This group includes both insomnias and hypersomnias, and is divided into three categories: intrinsic, extrinsic, and circadian rhythm sleep disorders. Intrinsic sleep disorders originate within the body and include narcolepsy, sleep apnea, and periodic limb movements.
Narcolepsy is associated with REM sleep and the central nervous system. It causes frequent sleep disturbances and thus excessive daytime drowsiness. Subjects may fall asleep without warning, experience cataplexy—muscle weakness associated with sudden emotional responses like anger, which may cause collapse—and temporarily be unable to move right before falling asleep or just after waking up. While narcolepsy is manageable clinically and brief naps of 10-20 minutes may be somewhat refreshing, there is no cure.
Apnea is the brief cessation of breathing. Obstructive sleep apnea is caused by the collapse of the upper airway passages that prevent air intake, while central apnea occurs when the diaphragm and chest muscles cease functioning momentarily. Both apneas result in a suffocating sensation, which goes unnoticed but causes enough arousal to enable breathing to begin again. Bed partners report excessive snoring and repeated brief pauses in breathing. Apneas may disrupt sleep as many as several hundred times a night, naturally resulting in excessive daytime sleepiness. Severe episodes can actually cause death, usually from heart failure. Treatment for obstructive apnea includes pumping air through a nasal mask to keep air passages open, while some success in treating central apnea can be obtained with drugs and mechanical breathing aids.
Periodic limb movement (PLM) and restless leg syndrome (RLS) result in sleep disruptions and therefore hypersomnia. PLM occurs during sleep and subjects experience involuntary leg jerks (sometimes arms also). The subject is unaware of these movements but bed partners complain of being kicked and hit. In RLS, "crawling" or "prickling" sensations seriously interfere with sleep onset. Although their causes are yet unknown, certain drugs, stretching, exercise, and avoiding stress and excessive tiredness seem to provide some relief.
Extrinsic sleep disorders are caused by external influences such as drugs and alcohol, poor sleep hygiene, high altitude, and lack of regular sleep limit-setting for children.
Drug and alcohol-related sleep disorders result from stimulant, sedative, and alcohol use, all of which can affect, and severely disrupt, the sleep-wake schedule. Stimulants, including amphetamines, caffeine, and some weight loss agents, can cause sleep disturbances and may eventually result in a "crash" and the need for excessively long periods of sleep. Prolonged use of sedatives, including sleeping pills, often result in severe "rebound insomnia" and daytime sleepiness. Sudden withdrawal also produces these effects. Alcohol, while increasing total sleep time, also increases arousal, snoring, and the incidence and severity of sleep apnea. Prolonged abuse severely reduces REM and delta (slow-wave) sleep, and sudden withdrawal results in severe sleep-onset difficulties, significantly reduced delta sleep, and "REM rebound," causing intense nightmares and anxiety dreams for prolonged periods.
Circadian rhythm sleep disorders either affect or are affected by circadian rhythms, which determine our approximate 25-hour biological sleep-wake pattern and other biological functions. Disorders may be transient or permanent.
Jet-lag and shift work-related circadian rhythm Disorders are transient. Because our biological clock runs slightly slower than the 24-hour Sun clock, it must adjust to external time cues like alarm clocks and school or work schedules. Circadian rhythms must therefore "phase-advance" to fit the imposed 24-hour day. The body has difficulty phase-advancing more than one hour each day, therefore people undergoing drastic time changes after long-distance air travel suffer from "jet lag." Hypersomnia, insomnia, and a decrease in alertness and performance are not uncommon and may last up to ten days, particularly after eastward trips longer than six hours. Night-shift workers, whether permanent or alternating between day and night shifts, experience similar symptoms, which may become chronic because circadian rhythms induce maximum sleepiness during the Sunclock's night and alertness during the Sun-clock's day, regardless of how long a person works nights.
Delayed sleep phase syndrome is a chronic condition in which waking to meet normal daily schedules is extremely difficult. Such people are often referred to as "night people" because they feel alert late in the day and at night while experiencing fatigue and sleepiness in the mornings and early afternoons. This is because their biological morning is the middle of the actual night. Phase-delaying the sleep-wake schedule by going to bed three hours later and sleeping three hours longer until the required morning arousal time is reached, can often synchronize the two. Exposure to artificial, high-intensity, full spectrum light from about 7-9 A.M. often proves helpful.
Advanced sleep phase syndrome is much less prevalent and shows the reverse pathology to phase-delayed syndrome. Phase-advancing the sleep-wake schedule and light therapy during evening hours may prove helpful.
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