Why do people need to sleep?
Understanding the prominent role of sleep in life and learning exactly why people need sleep are topics of much debate and speculation among sleep scientists. Recent animal studies have suggested that sleep is necessary for survival. For example, while rats normally live for two to three years, those deprived of REM sleep survive only about 5 weeks on average, and rats deprived of all sleep stages live only about 3 weeks. Sleep-deprived rats also develop abnormally low body temperatures and sores on their tail and paws. The sores may develop because the rats’ immune systems become impaired. Some studies suggest that sleep deprivation affects the immune system in detrimental ways.
The desire for sleep is strong. People may be able to deny themselves food or water for a few days, but they cannot go without sleep. Research has shown that severely sleep-deprived people become very uncomfortable and anxious and may even start to hallucinate*. This explains why prisoners-of-war sometimes are forced by their captors to stay awake for long periods of time: the captors know that prisoners are likely to become so desperate for sleep that they will eventually break down and share important information. Researchers have not been able to precisely explain the function that sleep serves. At one time it was thought that sleep provided a time for the brain to rest, but studies have shown that the brain’s neurons, or nerve cells, are just as active during sleep as when a person is awake. Some neurons are even more active during sleep. Another theory about the function of sleep is that sleep is essential for the proper storage of long-term memories by the brain.
People from every part of the world, hippos in the jungle, fish in aquariums – they all sleep! Sleep is as important as breathing or eating. In fact, people can survive longer without food than they can without sleep. Sleep is vital for giving your body a rest and allowing it to prepare for the next day. It’s like giving your body a mini-vacation. Sleep also gives your brain a chance to sort things out. Scientists aren’t exactly sure what kinds of organizing your brain does while you sleep, but they think that sleep may be the time when the brain sorts and stores information, replaces chemicals, and solves problems. The amount of sleep a person needs depends a lot on his age. Babies sleep a whole lot – about 16 or 17 hours a day! But many older people only need about six or seven hours of sleep a night. Most kids between the ages of five and 12 are somewhere in between – they sleep eight to ten hours a night.
Sleep may be a way of recharging the brain. The brain has a chance to shut down and repair neurons and to exercise important neuronal 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 problem, 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. When a person falls asleep and wakes up is largely determined by his or her circadian rhythm, a day-night cycle of about 24 hours.
