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The Stages of Sleeping

People need sleep as much as they need food or water, which is why sleep deprivation was considered an efficient means of torture used by the Russian KGB and the Japanese in World War II. Sleep is the period of time when the body gets a few hours to restore and repair the damage incurred during the day. A complete sleep cycle, which goes through five stages, takes about 100 minutes, and then the cycle begins again.

  1. Light Sleep Stages

    • The first sleep stage is that of transitioning to sleep, so the individual can easily be awakened. For about five minutes, the body relaxes and the eyes move slowly. In stage two, blood pressure slows down, body temperature decreases and eye movement stops. Adults spend almost half of their sleep time in the second stage. Light sleep takes 10 to 25 minutes, and then the body goes into the next stage, deep sleep.

    Deep Sleep Stages

    • Stages three and four are both deep sleep stages, but stage four is more intense than the previous one. Deep sleep is characterized by a drop in blood pressure and by blood flowing from the brain to the muscles, allowing them to relax and restore energy. The brain waves recorded during this stage are slow, and there is no eye movement or muscle activity. These two sleep stages are important in maintaining health, stimulating children's growth, repairing neurological and tissue damage and increasing the efficiency of the immune system.

    REM Sleep Stage

    • REM (rapid eye movement) sleep is the fifth stage. The first REM period usually starts about 90 minutes after a person falls asleep. Blood pressure and heart rate increase. The muscles are paralyzed and eyes move rapidly in all directions. Brain waves are similar to the ones that occur when the individual is awake. This is the stage when dreams occur, and if a person is awakened, he can remember his dream. While the REM stage accounts for 50 percent of infants' sleep, adults spend only about 20 percent in this stage, and the percentage decreases with age.

    Sleep Cycles

    • The five sleep stages have a cyclic succession following stage one, two, three and four and REM. The cycle repeats itself until the individual wakes up. A full sleep cycle takes from 90 to 110 minutes. The five stages differ in length one from another and from one cycle to another; for example, the REM stage is shorter during the first cycles of a night's sleep but lengthens as the night progresses.

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