Extreme temperatures and mortality: assessing effect modification by personal characteristics and specific cause of death in a multi-city case-only analysis.
BACKGROUND
Extremes of temperature are associated with short-term increases in daily mortality.


OBJECTIVE
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 (>/= 99 th 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.
Medina-Ramón
Mercedes
M
Department of Environmental Health, Harvard School of Public Health, Boston, Massachusetts, USA. mmedinar@hsph.harvard.edu
Zanobetti
Antonella
A
Cavanagh
David Paul
DP
Schwartz
Joel
J
D000293:Adolescent; D000328:Adult; D000368:Aged; D002648:Child; D002675:Child, Preschool; D002947:Cities / Q000453:epidemiology; D003710:Demography; D004522:Educational Status; D004781:Environmental Exposure / Q000009:adverse effects* / Q000266:history / Q000706:statistics & numerical data; D006304:Health Status; D049673:History, 20th Century; D006358:Hot Temperature / Q000009:adverse effects*; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008019:Life Style; D008875:Middle Aged; D009026:Mortality / Q000639:trends*; D012307:Risk Factors; D014481:United States