What is the Sleep?
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Although as humans, we spend about one third of our lives sleeping, a majority of us do not know much about sleep. It is widely believed that sleep is an idle state for the body and does not have any physical or mental significance. In fact, the exact opposite has been scientifically proven. Many of the complex brain and body level activities happen during sleep. On the contrary, some activities are more dynamic during sleep while some diseases occur only during sleep and disappear when the patient wakes up. This information is based on recent findings, as medical authorities have not delved further into the subject.

What Happens During Sleep?

Sleep does not mean losing consciousness or coma, but it is a special state experienced by humans, and a time when certain activities happen. When a person is awake, the brain has a certain electrical activity. Normal sleep consists of several stages of sleep. The first and the second phase are where the sleep is light. Then begin the third and fourth stages, known as the deep sleep phases. These two phases are important for the body to restore its activity, and the lack of these two phases of sleep results in fatigue and stress during the day. After about ninety minutes, the dreams phase begins. This is known as Rapid Eye Movement (REM) stage. Dreams occur during this stage; and it is an important phase to restore the activity of the mind. Going through all these stages of sleep once implies the completion of one sleep cycle. During normal human sleep (of 6-8 hours) a person passes through 4-6 such sleep cycles.

What is sleep?

How many hours of sleep does a normal person require?

Number of hours of sleep needed by a person varies greatly from one person to another. However, we are not sure if the number of hours of sleep needed by the same person remains constant because one might sleep for different number of hours daily. Most people recommend 8 hours of sleep per day. However, if we want a more accurate number, we need to consider an average of the number of hours for which most people sleep, this comes to 7-7.5 hours a day.

This does not necessarily mean that everyone needs to sleep for that many hours. Sleeping varies from less than 3 hours for some people to more than 10 hours for others. A study conducted at the National Center for Health Statistics in the United States of America found that:

  • 2/ 10 people sleep lesser than 6 hours a day - called short sleep people
  • 1/ 10 people sleep more than 9 hours a day - called long sleep people

Napoleon and Edison were known to have a very short sleep, while Aenictin was known for his long sleeping hours!

The exact number of hours of sleeping required is not known, but it does influence the productivity and creativity of an individual. Many people think that they need 8 hours of sleep a day, and believe that if the same is increased, they will become healthier. This is wrong. For example, if you sleep for only 5 hours at night but feel active the next day and do not suffer from problems then it is an ideal duration of sleep for you.

Sleep and Aging

As children grow, their sleep patterns and sleep requirements gradually change (see the information about Sleep In Children). When one attains puberty (about 24 years of age), the number of hours of sleep needed by the body does not change, it is actually the nature and the quality of sleep that changes.

Elders get little sleep, and it gradually becomes less effective and less comfortable. This is because the proportion of each stage of sleep varies (see information of Sleep In The Elderly). When a man reaches 50 years of age (60 years for women), the proportion of deep sleep (stages 3 and 4) steadily reduces has reaches very small amounts and might eventually disappear. In this age, unlike youth, elders wake up easily because of external noise. Hence, while the number of hours of sleep might be same, the nature of sleep is different. It is light and intermittent, causing drowsiness and increase in naps during the day.


Ahmed BaHammam, FACP, FCCP
Professor of Medicine
Director, University Sleep Disorders Center
College ofMedicine, King Saud University