Sleep Disorders
Sleep Disorders
Observation and classification of sleep disorders
The sleeping brain—the new frontier
Sleep disorders are chronic sleep irregularities, which drastically interfere with normal nighttime sleep or daytime functioning. There are about 70 different sleep disorders. Sleep-related problems are the most common complaint heard by doctors and psychiatrists, the two most common being insomnia (inability to go to sleep or stay asleep), and hyper-somnia (excessive daytime sleepiness). While most people experience both problems at some time, it is only when they cause serious intrusions into daily living that they warrant investigation as disorders.
Although sleep is a basic behavior in animals as well as humans, researchers still do not completely understand it. In the past 60 years, however, researchers have learned about the pattern of different types of sleep and its effects on breathing, heart rate, brain waves, and so on. Sleep disorders research, as a relatively new field of medicine, was stimulated by the discovery in 1953 of REM (rapid eye movement) sleep and the more recent discovery in the 1980s that certain irregular breathing patterns during sleep can cause serious illness and sometimes death. While medical knowledge of sleep disorders is expanding rapidly, clinical educational programs still barely touch on the subject, about which many physicians, psychiatrists and neurologists remain seriously undereducated.
Insomnias and hypersomnias
Insomnias include problems with sleep onset (taking longer than 30 minutes falling asleep), sleep maintenance (waking five or more times during the night or for a total of 30 minutes or more), early arousal (less than 6.5 hours of sleep over a typical night), light sleep, and conditioning (learning not to sleep by associating certain bedtime cues with the inability to sleep). Insomnias may be transient (lasting no longer than three weeks) or persistent. Most people experience transient insomnias, perhaps due to stress, excitement, illness, or even a sudden change to high altitude. These are treatable by short-term prescription drugs and, sometimes, relaxation techniques. When insomnia becomes persistent, it is usually classed as a disorder. Persistent insomnias may result from medical and/or psychiatric disorders, prescription drug use, and substance abuse, and often result in chronic fatigue, impaired daytime functioning, and hypersomnia.
Hypersomnias manifest as excessive daytime sleepiness, uncontrollable sleep attacks, and, in the extreme, causes people to fall asleep at highly inappropriate times, such as driving a car or when holding a conversation. Most hypersomnias, like narcolepsy and those associated with apnea (breathing cessation), are caused by some other disorder and are therefore symptomatic. Some, however, like idiopathic central nervous system (CNS) hypersomnia and Kleine-Levin syndrome, are termed idiopathic for their unknown origin. CNS hypersomnia causes a continuous state of sleepiness from which long naps and nighttime sleep provides no relief. This is usually a life-long disorder and treatment is still somewhat experimental and relatively ineffective. Kleine-Levin syndrome is a rare disorder seen three times as often in males as females, beginning in the late teens or twenties. Symptoms are periods of excessive sleepiness, excessive overeating, abnormal behavior, irritability, loss of sexual inhibition, and sometimes hallucinations. These periods may last days or weeks, occur one or more times a year, and disappear about the age of 40 years. Behavior between attacks is normal, and the sufferer often has little recall of the attack. Stimulant drugs may reduce sleepiness for brief periods, and lithium meets with some success in preventing recurrence.
Observation and classification of sleep disorders
Sleep abnormalities intrigued even the earliest medical writers who detailed difficulties that people experienced with falling asleep, staying asleep, or staying awake during the day. By 1885, Henry Lyman, a professor of neurology in Chicago, Illinois, classified insomnias into two groups: those resulting from either abnormal internal or physical functions; or from external, environmental influences. In 1912, Sir James Sawyer reclassified the causes as either medical; or psychic, toxic, or senile. Insomnias were divided into three categories in 1927: inability to fall asleep, recurrent waking episodes, and waking earlier in the morning than appropriate. Another reclassification, also into three categories, was made in 1930: insomnia/hypersomnia, unusual sleep-wake patterns, and parasomnias (interruption of sleep by abnormal physical occurrences). One change to that grouping was made in 1930 when hypersomnias and insomnias became separate categories.
Intense escalation of sleep study in the 1970s saw medical centers begin establishing sleep disorder clinics where researchers increasingly uncovered abnormalities in sleep patterns and events. It was during this decade that sleep disorders became an independent field of medical research and the increasing number of sleep disorders being identified necessitated formal classification.
Dyssomnias
This group includes both insomnias and hyper-somnias, 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 immediately before falling asleep or just after waking up. While narcolepsy is manageable clinically and brief naps of 10 to 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 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 human’s 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 the human biological clock runs slightly slower than the 24-hour solar 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 sun-clock’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 to 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.
Parasomnias
Parasomnias are events caused by physical intrusions into sleep that are thought to be triggered by the central nervous system. These dysfunctions do not interfere with actual sleep processes and do not cause insomnia or hypersomnia. They appear more frequently in children than adults.
Arousal disorders appear to be associated with neurological arousal mechanisms. They usually occur early in the night during slow-wave rather than REM sleep and are therefore not the acting out of a dream.
