The line is drawn, the fate is cast: urban–rural inequalities in the timing of initial health check-ups in China

Introduction Despite sustained advances in medical innovation and expanded access to healthcare services, inequalities in the uptake of health check-ups persist, pointing to enduring mechanisms in the reproduction of health inequalities. Although Fundamental Cause Theory (FCT) has been widely used to examine such inequalities, it has largely been operationalized at the individual level, with limited attention to institutional arrangements and insufficient consideration of how mechanisms of inequality shift over time. Methods Drawing on the 2014 life history data from the China Health and Retirement Longitudinal Study (CHARLS), this research employs accelerated failure time (AFT) models to assess how China’s hukou system operates as an institutional determinant shaping inequalities in the timing of initial health check-ups. We analyze blood pressure tests and blood tests for glucose or cholesterol, vision and dental exams, and breast and prostate cancer screenings to assess how inequality unfolds across different stages of medical innovation diffusion. Results The results indicate that urban hukou holders consistently undergo health check-ups earlier than their rural counterparts across all types of services. Among those with rural hukou , urban residence is associated with earlier uptake, particularly for blood tests, dental exams, and vision exams. As medical innovations diffuse, hukou -based inequalities tend to narrow for services at later stages of diffusion but widen for those at earlier stages. Discussion This research reveals a dynamic substitution of mechanisms through which health inequalities are reproduced, highlighting the enduring institutional influence of the hukou system and its interaction with the diffusion of medical innovations in sustaining health inequalities over time.