Air conditioning and intrahospital mortality during the 2003 heatwave in Portugal: evidence of a protective effect

Abstract

Receive free email alerts when new articles cite this article. Sign up in the Notes articles must include the digital object identifier (DOIs) and date of initial publication. priority; they are indexed by PubMed from initial publication. Citations to Advance online prior to final publication). Advance online articles are citable and establish publication yet appeared in the paper journal (edited, typeset versions may be posted when available Methods Historical cohort study design including all patients aged 45 or more who were hospitalised in the 7 days before the heatwave. The outcome was survival during the 18 days the heatwave lasted and during the 2 days after the end of the heatwave. A comparison group was also selected in four analogous periods without any heatwave event during January to May 2003. Data were obtained from the 2003 hospital discharges database. Air conditioning presence in hospital wards was determined using a survey sent to hospital administrations. A Cox-regression model was used to estimate the confounder-adjusted HR of death, during the heatwave and the comparison period, in patients in wards with air conditioning (AC+) versus patients in wards without air conditioning (ACÀ). Results 41 hospitals of mainland Portugal (49% of all hospitals in mainland Portugal) participated, and 2093 patients were enrolled. The overall confounder-adjusted HR of death in AC+ patients versus ACÀ patients was 0.60 (95% CI 0.37 to 0.97) for the heatwave period and 1.05 (95% CI 0.84 to 1.32) for the comparison group. Conclusions The study found strong evidence that, during the August 2003 heatwave, the presence of air conditioning in hospital wards was associated with an increased survival of patients admitted before the beginning of the climate event. The reduction of the risk of dying is estimated to be 40% (95% CI 3% to 63%). INTRODUCTIONIn Portugal, the consequences of heatwaves in mortality have been studied since 1988, 1 leading to the recognition of the magnitude and importance of this problem and to the development of a national Contingency Plan for Heatwaves, in operation since 2004. These studies also led to the observation that more than half of the excess deaths occurred in hospitalised patients, especially during the 2003 heatwave in Portugal, 3 raising the discussion about the role that absent or insufficient air conditioning of many hospital wards could have played in intrahospital mortality during heatwaves.Since then, Health Ministry directives were issued, and efforts have been made by hospital administration boards to install air conditioning equipments in hospital wards.International literature shows that the risk of death associated with excess heat is higher in patients with pre-existing cardiovascular and respiratory diseases than in the general population. 5The occurrence of heatwaves can increase mortality in patients with chronic diseases, namely pre-existing cardiovascular and respiratory diseases, older people, children and individuals from a low socio-economical background. 4e6St...

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