Socioeconomic and demographic vulnerabilities as primary determinants of heat-related mortality in the U.S.

Abstract

Abstract

Abstract Extreme heat events (EHEs) are becoming more frequent and severe across the United States, yet the drivers of heat-related mortality remain unevenly understood. This study examines how heat vulnerability and regional heat conditions shape all-cause mortality anomalies across the nine U.S. climate regions. Using a national dataset of extreme heat events and population-normalized mortality z-scores from 2014–2023, we compared the relative influence of socioeconomic, demographic, environmental, and heat-event characteristics on mortality outcomes. Across regions, socioeconomic and demographic vulnerabilities—particularly poverty, racial/ethnic composition, social isolation, limited green space, and older age—were the strongest predictors of elevated mortality during extreme heat. In contrast, event characteristics such as duration, temperature exceedance, and areal extent contributed comparatively little once socioeconomic and demographic vulnerability was accounted for. Mortality modelling performance varied widely by region, with particularly strong predictive signals in the Southwest, West, and South. These findings suggest that socioeconomic and demographic vulnerabilities, rather than meteorological extremes alone, may be more consistent drivers of heat-related mortality variation across U.S. climate regions. Targeted, region-specific heat-health strategies—especially those addressing social vulnerability and humidity exposure—are essential for reducing mortality risk under a warming climate.