Understanding Sleep Cycles

Understanding sleep cycles can be the key to getting sleep that is restorative. Knowing how your body functions while you are asleep and the important roles that different stages of sleep play during the night, can help you maintain a sleep schedule that is the most beneficial to your daytime health.

Understanding Sleep Cycles

Two Types of Sleep

There are two types of sleep according to Harvard Health Publications, Non-REM sleep (NREM) and REM sleep. REM stands for rapid eye movement, and is well known as the dreaming portion of sleep. NREM is separated into three stages N1 or drowsiness, N2 or light sleep, and N3 or deep sleep. The body moves in and out of these stages throughout the night, each stage varying in length as the night progresses.



N1 and N2 are the stages that transition the body into sleeping. During this time your brain waves begin to slow down and you begin to sleep, but you are still easily woken. It is during these stages of sleep that noise, or changes in the environment can waken you out of sleep.

N3 or deep sleep is when your brain slows down and your body restores physical energy. Helpguide.org suggests that deep sleep is essential for “stimulating growth and development, repairing muscles and tissues, and boosting your immune system.” Deep sleep is needed in order to feel physically well during the day. Harvard Health Publications state that young adults spend about 20% of their sleep in deep sleep, but this amount decreases significantly as a person ages. Deep sleep occurs in approximately half hour segments and happens more often during the beginning of the night.


During REM sleep the brain becomes very active. This is when you dream.  This is also when your brain is restored so that you are able to fully function mentally. Scientist are beginning to find that REM sleep plays significant roles in memory and learning as well as restoring mood enhancing hormones. To feel mentally aware during the day it is important to get enough REM sleep. Harvard Health Publications points out that REM stages become longer and more frequent towards the morning.

Plan For a Gentle Wake Up

One tip Helpguide.org gives for feeling better in the morning is to time your sleep in cycles of 90 minutes. You may be waking up feeling groggy if your alarm goes off during deep sleep. Depending on when you go to sleep, waking up a half an hour earlier may be more beneficial than sleeping more and waking during a deep sleep stage.

Because these sleep stages take place at different times and varying lengths throughout the night it is important to get a full night of sleep. For most adults, this is at least 7.5 hours for many adults it is more. In order to feel both mentally and physically restored and able to function optimally during the day, the body needs sufficient amounts of all cycles of sleep.


Photo “Alarm Clock 1” courtesy of Alan Cleaver


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