BackgroundMedical interns’ quality of life (QOL) are related to patient care quality, but the specific factors responsible for interns’ QOL have not been well studied. Herein we presented this nationwide, prospective study to examine the impact of working hours restrictions on the QOL among medical interns.MethodsThe study recruited 295 medical interns (age: 25.3 ± 2.1, male: 68.1%) from all the 8 medical colleges in Taiwan during the 2012–2013 academic years. Subjects were assessed for QOL by brief version of the World Health Organization Quality of Life Assessment (WHOQOL-BREF) and the 9-item Patient Health Questionnaire (PHQ-9) before and every 3 months during their internship. We also investigated their demographic data, working hours, workload characteristics, such as specialties of internship rotation, acceptance of new patients after 24-hour, and no 24-hour off within 7 days, and self-reported patient related burnout. We used generalized estimation equation to delineate the change of WHOQOL-BREF and PHQ-9 scores during internship. We used multivariate regression analysis to examine the associated factors of QOL.ResultsWHOQOL-BREF score significantly decreased during internship (baseline: 60.0 ± 9.7, 53.7 ± 9.3 at 3 months, then remained at 55 after 9 months). Acceptance of new patients after 24 hours of continuous duty (β = -2.089), no 24-hour off within 7 days (β = -1.748), score of patient related burnout (β = -2.50), and PHQ-9 depression score (β = -1.02) were associated with lower WHOQOL-BREF score. Working hours was not significantly associated with the QOL (p = .6268).ConclusionsOur findings revealed interns’ QOL significantly decreased during internship. Acceptance of new patients after 24-hour of continuous duty and patient related burnout predominantly impacted interns’ QOL and depression more than working hours did.