The study quantified the etiologic role of hypothesized risk factors for sleep disordered breathing, described progression of the pathophysiologic process, and tested causal hypotheses of adverse health outcomes. The study was conducted on a unique, established cohort of over 800 subjects, representative of middle-aged employed adults. Extensive baseline polysomnographic and other data were available on the established cohort of 800 subjects; additional cohorts of 50 perimenopausal women and 200 older adults were added for maximum study power. The research resulted in longitudinal data, over a 5-9 year period, on multiple parameters of sleep, breathing, risk factors and outcomes. The independent relative risks were calculated with multivariate techniques to express the temporal relationships for sleep disordered breathing etiologic factors and for consequences of sleep disordered breathing.