In this longitudinal study, follow-up polysomnography and other protocols are conducted on an established cohort of men and women (age 30-60 years at the time of initial recruitment in 1989), currently enrolled in the Wisconsin Sleep Cohort Study. The study aims to : 1) describe the natural history of SDB across middle and older age; 2) investigate associations of SDB with early and intermediate markers of cardiovascular dysfunction, damage, and cardiovascular disease; 3) investigate the longitudinal association of SDB in accelerated cognitive decline; 4) investigate the association of SDB and adverse sleep characteristics with age-related risk factors and outcomes.