Why is sleep important? That is still a subject of relatively intense research, but it is clear, from observational studies, that to humans and other mammals, as well as some species of fish, birds and even ants and fruit flies, sleeping is essential for survival.
Only in laboratory animals has sleep deprivation caused death. In the real world, it is impossible to stay awake for long periods of time because the brain will slip into a micro-sleep state regardless of what activity the person is performing.
The importance of sleep to the human body is indicated by the effects of chronic sleep deprivation. People can survive on just a few hours a night, as is the case with many insomniacs, but it causes or is associated with an assortment of health problems.
A 2005 study showed that people who slept only a few hours per night were more likely to suffer from type II diabetes.1 A later study indicated that insomniacs are more likely to be obese. This may have to do with the fact that experimental deprivation impairs the cells ability to absorb glucose.
Several studies indicate that not sleeping interferes with the brain’s ability to learn and store memories. There is some debate among scientists as to whether memory storage is one of the primary functions of sleep in humans, but to date, there is more evidence supporting the idea than contradicting it.
Animal studies have shown that sleep deprivation results in brain damage. This may be because of several things that occur while sleeping. During REM (rapid eye movement or the dream state), the body turns off neurotransmitters and allows the receptors to rest, regaining sensitivity. Neurotransmitters are involved in learning, mood, appetite, sensation and practically everything that the human body does.
During the non-REM phase, the body allows enzymes such as calpain to repair damage done to the cells by free radicals and to forge new pathways, which are involved in memory. So, the answer to "why is sleep important", has a lot to do with brain maintenance and repair.
When a person suffers from insomnia, their bodies produce more stress hormones and fewer growth hormones. Basically, this leads to cellular aging, as growth hormones are necessary for the replacement of cells, collagen fibers, bone, muscle, hair, skin, etc. It is believed that infants sleep more because their bodies are in a state of constant growth.
In order to get to sleep your body produces melatonin. Melatonin is the hormone that makes you feel tired at night and is produced when it becomes dark. That's why it is important to keep your bedroom dark for the best sleep.
Several animal studies concerning the importance of sleep showed that wound healing slows during sleep deprivation. This may have to do with the body's immune system function. When we are ill, we fall asleep more easily, particularly during the healing and recovery process. Sleep-deprived laboratory animals have significantly fewer white blood cells in circulation. White blood cells are essential for healing.
There is an obvious effect on a person’s ability to pay attention, operate a motor vehicle or participate in physical activities. Anyone that has ever suffered a night of not sleeping has noticed those things. Driver fatigue has been cited as the cause of one out of five serious motor vehicle injuries. Somewhere between 100,000 and 250,000 accidents per year in the US are related to driver fatigue, depending on what organization gathers the figures.
The importance of sleep in terms of the number of hours needed has to do with the animal’s natural metabolism. Rats, for example, need more hours, as many as 14 per day, because they have faster metabolisms. Elephants and giraffes, on the other hand, can get by on 3 or 4 hours, because they have slower metabolisms. This may be the reason that people who sleep less are more likely to be obese. It may indicate that they have slower metabolisms.
Why is sleep important? Without it, we simply cannot function normally.