Sleep Patterns
While we sleep, our bodies slow down. Our heart rate drops, our body temperature falls, and our brain activity changes. This is what allows us to move through different stages of sleep. These stages happen in a repeating pattern, known as sleep cycles.
We usually get our deepest sleep earlier in the night, with lighter sleep happening more towards the morning.
Scientists can study sleep using a test called an EEG (electroencephalogram), which measures the brain’s electrical activity while we sleep. This helps us understand what’s happening in the brain at each stage.
When we first fall asleep, we enter Non‑Rapid Eye Movement (NREM) sleep. This type of sleep has three stages, each one deeper than the last.
NREM sleep stages
NREM1
(3-5% of sleep)
A very light stage of sleep from which we can be easily roused. During this stage you may experience twitching or jerks.
NREM2
(45-50% of sleep)
Still quite a light sleep but your body is preparing for the deep sleep that is about to come. Breathing and heart rate slow down.
NREM3
(20-25% of sleep)
Deep stage of sleep also called slow wave sleep.This is the hardest stage to wake from, and you may feel confused if disturbed. It’s also the most restorative part of sleep, helping the body repair and recover.
After these stages, we move into Rapid Eye Movement (REM) sleep. This is when most dreaming happens. During REM sleep, brain activity becomes more active again, similar to being awake. This stage is especially important for learning, memory, and emotional health.
A full sleep cycle lasts about 90 minutes. To wake up feeling refreshed, we need to move through all stages of sleep. A good night’s sleep usually includes four to five full cycles.
When sleep is broken or disturbed, we may go through fewer cycles. This means we miss out on the deeper, more restorative stages — which can leave us feeling tired, foggy and unrefreshed the next day.
Good quality sleep isn’t just about hours in bed — it’s about letting your body move naturally through each stage of sleep.