Insomnia Definition and Prevalence

Definition and Prevalence
Unlike SDB, PLMS, or RBD, insomnia is not considered a sleep disorder in itself, but rather a complaint of insufficient and nonrestorative sleep. There are several possible causes for the insomnia complaint, including medical, psychiatric, drug and medication use, changes in circadian rhythms, and psychophysiologic issues.

Insomnia may be short or transient, lasting only a few days to a few weeks. Most often, transient insomnia may be related to a specific event, such as taking an exam, moving to a new house, starting a new job, divorce, or loss of a loved one. The anxiety associated with the stressful event may interfere with sleep and, if not resolved effectively, poor sleep habits may turn into long-term psychophysiologic insomnia.

The prevalence of insomnia increases with age. In a survey of more than 9000 elderly adults 65 years and older, 28% complained of difficulty initiating sleep, and 42% reported difficulty in both initiating and maintaining sleep. In a study done in the general practice, more than 50% of elderly patients reported insomnia, with 80% of those reporting that the insomnia was a chronic condition. Insomnia was associated with poor sleep hygiene and with depression. Women complained of insomnia more than men. The annual incidence rate of insomnia in the elderly was found to be 5% and was associated with depressed mood, respiratory symptoms, poor perceived health, physical disabilities, widowhood, and use of sedatives. Remission was estimated as 15% annually and was associated with improved self-perceived health, no new medical conditions such as heart disease and stroke, and improved physical functioning. African-American women were found to have a higher incidence of insomnia than either African-American men or Caucasian men and women.

Clinical Presentation
Insomnia may present as a difficulty in falling asleep, which is referred to as sleep onset insomnia, or as a difficulty in maintaining sleep throughout the night, which is called sleep maintenance insomnia. In sleep onset insomnia, the patient may lie in bed without falling asleep from 30 min to a few hours. With sleep maintenance insomnia, falling asleep is achieved easily, but the patient awakens one to several times during the night and has difficulty falling back to sleep. Some patients have both sleep onset and sleep maintenance insomnia. In the elderly, waking up too early in the morning and having difficulty getting back to sleep is particularly prevalent, often secondary to advanced sleep phase syndrome (ASPS). ASPS is a common circadian rhythm sleep disorder in the elderly, in which the timing of the sleep period is advanced to an earlier hour and wake-up time is correspondingly advanced as well.

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Revision date: July 4, 2011
Last revised: by Andrew G. Epstein, M.D.