Projected US Cardiovascular Disease Burden From Heat Exposure for Future Greenhouse Gas Scenarios

Importance: Climate change may reverse decades of improvements in cardiovascular disease (CVD) mortality in the US; however, comprehensive regional projections of heat-related CVD burden in the US are unavailable. Objective: To use the county-level observed (2010-2016) heat-related CVD burden in the US to obtain the projected rates through 2050 according to the mean (shared socioeconomic pathway SSP 2-4.5) and high (SSP5-8.5) greenhouse gas (GHG) emission pathways. Design, Setting, and Participants: This cross-sectional ecological analysis used county-level summary data including all counties in the contiguous US from 2010 through 2016 as baseline data with projections to 2030 and 2050 under SSP 2-4.5 and SSP 5-8.5 scenarios. Estimates of CVD related disability-adjusted life-year (DALY), years of life lost (YLL) and years lived with disability (YLD) were collected from all US counties between 2010 through 2016. Midyear population data were also collected for the same period. Daily mean temperature recordings were obtained for each county for this study period and for years 2030 and 2050 for the SSP 2-4.5 and SSP 5-8.5 pathways, which signify mean and high greenhouse emissions, respectively. These data were analyzed from August through December 2025. Exposures: Daily mean temperature in the baseline period (2010-2016) and years 2030 and 2050 for the 2 GHG emissions pathways (SSP2-4.5, SSP5-8.5) were obtained. County-specific mean annual heat excess was calculated as the difference between daily mean temperature and the county-specific theoretical minimum risk exposure level (TMREL) for the baseline period, as well as for each projected year's GHG emission pathway. Main Outcomes and Measures: Heat-attributable CVD burden measured in DALY per 100 000 population and population attributable fraction, stratified by age, income, and geography. Results: Baseline national median heat-attributable CVD burden was 138.5 DALYs per 100 000. The Pacific Northwest showed highest baseline burden, while Southern and Midwestern states demonstrated steepest projected increases. Under SSP5-8.5, burden increased to 418.2 DALYs per 100 000 by 2050, corresponding to approximately 50 000 to 70 000 additional annual cardiovascular deaths. Demographic aging contributes an additional 34% to heat-attributable CVD DALY independent of temperature increases by 2050. Middle-income and low-income counties experienced approximately twice the relative increases of high-income counties. Conclusions and Relevance: Heat-attributable CVD burden will increase substantially by 2050, disproportionately affecting economically vulnerable populations. Heat mitigation must become central to cardiovascular prevention, with targeted interventions prioritizing vulnerable communities.