Insomnia is the most prevalent type of sleep disorder; rates are as high as 10% in the general population and the prevalence increases with age (NIH 2005). Rates of chronic insomnia can be as high as 30% in older adults, greater in frequency and severity than any other age group (Petit, Azad, Byszewski, Sarazan, and Power 2003). Insomnia typically involves difficulties in initiating sleep, maintaining sleep, and/or waking too early. There can be substantial daytime dysfunction with the disorder, including fatigue and lethargy. Sometimes insomnia is secondary to other psychiatric disorders such as substance dependence or is subsumed as a core symptom, such as with major depressive disorder. Also, insomnia often manifests as a result of an underlying medical condition such as rheumatoid arthritis, cardiopulmonary disorders, or low back pain (NIH 2005). However, insomnia can be present in the absence of psychiatric or medical conditions, and in such cases is termed primary insomnia. The chronicity of primary insomnia can be long lasting, although few studies have characterized its natural course (NIH 2005). According to the Diagnostic and Statistical Manual—IV, Revised (Association 2000), primary insomnia diagnosis requires a duration of at least one month, but a number of clinical trials have extended entrance criteria to 6 months (Morin, Bastien, Guay, Radouco-Thomas, Leblanc, and Vallieres 2004).
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