Long term characterization of heat waves in Brazil and their impacts on mortality rates

Climate Change has increased the intensity, duration, and frequency of extreme weather events such as heatwaves (HW), which have impacts on ecosystems, economics, and human populations, including adverse health effects and the increase in the number of deaths due to the heat stress. However, there are still few studies evaluating the occurrence of adverse health due to HW in South America. Particularly in Brazil, regional differences in the effects of heatwaves are expected due to their continental dimensions, which makes it necessary to carry out local studies. This work presents a long term analysis of the occurrence of HW in the 14 major metropolitan regions (MRs) in Brazil, namely: Manaus, Belém, Salvador, Recife, Fortaleza, Goiânia, Brasília, Cuiabá, São Paulo, Rio de Janeiro, Belo Horizonte, Porto Alegre, Curitiba and Florianópolis. Observational temperature data (1970-2020) provided by the National Institute of Meteorology (INMET) were used to compute the Extreme Heat Factor (EHF) index, which was used to identify and classify HW in terms of severity.  Significant and positive trends in the frequency of HW were observed over decades in all MRs, particularly in the north (Manaus and Belém) and central west region (Goiania and Brasilia). Particularly, from 2014 to 2019, all the MRs presented HW regime every year, including severe and/or extreme events. In general, the longest and the most intense HW in Brazilian MRs occurred in the last decade (2010-2020), with the exception of the 1997–1998 El Niño-related events. Daily mortality and hospital admission data from the Brazilian Public Health System (SUS) were used to assess the relationships between HW and health. Results indicate excess mortality (observed to expected ratio) during HW events in the MRs studied, with the elderly being the most vulnerable age group, in agreement with previous studies. The cause of death and the gender susceptibility to HW were also analyzed, and the results vary among the different MRs. This work provides an extensive characterization of the occurrence of HW in Brazil and valuable insights for the implementation of public mitigation and adaptation strategies in some of the most populated regions of South America.

This work was supported by FIOCRUZ [grant VPPCB-003-FIO-19] and FAPERJ [grant E26/202.714/2019]. D.M.S. was supported by FIOCRUZ [grant VPPCB-003-FIO-19].