The long-term goal of this study is to provide population-based knowledge as a foundation for developing strategies to reduce the occurrence and morbidity of sleep-disordered breathing (SDB). Toward this goal, we propose a longitudinal study of middle-aged adults to characterize the natural history and biologic spectrum of SDB and test hypotheses regarding SDB causes and consequences. Our specific aims, listed below, will be accomplished by conducting follow-up polysomnography and other protocols on an established cohort (n=1400) of men and women, ages 35-70, currently enrolled in the Wisconsin Sleep Cohort Study. The proposed follow-up studies will yield data spanning 5-15 years, with 2-5 data collection points. In addition, we propose to conduct home polysomnography protocols on 200 Hmong adults. Our aims are: 1) Describe with optimal parameters the natural history and biologic spectrum of SDB; 2) Test the role of obesity and other risk factors in the occurrence and progression of SDB; 3) Test the hypothesis that SDB has a causal role in the development and exacerbation of elevated blood pressure and other cardiovascular disease risk factors; 4) Test the hypothesis that SDB causes behavioral morbidity, including extreme daytime sleepiness, cognitive impairment, motor vehicle accidents, and depression. 5) Characterize SDB and other sleep disorders in Hmong, a minority population at high risk for sudden death during sleep.