A Norwegian population-based study on the risk and prevalence of obstructive sleep apnea. The Akershus Sleep Apnea Project (ASAP).

The Berlin Questionnaire (BQ) is a widely used screening tool for obstructive sleep apnea (OSA), but its performance in the general population setting is unknown. The prevalence of OSA in middle-aged adults is not known in Norway. Accordingly, the aims of the current study were to evaluate the utility of the BQ for OSA screening in the general population and to estimate the prevalence of OSA in Norway. The study population consisted of 29,258 subjects (aged 30-65 years, 50% female) who received the BQ by mail. Of these, 16,302 (55.7%) responded. Five-hundred and eighteen subjects were included in the clinical sample and underwent in-hospital polysomnography. Screening properties and prevalence were estimated by a statistical model that adjusted for bias in the sampling procedure. Among the 16,302 respondents, 24.3% (95% confidence interval (CI)=23.6-25.0%) were classified by the BQ to be at high-risk of having OSA. Defining OSA as an apnea-hypopnea index (AHI) ≥5, the positive predictive value of the BQ was estimated to be 61.3%, the negative predictive value 66.2%, the sensitivity 37.2% and the specificity 84.0%. Estimated prevalences of OSA were 16% for AHI≥5 and 8% for AHI≥15. In conclusion, the BQ classified one out of four middle-aged Norwegians to be at high-risk of having OSA, but the screening properties of the BQ were suboptimal. The estimated prevalence of OSA was comparable to previous estimates from general populations in the USA, Australia and Europe.