Multidimensional drivers of diabetes prevalence among middle-aged and elderly in China: from a geographical perspective

With rapid urbanization and population aging in China, diabetes has become a major public health challenge for middle-aged and older adults. Understanding its spatiotemporal patterns and key drivers is essential for targeted prevention. However, geographical insights into the nonlinear relationships, threshold effects, and interactions between multidimensional drivers and diabetes prevalence are still lacking. Using national longitudinal data from the China Health and Retirement Longitudinal Study (CHARLS, 2011–2020), we developed a framework to capture the spatiotemporal dynamics of diabetes prevalence and to analyze its linear, nonlinear, threshold, and interaction effects with multidimensional drivers, including lifestyle, social, and ecological environmental factors. Spatial autocorrelation analysis identified the clustering patterns, while a Random Forest–SHAP approach quantified and interpreted the contributions of these drivers. Prevalence exhibited a “rise-then-decline” pattern, peaking in 2018. Significant spatial clustering was observed, with northeast and central-eastern China as hotspots and the southwest as a coldspot. Body mass index (BMI) was the most influential driver, and its impact on diabetes prevalence increased sharply once it exceeded 24 kg/m². Among all multidimensional drivers, BMI also displayed the strongest synergistic effects with other factors, while ecosystem quality was inversely related to prevalence, providing quantifiable protective effects, most pronounced within the 0.38–0.62 index range. This integrated geographical framework effectively captures spatiotemporal trends and complex driver relationships, constituting a transferable model for other chronic disease studies. The findings highlight pronounced spatial disparities and identify actionable risk thresholds for BMI and ecosystem quality, providing a robust evidence base for precision prevention, targeted regional interventions, and advancing the “Healthy China” initiative and active ageing.