Types of Sleep Disorders
Sleep disorders are classified into three major categories:
- lack of sleep (e.g., insomnia)
- disturbed sleep (e.g., sleep apnea, REM sleep behavior disorder, restless leg syndrome [RLS,also called Willis-Ekbom disease], periodic limb movement disorder[PLMD]), and excessive sleep (e.g., narcolepsy).
Lack of Sleep
Insomnia is the inability to fall asleep. It is a common sleep problem that most people experience at least occasionally. When it occurs, people feel tired much of the time and often worry a lot about not getting enough sleep. Consequently, insomnia often disrupts daily life.
Insomnia can result from the following:
- Diet (e.g., intake of caffeine or alcohol)
- Emotional difficulties
- Underlying disease
- Other factors
For short-term insomnia, sleeping pills can be effective. For long-term insomnia, however, sleeping pills can actually worsen the condition.
Sleep deprivation is not actually a disorder; it simply indicates that a person has not been getting enough sleep. Inadequate sleep can affect judgment, reaction-time, hand-eye coordination, memory, and general well-being.
Studies have shown that sleep deprivation also can damage the immune system. Feeling drowsy during the day, falling asleep for very short periods of time (5 minutes or so), or regularly falling asleep immediately after lying down may indicate sleep deprivation.
Sleep apnea is interrupted breathing during sleep. It usually occurs because of a mechanical problem in the windpipe, but it also can indicate a neurological disorder involving nerve cells (neurons). As people age, muscle tone relaxes, which may cause the windpipe to collapse.
This condition, called obstructive sleep apnea (OSA), results in loud snoring and blocked air flow through the windpipe that lasts from 10 to 60 seconds. It may appear that the person is gasping or snorting. When this occurs, the brain quickly reacts to the sudden lack of oxygen, the muscles tighten, and the windpipe opens.
Narrow nasal passages, enlarged tonsils, and obesity are factors that may contribute to obstructive sleep apnea. The condition may also be related to the use of alcohol or sedatives, as well as smoking.
Patients with sleep apnea lose sleep because every time the windpipe closes, the person has to wake up enough to contract those muscles and resume breathing. As a result, the sleep cycle can be interrupted as many as 100 times a night.
In addition, every time the windpipe closes, the brain is deprived of oxygen. This lack of oxygen eventually can cause problems morning headaches and decreased mental function. People who have sleep apnea are at increased risk for heart disease and stroke.
REM sleep behavior disorder causes disruptions in the brain during REM sleep. During REM (i.e., the dream phase of sleep), an area of the brainstem called the pons sends signals to the cerebral cortex, which is the area of the brain responsible for thinking and organizing information. The pons also sends signals to muscles in the body during REM, causing a type of temporary paralysis.
In a person with REM sleep behavior disorder, these signals translate into images that make up dreams. If the signals are interfered with, the person may physically act out dreams during sleep. For example, if a patient with REM sleep behavior disorder dreams about running, he or she might actually get up and run. As a result of this condition, patients may injure themselves or others. REM sleep behavior disorder is rare.
Restless legs syndrome (RLS; also called Willis-Ekbom disease) and periodic limb movement disorder (PLMD) are common sleep disorders, especially in the elderly. RLS is a genetic disorder resulting in prickly or tingling sensations in the leg that cause patients to want to move their legs. It often results in insomnia. PLMD causes jerking in the legs or arms that occurs frequently during resting or sleeping. Jerking may occur as many as 3 times in a minute and each jerk can wake the patient.
Narcolepsy is a condition that causes patients to fall asleep uncontrollably throughout the day for periods lasting less than a minute to more than half an hour. These sleep attacks can occur at anytime, even while the person is engaged in an activity. During sleep, narcoleptics have an abnormal sleep pattern: They enter REM sleep prematurely without going through the normal sequence of sleep stages.
Narcolepsy usually is a genetic (inherited) disorder, although it may be associated with brain damage or neurological disease. The condition usually develops between the ages of 15 and 30. Some people with narcolepsy experience increased sleep attacks during pregnancy, illness, fever, or stressful periods. Patients with narcolepsy often feel tired most of the time. Other symptoms of the condition include cataplexy, sleep paralysis, and hypnagogic hallucinations.
Cataplexy is weakness or paralysis of the muscles. In narcoleptic patients, it may be triggered by tiredness and intense emotions and may be accompanied by short, sudden episodes of laughter or anger. When cataplexy occurs, persons who are standing may fall down.
Sleep paralysis is the inability to move the arms, legs, or entire body that occurs when a person is falling asleep or waking up. It usually lasts a very brief period of time. People who experience sleep paralysis may become very anxious and often regain movement only if they hear a loud noise or another stimulus.
Hypnagogic hallucinations or pre-sleep dreams, are dream-like hallucinations that occur in the transition between being awake and being asleep. Often, they are very vivid, frightening dreams.