It has been recognised that poor sleep quantity (i.e. short sleep duration) is associated with an increased risk for physical and mental diseases. However, there have been fewer studies on the associations of poor sleep quality with physical and mental health.

The subjects were 3684 (2471 males and 1213 females) employees aged 20-65 working in local government in Japan. A questionnaire survey was conducted in January 2003. Sleep quality and physical and mental health were evaluated using Pittsburgh Sleep Quality Index (PSQI) and Short Form 36 (SF-36), respectively. Logistic regression analysis was used to evaluate whether each subscale of PSQI was independently associated with poor physical and mental health (the lowest 25 percentile of the Physical and Mental Component Summary (PCS and MCS) Scores of SF-36), after adjustment for potential confounding factors.

Subjective sleep quality, sleep disturbances, use of sleep medication, and daytime dysfunction were significantly associated with poor physical health. Subjective sleep quality, sleep latency, sleep disturbances, and daytime dysfunction were significantly associated with poor mental health. The associations of subscale scores of poor sleep quality with health were relatively stronger for poor mental health than for poor physical health. Sleep duration (i.e. sleep quantity) was not associated with poor physical and mental health.

Some of the poor sleep quality measures were independently associated with both poor physical and mental health of Japanese civil servants. Longitudinal study is necessary to confirm the causal relationships between sleep quality and health.