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Research Article Advance Publication

Environ Health Perspect; DOI:10.1289/ehp.1206132

Heat, Heat Waves, and Hospital Admissions among the Elderly in the United States, 1992–2006

Carina J. Gronlund,1 Antonella Zanobetti,2 Joel D. Schwartz,2 Gregory A. Wellenius,3 and Marie S. O’Neill1,4
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1University of Michigan School of Public Health, Department of Environmental Health Sciences, Ann Arbor, Michigan, USA; 2Harvard School of Public Health, Department of Environmental Health, Boston, Massachusetts, USA; 3Brown University, Department of Epidemiology, Providence, Rhode Island, USA; 4University of Michigan School of Public Health, Department of Epidemiology and Risk Science Center, Ann Arbor, Michigan, USA
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This EHP Advance Publication article has been peer-reviewed, revised, and accepted for publication. EHP Advance Publication articles are completely citable using the DOI number assigned to the article. This document will be replaced with the copyedited and formatted version as soon as it is available. Through the DOI number used in the citation, you will be able to access this document at each stage of the publication process.

Citation: Gronlund CJ, Zanobetti A, Schwartz JD, Wellenius GA, O’Neill MS. Heat, Heat Waves, and Hospital Admissions among the Elderly in the United States, 1992–2006. Environ Health Perspect;

Received: 12 October 2012
Accepted: 4 June 2014
Advance Publication: 6 June 2014

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Background: Heat-wave frequency, intensity and duration are increasing with global climate change. The association between heat and mortality in the elderly is well documented, but less is known regarding associations with hospital admissions.

Objectives: To determine associations between moderate and extreme heat, heat waves and hospital admissions for non-accidental causes among Medicare beneficiaries aged ≥65 years in 114 cities across 5 U.S. climate zones.

Methods: We used Medicare inpatient billing records and city-specific temperature, humidity and ozone data from 1992-2006 in a time-stratified case-crossover design to estimate the association between hospitalization and moderate (90th percentile of apparent temperature (AT)) and extreme (99th percentile of AT) heat and heat waves (AT above the 95th percentile over 2-8 days). In sensitivity analyses we additionally considered confounding by ozone and holidays, different temperature metrics, and alternate models of the exposure-response relationship.

Results: Associations between moderate heat and hospital admissions were minimal, but extreme heat was associated with a 3% (95% CI: 2%, 4%) increase in all-cause hospital admissions over the following 8 days. In cause-specific analyses, extreme heat was associated with increased hospitalizations for renal (15%, 95% CI: 9%, 21%) and respiratory (4%, 95% CI: 2%, 7%) diseases, but not for cardiovascular diseases. An added heat-wave effect was observed for renal and respiratory admissions.

Conclusion: Extreme heat is associated with increased hospital admissions, particularly for renal causes, among the elderly in the U.S.

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