Spatiotemporal effects of sustainability dimensions on old-age healthy life expectancy in ecologically fragile regions

Population ageing poses major sustainability challenges in ecologically fragile and socioeconomically disadvantaged regions. Understanding how sustainability conditions are associated with healthy ageing is essential for designing effective development strategies in such contexts. This study investigates the associations between multidimensional sustainability conditions and old-age healthy life expectancy (OHLE) across 1,376 counties in ecologically fragile Kashin–Beck disease (KBD)-endemic and surrounding areas in China from 2005 to 2020. Sustainability conditions were assessed through ecological, economic, and social dimensions using a multidimensional indicator framework. Bayesian spatiotemporal hierarchical modeling was applied to quantify the spatial heterogeneity and temporal dynamics in sustainability–health relationships. Results show that the temporal dynamics of the indicators explain more than 90% of the variation in OHLE, highlighting the dominant role of long-term development trajectories. Economic sustainability accounted for the largest share of explained variation (61.93%, 95% CI: 58.77–66.03) and showed relatively stable effects, whereas social sustainability exhibited strong marginal impacts (β = 11.66, 95% CI: 10.85–12.48) and pronounced spatiotemporal non-stationarity, particularly in endemic counties. Over time, the association between ecological sustainability and OHLE gradually increased. Meanwhile, regions where social sustainability made a greater contribution to OHLE shifted from the Qinghai-Tibet Plateau to more developed regions. These findings reveal differentiated contributions of sustainability dimensions in supporting healthy ageing in ecologically fragile regions and highlight the importance of integrating multidimensional sustainability considerations into policies addressing population ageing challenges.