What are sleep stages and why are they important?
Many of us already know about the importance of sleep, but do you know about the four stages of sleep and the role each plays?
The recommended amount of sleep for the average adult is between seven and nine hours of high-quality, uninterrupted sleep. Achieving this target enables your body and brain to fully recover and re-energize. During sleep, your body repairs muscle or tissue damage, your cells grow and divide, and your brain processes information that it has received that day.
There are different stages of sleep, and you go through each one of these stages between four and six times each night (as long as you are sleeping without interruptions). Each stage is essential for a healthy and restorative night of sleep.
Sleep stages and their importance
There are four main stages of sleep, each one lasting a different length of time and being associated with unique brain wave patterns.
Stage 1 - non-REM N1, lasting 1 to 5 minutes
Stage 2 - non-REM N2, lasting 10 to 60 minutes
Stage 3 - non-REM N3, lasting 20 to 40 minutes
Stage 4 - REM sleep, lasting 10 to 60 minutes
Stage 1 - Non-REM N1
Non-REM N1 is the stage that occurs when you first fall asleep and lasts about 1- 5 minutes. The body isn't completely relaxed at this stage and the brain activity hasn't fully slowed down yet. It's easy to wake up during this stage of sleep.
Stage 2 - Non-REM N2
During the second stage of sleep, your body starts to relax a little more. Your breathing and heart rate slow down, and your body temperature drops slightly. Your brain waves are also starting to change, and your eye movement stops. This stage may only last 10 minutes at the start of the night but lasts longer during subsequent sleep cycles in the same night.
Stage 3 - Non-REM N3
N3 is also known as deep sleep. During this stage of the sleep cycle, your muscles are fully relaxed, and your breathing rate and heart rate are at their lowest. Your brain activity has a characteristic display of delta waves, and it's difficult to wake up when you're in this stage of the sleep cycle. It's thought that the deep sleep that you experience in N3 is essential for recovery and growth.
Stage 4 - REM sleep
REM stands for Rapid Eye Movement. It refers to the stage of sleep in which your brain activity ramps up, and on a functional MRI (fMRI) scan, brain waves resemble the activity of your brain when you're awake.
This stage of your sleep is essential for processing emotions and memories. It is also the stage of sleep in which you experience the most vivid dreams, which may contribute to creativity and problem solving. The length of time that you're in REM sleep increases during the course of the night as you go through each stage of the sleep cycle again and again.