The natural history of insomnia and its relationship to respiratory symptoms.

BACKGROUND: Although insomnia is a frequent complaint among patients, epidemiologic study has been limited. Researchers have reported a wide range in the prevalence of this complaint in a variety of selected populations. Other parameters, such as incidence and remission rates, have not been reported.

METHODS: Subjects of the Tucson (Ariz) Epidemiologic Study of Obstructive Lung Disease were asked questions about trouble sleeping in the 1984-1985 (survey I) and 1990-1992 (survey II) surveys. Answers were analyzed along with responses to questions about age, sex, respiratory symptoms, and drug and alcohol use for sleep.

RESULTS: The prevalence of insomnia was similar in both surveys, 34.4% in survey I and 34.1% in survey II. Women had a higher prevalence of insomnia than men in both surveys, and insomnia was more common among older subjects (50.6% of the women aged 65 years or older had insomnia in survey II). In addition, the incidence of new insomnia in survey II was higher in the same groups. Grouping subjects by respiratory symptoms, we found that the prevalence of insomnia was significantly related to cough, dyspnea, or wheeze. Furthermore, subjects with persistent or new respiratory symptoms at survey II were less likely to have remission of insomnia by that survey (31.6% vs 51.5%; P < .05; odds ratio, 0.43) and more likely to develop new insomnia (28.6% vs 14.5%; P < 05; odds ratio, 2.36) than subjects with either no symptoms or disappearance of their symptoms by survey II.

CONCLUSIONS: In our population, insomnia is a common dynamic complaint whose frequency waxes and wanes in association with respiratory symptoms.