A good night's sleep consists of five distinct and separate stages: Stages 1 through 4, then the REM stage. You move through these stages over and over again while you sleep in cycles that occur about five times a night. But the stages do not happen in chronological order, according to the website Healthcommunities. Stage 3 generally happens twice in each cycle because each time you hit stage 4, you go back to stage 3, then stage 2, before you finally reach the REM stage. Then the whole cycle begins all over again.
Definition
Stage 3 -- also called slow wave sleep or delta sleep -- is the first of two periods of deep sleep, stages 3 and 4. It is not quite as heavy as stage 4. Your brain activity occurs in high, slow waves during this time.
Duration
Moving through an entire sleep cycle usually takes about 90 minutes, according to Healthcommunities, with each stage using up between five and 15 minutes of the overall time frame. Your first cycle of the night is usually the shortest because in each subsequent cycle, REM sleep increases. But Stage 3 deep sleep shortens as the night goes on. You get your longest period of slow wave stage 3 sleep earlier in the night. Age decreases stage 3 sleep even in the first cycle, however, so the elderly tend to get less deep sleep. Overall, you will spend approximately 30 percent of each night in stage 3 sleep.
Characteristics
When you are in the five to 15 minute stage 3 segment of a sleep cycle, it is hard for you to wake up. If you do awake, you'll feel groggy and disoriented. The delta sleep of stages 3 and 4 is when you are most likely to walk or talk in your sleep, but you are not likely to dream. Children who are prone to wetting the bed or to night terrors will exhibit those behaviors during this time.
Importance
Deep sleep is restorative sleep. During this time period, your body repairs muscle and tissue damage and recharges your immune system. In children, growth is stimulated during stage 3 sleep.
Deprivation
If you are a healthy adult, you need between 7.5 and 9 hours of sleep a night, according to the National Institutes of Health. Of all the sleep you might lose, the deep sleep, stages 3 and 4 have the most negative impact on your health. The National Institute of Neurological Disorders and Stroke suggests that adenosine, a chemical in the body, accumulates in the blood during waking hours. When there is enough of it, your body begins craving sleep. While you sleep, adenosine depletes again. If you are not sleeping enough, high quantities will remain in your blood, making you feel constantly drowsy.
Tip
If you are in the stage 3 time frame when your alarm goes off in the morning, you are going to find it hard to rouse and get out of bed. HelpGuide suggests setting your alarm for a time that is a multiple of 90 minute cycles, which is average for most people. This increases the likelihood that you will wake at the end of a sleep cycle, not in stage 3. Ideally, you should set your wake-up call for 7.5 hours after you go to sleep, because six hours will probably not be enough.
