 Sleep is absolutely essential for normal, healthy function of human organism. Medical professionals and scientists do not completely understand this complicated, necessary, physiological phenomenon. National Institute of Neurological Disorders and Stroke reports that about 40 million people in the United States suffer from chronic long-term disorders yearly and 20 million people suffer from occasional sleep problems.
There are more than 70 different sleep disorders. They are usually divided into three categories:
- lack of sleep (insomnia)
- disturbed sleep (obstructive sleep apnea)
- excessive sleep (narcolepsy)
In prevalent number of cases, sleep disorders can be easily managed once they are correctly diagnosed. Insomnia is the most common sleep disorder in our society. The interesting fact is that it occurs more often in women and in the elderly.
The quantity of sleep that a person needs for normal functioning depends on several factors. For example, infants sleep most of the day (approximately 16 hours), teenagers usually need nearly 9 hours a day, and adults need about 7 to 8 hours a night. Although elderly people require about as much sleep as young people, they usually sleep for shorter periods and spend less time in deep stages of sleep. It has been proved that about 50% of adults over the age of 65 have some type of sleep disorder. In fact, it is not clear whether this is a normal part of aging or a result of medicines that elderly people usually use.
The processes of falling asleep and waking up are regulated by numerous chemical changes in the brain and in the blood. Foods and medications that change the balance of these chemicals also influence on our sleep. For example, caffeine can cause insomnia; smoking and alcohol can result in a loss of REM (rapid eye movement) and in a loss of deep sleep. REM and deep sleep are essential components of the normal sleep cycle.
Sleep is a dynamic process during which the brain is very active. There are recognized five stages of sleep, each of which is distinguished by a different type of brain activity.
Sleep Stages
- Stage 1 occurs while a person is falling asleep, during it muscles begin to relax and a person can be easily awakened. It makes up about 5% of a normal adult’s sleep time.
- Stage 2. During it brain activity slows down and eye movement stops. Stage 2 represents about 50% of all sleep time.
- Stage 3 and 4 compose deep sleep, during which all muscle and eye movements stop. They also called delta or slow wave sleep; these are the deepest levels of human sleep. It can be difficult to wake a person during these stages. They account for 10-20% of human sleep time.
- REM sleep represents of about 20-25% of total sleep time. During this stage dreams occur. The eyes move, the muscles of the body strengthen, the heart beating increases, breathing becomes more irregular and rapid, and the blood pressure rises.
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