| Extreme Temperatures and Mortality: Assessing Effect Modification by Personal Characteristics and Specific Cause of Death in a Multi-City Case-Only Analysis Mercedes Medina-Ramón,1 Antonella Zanobetti,1 David Paul Cavanagh,1 and Joel Schwartz1,2 1Department of Environmental Health, and 2Department of Epidemiology, Harvard School of Public Health, Boston, Massachusetts, USA. Abstract
Background: Extremes of temperature are associated with short-term increases in daily mortality. Objectives: We set out to identify subpopulations and mortality causes with increased susceptibility to temperature extremes. Methods: We conducted a case-only analysis using daily mortality and hourly weather data from 50 U.S. cities for the period 1989–2000, covering a total of 7,789,655 deaths. We used distributions of daily minimum and maximum temperature in each city to define extremely hot days (≥ 99th percentile) and extremely cold days (≤ 1st percentile) , respectively. For each (hypothesized) effect modifier, a city-specific logistic regression model was fitted and an overall estimate calculated in a subsequent meta-analysis. Results: Older subjects [odds ratio (OR) = 1.020 ; 95% confidence interval (CI) , 1.005–1.034], diabetics (OR = 1.035 ; 95% CI, 1.010–1.062) , blacks (OR = 1.037 ; 95% CI, 1.016–1.059) , and those dying outside a hospital (OR = 1.066 ; 95% CI, 1.036–1.098) were more susceptible to extreme heat, with some differences observed between those dying from a cardiovascular disease and other decedents. Cardiovascular deaths (OR = 1.053 ; 95% CI, 1.036–1.070) , and especially cardiac arrest deaths (OR = 1.137 ; 95% CI, 1.051–1.230) , showed a greater relative increase on extremely cold days, whereas the increase in heat-related mortality was marginally higher for those with coexisting atrial fibrillation (OR = 1.059 ; 95% CI, 0.996–1.125) . Conclusions: In this study we identified several subpopulations and mortality causes particularly susceptible to temperature extremes. This knowledge may contribute to establishing health programs that would better protect the vulnerable. Key words: cause of death, cold, effect modifiers (epidemiology) , heat, mortality, temperature, weather. Environ Health Perspect 114:1331–1336 (2006) . doi:10.1289/ehp.9074 available via http://dx.doi.org/ [Online 6 July 2006]
Address correspondence to M. Medina-Ramón, Department of Environmental Health, Harvard School of Public Health, 401 Park Dr., Landmark Center, Suite 415-E West, Boston, MA 02215. Telephone: (617) 384-8742. Fax: (617) 384-8745. E-mail: mmedinar@hsph.harvard.edu This study was funded by EPA Grant R-82735301-7 and NIEHS grant ES-0002. The authors declare they have no competing financial interests. Received 6 February 2006 ; accepted 5 July 2006.
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