Excess mortality and morbidity during the July 2006 heat wave in Porto, Portugal

Abstract

The purpose of this study was to understand the effects of the July 2006 heat wave through the use of the heat index, in mortality (all causes) and morbidity (all causes, respiratory and circulatory diseases) in general, and in people over 74years and by gender, in Porto. In this paper, the Poisson generalized additive regression model was used to estimate the impact of apparent temperature (heat index) and daily mortality and morbidity during the July 2006 heat wave. Daily mortality, morbidity and heat index were correlated with lags of apparent temperature up to 7days using Pearson correlation. For a 1°C increase in mean apparent temperature we observed a 2.7% (95% CI: 1.7-3.6%) increase in mortality (all cause), a 1.7% (95% CI: 0.6-2.9%) increase in respiratory morbidity, a 2.2% (95% CI: 0.4-4.1%) increase in respiratory morbidity in women, a 5.4% (95%CI: 1.1-6.6%) increase in chronic obstructive pulmonary morbidity, and a 7.5% (95% CI: 1.3-14.1%) increase in chronic obstructive pulmonary morbidity in women, for the entire population. For people ≥ 75years, our results showed a 3.3% increase (95% CI: 1.7-5.0%) in respiratory morbidity, a 2.7% (95% CI: 0.4-5.1%) increase in respiratory morbidity in men, a 3.9% (95%CI: 1.6-6.3%) increase in respiratory morbidity in women, a 7.0% (95% CI: 1.1-13.2%) in chronic obstructive pulmonary disease, and a 9.0% (95% CI: 0.3-18.5%) in chronic obstructive pulmonary disease in women. The use of heat index in a Mediterranean tempered climate enabled the identification of the effects of the July 2006 heat wave in mortality due to all causes and in respiratory morbidity of the general population, as well as in respiratory morbidity of individuals with more than 74years of age.