Association between precipitation and mortality due to diarrheal diseases by climate zone: A multi-country modeling study

Abstract

Background: Precipitation could affect the transmission of diarrheal diseases. The diverse precipitation patterns across different climates might influence the degree of diarrheal risk from precipitation. This study determined the associations between precipitation and diarrheal mortality in tropical, temperate, and arid climate regions.

Methods: Daily counts of diarrheal mortality and 28-day cumulative precipitation from 1997 to 2019 were analyzed across 29 locations in eight middle-income countries (Argentina, Brazil, Costa Rica, India, Peru, the Philippines, South Africa, and Thailand). A two-stage approach was employed: the first stage is conditional Poisson regression models for each location, and the second stage is meta-analysis for pooling location-specific coefficients by climate zone.

Results: In tropical climates, higher precipitation increases the risk of diarrheal mortality. Under extremely wet conditions (95th percentile of 28-day cumulative precipitation), diarrheal mortality increased by 17.8% (95% confidence interval [CI] = 10.4%, 25.7%) compared with minimum-risk precipitation. For temperate and arid climates, diarrheal mortality increases in both dry and wet conditions. In extremely dry conditions (fifth percentile of 28-day cumulative precipitation), diarrheal mortality risk increases by 3.8% (95% CI = 1.2%, 6.5%) for temperate and 5.5% (95% CI = 1.0%, 10.2%) for arid climates. Similarly, under extremely wet conditions, diarrheal mortality risk increases by 2.5% (95% CI = -0.1%, 5.1%) for temperate and 4.1% (95% CI = 1.1%, 7.3%) for arid climates.

Conclusions: Associations between precipitation and diarrheal mortality exhibit variations across different climate zones. It is crucial to consider climate-specific variations when generating global projections of future precipitation-related diarrheal mortality.

Keywords: Diarrheal mortality; Meta-analysis; Poisson regression models; Precipitation.

Figure 1.

Monthly averages of total diarrheal deaths and 28-day cumulative precipitation by climate and country. Climate A, B, and C refer to tropical, arid, and temperate, respectively. Red circles refer to diarrheal deaths, and blue bars refer to 28-day cumulative (running sums) precipitation in millimeters. n refers to the number of included within-country climatic regions.

Figure 2.

Associations between precipitation and diarrheal mortality by climate–country. Climate A, B, and C refer to tropical, arid, and temperate, respectively. The y axis is relative risk (RR) and its 95% CI, and the x axis is 28-day cumulative (running sums) precipitation in millimeters. Black lines and gray areas are the RR means and 95% CI, respectively. Orange, blue, and red vertical lines are 5th, 50th, and 95th precipitation percentiles, respectively. n refers to the number of included within-country climatic regions.

Figure 3.

Associations between precipitation and diarrheal mortality by main climate zone. The y axis is relative risk (RR) and its 95% CI, and the x axis is 28-day cumulative (running sums) precipitation in millimeters. Black lines and gray areas are the RR means and 95% CI, respectively. Blue lines are 5th, 50th, and 95th precipitation percentiles. n refers to the number of included within-country climatic regions.