Epidemiological study on sleep habits and insomnia of new outpatients visiting general hospitals in Japan

A large scale epidemiological survey of sleep habits, specifically for insominia, was conducted using 6277 new outpatients from 11 general hospitals in Japan. They were requested to answer a questionnaire newly designed for this study, which consisted of 34 questions concerning socio-demographic characteristics, current medical conditions, sleep habits, current or past sleep complaints, symptoms of parasomnia, use of hypnotics/anxiolytics and other aspects of daily life. Insomnia was the focus of analysis using χ2 statistics and, additionally, logistic regression to explore the predictors of insomnia. Bedtime was 23:30 and wake-up time was 6:35 on average, with a mean sleep time of 6.77 h on weekdays. The number of subjects with current sleep complaints was 1276, of which 735 (11.7% of the total sample) had insomnia lasting for 1 month or more. Only 37.6% of those were taking hypnotics and/or anxiolytics. Old age, female sex, neurology, psychiatry, early bedtime, late wake-up time, living alone and dissatisfication with the bedroom environment for sleep were found to be associated with long-term insomnia. This study helps to provide a framework for further studies using the general population.