Overtime work and the incidence of long-term sickness absence due to mental disorders: A prospective cohort study.

BACKGROUND Although previous research has focused on the association between long working hours and several mental health outcomes, little is known about the association in relation to mental health-related sickness absence, which is a measure of productive loss. We aimed to investigate the association between overtime work and the incidence of long-term sickness absence due to mental disorders. METHODS Data came from the Japan Epidemiology Collaboration on Occupational Health Study (J-ECOH). A total of 47,422 subjects were followed-up in the period between April 2012 and March 2017. Information on long-term sickness absence (LTSA) was obtained via a study-specific registry. Baseline information was obtained at an annual health checkup in 2011; overtime working hours were categorized into <45; 45-79; 80-99; and ≥100 hours/month. RESULTS During a total follow-up period of 211,443 person-years, 536 people took LTSA due to mental disorders. A Cox proportional hazards model was revealed that compared to those with less than 45 hours/month of overtime work, those with 45-79 hours/month were at a lower risk of LTSA due to mental health problems (hazard ratio [HR] = 0.63, 95% confidence interval [CI] = 0.55-0.72) while those with overtime work of ≥100 hours/month had a 2.11 times (95%CI = 1.10-4.07) higher risk of LTSA due to mental health problems. CONCLUSION Engaging in excessive overtime work was linked with a higher risk of LTSA due to mental health problems while the lower risk observed among individuals working 45-79 hours/month of overtime work might have been due to a healthy worker effect.