Risk factors for mortality during a heat-wave in Bari (Italy), summer 2005

Introduction: The Italian Heat Health Watch Warning System (HHWWS) was set up following the over 3000 excess deaths which occurred in Italy during the heat wave of 2003, In June 2005 the warning system issued a heat warning in various Italian cities. Methods: A case control study was performed in one of these cities (Bari) in order to identify individual and environmental risk factors as well as preventive strategies for reducing mortality during future heat waves. Cases were defined as subjects aged <65 years who had died during the heat wave and whose death certificate listed one of the following as the cause of death: heat, cardiovascular or cerebrovascular disorders, neurocognitive disorders, dehydration or fever/infection not otherwise specified. For each case, three age-matched controls were randomly selected among individuals followed by the same general practitioner as the case. All variables significantly associated with mortality (<0.1) in the univariate analysis were entered into a conditional logistic regression model and the population attributable fraction (PAF) was calculated for significant variables (at p<0.05). Results: Twenty cases and sixty controls were included in the study. In 17 cases (89%) death had occurred at home and 11(55%) of these were cardiovascular- related deaths. At the multivariate analysis, the factors significantly associated with mortality risk during the heat wave were: having a functioning air conditioner at home [OR:0.09(95% CI 0.01-1.00)], having an Activities of Daily Living score <2 [OR:21.0(95%CI 1.81-242.47)] and having been hospitalized the year preceding death [OR:18.1(95%CI 2.04-160.51)]. Conclusions: Public health interventions during heat waves should include the provision of access to an air conditioned environment. Subjects with impaired health (especially if recently hospitalized) and with significant limitations in their activities of daily living are probably at higher risk during heat waves.