Effect of unequal employment status on workers' health: results from a Japanese national survey.

This study assesses the possibility of a period effect on Japanese workers' health and its association with historical changes in the work environment. We used multi-year national cross-sectional surveys, the Comprehensive Survey of Living Conditions for 2001, 2004, and 2007, and estimated the period effect on the health of employed workers aged 18-65 years. The prevalence of ill-health indicators (poor self-rated health status, subjective symptoms, and the number of respondents receiving consultations from medical doctors and other health professionals) significantly increased during this period. Deteriorating trends in these health indicators persisted after adjusting for age and cohort effects and for individual factors such as employment, marital, and child-rearing status. Furthermore, after adjusting for income level as an individual factor, deteriorating trends remained for the poor self-rated health status of male employees, subjective symptoms of female employees, and receiving medical consultations for both genders. The health status of employed workers in Japan deteriorated, especially from 2004 to 2007, regardless of age and cohort effects. After taking individual socio-economic factors and the effects of the recession on society into consideration, we hypothesized a posteriori that the increase in precarious non-regular work may be the main factor underlying this period effect and may be the cause of the deterioration in workers' health.