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Chapter 182 Insomnia

image General Considerations

Insomnia represents one of the most common complaints seen by physicians. Within the course of a year, up to 30% of the population suffers from insomnia, and roughly 10% of the adult population has chronic insomnia.1 Many use over-the-counter (OTC) medications to combat the problem, and others seek stronger sedatives. Approximately 12.5% of the adult population uses a prescribed anxiolytic or sedative hypnotic in the course of a year; about 2% of the population takes one on any given day. More than one half of these drugs, especially benzodiazepines, are prescribed by primary care physicians. Nearly 100 million prescriptions are written each year for these drugs.2

A thorough history and physical examination are indicated in the patient presenting with insomnia, because it is a symptom that can have many causes (Table 182-1). Psychological factors account for 50% of all insomnias evaluated in sleep laboratories.1 Insomnia is closely associated with affective disorders (see Chapter 142). Cognitive behavioral therapy is often indicated and can produce effective improvements in sleep quality.3 A detailed recreational, prescription, and nonprescription drug-use history, along with a dietary and beverage history, are also required to determine whether the patient is consuming any stimulants or other agents known to interfere with sleep. The following agents may be responsible:

TABLE 182-1 Causes of Insomnia*

Sleep-onset insomnia Sleep-maintenance insomnia
Anxiety or tension Depression
Environmental change Environmental change
Emotional arousal Sleep apnea
Fear of insomnia Nocturnal myoclonus
Phobia of sleep Hypoglycemia
Disruptive environment Parasomnias
Pain or discomfort Pain or discomfort
Caffeine Drugs
Alcohol Alcohol

* The boundary between the categories is not entirely distinct.

Among serious diseases to be considered in the differential diagnosis are narcolepsy and sleep apnea syndromes. Sleep apnea is the most common example of sleep-disordered breathing. First described in 1965, sleep apnea is a breathing disorder characterized by brief interruptions of breathing during sleep. These breathing pauses are almost always accompanied by snoring between apneic episodes, although not everyone who snores has this condition. Sleep apnea can also be characterized by choking sensations. The frequent interruptions of deep, restorative sleep often lead to excessive daytime sleepiness and may be associated with an early-morning headache. Approximately 18 million Americans are thought to suffer from sleep apnea.

Early recognition and treatment of sleep apnea are important because it is associated with marked daytime fatigue, irregular heartbeat, high blood pressure, heart attack, and stroke as well as a loss of memory function and other intellectual capabilities. The patient usually does not know he or she has a problem and may not believe it when told. If a person snores heavily or his or her sleep partner has noted periods of interrupted breathing during sleep, it is important that such a person see a doctor. Sleep apnea should also be considered in anyone with significant daytime drowsiness or changes in intellectual function. Sleep apnea can be properly diagnosed only through the services of a sleep disorder specialist, usually in a sleep laboratory.

Sleep apnea is most often caused by narrowing of the airway by an excess accumulation of fatty tissue, causing obstructive sleep apnea. With a narrowed airway, the person continues efforts to breathe, but air cannot easily flow into or out of the nose or mouth. This narrowing results in heavy snoring, periods of no breathing, and frequent arousals (causing abrupt changes from deep sleep to light sleep). Ingestion of alcohol and sleeping pills increases the frequency and duration of breathing pauses in people with sleep apnea. In some cases sleep apnea occurs even if no airway obstruction or snoring is present. This form of sleep apnea, central sleep apnea, is caused by a loss of perfect control over breathing by the brain.

In both obstructive and central sleep apneas, obesity is the major risk factor, and weight loss is the most important aspect of long-term management. People with sleep apnea experience periods of anoxia (oxygen deprivation of the brain) with each apneic episode, which ends in arousal and a reinitiation of breathing. Seldom does the sufferer awaken enough to be aware of the problem. However, the combination of frequent periods of oxygen deprivation (20 to several hundred times per night) and the greatly disturbed sleep can greatly diminish the sufferer’s quality of life and lead to serious problems.4

The most common treatment of sleep apnea is the use of nasal continuous positive airway pressure (CPAP). In this procedure, the patient wears a mask over the nose during sleep and pressure from an air blower forces air through the nasal passages. The air pressure is adjusted so that it is just enough to prevent the throat from collapsing during sleep. The pressure is constant and continuous. Nasal CPAP prevents airway closure while in use, but episodes of apnea return when CPAP is stopped or used improperly. Surgery to reduce soft tissue in the throat or soft palate should be used only as a last resort because it often does not work or can make the problem worse. Laser-assisted uvulopalatoplasty is a highly promoted surgical option. In this procedure lasers are used to surgically remove excessive soft tissue from the back of the throat and the palate. It works well initially in about 90% of sleep apnea sufferers, but within a year many people are the same as or even worse than before because of the scar tissue that invariably forms.4

Normal Sleep Patterns

Human sleep is perhaps one of the least understood physiologic processes. Its value to human health and proper functioning is without question. Sleep is absolutely essential to both the body and the mind. Impaired sleep, altered sleep patterns, and sleep deprivation impair mental and physical function.

Normal adult sleep-wake patterns repeat themselves on an approximately 24-hour cycle, of which sleep constitutes one third. Exactly how much sleep is required varies from one person to the next. Sleep tends to decrease with age, but whether this tendency is a normal or abnormal progression is unknown. A 1-year-old baby requires about 14 hours of sleep a day, a 5-year-old about 12 hours, and adults about 7 to 9 hours. Women tend to require more sleep than men. The elderly tend to sleep less at night but doze more during the day than do younger adults.

From observations of eye movement and electroencephalographic (EEG) recordings, sleep is divided into two distinct types: rapid eye movement (REM) sleep and non-REM sleep. During REM sleep, the eyes move rapidly and dreaming takes place. When people are awakened during non-REM sleep, they report that they were thinking about everyday matters but rarely report dreams.

Non-REM sleep is divided into stages 1 through 4 according to level of EEG activity and ease of arousal. As sleep progresses, there is a deepening of sleep and slower brainwave activity until REM sleep ensues, when suddenly the brain becomes much more active. In adults, the first REM sleep cycle is usually triggered 90 minutes after going to sleep and lasts about 5 to 10 minutes. After the flurry of activity, brainwave patterns return to those of non-REM sleep for another 90-minute sleep cycle.

Each night most adults experience five or more sleep cycles. REM sleep periods grow progressively longer as sleep continues; the last sleep cycle may produce a REM sleep period that can last about an hour. Non-REM sleep lasts approximately 50% of this 90-minute sleep cycle in infants and about 80% in adults. As people age, in addition to less REM sleep, they tend to awaken at the transition from non-REM to REM sleep.