Beyond Ageing: Spatial and Social Inequalities in Incident Edentulism Among Older Chinese Adults.

UNLABELLED: Edentulism is a severe endpoint of oral-health deterioration and a major challenge for healthy ageing. This study aimed to identify high-risk populations, high-risk areas, and city-year contextual correlates of incident edentulism among middle-aged and older Chinese adults. METHODS: Longitudinal data from the China Health and Retirement Longitudinal Study from 2011 to 2018 were analysed. A total of 43,478 at-risk person-intervals from 19,590 unique participants and 2251 incident edentulism events were included. We integrated spatial mapping, spatial autocorrelation analysis, machine-learning-based feature selection and model comparison, SHAP-based exploratory interpretation, and inequality assessment. Incident edentulism was analysed as an interval-specific incidence proportion. RESULTS: City-level incidence proportions ranged from 0.00% to 10.71% and showed significant spatial autocorrelation (Global Moran's I = 0.137, P = .004). High-incident areas frequently co-occurred with disadvantaged city-year contextual markers, including higher low-education share, stronger rural residence structure, higher agricultural hukou share, and lower household consumption. XGBoost was retained as the primary interpretable tree-based model for SHAP interpretation (internal-test ROC-AUC = 0.730; temporal-validation ROC-AUC = 0.694). SHAP analysis identified age as the largest contributor to model output (mean |SHAP| = 0.6007). Inequality assessment further confirmed higher risks among older adults aged ≥70 years (adjusted OR = 4.384, P < .001), individuals with primary education or below (OR = 1.684, P < .001), agricultural hukou (OR = 1.319, P < .001), disability (OR = 1.181, P = .002), and IADL limitation (OR = 1.131, P = .032). CONCLUSION: Incident edentulism was associated with individual socioeconomic and functional vulnerability and showed exploratory spatial patterning across Chinese cities. CLINICAL RELEVANCE: Targeted oral-health prevention and tooth-retention strategies are needed for vulnerable older adults, especially those with socioeconomic or functional disadvantages and those living in disadvantaged or ruralized areas.