Sleep revision

Sleep

A dynamic and actively produced brain state, it is not passive or static because we don’t turn off during sleep, some brain regions are more active during sleep than wake, though some are lower

4 stages of sleep

• NREM stage 1

• NREM stage 2

• NREM stage 3

• REM sleep

NREM stage 1

Transition period between wakefulness and sleep, 5-10 mins

NREM stage 2

Intermediate sleep, body temperature drops and heart rate slows, brain begins to produce sleep spindles, lasts 20 mins

NREM stage 3

Deep restorative sleep, muscles relax, blood pressure and breathing rates drops and the deepest sleep occurs

REM sleep

Brain becomes more active and body becomes relaxed and immobilised, dreams occur, eyes move rapidly, associated with offline reprocessing of memories and learning

Sleep wearables

• Sleep headband

• Wrist-worn trackers

Sleep headband

Seven sensors measure brain activity (EEG), heart rate, respiration and movement

Wrist-worn trackers

Records movements and sleep algorithms estimate sleep parametres

Circadian rhythms

Our bodies synchronise with the light/dark cycle and allows us to anticipate when it is day and night and thus the right time to do things (like sleep), follows a near 24hr clock

Disrupted circadian clock associated with

• Depression

• Insomnia

• Deficits in mood and vigilance

• Reduced frontal brain activity

What disturbs circadian clock

• Environment - light at light, decreased daylight exposure

• Behavioural - shift work, late eating

• Physiological - neurodegenerative diseases, low melatonin

• Genetic factors - polymorphisms in clock genes

Sleep in autism

Autistic people experience more sleep difficulties

• 5 fold more insomnia than general population

• More night terrors and nightmares

• They might have a melatonin disruption, but unknown why

McLean et al. (2021)

Autistic adults had poorer sleep quality, higher perceived stress nad lower QoL

Sleep in ADHD

• 60-70% report sleep problems/insomnia

• 1/3 have a circadian rhythm problem

• Twice as likely to have narcolepsy

Nair et al. (2025)

Higher ADHD traits associated with higher insomnia symptom severity and lower sleep quality

Insomnia

Persistent difficulty falling asleep, staying asleep, or waking up too early, leading to poor sleep quality, daytime tiredness and impaired functioning

Night terrors

Awaking from sleep in a terrified state, person appears confused but unable to communicate, they are difficult to wake up and usually forget what’s happened the day after

Narcolepsy

A chronic, hereditary autoimmune disorder characterised by excessive daytime sleepiness and sleep attacks

Sleep spindles

Brief, rapid bursts of brainwave activity that are crucial for memory and learning

Melatonin

Hormone that regulates the circadian rhythm by releasing in darkness and falling in daylight