Sleep cycle refers to the cycles of sleep that we go through each night. If you would like to learn how to sleep well, then it’s a good idea to have a basic understanding of what a sleep cycle is.
I found a useful resource from the National Sleep Foundation in its publication called “Sleep-Wake Cycle: It’s Physiology and Impact on Health”.
The National Sleep Foundation states that:
“A complete sleep cycle consists of NREM and REM cycles that alternate every 90 to 110 minutes and is repeated four to six times per night.” (National Sleep Foundation (2006): Sleep Wake Cycle page 6)
NREM stands for non rapid eye moment sleep and REM stands for rapid eye moment sleep.
For each sleep cycle that you go through, you will cycle through multiple stages of sleep and alternate between the different stages. There are essentially 5 stages of sleep consisting of both REM and non REM sleep.
Stage 1 sleep is characterized by drowsiness, Stage 2 is the light sleep stage, Stages 3 and 4 is the deep sleep stage and Stage 5 is the dream sleep stage.
Stage 5 sleep is also known as REM sleep which is characterized by rapid eye movement. Stage 1 to 4 sleep refers to non REM sleep or NREM sleep which refers to stages of non rapid eye moment sleep.
It’s funny how some mornings you can experience that feeling of being very groggy whereas on other mornings you can get up and feel awake straight away.
If you have woken up during a sleep cycle like Stage 3 or 4 which is the deep sleep stage, then it is likely that you will be feeling more groggy.
How you feel when you wake up will be dependent on factors such as how many sleep cycles you have completed during the night and at what stage of your sleep cycle you have woken up.
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