ABSTRACT
<b>OBJECTIVE</b> : This study was conducted in a Japanese population to better understand the association between insomnia and sleeping prone.<br><b>METHODS</b> : A cross sectional questionnaire study was conducted with outpatients of St. Luke's International Hospital in August, 2007. Information on sleep position habits, symptoms, quality of life, and sleep quality was collected. The Athens Insomnia Scale (AIS) was used to measure sleep quality. Participants with an AIS score of 4 or higher were categorized as sub-threshold insomnia and as the insomnia group.<br><b>RESULTS</b> : Of the 784 subjects who returned completed questionnaires (response rate=65%) 30.4% were men. About 13% of the respondents slept in the prone position at least three times a week. Based on multivariate adjusted logistic regression analysis, there was a significant association between sleeping prone and having no problem with insomnia (odds ratio, 0.61 ; 95% CI, 0.38-0.99).<br><b>CONCLUSION</b> : These data suggest that sleeping in the prone position is associated with good quality sleep.