The study utilized an extremely rich source of data collected on the Wisconsin Sleep Cohort, one of the largest cohort studies of SDB and one with the longest periods of follow-up, to address a broad array of questions related to the pathogenesis and risk of SDB in the general community. The data-set was obtained between 1988 and 1998 in a population of 1400 workers age 30 to 60 years, including an overnight sleep polysomnographic in-lab study conducted on two occasions over an eight year period. The dataset contained a computerized analysis of over 300,000 apneas and hypopneas in this non-clinical population.