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Air conditioning and intrahospital mortality during the 2003 heatwave in Portugal: evidence of a protective effect
  1. Baltazar Nunes,
  2. Eleonora Paixão,
  3. Carlos Matias Dias,
  4. Paulo Nogueira,
  5. José Marinho Falcão
  1. Department of Epidemiology, Instituto Nacional de Saúde Dr Ricardo Jorge, Lisboa, Portugal
  1. Correspondence to Mr Baltazar Nunes, Instituto Nacional de Saúde Dr Ricardo Jorge, Department of Epidemiology, Av. Padre Cruz P-1649-016 Lisboa, Portugal; baltazar.nunes{at}


Objectives The objective of the study was to analyse the association between the presence of air conditioning in hospital wards and the intrahospital mortality during the 2003 heatwave, in mainland Portugal.

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 (AC−).

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 AC− 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%).

  • Heatwaves
  • air conditioning
  • hospital mortality
  • epidemiology
  • mortality studies
  • environment

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  • List of participating hospitals: Centro Hospitalar Caldas da Rainha, Centro Hospitalar Vale do Sousa, Centro Hospitalar de Coimbra, Centro Hospitalar Vila Nova de Gaia, Hospital Distrital de Águeda, Hospital Distrital de Alcobaça, Hospital Distrital de Amarante, Hospital Distrital de Barcelos, Hospital Distrital de Beja, Hospital Distrital de Bragança, Hospital Distrital de Castelo Branco, Hospital Distrital de Chaves, Hospital Distrital de Covilhã, Hospital Distrital de Elvas, Hospital Distrital de Estarreja, Hospital Distrital de Fafe, Hospital Distrital da Foz, Hospital Distrital do Fundão, Hospital Distrital da Guarda, Hospital Distrital de Guimarães, Hospital Distrital de Leiria, Hospital Distrital de Matosinhos, Hospital Distrital de Macedo de Cavaleiros, Hospital Distrital de Mirandela, Hospital Distrital de Peniche, Hospital Distrital do Pombal, Hospital Distrital de Portalegre, Hospital Distrital de Portimão, Hospital Distrital da Povoa do Varzim, Hospital Distrital de Santo Tirso, Hospital Distrital de São João da Madeira, Hospital Distrital de Tondela, Hospital Distrital de Valongo, Hospital Distrital de Viana do Castelo, Hospital Distrital de Vila Nova Famalicão, Hospital Distrital de Viseu, Hospital de Santo António, Hospital Universidade Coimbra, Hospital da Feira, Hospital de Santa Maria, Hospital de São João, Hospital Joaquim Urbano, Hospital São Marcos, Instituto Português de Oncologia de Coimbra and Instituto Português de Oncologia do Porto.

  • Competing interests None.

  • Provenance and peer review Not commissioned; externally peer reviewed.