Impact of mass resident physician resignation on inpatient mortality and admissions in Korea

Objective In February 2024, over 90% of South Korea's resident physicians resigned in protest of government medical school expansion policies, creating an unprecedented healthcare crisis. This study examined whether this mass exodus affected patient outcomes in critical internal medicine departments, where residents traditionally provide 24-h coverage and frontline care. Study design A multicenter, retrospective observational study using interrupted time series analysis. Methods We analyzed data from eight major referral hospitals in the Catholic Medical Center network, examining 124,032 hospitalizations across four internal medicine subspecialties (pulmonology, gastroenterology/hepatology, cardiology, and nephrology) during 52 weeks before and after the February 2024 crisis. We assessed changes in hospital admissions, ICU utilization, and in-hospital mortality rates. Results Total hospital admissions decreased by 17.4% post-crisis (from 67,917 to 56,115), with the largest reductions in pulmonology (23.1%) and nephrology (24.9%). While absolute numbers of ICU-level care events and deaths declined, mortality rates per 1000 inpatients and per 100 ICU cases remained stable overall. Regression analyses confirmed significant reductions in weekly mortality counts (adjusted for time-varying confounders) but no increase in normalized mortality rates. Department-level analysis showed heterogeneous effects, with gastroenterology/hepatology demonstrating mortality reductions and pulmonology showing slight increases in ICU-adjusted mortality. Conclusions Inpatient mortality did not increase following the mass resident resignation. However, this was observed alongside a marked reduction in admissions and an increased proportion of critically ill patients, consistent with selective prioritization of higher-acuity admission. These findings suggest that apparent stability in mortality metrics masked significant access limitations and unsustainable workforce burden.