Sleeping Disorders

Introduction to Sleep

What and How Important is Sleep

Sleep is a highly complex physiological process that is not fully understood.  However, what is known is that sleep is absolutely crucial for our bodies and minds to be able to continue normal, healthy function.
Sleep is a periodic state of rest during which our awareness and consciousness of our surroundings are halted.  This suspension or interruption of perception is the most significant characteristic of sleep and is what differentiates it from the normal waking state.  During sleep, the following changes occur:
· Decreased movement of the skeletal muscles,
· Slowed-down metabolism, and,
· Changes in the complex and active brain wave patterns.
Sleep is essential for a healthy body and mind.
Falling asleep and waking up are controlled by various chemical changes in the brain and in the blood.  Foods and medicines that alter the balance of these chemicals can affect how quickly we fall asleep and the quality of our sleep.
According to the National Institute of Neurological Disorders and Stroke, approximately 40 million people in the United States suffer from chronic long-term sleep disorders each year, with an additional 20 million people suffering occasional sleeping problems.

Why Does the Body Need Sleep?

It is not clear exactly why the body requires sleep, although inadequate sleep can have severe detrimental effects on health and brain function.
Sleep helps the body restore and rejuvenate in many different ways including:
· Body Maintenance: Sleep is essential for healthy cell growth and for cell and tissue repair.
· Growth and Development: Children need much more sleep than adults to allow for the necessary growth and development changes in their bodies to occur properly.  During sleep, growth hormones are released, and these hormones are crucial to proper physical and mental development.  The effects (positive and negative) of sleep for babies and children are magnified depending on whether they get enough sleep or insufficient sleep.  For example, tired children are often cranky, uncooperative, and difficult.
· Immune System: Sleep enables the immune system to function effectively.  Without proper sleep, the immune system can become weakened and, as a result, the body may become more vulnerable to infection and disease.  During deep sleep, the body’s cells increase production while proteins break down at a slower rate.
· Memory, Learning and Social Processes: Sleep enables the brain to encode and store recently received information.  REM sleep activates the parts of the brain that deal with learning.  During sleep, various parts of the brain slow down, including the parts of the brain that control emotions, decision-making and social interactions.  The resting of these parts of the brain during sleep allow optimal performance when awake.  Without sufficient sleep, people are far less effective at learning new skills or retaining or recalling recently learned information.
· Nervous System: Neurons regenerate and repair during sleep so that our bodies can continue to function as effectively as possible both physically and mentally.  In people that experience sleep deprivation, neurons become unable to perform effectively and nervous system function is impaired.  In people who have suffered extreme sleep deprivation, drastic and permanent brain and personality changes can occur.

