Effects of Drought on Mortality in Macro Urban Areas of Brazil Between 2000 and 2019

Abstract

A significant fraction of Brazil's population has been exposed to drought in recent years, a situation that is expected to worsen in frequency and intensity due to climate change. This constitutes a current key environmental health concern, especially in densely urban areas such as several big cities and suburbs. For the first time, a comprehensive assessment of the short-term drought effects on weekly non-external, circulatory, and respiratory mortality was conducted in 13 major Brazilian macro-urban areas across 2000-2019. We applied quasi-Poisson regression models adjusted by temperature to explore the association between drought (defined by the Standardized Precipitation-Evapotranspiration Index) and the different mortality causes by location, sex, and age groups. We next conducted multivariate meta-analytical models separated by cause and population groups to pool individual estimates. Impact measures were expressed as the attributable fractions among the exposed population, from the relative risks (RRs). Overall, a positive association between drought exposure and mortality was evidenced in the total population, with RRs varying from 1.003 [95% CI: 0.999-1.007] to 1.010 [0.996-1.025] for non-external mortality related to moderate and extreme drought conditions, from 1.002 [0.997-1.007] to 1.008 [0.991-1.026] for circulatory mortality, and from 1.004 [0.995-1.013] to 1.013 [0.983-1.044] for respiratory mortality. Females, children, and the elderly population were the most affected groups, for whom a robust positive association was found. The study also revealed high heterogeneity between locations. We suggest that policies and action plans should pay special attention to vulnerable populations to promote efficient measures to reduce vulnerability and risks associated with droughts.

Keywords: Brazil; age ranges; drought; gender assessment; mortality; vulnerability.

Figure 1

Map of South America representing the study region of Brazil divided into five macro‐regions where the 13 analyzed locations are placed. Each location is denoted with numbers, and their geographical extension is also displayed. The code colors represent the five macro‐regions across the country, namely North (green), Northeast (red), Southeast (yellow), South (purple), and Central‐West (pink). The geographical extension (in km²) and the number of inhabitants (in millions, data from IBGE [2021]) are indicated for each location. MR: Metropolitan Region. RIDE‐DF: Development Integrated Region of the Federal District and Surrounding Areas.

Figure 2

(a) The overall short‐term association between drought and non‐external mortality expressed in relative risk and 95% confidence intervals per each category of drought severity measured by the Standardized Precipitation‐Evapotranspiration Index calculated at 1 month of accumulation (SPEI1) in Brazil from 2000 to 2019. (b) The attributable fractions among the exposed population and 95% confidence intervals (in percentage) to extreme drought for the different causes of death and population groups.

Figure 3

Specific association between extreme drought conditions and non‐external mortality in terms of relative risks and the 95% confidence intervals across the population separated by sex groups and age ranges in each Brazilian location between 2000 and 2019. Drought events were measured by the Standardized Precipitation‐Evapotranspiration Index obtained at one month of accumulation (SPEI‐1).