Understanding Sleep Cycles | Sleep Science



As we fall asleep each night our brain is still very active and goes through various patterns of activity. Whilst sleeping we enter Five different stages of sleep called sleep cycles. Each stage has its own purpose, and we cycle through these different stages multiple times a night.

Stage 1

Stage one is a very Light sleep, this stage only last a few minutes. Here we begin drifting in and out of sleep your eye movement slows down. Your brain then begins producing Alpha and Theta waves, this lasts for around Seven minutes. In this light stage of sleep you can easily be awoken from your sleep by ongoing disturbances around you.

Stage 2

Stage Two is also a state of light sleep. As your body gets ready to drop into the next stage of deep sleep your heart rate slows and your blood pressure drops. Here your brain wave frequency creates what is known as spindles this signals you’re about to drop into the next stage of sleep.

Light sleep

Though stages 1-2 are light sleep stages this doesn’t mean they aren’t important to our health. In fact, these light stages of sleep can take up over half of our time spent asleep every night. This time spent in Light sleep is when our body processes things like memories and emotions. During this stage your metabolism begins working hard, balancing out hormones like Gherlin and Leptin (which control when you feel hungry or full) .With out light sleep you can produce too much of the hormone which makes you feel hungry leading to overeating. The Light stage of sleep proves very important to both mental and physical restoration of the body.

Stage 3

Stage Three is the very beginning of your deep sleep. Your brain starts pumping more Delta waves sending you deeper into your sleep. You will no longer experience muscle or eye movement in this stage of sleep.

Stage 4

Stage Four you are now fully submerged into a deep sleep. All eye and muscles activity has fully stopped. In this stage it will become a lot harder to be awoken from surrounding activity or noises. The delta waves produced from your brain push you further into your deep sleep making being awoken much more difficult and preparing you for your next stage of sleep.

Deep sleep

Stages 3-4 are when deep sleep sets in, during this time our body goes through a lot of repair and rebuilding. Growth hormones are released and our body begins repairing and building muscle tissue. Your immune system is also strengthened during this time helping us keep healthy and fight any infections. Deep sleep is also the stage that will leave you feeling refreshed building up energy ready for the next day.


REM is the final sleep stage, REM Stands for Rapid Eye Movement, it has this name as our eyes begin darting around quickly in different directions when we enter REM sleep. This stage of sleep our brain is very active and we begin to dream. Our heart rate and blood pressure all increase in this stage and our breathing becomes quick, shallow and slightly irregular. An average adult can experience REM around Five to Six times a night. REM sleep tends to start out lasting around only ten minutes, and becomes longer and longer every time you enter a new cycle. Towards the end of your sleep you can experience REM sleep for up to an hour.


This REM stage of sleep is incredibly important, our brains begin processing things we have learnt throughout the day. This REM sleep helps improve memory function, and transforms things we have learnt into our long term memory. This stage of sleep is very active for the brain more so than the previous stages of sleep.



Hope to see you next time with another episode of sleep science….

Catch up on our previous sleep science article here.