Effects of high summer temperatures on mortality in 50 Spanish cities

BACKGROUND: Periods of high temperature have been widely found to be associated with excess mortality but with variable relationships in different cities. How these specifics depend on climatic and other characteristics of cities is not well understood. We assess summer temperature-mortality relationships using data from 50 provincial capitals in Spain, during the period 1990-2004. METHODS: Poisson time series regression analyses were applied to daily temperature and mortality data, adjusting for potential confounding seasonal factors. Associations of heat with mortality were summarised for each city as the risk increments at the 99th compared to the 90th percentiles of the whole-year temperature distributions, as predicted from spline curves. RESULTS: Risk increments averaged 14.6% between both centiles, or 3.3% per 1 Celsius degree. Although risk increments varied substantially between cities, the range of temperature from the 90th to 99th centile was the only characteristic independently significantly associated with them. The heat increment did not depend on other city climatic, socio-demographic and geographic determinants. CONCLUSIONS: Cities in Spain are partially adapted to high mean summer temperatures but not to high variation in summer temperatures.This work was supported by a Salvador Madariaga’s grant of the Ministry of Education of the Spanish Government (PRX12/00515) and conducted while Aurelio Tobías was visiting the London School of Hygiene and Tropical Medicine (UK). We acknowledge support of the publication fee by the CSIC Open Access Publication Support Initiative through its Unit of Information Resources for Research (URICI). Antonio Gasparrini was supported by a Methodology Research fellowship awarded by Medical Research Council-UK (grant ID G1002296). Julio Diaz was funded by a grant from the Strategic Health Action ISCIII (FIS Project ENPY1001/13). To Fernando Simon, from the Alert and Emergency Unit of the National Centre of Epidemiology, to provide data.S