Stages of Sleep

Sleep is a dynamic process during which parts of the brain can be very active.  There are five recognized stages of sleep, each of which is characterized by different types of brain activity:
· Stage 1 - Drowsiness
· Stage 2 - Light Sleep
· Stage 3 - Deep Sleep
· Stage 4 - Deep Sleep
· Stage 5 - Rapid Eye Movement (REM) Sleep
Stages 1 through 4 are also known as Non-Rapid Eye Movement (NREM) Sleep.
The body cycles through the different sleep stages from stage 1 to REM, and then begins the cycle again with stage 1, throughout the rest period.  Each stage represents a different physical and mental state of the body. During some stages, the body is in a lighter sleep and can be awakened more easily, while others indicate a very deep sleep.  All are essential to a proper night's sleep.
Stage 1 is a period of drowsiness during which the muscles begin to relax, the eyes move very slowly, and a person can be easily awakened.  In Stage 1, we may drift in and out of sleep for about 5 to 10 minutes before moving onto the next stage of sleep.
Stage 2 sleep is a deeper sleep than Stage 1, but it is still classified as light sleep, where eye movement stops and brain activity slows down with occasional bursts of rapid waves, called sleep spindles.  Also during Stage 2, the heart rate drops and body temperature decreases.
Stages 3 and 4 comprise deep sleep, during which all eye and muscle movement ceases.  In these stages, it can be difficult to wake a person.  Stage 3 is characterized by very slow brain waves (called delta waves), interspersed with smaller, faster waves.  In Stage 4 sleep, the brain waves are virtually all very slow delta waves.  Stage 3 and 4 sleep is often called Slow Wave Sleep (SWS) for this reason.  It is very difficult to wake someone during Stages 3 and 4, and during these deep stages of sleep some people may experience sleepwalking or night terrors, and children may experience bedwetting.  People awakened during deep sleep do not adjust immediately and often feel groggy and disoriented for several minutes after they wake up.
It is during REM sleep that dreams occur.  Also during REM sleep, the muscles of the body stiffen the limb muscles may become temporarily paralyzed, the eyes move rapidly in various directions, the heart rate increases, breathing becomes more rapid and irregular, and the blood pressure rises.  Males may also develop penile erections.
Normally, approximately 50% of sleep time is spent in Stage 2 sleep, and about 20% is spent in REM sleep.  For an average 8 hours of sleep, about 4 hours are spent in Stage 2 sleep and 1.5 to 2 hours are REM sleep.  The remaining 30 percent of sleep time is split among the other stages.  After a person falls asleep, the first REM sleep period generally happens 70-90 minutes later.
A complete sleep cycle, from the beginning of stage 1 to the end of REM, usually takes about an hour and a half to an hour and 50 minutes.  These sleep stages cycle through and occur multiple times during an average night of sleep.  On average, a person will cycle through the all of the stages of sleep four or five times in an eight hour rest period.
The first cycles of the stages of sleep of the night tend to have shorter REM periods and longer periods of deep sleep (Stages 3 and 4).  However, as the rest period progresses, this trend reverses and the later cycles have longer REM periods and shorter deep sleep periods (Stages 3 and 4).  Towards the end of the rest period, most sleepers spend almost all of their time in stages 1, 2 and REM sleep with very little deep sleep (Stages 3 and 4).
Infants are unique in that they spend approximately 50 percent of their sleep time in REM sleep.
REM and deep sleep (Stages 3 and 4) are particularly important stages of a normal sleep cycle.

How Much Sleep is Required

The amount of sleep that a person needs to function normally depends on several factors, such as age and pregnancy status.
The following are how
· Infants and Children: Infants normally sleep for most of the day (about 16 hours).  Children from 6 months to about 3 years of age only require about 14 hours of sleep.  Young children generally get their sleep from a combination of nighttime sleep and daytime naps.
· Teenagers: usually need about 9 hours a day of sleep.  Sleep is especially crucial for teenagers because growth hormones are secreted while they are sleeping.  These hormones are essential during puberty and growth spurts.
· Adults: need an average of 7 to 8 hours a day.  Some adults may require more (up to 10 hours) or less (as few as 5 hours) of sleep.  It should be noted that a recent research study conducted by Boston University School of Medicine found that study participants who reported sleeping less than 6 hours or more than 9 hours a day had an increased incidence of diabetes, compared to those who slept 7-8 hours. 
· Elderly Adults: require about as much sleep as young adults (8-9 hours a day), however, they usually sleep for shorter periods and spend less time in the deepest stages of sleep.
· Pregnant Women: need significantly more sleep than usual, especially during the first trimester of pregnancy.
About 50% of adults over the age of 65 have some type of sleep disorder, although it is not clear whether this is a normal part of aging or a result of medications that older people commonly use.

What Causes a Lack of Sleep

In addition to various sleep disorders (discussed below), a range of other factors can cause a lack of sleep.  For example:
· Caffeine,
· Antidepressants, smoking, and alcohol,
· Changes in life style, such as shift work changes,
· Back and neck problems,
· Environmental noise,
· Sciatica (pain in the leg),
· Incontinence
These can each cause a loss of sleep and/or disturbed sleep.
In addition, various drugs can affect the ratio of the various stages of sleep, thus affecting the overall quality of sleep.

Types of Sleeping Disorders