Scientists have not determined exactly why people need sleep, but they know that we must sleep and that people can survive longer without food than without sleep. People are not alone in the need for sleep. All mammals, reptiles and birds sleep.
Scientists have proposed the following theories on why we require sleep:
- Sleep may be a way of recharging the brain. The brain has a chance to shut down and repair neurons and to exercise important neural connections that might otherwise deteriorate due to lack of activity.
- Sleep gives the brain an opportunity to reorganize data to help find a solution to problems, process newly learned information and organize and archive memories.
- Sleep lowers a person’s metabolic rate and energy consumption.
- The cardiovascular system also gets a break during sleep. Researchers have found that people with normal or high blood pressure experience a 20 to 30% reduction in blood pressure and 10 to 20% reduction in heart rate.
- During sleep, the body has a chance to replace chemicals and repair muscles, other tissues and aging or dead cells.
- In children and young adults, growth hormones are released during deep sleep.
The discovery of rapid eye movement, or REM, sleep in 1953 awakened scientists to the realization that sleep was not “a simple turning off of the brain,” but an active, organized physiological process, said Dr. Jerome Siegel, a professor of psychiatry and bio-behavioral sciences at the University of California at Los Angeles. Five decades later, few researchers would dispute that sleep serves some critical — if unknown — biological purpose.
The most promising theory so far, some experts believe, proposes that REM sleep plays a role in brain development. Newborns spend more time in REM than adults. Animals that spend long periods in REM are also more immature at birth. In the meantime, the search continues. The answer, experts say, may turn out to be something obvious or something not yet dreamed of.
