It is estimated that over 50% of adults aged 65 and older report some sleep disruption, while about 20% suffer from chronic insomnia. Obstructive sleep apnea, a major cause of daytime drowsiness, occurs in an estimated 20-60% of older people, depending on the definition used and the specific population being studied. Despite the high prevalence of sleep disorders in the elderly, there have been relatively few studies focused on the consequences. Most studies have been limited by cross-sectional design, small sample size, or lack of comprehensive and objective assessment of sleep. The proposed study, Outcomes of Sleep Disorders in Older Men, will take advantage of the established cohort that has been recruited for the Osteoporotic Fractures in Men (MrOS) study (5U01AR045647-Dr. Eric Orwoll, PI). MrOS, a 7-year study that began in July 1999, is a multi-center prospective study of approximately 6000 men aged 65 and older. During the MrOS baseline visit, a broad variety of measurements were collected, including body composition and body fat distribution (by DEXA and quantitative computed tomography), bone density, anthropometry, performance-based tests of strength and balance, medical history, medication use, smoking and alcohol use, and other parameters. Blood, urine, and DNA specimens have been archived for use in future studies of importance to the health of older men. In a subcohort of 3000 MrOS participants, we propose to add comprehensive and accurate assessments of sleep using in-home polysomnography, wrist actigraphy, questionnaires and other measures; and prospective adjudication of CVD events, to the extensive measures that have already been performed or planned in the MrOS cohort study. These new measures will enable us to test several important hypotheses: 1) to characterize the associations between sleep disruption and subsequent CVD events during 3.5 years of follow-up, 2) to determine if sleep disturbances are associated with an increased risk of total and cause-specific mortality in older men, 3) to test whether sleep disturbances are associated with increased risk of falls and decreased physical function, 4) to test whether sleep disturbances are associated with impaired cognitive function in older men, and 5) to test whether sleep disorders are associated with bone density and fracture risk in older men. We will also supplement the bank of MrOS specimens to allow for testing of future hypotheses concerning the role of sleep in the development of age-related diseases and conditions.