In brief
Each night you cycle several times through non-REM sleep, from light to deep, and REM sleep. Deep sleep comes mostly early in the night and REM sleep later.
- Most adults need 7 to 9 hours of sleep a night, according to healthdirect and the Sleep Health Foundation.
- Caffeine counteracts sleepiness by blocking the actions of adenosine.
- Alcohol can disrupt your sleep cycles, leading to poorer quality sleep.
How it works
Stage 1 non-REM sleep is the changeover from being awake to sleep, stage 2 is light sleep, and stage 3 is the deep sleep you need to feel refreshed in the morning. REM sleep, when your eyes move rapidly and most dreaming happens, first occurs about 90 minutes after falling asleep.
Deep sleep comes in longer periods during the first half of the night, and REM periods grow longer later on. Memory consolidation most likely needs both non-REM and REM sleep, and sleep may also help remove toxins that build up in the brain while you are awake.
Connections
4 connections on the map. Select a topic to read its page.
Sleep stages can be worsened by
Breathing pauses in sleep apnoea are followed by brief wake-ups, which can happen many times a night.
Alcohol can disrupt your sleep cycles, leading to poorer quality sleep.
Source: healthdirect Australia, Sleep
Sleep stages is controlled by
Your body clock helps control when you feel sleepy and when you are typically awake.
Sources: healthdirect Australia, Sleep; National Institute of General Medical Sciences (NIH), Circadian rhythms
Sleep stages is supported by
Melatonin helps get your body ready for sleep, and its levels rise about two hours before sleep.
Sources
Each connection above names its own source. See every source AskBioMap uses.
Summarised from the NIH, healthdirect and the Sleep Health Foundation. Sources read on 13 and 16 October 2026. General education only, not medical advice. Spotted a mistake? Please tell us through the HuBu-Intel contact page.