Excerpt from Insomnia

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Background

Insomnia is defined as difficulty with sleep initiation, maintenance, or quality despite adequate time and opportunity that occurs on a repeat basis and results in some form of daytime impairment. It is the most commonly reported sleep-related problem, with approximately 10-15% of Americans having daytime impairment as a result of the sleep disturbance, and is associated with a variety of medical, psychiatric, and sleep disorders. A comprehensive history and physical examination is essential for determining the underlying etiology of insomnia.

A patient's report of insomnia is nonspecific and can encompass a variety of concerns, including difficulty falling asleep, awakening early or easily, problems with returning to sleep after awakening, or a general poor quality of sleep. Therefore, the patient must define what he or she means by insomnia. In order to be considered a disorder, the insomnia should be accompanied by daytime sleepiness, loss of concentration, irritability, worries about sleep, loss of motivation, or other evidence of daytime impairment that is associated with the sleep difficulty.

Insomnia is commonly divided into 3 types based on duration. The first type is transient insomnia. Transient insomnia lasts up to 1 week and is often referred to as adjustment sleep disorder because it is caused most often by an acute situational stress, such as a new job, upcoming deadline, or examination. It is often recurrent with new or similar stresses. The second type, short-term insomnia, is defined as that lasting 1-6 months and is usually associated with more persistent stressful situational (death or illness) or environmental (noise) factors. The third type is chronic insomnia. Chronic insomnia is any insomnia lasting more than 6 months and is associated with a wide variety of disorders.

Other related eMedicine articles include Insomnia (neurology focus) and Primary Insomnia. In addition, the following Medscape CME courses are available:

• Insomnia: Impact on Health and Quality of Life
• Insomnia and Comorbid Anxiety
• The Treatment of Insomnia in Older Adults

Pathophysiology

Determinants of insomnia

Insomnia is usually a result of an interaction of biological, physical, psychological, and environmental factors.

While transient insomnia can occur in any person, chronic insomnia appears to develop only in a subset of patients who may have predisposing factors. The evidence supporting this theory indicates that, compared with persons who have normal sleep, persons 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 increased 24-hour metabolic rates,¹ (5) have more night-to-night variability in their sleep, and (6) may have more beta electroencephalogram activity (a pattern observed during memory processing/performing tasks) at sleep onset.

In experimental models of insomnia, normal subjects deprived of sleep do not demonstrate the same abnormalities in metabolism, daytime sleepiness, and personality as subjects with insomnia. In an experimental model in which normal subjects were given caffeine, causing a state of hyperarousal, the normal subjects had changes in metabolism, daytime sleepiness, and personality similar to subjects with insomnia.² These results support a theory that insomnia is a manifestation of hyperarousal. In other words, the poor sleep itself may not be the cause of the daytime dysfunction, but merely the nocturnal manifestation of a general disorder of hyperarousability.

One theory holds that chronic insomnia is the result of 3 components: predisposing factors, precipitating factors, and perpetuating factors. Patients who develop chronic insomnia are thought to have predisposing factors that put them at risk. These factors may cause the occasional night of poor sleep, but, in general, the patient sleeps well until a precipitating event (eg, death or other life stress) occurs. Then, the patient develops acute insomnia. If the patient develops bad sleep habits or other perpetuating factors, chronic insomnia develops despite the removal of the precipitating factor. This theory is illustrated in Media File 1.

Frequency

United States

In a 1991 survey, 30-35% of adult Americans reported difficulty sleeping in the past year and 10% reported the insomnia to be chronic, severe, or both. Despite the high prevalence, only 5% of individuals with chronic insomnia visited a clinician specifically to discuss their insomnia, while only 26% discussed their insomnia during a visit made for another problem.

International

A study from Quebec indicated an overall prevalence rate of insomnia of approximately 20% in French Canadians. A study of young adults in Switzerland indicated a 9% rate of chronic insomnia. A World Health Organization study of 15 sites found a prevalence rate of approximately 27% for patients reporting "difficulty sleeping."

Mortality/Morbidity

Insomnia is associated with a variety of symptoms related to daytime functioning.

• Individuals with insomnia report an impaired ability to concentrate, poor memory, difficulty coping with minor irritations, and decreased ability to enjoy family and social relationships.
• Individuals with insomnia are more than twice as likely to have a fatigue-related motor vehicle accident.
• The mortality rate appears to be higher in patients who sleep fewer than 5 hours each night.

Sex

The prevalence rate of reported insomnia is higher in women than in men (approximately 40% vs 30%).

Age

Frequency increases with age.

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