title: Heat, heat waves, and hospital admissions among the elderly in the United States, 1992-2006.
abstract: 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.
  
  
  OBJECTIVE
  Our goal was to determine associations between moderate and extreme heat, heat waves, and hospital admissions for nonaccidental causes among Medicare beneficiaries ≥ 65 years of age in 114 cities across five U.S. climate zones.
  
  
  METHODS
  We used Medicare inpatient billing records and city-specific data on temperature, humidity, and ozone from 1992 through 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 subsequent 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.
  
  
  CONCLUSIONS
  Extreme heat is associated with increased hospital admissions, particularly for renal causes, among the elderly in the United States.
authors.affiliation: Department of Environmental Health Sciences, University of Michigan School of Public Health, Ann Arbor, Michigan, USA.
authors.forename: Carina J
authors.initials: CJ
authors.lastname: Gronlund
authors.forename: Antonella
authors.initials: A
authors.lastname: Zanobetti
authors.forename: Joel D
authors.initials: JD
authors.lastname: Schwartz
authors.forename: Gregory A
authors.initials: GA
authors.lastname: Wellenius
authors.forename: Marie S
authors.initials: MS
authors.lastname: O'Neill
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D002318:Cardiovascular Diseases / Q000453:epidemiology; D057231:Climate Change; D018592:Cross-Over Studies; D055874:Extreme Heat / Q000009:adverse effects; D006760:Hospitalization / Q000706:statistics & numerical data*; D006801:Humans; D006813:Humidity; D007674:Kidney Diseases / Q000453:epidemiology; D010126:Ozone / Q000032:analysis; D012140:Respiratory Tract Diseases / Q000453:epidemiology; D014481:United States; D014505:Urban Population
chemical_list: D010126:Ozone