Moderating effects of psychological job strain on the relationship between working hours and health: an examination of white-collar workers employed by a Japanese manufacturing company.

The effects of working hours on health were examined taking psychological job strain into account. White-collar workers employed at the main office of a Japanese manufacturing company provided data for analysis done in 1997. The eligible subjects were 286 workers aged 20-39. Causal relationships between working hours, health, and psychological job strain were examined by covariance structure analyses. The main findings were as follows: Not only working hours but also sleeping hours and vacations affected the workers' effort to deal with work as a work-related hour factor. Decision authority and skill discretion of Karasek's psychological job strain items significantly constituted a discretion in the work factor, and this factor moderated the effects of the work-related hour factor on health. The effects of psychological job strain, especially discretion, must always be taken into account in examinations of working hours and health.