Objectives. A nationwide study of the impact of high temperature on respiratory disease hospitalizations among older adults (65+) living in large urban centers. Methods. Daily rates of short-stay, inpatient respiratory hospitalizations were examined with respect to variations in ZIP-code-level daily mean temperature in the 120 largest US cities between 2000-2017. For each city, we estimated cumulative associations (lag-days 0-6) between warm-season temperatures (June-September) and cause-specific respiratory hospitalizations using time-stratified conditional quasi-Poisson regression with distributed lag non-linear models. We estimated nationwide associations using meta-regression and updated city-specific associations via best linear unbiased prediction. With stratified models, we explored effect modification by age, sex, and race (Black/white). Results were reported as percent change in hospitalizations at high temperatures (95th percentile) compared to median temperatures for each outcome, demographic-group, and metropolitan area. Excess hospitalization rates were estimated for days above median temperatures. Results. At high temperatures, we observed increases in the percent of all-cause respiratory hospitalizations [1.2 (0.4, 2.0)], primarily driven by an increase in respiratory tract infections [1.8 (0.6, 3.0)], and chronic respiratory diseases/respiratory failure [1.2 (0.0, 2.4)]. East North Central, New England, Mid-Atlantic, and Pacific cities accounted for 98.5% of the excess burden. By demographic group, we observed disproportionate burdens of heat-related respiratory hospitalizations among the oldest beneficiaries (85+ years), and among Black beneficiaries living in South Atlantic cities. Conclusion. This study found robust impacts of high temperature on respiratory failure and chronic inflammatory and fibrotic diseases among older adults. The geographic variation suggests that contextual factors account for disproportionate burdens.

The authors have declared no competing interest.

This research was supported by cooperative agreement, Grant CR84033801, between the U.S. EPA and University of North Carolina-Chapel Hill. The content of this manuscript is solely the responsibility of the authors and does not necessarily reflect the views and policies of the U.S. EPA. Further, U.S. EPA does not endorse the purchase of any commercial products or services mentioned in this manuscript.

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Medicare hospitalization data are restricted by IRB protocols and data use agreements with Centers for Medicaid and Medicare (CMS) but other researchers may obtain the same Medicare data directly from CMS. Daily meteorological data are publicly available from the National Oceanic and Atmospheric Administrations National Climatic Data Centers Global Surface Summary of the Day database. American Community Survey (ACS) data are publicly available through the Census Bureau.