Nonlinear association between provincial implementation intensity of county-level medical communities and patient flow patterns

Introduction As a key initiative of China’s healthcare system reform, tightly integrated county-level medical communities (CCMCs) are designed to optimize the allocation of high-quality medical resources and advance the tiered healthcare delivery system. However, evidence on their policy effects remains mixed, and most studies treat CCMC construction as a binary intervention while overlooking continuous variations in implementation intensity. Meanwhile, the international literature on integrated care and referral governance focuses largely on established universal health systems, with limited attention to how progressive reforms unfold nonlinearly in developing countries facing resource constraints and patient outflows. This study addresses two unresolved questions: does intensifying CCMC construction continuously promote local patient retention, or does it initially generate patient diversion toward county-level hospitals at the expense of grassroots resources?. Methods Departing from prior work that relies on dummy variables, we construct a multidimensional CCMC Construction Intensity Index (CII) covering policy coverage, organizational integration, and institutional safeguards. Using provincial panel data from 2014 to 2024 and a two-way fixed-effects model, we identify the causal relationship between CII and patient flow patterns. Results We observe a U-shaped association between CII and the relative scale of in-county visits, though this association is attenuated under more demanding trend controls and the estimated inflection point shows some sensitivity to sample composition. At lower levels of construction intensity, patient diversion toward county hospitals accompanies the resource integration process; once intensity crosses the threshold, substantive integration and long-term mechanisms are gradually unleashed, and patient retention within counties begins to dominate. This pattern is mirrored by an inverted U-shaped trend in out-of-county care-seeking. Heterogeneity analysis shows that these patterns are more pronounced in western regions and in areas with a higher density of private hospitals; within grassroots facilities, benefits accrue primarily to township health centers, while community stations and village clinics lag behind. Discussion Theoretically, this study reveals that CCMC development in China follows a threshold-dependent trajectory, contributing Chinese evidence on the nonlinear evolution of referral dynamics to the global integrated care literature and helping reconcile mixed prior findings. From a policy perspective, the findings offer empirical support for calibrating implementation intensity to local contexts and for prioritizing township health centers as the main recipients of resource devolution, so as to mitigate early-stage patient diversion and support the gradual advancement of the tiered healthcare system.