Sleep

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What is sleep?

There are over 20 definitions of "sleep" in several dictionaries. The first, a verb, seems most appropriate: "to take the rest afforded by a suspension of voluntary bodily functions and the natural suspension, complete or partial, of consciousness; cease being awake."

Physiologically, sleep is a complex process of restoration and renewal for the body. Scientists still do not have a definitive explanation for why humans have a need for sleep. We do know that sleep is not a passive process or "switching off" of body functions; sleep is believed to be important in many physiologic processes including the processing of experiences and the consolidation of memories. It is also clear that sleep is essential, not only for humans but for almost all animals.

The importance of sleep is underscored by the symptoms experienced by those suffering from sleep problems. People suffering from sleep disorders do not get adequate or restorative sleep, and sleep deprivation is associated with a number of both physical and emotional disturbances. In addition, sleep is influenced by the circadian rhythms (regular body changes in mental and physical characteristics that occur in the course of about 24 hours). These are controlled by brain neurons that respond to light, temperature and hormones and other signals and comprise the body's biological clock. This clock helps regulate the "normal" awake and sleep cycles. Disruption of these cycles can make people sleepy, or somnolent, at times people want to be awake. For example, travelers experience "jet lag" when they cross time zones. When a New Yorker arrives in Paris at midnight Paris time, his or her body continues to operate (their biological clock) on New York time. It may take some time (about 1-3 days) to reset a person's biologic clock, depending on how much it has been altered by the time change. Different organ systems in the body recover at different rates.

There is evidence that some aspects of sleep are under genetic influence; a gene termed DEC2 is being investigated as causing people that possess it to require only about 6 hours of sleep. Researchers have only begun to examine the genetics involved in sleep.

Medically Reviewed by a Doctor on 1/6/2014

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Sleep - Problems Experienced Question: What sleep problems have you experienced?
Sleep - Treatment Question: Please discuss any treatments you have tried for your sleep problems.
Sleep - Deprivation Symptoms Question: Besides lack of sleep, what other symptoms have you experienced with sleep deprivation?
Are you sleep deprived?

Are You Sleep Deprived?

Medical Author: Melissa Conrad Stöppler, MD
Medical Editor: Jay W. Marks, MD

No matter how much sleep you need, if you don't get enough, you will suffer the effects of sleep deprivation. Research has shown that in tests of driving ability and hand-eye coordination, people deprived of sleep perform as badly as, or even worse than, people who are intoxicated. It's no wonder that drowsiness is a major cause of traffic accidents and deaths.

Individuals vary in their need for sleep. Some people require nine or more hours of sleep per night, while others may not feel deprived after just five hours of sleep. But the average adult requires seven to eight hours of sleep per night.

Are you getting enough sleep? Ask yourself the following questions:

  1. Do you often feel drowsy during the day?
  2. Do you usually fall asleep within the first five minutes after lying down in bed?


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