Normal Sleep Physiology

•    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.

Insomnia

•    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).

Narcolepsy

•    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.

Sleep Apnoea

•    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.

Parasomnias

•    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.