Uncovering social and environmental factors that increase the burden of climate-sensitive diarrheal infections on children

Abstract

Climate-sensitive infectious diseases are an issue of growing concern due to global warming and the related increase in the incidence of extreme weather and climate events. Diarrhea, which is strongly associated with climatic factors, remains among the leading causes of child death globally, disproportionately affecting populations in low- and middle-income countries (LMICs). We use survey data for 51 LMICs between 2000 and 2019 in combination with gridded climate data to estimate the association between precipitation shocks and reported symptoms of diarrheal illness in young children. We account for differences in exposure risk by climate type and explore the modifying role of various social factors. We find that droughts are positively associated with diarrhea in the tropical savanna regions, particularly during the dry season and dry-to-wet and wet-to-dry transition seasons. In the humid subtropical regions, we find that heavy precipitation events are associated with increased risk of diarrhea during the dry season and the transition from dry-to-wet season. Our analysis of effect modifiers highlights certain social vulnerabilities that exacerbate these associations in the two climate zones and present opportunities for public health intervention. For example, we show that stool disposal practices, child feeding practices, and immunizing against the rotavirus modify the association between drought and diarrhea in the tropical savanna regions. In the humid subtropical regions, household's source of water and water disinfection practices modify the association between heavy precipitation and diarrhea. The evidence of effect modification varies depending on the type and duration of the precipitation shock.

Keywords: child feeding practices; childhood diarrhea; hygiene; immunization; precipitation.

Fig. 1.

Associations between diarrhea symptoms and 4-wk precipitation anomalies by climate type. Panels A and B show adjusted odds ratios (aOR) for diarrhea (solid lines) with 95% CIs (dashed lines) based on a restricted cubic regression spline. The histograms show the distribution of observations at various levels of precipitation anomalies. Panels C shows the associations between diarrhea and categories of dry precipitation anomalies by level of severity for the tropical savanna zone. Panel E shows the associations between diarrhea and categories of wet precipitation anomalies by level of severity for the humid subtropical zone. Panels D shows the associations between diarrhea and severe dry anomalies for the tropical savanna zone by season of exposure. Panel F shows the associations between diarrhea and severe wet anomalies for the humid subtropical zone by season of exposure. All estimates are adjusted for potential confounders (see Methods). Detailed results are available in SI Appendix, Tables S6- S9.

Fig. 2.

Associations between diarrhea symptoms and precipitation shocks by climate zone, exposure period, and various effect modifiers. Panel A shows the associations between diarrhea and severe dry anomalies for the tropical savanna zone. Panel B shows the associations between diarrhea and severe wet anomalies for the humid subtropical zone. Feeding practices are assessed for children between 6 and 23 mo of age due to data availability. Rotavirus immunization is assessed for children between 3 and 35 mo of age and for a limited number of countries due to data availability. Detailed results are available in SI Appendix, Tables S10 and S11. All estimates are adjusted for potential confounders (see Methods). Wald test is used to determine statistically significant pairwise differences in effect estimates between effect modifier categories.