From Rising Medical Spending to Household Debt Transitions: Four-Party Sharing and Transfer of Medical Financial Risk After Hospitalization

We use China Family Panel Studies data to construct a four-party model of local government, healthcare providers, a service-integration platform, and older households and examine why medical spending rises after hospitalization while changes in household debt are not statistically detectable in the next survey wave. The model combines a Stackelberg game, quantal response equilibrium, and Markov state transitions to analyze protection payments, cost formation, service coordination, and household financing. The empirical results show that medical consumption and household out-of-pocket payments increase during hospitalization waves, whereas the effects on debt entry and debt persistence are not statistically detectable, and the debt-persistence estimate is imprecise. Under literature-supported directions and normalized parameters, the scenarios associate stronger protection, lower provider coordination costs, and higher net returns to platform accountability with lower household financing. Financing costs first affect financing strategies and then affect two-year debt states. By incorporating debt transitions into a multi-party framework for medical financial protection, the analysis connects protection payments, household financing, and financial states to clarify the observed debt-transition pattern.