Impact of heat and cold waves on circulatory-cause and respiratory-cause mortality in Spain: 1975–2008

Abstract

Few studies have analysed the impact of heat and cold waves on mortality in a given population over the same time period and still fewer studies have analysed this impact in terms of cause-specific mortality. This study analysed the impact of both heat and cold waves on daily all-cause, circulatory-cause and respiratory-cause mortality in the region of Castile-La Mancha (CLM) 1975–2008. The dependent variable was daily all-, circulatory- and respiratory-cause mortality registered in CLM from 01-01-75 to 31-12-08, and the independent variables were maximum, minimum, mean daily temperature daily relative humidity and mean daily air pressure and other related variables, such as heat-wave duration, heat-wave number and pressure trend. Time-series analyses were performed using autoregressive integrated moving average models. The impact of heat on daily mortality was greater than that of cold, with a difference which proved statistically significant for all- and circulatory-cause mortality but not for respiratory-cause mortality. While 16.5 % CI 95 % (15.5–17.4) of summer mortality in CLM was attributable to heat, 12.9 % CI 95 % (12.2–13.8) of daily winter mortality was attributable to low temperatures. The variable, heat-wave duration, was of major importance in all-cause and respiratory-cause mortality, with wave persistence being related to a mean 3.5 % increase in daily organic-cause mortality. Although heat waves have a greater impact on daily mortality than do cold waves, the fact that there were more cold-wave than heat-wave days during the period analysed, coupled with the diseases implicated, means that specific prevention plans should be implemented for both extreme thermal events.