The proportion of sleep apnea syndrome (SAS) in the general adult population that goes undiagnosed was estimated from a sample of 4,925 employed adults. Questionnaire data on doctor-diagnosed sleep apnea were followed up to ascertain the prevalence of diagnosed sleep apnea. In-laboratory polysomnography on a subset of 1,090 participants was used to estimate screen-detected sleep apnea. In this population, without obvious barriers to health care for sleep disorders, we estimate that 93% of women and 82% of men with moderate to severe SAS have not been clinically diagnosed. These findings provide a baseline for assessing health care resource needs for sleep apnea. Key Words: Sleep apnea-Epidemiology-Sleep disorders-Prevalence.

The disparity between the high prevalence of occult sleep apnea in the general population and the presumed low level of its clinical recognition has prompted concern that clinically significant disease is being missed (1-3). The diagnosed prevalence, however, has never been measured, so the magnitude of the disparity is unknown. To address this, we determined the prevalences of clinically diagnosed and screen-detected sleep apena syndrome (SAS) in the Wisconsin sleep cohort study, an ongoing population-based study.