A characterization of U.S. heat-related deaths during drought and non-drought conditions (2000-2018)

Extreme heat and drought conditions are expected to increase in severity and frequency, as these two climate events are often linked with compounding feedback loops that exacerbate each hazard. Prior studies have evaluated mortality separately during heat and drought without considering impacts of compound hazards. This study characterizes heat-related mortality (HRM) and drought in the conterminous United States (U.S.). HRM was identified from the multiple cause of death data from the National Center for Health Statistics, U.S., 2000–2018. Drought was defined by the United States Drought Monitor at the county-month scale. HRM was defined by ICD-10 codes. Crude HRM rates were adjusted for frequency of drought. There were 13 416 heat-related deaths during the 19 year study period. National HRM (rates per 100 000 population) was higher during drought (0.31 (95% CI 0.30–0.32)) compared to non-drought (0.12 (95% CI 0.12–0.13)). Non-white, males, older adults, and metro counties experienced higher mortality rates than their counterparts. HRM increased by age, and adults aged 65+ experienced the greatest burden. During drought, American Indian/Alaska Native (0.93 (95% CI 0.79–1.09)) had the highest HRM, followed by Hispanic/Latino (0.56 (95% CI 0.54–0.59)). HRM was highest in large central metro counties (0.44 (95% CI 0.43–0.46) vs rural noncore 0.37 (95% CI 0.34–0.40)) during drought, however, rural had higher rates during non-drought conditions (0.19 (95% CI 0.17–0.20) vs 0.15 (95% CI 0.14–0.15)). Our results describe the impact of drought on HRM overall, with certain subpopulations disproportionately affected. Future research into the contributing factors is needed to prevent heat-related deaths among vulnerable subgroups.