Sleep is one of nature`s greatest inventions and blessings of life. It is a periodic rest of the body, which is absolutely essential for its efficient functioning. It has been called "most cheering restorative of tired bodies," since sleep repairs the wear and tear of the body and mind incurred during waking hours. Sleep is thus a vital element in man`s mental as well as physical life, since the loss of sleep exerts seriously detrimental effects upon the nervous system. Long periods of wakefulness may cause profound psychological changes such as loss of memory, irritability, hallucination and even schizophrenic manifestations.

For correct living, however, it is essential to differentiate between sleep and rest. At rest the body is disturbed by all exterior noises; but in sleep it is screened from them by partial loss of consciousness. During rest the limbs are normal, but in sleep they swell. Blood flows from the brain, distends the arteries, and makes the limbs bigger. In sleep more muscles are relaxed than in rest, though without knowing the sleeping person changes his position about 35 times in one night. Many organs, which work during rest, suspend their activities in sleep. Thus, the recouping value of sleep is much more than that of rest or simple lying down.

Many theories of sleep have been advanced to explain the temporary loss of consciousness, which we know as sleep. Although the various theories have certain amounts of experimental evidence to support them, none has really solved what is the most mysterious process in our lives. All we know is that sleep substitutes constructive measures for the destructive processes of our waking hours and that we cannot live without sleep. The average amount of sleep needed to feel well rested is seven-and-a-half hours, though individuals vary from six to nine hours. On the whole, women sleep from 45 minutes to one hour more than men. The amount of sleep required varies at different ages as follows:
New born: 18 to 20 hours
Growing children: 10 to 12 hours
Adults: 6 to 9 hours
Aged persons: 5 to 7 hours

Throughout the sleep the depth of ordinary restful sleep fluctuates. In most adults, sleep deepens through the first hour, after which it lightens rather sharply and then more gradually until morning or until the usual time of wakening. However in growing children sleep deepens a second time for a little while. Two hours before and two hours after midnight are the most valuable for sleep of all the twenty-four hours of the day and in at this time, the mental and physical vigour are at their lowest ebb and sleep is soundest and most natural.

Sleeping well is an art. It needs a perfect blend of healthy habits and control of mind. A clean body and mind, relaxed mood, physical exercises, and perfect dietary control are some of the basic sleep-inducing methods. The sleeping place should be well ventilated, with balanced temperature and free from noises. The bed should be neither too hard nor too soft, but comfortable. The pillow should not be too hard or too high. The bedclothes should be loose-fitting and light coloured. Another important rule is not to eat heavy food shortly before bedtime.