REM Sleep Behavior Disorder

REM sleep behaviour disorder (RBD) is loss of normal REM muscle atonia, allowing dream enactment with vocalisations or violent movements, confirmed by REM sleep without atonia on polysomnography.

• Prevalence 0.5 to 1% of older adults; men over 50 predominate.
• Idiopathic RBD (isolated) converts to alpha synucleinopathy (Parkinson disease, dementia with Lewy bodies, multiple system atrophy) in over 70 to 80% over 10 to 15 years.
• Secondary: antidepressants (SSRIs, SNRIs, TCAs), narcolepsy, brainstem lesions, autoimmune disease.
• Injuries to patient and bed partner are common.

• Shouting, punching, kicking, falling out of bed during sleep, usually in last third of night, with recall of action filled dreams when awakened; patients rouse easily and are alert.
• Prodromal: constipation, hyposmia, orthostatic hypotension, colour vision loss, mild cognitive or motor changes.
• Bruising, lacerations, subdural haematoma.

• Video polysomnography showing REM sleep without atonia (required) with dream enactment.
• Screening: REM Sleep Behaviour Disorder Screening Questionnaire, Mayo Sleep Questionnaire.
• Exclude sleepwalking, nightmare disorder, obstructive sleep apnoea (pseudo RBD), nocturnal seizures, PTSD, medication effects.
• Neurological examination, olfactory testing, autonomic evaluation; MRI brain; DaTscan for biomarker.
• Counsel on neurodegeneration risk and clinical trials.

• Safety first: remove sharp objects, pad bed or place mattress on floor, separate partner, bed alarm.
• Clonazepam 0.25 to 2 mg at night (effective in 80 to 90%; caution with falls, cognitive impairment, sleep apnoea, in older patients).
• Melatonin 3 to 12 mg at night (safer, particularly in older adults and dementia), as first line or add on.
• Alternatives: pramipexole 0.125 to 0.5 mg, rivastigmine 4.6 to 9.5 mg patch in mild cognitive impairment, sodium oxybate in some.
• Review and switch causative antidepressants (bupropion has lower risk), treat sleep apnoea.
• Neurological follow up every 6 to 12 months for early parkinsonism or cognitive decline.