Three-shift system increases job-related stress in Japanese workers.

We assessed the relationship between shift work and job stress. The target subjects were 4,962 male workers (3,078 day workers and 1,884 shift workers) aged 18 to 60 yr who work in a Japanese steel company. We used the "Brief Job Stress Questionnaire", which was developed by a research group organized by the Japanese Ministry of Labour. We evaluated the effect of shift work on job stress using logistic regression analysis including age, lifestyle factors, work conditions, marital status, and living arrangements in the model. Job schedule type was significantly associated with job control, with an odds ratio of 2.22 for shift workers compared to day workers. The logistic regression analysis revealed that the odd ratios for having one or more stressor items in an unfavorable condition were significantly higher for shift workers compared to day workers. Increase in the amount of overtime and decrease in the number of holidays led to a significant deterioration in job stress. Our study reveals that the 3-shift system of employment increases work-related stress, and that job control is low among shift workers. To reduce job stress in this occupational population, a reduction in the amount of overtime and an increase in the number of holidays seem to be useful interventions.