With long hours of work, might depression then lurk? A nationwide prospective follow-up study among Danish senior medical consultants.

Objective: The aim of this study was to examine depression as a potential negative health effect of long work hours, anticipating an exposure-response relationship.

Method: A nationwide prospective cohort study of 2790 Danish senior medical consultants was conducted (61.7% response rate). With the consent of Danish Data Protection Agency, data from a questionnaire survey was linked with data from a Medical Products Agency Register. Long work hours were defined based on a self-reported average of weekly work hours >40, while redemption of anti-depressive (AD) drug prescriptions defined depression. Proportional hazards Cox regression analyses were conducted adjusting for gender, age, marital status, medical specialty, decision authority at work, work social support, quantitative work demands, and AD drugs prescribed before baseline.

Results: Long weekly work hours did not increase the risk of redeeming AD drug prescriptions at all times during follow-up compared to the reference of 37-40 work hours [41-44 hours: hazard ratio (HR) 0.95, 95% confidence interval (95% CI) 0.5-1.8; 45-49 hours: HR 0.88, 95% CI 0.4-1.8; 50-54 hours: HR 0.83, 95% CI 0.3-2.1; 55-59 hours: HR 0.67, 95% CI 0.2-2.9; ≥ 60 hours: HR 0.48, 95% CI 0.1-3.7]. The same result emerged when work hours was applied in a continuous form (from 25-36 hours to 37-40 hours to 41-44 hours and so on) (HR 0.93, 95% CI 0.76-1.13) and when robust analyses were conducted (data not shown).

Conclusions: This study does not support the anticipation that long work hours increase the risk of depression. If anything, long work hours vaguely appear to decrease the risk of redeeming AD drug prescriptions.