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.

I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained.

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The details of the IRB/oversight body that provided approval or exemption for the research described are given below:

The United States Environmental Protection Agency Human Research Review Board approved this study and granted exemption from informed consent requirements

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Contributions: CRO, SEC, MWT, LMN, IJ, MER, AGR designed the study and directed its implementation. LMN, AGR, KLH, SEC provided exposure data, analytical design and modelling assistance. CRO analyzed the data. CRO, SEC, MWT, LMN, EMM, MER, IJ, AGR, AJG, and MER interpreted the results. SEC and EMM provided analytical and visualization support. SEC developed many of the R programs used in analysis. CRO, SEC, MWT, LMN, IJ, AGR, AJG, MER wrote the manuscript. All co-authors reviewed and edited the manuscript.

Funding: 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.

Data sharing statement: 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 Administration’s National Climatic Data Center’s Global Surface Summary of the Day database (National Oceanic and Atmospheric Administration, 2022). American Community Survey (ACS) data are publicly available through the Census Bureau.

Ethics approval: Ethics approval was obtained by the EPA Institutional Review Board (IRB number: IRB00006222).

Declaration of competing financial interests (CFI): The authors declare they have no actual or potential competing financial interests.

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.