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Original research
Ambient heat and hospitalisation for COPD in Brazil: a nationwide case-crossover study
  1. Qi Zhao1,2,
  2. Shanshan Li2,
  3. Micheline de Sousa Zanotti Stagliorio Coelho3,
  4. Paulo Hilário Nascimento Saldiva3,
  5. Rongbin Xu2,
  6. Rachel R Huxley4,
  7. Michael J Abramson2,
  8. Yuming Guo1,2
  1. 1 School of Public Health and Management, Binzhou Medical University, Yantai, Shandong, China
  2. 2 Department of Epidemiology and Preventive Medicine, School of Public Health and Preventive Medicine, Monash University, Melbourne, Victoria, Australia
  3. 3 Institute of Advanced Studies, University of São Paulo, São Paulo, São Paulo, Brazil
  4. 4 College of Science, Health and Engineering, La Trobe University, Melbourne, Victoria, Australia
  1. Correspondence to Professor Yuming Guo, Department of Epidemiology and Preventive Medicine, Monash University, Melbourne, VIC, Australia; Yuming.guo{at}; Dr Shanshan Li, Department of Epidemiology and Preventive Medicine, Monash University, Melbourne, VIC, Australia; Shanshan.Li{at}


Background Heat exposure has been related to increased morbidity and mortality for several health outcomes. There is little evidence whether this is also true for COPD. This study quantified the relationship between ambient heat and hospitalisation for COPD in the Brazilian population.

Methods Data on hospitalisations for COPD and weather conditions were collected from 1642 cities during the 2000–2015 hot seasons. A time-stratified, case-crossover design was used for city-specific analyses, which were then pooled at the regional and national levels using random-effect meta-analyses. Stratified analyses were performed by sex, age group and early/late hot season. Annual change in the association was examined using a random-effect meta-regression model.

Results The OR of hospitalisation was 1.05 (95% CI 1.04 to 1.06) for every 5℃ increase in daily mean temperature at the national level, with the effect estimate stronger in the late hot season compared with the early hot season. The effect was similar in women and in men but was greatest for those aged ≥75 years. The association was stronger in the central west and southeast regions and minimal in the northeast. Assuming a causal relationship, 7.2% of admissions were attributable to heat exposure. There was no significant temporal decline in the impact of ambient heat over the 16-year study period.

Conclusion In Brazil, exposure to ambient heat was positively associated with hospitalisation for COPD, particularly during the late hot season. These data add to the growing evidence base implicating global warming as being an important contributor to the future healthcare burden.

  • COPD epidemiology
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  • Contributors YG, SL and QZ were responsible for the study concept and design. QZ did the data analysis. QZ, YG, SL, RRH, MJA, MdSZSC, PHNS and RX interpreted the data. QZ drafted the manuscript. QZ, YG and SL had full access to all the data in the study and take responsibility for the integrity of the data and the accuracy of the data. The corresponding authors attest that all listed authors meet the authorship criteria and that no others meeting the criteria have been omitted.

  • Funding QZ was supported by a Monash Graduate Scholarship, Monash International Postgraduate Research Scholarship and Monash Postgraduate Publications Award. SL was supported by an Early Career Fellowship of the Australian National Health and Medical Research Council (APP1109193). YG was supported by a Career Development Fellowship of the Australian National Health and Medical Research Council (APP1107107 and APP1163693).

  • Competing interests MJA holds investigator-initiated grants from Pfizer and Boehringer Ingelheim, and consultancy fee from Sanofi for unrelated research.

  • Patient consent for publication Not required.

  • Ethics approval Ethical approval was not required for secondary analysis of aggregate anonymised data from the Brazilian Hospital Information System.

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

  • Data availability statement No data are available.

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