Work and family characteristics as determinants of socioeconomic and sex inequalities in sleep: The Japanese Civil Servants Study

STUDY OBJECTIVE: To clarify whether socioeconomic and sex inequalities in poor sleep quality are explained by socioeconomic and sex differences in work and family characteristics. DESIGN: A cross-sectional study. PARTICIPANTS: Three thousand five hundred fifty-six employees (2397 men and 1159 women) aged 20 to 65 years in local government in Japan. MEASUREMENTS: Respondents completed a self-administered questionnaire that asked about sleep quality, as measured by the Pittsburgh Sleep Quality Index; work characteristics, as measured by the job-demand-control-support model, work hours, and shift work; and family characteristics, such as family structure and family-work conflicts. RESULTS: Lower control at work, higher work demands, lower social support, shorter and longer working hours, shift work, being single, higher family-to-work conflict, and higher work-to-family conflict were independently associated with poorer sleep quality in both men and women. In men, the age-adjusted odds ratio (OR) of low-grade employees for poor sleep quality was 1.64 (95% confidence interval: 1.14-2.36) in comparison with high-grade employees. The difference in sleep was attenuated when work and family characteristics were adjusted for (OR=1.25 [0.84-1.86]). Among women, there was no significant grade difference in sleep. Women tended to have poorer sleep quality than men (the age-adjusted OR=1.75 [1.49-2.06]). The sex difference was attenuated and no longer significant when adjustments were made for work and family characteristics (OR=1.04 [0.85-1.27]). CONCLUSIONS: The results of this study suggest that work and family characteristics may be important for reducing socioeconomic and sex inequalities in sleep. Sex differences in the pattern of socioeconomic inequalities in sleep deserve further research.