Sleep disturbance and REM Sleep Behaviour Disorder

Why sleep changes in dementia

Sleep is regulated by brain networks that are particularly vulnerable in dementia: the suprachiasmatic nucleus (the body clock), the brainstem nuclei that control rapid eye movement (REM) sleep, and the prefrontal cortex that maintains daytime alertness. As these networks degenerate, sleep becomes fragmented, less restorative, and more easily disrupted by environmental factors.

Untreated sleep disturbance worsens cognition, mood, agitation and falls risk. Treating it well is one of the more impactful supportive measures available.

The common sleep problems

Insomnia

Difficulty falling asleep, frequent waking, or early waking. Common in mild and moderate dementia. Multiple contributors usually coexist: anxiety, low daytime activity, daytime napping, alcohol, medications, pain, urinary frequency, and a noisy or bright sleep environment.

Day-night reversal

Sleeping for long periods in the day and being awake at night. More common in moderate dementia and in care home settings where daytime stimulation is reduced. Restoring daytime light, structure and activity is the most effective single intervention.

Sundowning

Late-afternoon restlessness, anxiety, confusion or agitation, peaking around 4 to 7 pm. Affects up to 20 per cent of people with dementia at some stage. Triggers include fatigue, dim light, hunger, unmet needs, and the transition from busy daytime to quieter evening.

REM Sleep Behaviour Disorder

Acting out dreams: shouting, calling out, fighting movements, jumping out of bed. Normally, REM sleep paralyses skeletal muscle to prevent dream enactment; in REM Sleep Behaviour Disorder this paralysis fails. The disorder may pre-date cognitive symptoms by many years and is highly specific to Dementia with Lewy Bodies and the broader alpha-synuclein spectrum (Parkinson's Disease, multiple system atrophy).

Sleep Apnoea

Obstructive Sleep Apnoea is common in older adults and an independent risk factor for cognitive decline. It is often missed because daytime symptoms (sleepiness, morning headache, low mood) are attributed to dementia or ageing. Snoring, witnessed apnoeas, and daytime sleepiness should prompt a sleep study referral.

How sleep is assessed

A simple sleep diary kept for two weeks is the most useful starting point. Note time to bed, time to sleep, awakenings, time of waking, daytime naps, and any unusual events. The Epworth Sleepiness Scale screens for daytime sleepiness suggestive of Sleep Apnoea. Where REM Sleep Behaviour Disorder is suspected, formal polysomnography in a sleep laboratory confirms the diagnosis.

What helps: sleep hygiene

Most sleep disturbance responds to consistent non-pharmacological measures over 4 to 8 weeks. Together these constitute "sleep hygiene":

• Wake at the same time every day, including weekends;
• Get bright light exposure in the morning, ideally outdoors;
• Limit daytime naps to under 30 minutes, and not after 3 pm;
• Stay physically active during the day;
• Avoid caffeine after midday and limit alcohol;
• Eat dinner two to three hours before bed;
• Dim lights in the evening; avoid bright screens in the hour before sleep;
• Keep the bedroom cool, dark and quiet;
• Use the bedroom for sleep only (and intimacy), not for television or work.

For sundowning specifically, schedule the most demanding activities earlier in the day, increase light in the late afternoon, offer a small snack and a calming activity (music, gentle walk) at the typical sundown time.

Medication

NICE NG97 recommends a non-pharmacological approach first. Where medication is needed:

Melatonin

Prolonged-release Melatonin (2 mg in the evening) is licensed in the UK for primary insomnia in adults aged 55 and over. Higher doses (3 to 6 mg) are widely used in REM Sleep Behaviour Disorder under specialist supervision. Melatonin is well tolerated and has few interactions.

Trazodone

Low-dose Trazodone (25 to 100 mg at night) is widely used for insomnia in dementia. Evidence is modest but real-world use is common. Hypotension and morning drowsiness are the main concerns.

Mirtazapine

Mirtazapine 15 mg at night can be useful where depression, anxiety, weight loss and insomnia coexist.

What to avoid

• Benzodiazepines (Diazepam, Lorazepam, Temazepam) routinely; they worsen confusion, falls and cognition;
• Zopiclone and Zolpidem ("Z-drugs") routinely, for the same reasons;
• Sedating antihistamines (Promethazine, Diphenhydramine), which have an anticholinergic burden that worsens cognition.

REM Sleep Behaviour Disorder specifically

Treatment is supportive of safety (padded bedrails, partner in a separate bed if injuries occur), with Melatonin first-line and low-dose Clonazepam (0.5 mg at night) as a second-line specialist option. Where REM Sleep Behaviour Disorder is confirmed, a discussion about Dementia with Lewy Bodies and Parkinson's Disease risk is appropriate.

When to seek help

Three thresholds prompt clinical review:

• Persistent insomnia, day-night reversal or sundowning despite four to eight weeks of non-pharmacological measures;
• Snoring, witnessed apnoeas or excessive daytime sleepiness (consider Obstructive Sleep Apnoea);
• Dream enactment or unusual nocturnal movements (consider REM Sleep Behaviour Disorder).

For private review of sleep disturbance in dementia, The Dementia Service can include this in the structured assessment letter and signpost to onward sleep medicine where indicated.