Association between long working hours of doctors and the seriousness of adverse events: a cross-sectional study using national adverse event reporting system data in Japan.

The association between doctors' long working hours and the seriousness of adverse events with high patient impact has not been fully confirmed. Most previous studies were based on work hour regulations using more than 80 hours per week as an indicator of long working hours. We aimed to assess the association using a shorter indicator as the cut-off for long working hours among hospital doctors including senior doctors. This cross-sectional study used 12,245 adverse event reports from the Japan Council for Quality Health Care. We defined long working hours as 55 hours or more in the week before the adverse event and assessed the association with the seriousness of adverse events with high patient impact. The results showed that doctors working 55 or more hours in the preceding week were more likely to be involved in serious adverse events than those working fewer hours (odds ratio (OR) 1.22, 95% confidence interval (CI): 1.12-1.32). This association remained significant after adjusting for all covariates (OR 1.18, 95% CI: 1.08-1.28). Senior doctors were more likely to be involved in serious adverse events. Long working hours among doctors were associated with the seriousness of adverse events.