant principles of internal medicine and is designed to aid learning and pattern recognition.
Medical disclaimer:
This content is designed for postgraduate medical examination revision and does not constitute medical advice, diagnosis, or treatment guidance and must not be used as a substitute for professional clinical judgement, local guidelines, or specialist consultation. Clinical decisions should always be made in the context of individual patient circumstances and current national guidance.
