Association between mental health and duty hours of postgraduate residents in Japan: a nationwide cross-sectional study

The new duty hour (DH) limit for doctors in Japan will begin in 2024, setting the maximum DHs for postgraduate residents at approximately 80 h weekly. To set appropriate limits, understanding the association between DHs and psychological health is necessary. Thus, we assessed the relationship between residents’ psychological health and DHs. We conducted a cross-sectional study involving examinees of the General Medicine In-training Examination 2020. Mental health outcomes were measured dichotomously using the Patient Health Questionnaire-2 for depression and Mini-Z 2.0, for burnout, stress, and satisfaction. Weekly DHs were measured in seven categories at 10-h intervals. The prevalence ratios (PRs) between the DH categories were estimated for each outcome. Of the 6045 residents who provided data on DHs and psychological outcomes, 37.3% showed signs of depression, 21.6% experienced burn out, and 39.2% were highly stressed. In contrast, 62.3% were highly satisfied with their training. Proportions of burnout were higher among residents in Category 6 (≥ 90 and