Since the studies reviewed are extremely heterogeneous, the lack of clearly defined selective criteria makes it impossible for the reader to form an opinion on this topic. First, some of the research focuses on subjects other than OSA (eg, sleep-disordered breathing2 or complaints such as snoring and daytime sleepiness3). Second, different methods of diagnosis are used in the studies that deal specifically with OSA. In some studies, cases were diagnosed objectively using polygraphy or polysomnography, while in other studies, a broader definition of suspected OSA was adopted, based on standardized or nonstandardized questionnaires. Third, the review fails to assess the quality of the studies. This means that findings of unequal quality could be placed on the same level.