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von Klot, S. ; Zanobetti, A.* ; Schwartz, J.*

Influenza epidemics, seasonality, and the effects of cold weather on cardiovascular mortality.

Epidemiology 20, S252-S252 (2009)
DOI
Open Access Green möglich sobald Postprint bei der ZB eingereicht worden ist.
Epidemiological studies have shown that extremes in ambient temperature are associated with short term increases in mortality. To control for seasonality, most previous time series studies used non-parametric functions of time. We conducted a US multi-city study evaluating whether adjustment for influenza epidemics changes the exposure-response function of temperature, and whether controlling for the remaining seasonal pattern could be modeled more simply. Counts of daily cardiovascular deaths and of emergency hospital admissions of the elderly for pneumonia during 1992-2000 were obtained for 48 cities. Applying city-specific Quasi-Poisson regression models we estimated the association between daily cardiovascular mortality and temperature. Models included day-of-the-week indicators and regression splines of temperature, relative humidity, barometric pressure. In the base model a regression spline of date with five degrees of freedom (df) per year captured trend and seasonality. In the alternative model a regression spline of pneumonia admissions, a sinusoidal function of time, and a regression spline of date with ten df were included instead. Temperatures were lower in the north-east compared to the south-west and the range differed greatly. The alternative model fit the data better than the base model based on GSV-scores, capturing well the regular seasonal pattern as well as the irregular pattern of the outcome. The temperature-response function was mostly U- or J-shaped and not greatly affected by adjusting for influenza. The pooled estimated increase in risk for a temperature decrease from 0 to -5°C was 1.6% (95% confidence interval (CI) 0.9-2.4%) in the base and 1.9% (95% CI 1.2-2.6%) in the alternative model. This study on the effect of temperature on mortality shows that including epidemic data explained most of the irregular seasonal pattern, allowing more parsimonious models than when adjusting for seasonality only with smooth functions of time. The effect of cold temperature is not confounded by epidemics.
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Publikationstyp Artikel: Journalartikel
Dokumenttyp Wissenschaftlicher Artikel
Korrespondenzautor
ISSN (print) / ISBN 1044-3983
e-ISSN 1531-5487
Zeitschrift Epidemiology
Quellenangaben Band: 20, Heft: 6, Seiten: S252-S252 Artikelnummer: , Supplement: ,
Verlag Lippincott Williams & Wilkins
Nichtpatentliteratur Publikationen
Begutachtungsstatus Peer reviewed
Institut(e) Institute of Epidemiology (EPI)