What Do You Know About Sleep?
Sleep is as important as the food you eat and the air you breathe. Find out more about sleep by taking this quiz.
Each night when you sleep, you move through several stages. How long does a complete sleep cycle take to complete?
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You pass through five stages of sleep during one sleep cycle: 1, 2, 3, 4, and REM, which stands for rapid eye movement. One complete cycle takes 90 to 110 minutes. Stage 1 is the transition from wakefulness to deeper sleep. Stage 2 is intermediate sleep and accounts for 40 to 50 percent of adult sleep time. Stage 3 and 4 are deep sleep and account for approximately 20 percent of sleep time. Adults spend about 20 percent of their time in REM sleep, when dreams occur. (Infants spend about half their sleeping hours in REM sleep.) During REM cycles, the brain is as active as when you are awake. The length of REM periods varies with the time of night. The first REM sleep period usually occurs about 70 to 90 minutes after you fall asleep, according to the NINDS. The first sleep cycles of the night contain relatively short REM periods and long periods of deep sleep. As the night progresses, REM sleep periods become longer and the deep sleep periods decrease in length.
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