The fact that we sleep approximately one third of our life may seem a waste of time, but sleep is a condition of survival. It is also a period of intense activity, full of bizarre and dramatic events. Sleep is as essential to us as air, food and water because it refreshes the body and prevents exhaustion. According to William Dement, one of the founders of modern sleep medicine, author of article "Sleep Debt and the Mortgaged Mind", "the feeling of being tired and needing sleep is a basic drive of nature, like hunger" we are driven to sleep and if we go long enough without rest, we can think of nothing else (539).
Although the importance of sleep is often discussed, scientists still do not know exactly why it is so important for our survival. Human beings, plants, and animals, we all have a biological clock that tells us when to eat, drink, sleep or wake up. In our century, everything is going with an amazing speed and students are struggling to cope with this speed and sleep is often neglected because of the busy daily schedules, which include working, studying, and socializing.
The amount of sleep we need each day varies through life. An infant sleeps in rounds of one or two hours, and then wakes up hungry and restless. Overall he sleeps about 16 hours a day. As the baby grows, he will sleep longer periods at night and less during the day. At the age of three or four, most children sleep at least 12 uninterrupted hours per night, and most of them take an afternoon nap. A teenager normally sleeps ten hours a night and an adult sleeps around eight hours a night. The amount of sleep a person needs depends on many factors, such as, the activity, the workload and stress during the day, and habits acquired over the life.