Excerpt from Insomnia

Synonyms, Key Words, and Related Terms: sleep disorder, sleep problem, sleep symptom, sleep complaint, sleeplessness, inability to sleep, transient insomnia, short-term insomnia, chronic insomnia

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Background: Insomnia is the most common sleep complaint. It is a perception that sleep quality is inadequate or nonrestorative, despite the adequate opportunity to sleep. That insomnia is a symptom, not a disease, is important to note; it is associated with a variety of medical, psychiatric, and sleep disorders (see Causes). A comprehensive history and physical examination are essential to determine the etiology of the insomnia.

The complaint of insomnia encompasses many sleep problems. These include difficulty falling asleep, sleeping too lightly, being easily disrupted with multiple spontaneous awakenings, or early morning awakenings with inability to fall back asleep. The timing of insomnia is important in determining its etiology. Therefore, having each patient define what he or she means by insomnia is essential.

To be considered a disorder, the complaint of insomnia should be accompanied by distress and/or impairment in daytime functioning (see Morbidity).

On the basis of duration, insomnia is commonly divided into the following 3 types:

Transient insomnia lasts up to 1 week and often is referred to as adjustment sleep disorder because it most often is caused by an acute situational stress, such as a new job, upcoming deadline, or exam. It often recurs with new or similar stresses.
Short-term insomnia lasts for 1-6 months and is usually associated with more persistent stressful situational (death or illness of a loved one) or environmental (noise) factors.
Chronic insomnia is any insomnia lasting more than 6 months and is associated with a wide variety of disorders (to be discussed later).

Pathophysiology: Insomnia usually results from an interaction of biological, physical, psychological, and environmental factors.

Although transient insomnia can occur in any person, chronic insomnia appears to develop only in a subset of patients who may have predisposing factors. Evidence for this theory includes the following:

When compared to control subjects, individual with insomnia (1) have higher rates of depression and anxiety, (2) score higher on scales of arousal, (3) have longer daytime sleep latency, (4) have an increased 24-hour metabolic rate, (5) have more night-to-night variability in their sleep, and (6) may have more beta EEG activity (an EEG pattern seen during memory processing/performing tasks) at sleep onset.
In experimental models of insomnia, control subjects deprived of sleep do not demonstrate the same abnormalities in metabolism, daytime sleepiness, and personality as persons with insomnia.
In an experimental model of giving control subjects caffeine, causing a state of hyperarousal, the control subjects did have changes in metabolism, daytime sleepiness, and personality similar to those seen in individuals with insomnia.

These results support a theory that insomnia is a manifestation of hyperarousal. In other words, the poor sleep may not itself be the cause of the daytime dysfunction but merely the nocturnal manifestation of a general disorder of hyperarousability.

Therefore, chronic insomnia is believed to primarily occur in patients with predisposing factors. These factors may cause the occasional night of poor sleep, but in general, the patient sleeps well until the occurrence of a precipitating event, such as death or other life stress. Then, acute insomnia develops. If poor sleep habits or other perpetuating factors occur, chronic insomnia develops despite the removal of the precipitating factor. This theory is illustrated in Image 1.

Frequency:

In the US: In a 1991 survey, 30-35% of adult Americans reported difficulty sleeping in the past year and 10% reported the insomnia to be chronic and/or severe. Despite the high prev .....
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