The Stages of Sleep

There are four phases of sleep: stages 1, 2, 3, and REM (rapid eye movement). Usually when you are sleeping, you begin at stage 1 and go through each stage until reaching REM sleep, and then you begin the cycle again. Each complete sleep cycle takes from 90 to 110 minutes. Your brain acts differently in each stage of sleep. In some of the stages, your body may make movements, but in others your arms and legs will stay immobile. Having good sleep habits will make sure you get each type of sleep you need.

Stage 1

Stage 1 sleep is light sleep. You experience a drifting in and out of sleep. You can be easily woken up. Your eye movement and body movements slow down. You may experience sudden, jerking movements of your legs or other muscles. These are known as hypnic myoclonia or myoclonic jerks. These “sleep starts” can give a sensation of falling. They are caused by the motor areas of the brain being spontaneously stimulated.

Stage 2

Between 45 and 55 percent of your time sleeping is spent in stage 2 sleep. During this stage, eye movement stops, and your brain waves (a measure of the activity level of the brain) become slower. There will also be brief bursts of rapid brain activity called sleep spindles.

Stage 3

Stage 3 is known as deep sleep. During stage 3 sleep, it can be very difficult to wake someone up. In this stage, the brain is making slow delta waves almost exclusively. This stage is important for feeling refreshed in the morning. If this stage is too short, sleep will not feel satisfying.

REM Sleep – Rapid Eye Movement

During REM sleep, your brain activity increases and your breathing also becomes fast, irregular, and shallow. Your eyes will move rapidly, and your muscles become immobile. Heart rate and blood pressure increase. Men may develop erections. About 20 percent of sleep is REM sleep for adults.

While we dream in all stages of sleep, it is more common and intense during REM sleep. You are also more likely to recall REM dreams than dreams in any other stage of sleep.

This sleep phase begins about 70 to 100 minutes after you fall asleep. The first sleep cycle has a shorter phase of REM sleep. Toward morning, the time spent in REM sleep increases, while deep sleep stages decrease.

Researchers do not fully understand REM sleep and dreaming. They know, however, that they are important in the creation of long-term memories. If a person’s REM sleep is disrupted, the next sleep cycle does not follow the normal order, but often goes directly to REM sleep until the previous night’s lost REM time is made up.