Sleepwalking occurs during sleep. The subject may seem wide awake but displays a blank expression, seldom responds when spoken to, is difficult to awaken, moves clumsily, and sometimes bumps into objects, although they will often maneuver effectively around them. Some sleepwalkers perform dangerous activities, like driving a car. Although rarely in the case with children, serious injuries can occur. Subjects displaying dangerous tendencies should take precautions like locking windows and doors. Episodes average about ten minutes, seldom occur more than once in any given night, and are seldom remembered.
Night or sleep terrors are sudden partial awakenings during non-REM sleep. Traditionally, a sufferer sits bolt upright in bed in a state of extreme panic, screams loudly, sweats heavily, and displays a rapid heart beat and dilated pupils. The patient will sometimes talk, and might even flee from bed in terror, often running into objects and causing injury. Episodes last about 15 minutes, after which sleep returns easily. There is seldom any recollection of the event. If woken, the subject may display violence and confusion and should, instead, be gently guided back to bed.
Rapid eye movement (REM) sleep parasomnias take place during sleep and include nightmares and the recently discovered REM sleep behavior disorder. This potentially injurious disorder is seen mostly in elderly men and results in aggressive behavior while sound asleep such as punching, kicking, fighting, and leaping from bed in an attempt to act out a dream.
Subjects report their dreams, usually of being attacked or chased, become more violent and vivid over the years. Some sufferers even tie themselves into bed to avoid injury. Unfortunately, this disorder was seriously misdiagnosed until recently. It is now readily diagnosable and easily treated.
Sleep-wake transition disorders usually occur during transition from one sleep stage to another, or while falling asleep or waking up. Manifestations include sleeptalking, leg cramps, headbanging, hypnic jerks (sleep starts), and teeth-grinding.
Other parasomnias include excessive snoring, abnormal swallowing, bedwetting, sleep paralysis, and for some individuals, sudden unexplained death during sleep.
Diagnosis of sleep disorders
Identifying each specific sleep disorder is imperative for effective treatment, as treatment for one may adversely effect another. While sleeping pills may help in some instances, in others they exacerbate the problem. The most important step in diagnosis is the sleep history, a highly detailed diary of symptoms and sleep-wake patterns. The patient records events such as daily schedule; family history of sleep complaints; prescription or non-prescription drug use; and symptoms— when they occur, how long they last, their intensity, whether they are seasonal, what improves or worsens them, and effects of stress, family or environmental factors. Important contributors are family members or friends; for example, a bed partner or parent may be the only observer of unusual occurrences during the patient’s sleep.
The sleeping brain—the new frontier
Many undiscovered secrets lie hidden behind the doors of sleep and its related disorders. However, the future looks bright for sufferers of sleep disorders. Intense interest from researchers, satisfaction of an increasing number of accurately diagnosed and treated patients, advances in technology, and the formation of a National Institute of Health Commission on Sleep by the U.S. Congress, suggest that research, training, education, and recognition in this area of medicine will continue to flourish.
Resources
BOOKS
Billiard, Michel, ed. (translated by Angela Kent). Sleep: Physiology, Investigations, and Medicine. New York: Kluwer Academic/Plenum, 2003.
Horne, James A. Sleepfaring: A Journey Through the Science of Sleep. Oxford, UK: Oxford University Press, 2006.
KEY TERMS
Apnea —Cessation of breathing.
Delta sleep —Slow-wave, stage 4 sleep that normally occurs before the onset of REM sleep.
Extrinsic —Caused by something on the outside.
Hypersomnia —Excessive daytime sleepiness.
Idiopathic —Disease of unknown origin.
Insomnia —Inability to go to sleep or stay asleep.
Intrinsic —Not dependent on external circumstances.
Parasomnia —Interruption of sleep by abnormal physical occurrences.
Polysomnography —Electronic monitoring equipment measuring brain waves, eye and muscle movement, heart rate, and other physiological functions.
REM sleep —Rapid eye movement sleep that is characterized by dreaming, active brain activity, and numerous eye movements.
Lader, Malcolm, Daniel P. Cardinali, and S.R. Pandi-Perumal, eds. Sleep and Sleep Disorders: A Neuropsychopharmacological Approach. New York: Springer, 2005.
Lee-Chiong, Teofilo L. Sleep: A Comprehensive Handbook. Hoboken, NJ: Wiley-Liss, 2006.
Mattson, Mark P., ed. Sleep and Aging. Amsterdam, Netherlands: Elsevier, 2005.
Mindell, Jodi A. A Clinical Guide to Pediatric Sleep: Diagnosis and Management of Sleep Problems. Philadelphia, PA: Lippincott Williams & Wilkins, 2003.
Moorcroft, William H. Understanding Sleep and Dreaming. New York: Springer, 2005.
Rosen, Marvin. Sleep and Dreaming. Philadelphia, PA: Chelsea House Publishers, 2005.
Steriade, Mircea. Brain Control of Wakefulness and Sleep. New York: Springer, 2005.
Marie L. Thompson