Clinical and socioeconomic correlates of insomnia.

Insomnia is characterized by difficulty falling asleep (sleep onset disturbance), difficulty staying asleep (sleep maintenance disturbance), or poor quality (nonrestorative) sleep, leading to impairment of next-day functioning, including psychological distress. Published prevalence estimates of insomnia vary considerably, very likely due to differences in definitions, study setting, and data collection methods. However, estimates based on large population-based surveys provide a rather constant prevalence rate for chronic insomnia in the United States of about 10% (approximately 25 million people). Chronic insomnia is associated with numerous physical and psychiatric conditions and is more common in women and the elderly. Although it is often perceived as a symptom of depression, insomnia is also a precursor of depression and is associated with a substantial increase in the relative risk of major depression. Chronic insomnia is correlated with impaired mood, subjective functioning, and quality of life and, in some cases, with increased daytime sleepiness and accident risk. Those reporting insomnia have higher rates of absenteeism and health care utilization. Direct costs of insomnia have been estimated to be $13.9 billion annually, with a large majority of costs attributable to nursing home care. Chronic insomnia is a common problem, often associated with negative waking mood or function. As such, heightened clinical attention and clinical research appear warranted.