Impact of heat on respiratory hospitalizations among older adults living in 120 large US urban areas

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. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement 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. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes 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 I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes 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.