Sleep basics
On a good night, you might get into bed, fall fast asleep and, as far as you’re concerned, stay that way
until your morning alarm sounds, right?
But don’t be fooled – there’s much more going on in your brain throughout a sound night’s sleep than you might think. In fact, sleep is anything but ‘uniform ’.
The first thing to know is that sleep occurs in cycles and you experience four, five or six sleep cycles every night.
A single cycle contains four different sleep stages, and the length of each cycle, as well as how long you’ll spend in each sleep stage, tends to vary throughout the night.
Roughly speaking, each sleep cycle lasts between 70 and 120 minutes, and the first cycle of the night is usually the shortest .
Get to know the stages of sleep
There are four stages of sleep – three non-rapid eye movement (REM) stages and one REM stage. Typically, a sleep cycle begins with Stage 1 sleep and ends with Stage 4.
Stage 1
This is when you’re just dozing off. It usually only lasts for a few minutes and is a very light type of sleep that you can be easily woken from if things aren’t quiet or you’re disturbed.
While your body doesn’t fully relax during this stage, brain activities start to slow, often with periods of brief movements, which present as those ‘twitches’ you might experience sometimes as you’re falling asleep .
Stage 2
In this stage, your muscles relax, your breathing and heart rate slows and your temperature falls. Brain activity also slows. In the first sleep cycle of a night, Stage 2 lasts for 10-25 minutes, becoming gradually longer in each subsequent sleep cycle.
Over the course of a night, you’ll spend about 50 per cent of your sleep time in this stage .
Stage 3
Also known as slow-wave sleep, Stage 3 is the deep, restorative sleep that’s thought to be most essential for maintaining good health and for supporting brain-related tasks such as memory and creativity.
During your first few sleep cycles, stage 3 lasts for 20-40 minutes but then gets shorter and shorter in later sleep cycles .
Stage 4
Also called REM sleep, as the name suggests, it’s during this stage that your eyes move rapidly behind closed eyelids thanks to your brain’s activity picking up significantly.
A type of sleep that’s also important for cognitive functions like memory, learning and creativity, you’ll have your most vivid dreams during REM sleep, even though dreams can – and do – occur during any sleep stage.
Thankfully, another feature of REM sleep is that your arm and leg muscles become temporarily paralysed, which prevents you from acting out those vivid dreams.
In early sleep cycles, REM sleep usually only lasts for a few minutes, but in later cycles, it can last up to an hour. REM sleep makes up about 25 per cent of your total sleep time .
What sleep stage matters the most?
While every sleep stage is slightly different, they’re all important, not only because they act as transition phases from one stage to the next, but because they allow your brain and body to develop, repair and recuperate.
That said, it’s a lack of stage 3 and REM sleep that’s thought to trigger the impact that
not getting enough sleep can have on your health and wellbeing .
