Social Deprivation as a Key Driver of Spatial Disparities in End-Stage Kidney Disease Incidence

Background Despite France's universal healthcare system, significant geographic disparities in the incidence of end-stage kidney disease (ESKD) persist. We hypothesized that social deprivation is a major driver of these spatial variations, independent of healthcare access and clinical risk factors, and that its contribution is stable over time. Methods We conducted an ecological study including 102,226 incident ESKD cases across 34,830 municipalities in metropolitan France from 2012 to 2021, using data from the national REIN registry. A Bayesian hierarchical spatiotemporal model was used to estimate the association between ESKD incidence and ecological-level covariates: social deprivation (measured by the French European Deprivation Index), diabetes prevalence, dialysis center accessibility, and long-term exposure to PM2.5. We estimated the population-attributable fraction of ESKD incidence for each factor under various counterfactual scenarios. Results Social deprivation was strongly associated with ESKD incidence (RR per 1 SD increase in EDI: 1.10 [95% CrI: 1.09–1.11]) and explained 34.7% of its spatial variability. The association was only partially mediated by diabetes prevalence (mediation proportion: 15.3% [95% CI 12.5-18.2]). The model incorporating all covariates explained 49.9% of the observed spatial heterogeneity. The effect of social deprivation remained consistent over time. Reducing deprivation in the most disadvantaged areas to the levels of the 5th, 25th, and 50th percentiles of less deprived areas could have prevented an estimated 23,092, 17,450, and 13,601 ESKD cases, respectively, over the study period. Conclusions Social deprivation is the leading ecological determinant of spatial disparities in ESKD incidence in France, with limited mediation by clinical factors and persistent effects despite universal healthcare. These findings underscore the need to address social determinants of health and to adapt kidney care delivery models to better reach socioeconomically disadvantaged populations.