Trends and socioeconomic inequities in insomnia-related symptoms among Japanese adults from 1995 to 2013.

BACKGROUND

Although insomnia prevalence is increasing in developed countries, little is known about trends in sleep problems among Japanese adults according to socioeconomic status. Therefore, we aimed to determine trends and socioeconomic inequalities in insomnia-related symptom (IRS) in Japan using nationally representative data.

METHODS

The IRSs were based on past subjective sleeping difficulty. Using data from the Comprehensive Survey of Living Conditions for every 3 years from 1995 to 2013, we built multivariable Poisson regression models, with IRS as an outcome and survey year and socioeconomic status variables as explanatory variables.

RESULTS

Data from 513,223 Japanese adults were analyzed. Age- and sex-adjusted IRS prevalence was the lowest in 1995, highest in 2007, and decreased from 2007 to 2013. The IRSs were more frequently reported in unemployed or self-employed individuals aged 20-64 years; those with the lowest household expenditure level, except among women aged ≥65 years; and those divorced, separated, or single, especially among women aged 20-64 years.

LIMITATIONS: First, the repeated cross-sectional study design prevented the exclusion of the possibility of reversal of causality between factors. Second, data on insomnia-related lifestyle behaviors were unavailable. Third, the IRSs examined did not meet established clinical criteria for clinical insomnia. Fourth and fifth, information and selection biases could exist because of self-reported data and a small sample size, respectively.

CONCLUSIONS

These results could aid in developing more effective prevention strategies for sleep problems and provide benchmarks for monitoring sleep health trends in Japan and other East Asian countries.