Abstract
Objective: Previous reports on sleep epidemiology have demonstrated that insomnia was more prevalent in women than in men. However, it remains to be elucidated whether similar female predominance may be true for different symptomatic subtypes of insomnia. We surveyed prevalence of insomnia subtypes among Japanese general adult population and examined the gender difference after adjusting for the confounding effect of sociodemographic factors. Methods: Cross-sectional surveys with a face-to-face interview were conducted in August and September, 2009, as part of the Nihon University Sleep and Mental Health Epidemiology Project (NUSMEP). Data from 2,559 people aged 20 years or older were analyzed (response rate 54.0%). Participants completed a questionnaire on sleep problems including the presence or absence of insomnia (i.e., difficulty initiating sleep (DIS), difficulty maintaining sleep (DMS), and early morning awakening (EMA)). Results: DIS occurring at least three nights per week was reported by 7.2% (men: 5.5%, women: 8.5%), DMS by 15.2% (men: 13.4%, women: 16.6%), EMA by 5.2% (men: 5.3%, women: 5.0%), giving the prevalence of 18.8% (men: 17.0%, women: 20.3%) regarding those who had any insomnia symptom. The overall prevalence of DIS, DMS, and any insomnia symptom was significantly higher in women than in men. Multiple logistic regression analyses revealed that only DIS was significantly associated with women after adjustment for the confounding effect of sociodemographic factors. Conclusions: This study has demonstrated that DIS played an important role in significance of gender difference of insomnia.
