Challenges and Opportunities in Estimating the Mortality Burden Related to Heat Exposure: Maricopa County, Arizona, 2019-2023.

Abstract

<b>Objectives.</b> To estimate the mortality burden attributable to daily mean temperatures during the heat season (April through October) in Maricopa County, Arizona. <b>Methods.</b> We examined the effects of heat exposure on 126 854 deaths that occurred in Maricopa County during the 2019 to 2023 heat seasons. Using a quasi-Poisson regression with distributed lag nonlinear models, we estimated the cumulative relative risk (relative to 77°F) between population-weighted daily mean temperatures and all-cause mortality over a lag period of 3 days. <b>Results.</b> At 99°F (the 95th percentile of the population-weighted daily mean temperature), we observed an 11% (95% confidence interval [CI] = 7%, 16%) increase in daily all-cause mortality relative to 77°F. Overall, 3036 (95% empirical CI = 968, 4887) deaths were attributable to heat, which is 57% more deaths than identified through epidemiological heat surveillance. <b>Conclusions.</b> The mortality burden increases with increasing population-weighted daily mean temperatures, indicating that the effects of heat on mortality can be indirect and incompletely captured by routine surveillance. <b>Public Health Implications.</b> Statistical approaches can help estimate the mortality burden associated with heat exposure, complementing countywide surveillance efforts that provide actionable insights into enhancing heat prevention strategies. (<i>Am J Public Health</i>. 2026;116(6):810-813. https://doi.org/10.2105/AJPH.2026.308443).