Over the past decades, urban shrinkage has caused disparities in healthcare provision across regions. While some studies have demonstrated inequalities in treatable mortality (TM) associated with this trend, the interrelationships among urban shrinkage, healthcare provision, and TM remain unexplored. Against this backdrop, this study examines the dynamic interactions among the TM rate, healthcare provision—represented as the number of physicians or inpatient rooms per 100 population—and the net inflow rate of the young population in South Korea from 2012 to 2022, using panel vector autoregressive models and Granger causality test. The results suggest that the expansion of inpatient rooms is the most effective factors in reducing TM. In contrast, the number of physicians did not lead TM changes, implying that mere presence of medical personnel is insufficient for the purpose. Additionally, an increase in the TM rate discourages the inflow of young population, whereas a higher inflow of young population promotes growth in both healthcare provision indicators. All variables exhibited self-reinforcing dynamics, suggesting that disparities in public health, medical resources, and urban shrinkage are likely to persist without targeted intervention. It is therefore crucial to address these issues before the situation deteriorates further. Our findings offer valuable insights for sustainable regional development and informing public health strategies amid ongoing global urban shrinkage.