title: Fine-scale spatial variability of heat-related mortality in Philadelphia County, USA, from 1983-2008: a case-series analysis.
abstract: BACKGROUND
  High temperature and humidity conditions are associated with short-term elevations in the mortality rate in many United States cities. Previous research has quantified this relationship in an aggregate manner over large metropolitan areas, but within these areas the response may differ based on local-scale variability in climate, population characteristics, and socio-economic factors.
  
  
  METHODS
  We compared the mortality response for 48 Zip Code Tabulation Areas (ZCTAs) comprising Philadelphia County, PA to determine if certain areas are associated with elevated risk during high heat stress conditions. A randomization test was used to identify mortality exceedances for various apparent temperature thresholds at both the city and local scale. We then sought to identify the environmental, demographic, and social factors associated with high-risk areas via principal components regression.
  
  
  RESULTS
  Citywide mortality increases by 9.3% on days following those with apparent temperatures over 34°C observed at 7:00 p.m. local time. During these conditions, elevated mortality rates were found for 10 of the 48 ZCTAs concentrated in the west-central portion of the County. Factors related to high heat mortality risk included proximity to locally high surface temperatures, low socioeconomic status, high density residential zoning, and age.
  
  
  CONCLUSIONS
  Within the larger Philadelphia metropolitan area, there exists statistically significant fine-scale spatial variability in the mortality response to high apparent temperatures. Future heat warning systems and mitigation and intervention measures could target these high risk areas to reduce the burden of extreme weather on summertime morbidity and mortality.
authors.affiliation: Department of Environmental Sciences, University of Virginia, Charlottesville, USA. dmh4j@virginia.edu
authors.forename: David M
authors.initials: DM
authors.lastname: Hondula
authors.forename: Robert E
authors.initials: RE
authors.lastname: Davis
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: Leisten
authors.forename: Michael V
authors.initials: MV
authors.lastname: Saha
authors.forename: Lindsay M
authors.initials: LM
authors.lastname: Veazey
authors.forename: Carleigh R
authors.initials: CR
authors.lastname: Wegner
mesh_terms: D000367:Age Factors; D000368:Aged; D018882:Heat Stress Disorders / Q000453:epidemiology / Q000209:etiology / Q000401:mortality*; D006358:Hot Temperature / Q000009:adverse effects; D006801:Humans; D008875:Middle Aged; D015143:Philadelphia / Q000453:epidemiology; D025341:Principal Component Analysis; D012044:Regression Analysis; D012307:Risk Factors; D012621:Seasons; D012923:Social Class; D012959:Socioeconomic Factors; D013997:Time Factors; D014505:Urban Population