Decadal Decline in Heat-Attributed Excess Mortality and Evolving Population Vulnerability: Evidence from a Neighborhood-Scale Study.

While prior research has established the mortality risk of heat waves, limited evidence exists on the temporal dynamics of excess mortality and premature death burden, particularly at fine spatial scales. Here, we assessed decadal changes in heat-attributed excess mortality and years of life lost (YLL) with rapid aging. We analyzed daily mortality and meteorological data from 211 neighborhoods in Shanghai, China, during two warm-season periods (June-September, 2009-2011 and 2019-2021). A quasi-Poisson regression coupled with a distributed lag non-linear model was used to estimate neighborhood-specific associations between heat waves and YLL rates (per 100,000 population), followed by multivariate meta-analysis. Heat-attributable burden was further quantified using YLL per death and annual excess deaths (ED). Our results revealed a substantial decline in heat-attributed mortality burden over the decade. YLL per death decreased from 1.00 (95% CI: 0.85, 1.15) years to 0.19 (95% CI: 0.06, 0.32), and annual ED dropped from 327 (95% CI: 277, 380) to 64 (95% CI: 58, 66). The duration of lagged heat effects also shortened. Stratified analyses showed persistently higher excess mortality among males, older adults, and those with lower education, while YLL burden shifted from males to females. Individuals aged 0-64 and the less educated exhibited higher YLL per death across periods. This neighborhood-level analysis provides robust empirical evidence of declining excess mortality and dynamic vulnerability transitions under intensifying heat exposure. The findings underscore the need for spatially adaptive and demographically targeted heat adaptation strategies for ongoing climate change and urban aging.