It is estimated that over 50 percent of adults aged 65 and older report some sleep disruption, while about 20 percent suffer from chronic insomnia. Obstructive sleep apnea, a major cause of daytime drowsiness, occurs in an estimated 20-60 percent 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 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 6,000 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 dual energy X-ray absorptiometry (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 Blood, urine, and DNA specimens have been archived for use in future studies of importance to the health of older men.