Floods and Diarrhea Risk in Young Children in Low- and Middle-Income Countries

Key Points Question Is there an association between flood exposure and diarrhea risk among children younger than 5 years living in low- and middle-income countries? Findings In this multicountry cross-sectional study of 639 250 children, exposure to floods was found to be associated with a higher prevalence of diarrhea, driven by extreme flood events, floods that lasted more than 2 weeks, and floods preceded by droughts. Meaning These findings suggest that more effective measures are warranted to protect children’s health from compound extreme weather events, including floods and drought, which are projected to increase in frequency and intensity due to climate change.

We downloaded and rescaled monthly mean temperature and total rainfall at a resolution of 0.1° (~10×10 km) during the same study period from the fifth generation European Centre for Medium-Range Weather Forecasts atmospheric reanalysis of the global climate (ERA5-Land). 1 We calculated our drought indicator following the methodology of our previous work. 2Briefly, we assessed drought condition by the standardized precipitation evapotranspiration index (SPEI), which offers a more accurate and robust measure than precipitation alone by computing the climatic water balance between the available water content of soil and vegetation and the atmospheric evaporative demand. 3We linked gridded 3-month, 6-month,12-month, and 24month SPEI, monthly mean temperature, and monthly total rainfall with each child according to the geographic coordinates of each survey cluster and the month and year when the mother was interviewed.Exposure to drought was defined as SPEI ≤ -0.5 and non-exposure to drought was defined as SPEI > -0.5. 4

eMethods 2. Model Specification of Main Analysis
We employed binomial generalized linear mixed effects logistic regression models to quantify the associations between exposure to floods and risk of diarrhea among children: where i is the index for each individual child and j is the DHS survey cluster in a specific country.
Pi is the probability of having diarrhea.Xj is the binary indicator representing flood exposure (yes or no) for cluster j.COVi is a matrix of individual and household baseline characteristics, including child's sex and age, maternal education, urban/rural residence, and wealth index.φj is the monthly total rainfall in the month of the interview at cluster j. λ is a matrix of categorical survey month and a natural cubic spline of survey year with three degrees of freedom to adjust for seasonality and long-term trend, respectively.ωj denotes the nested random intercepts for survey cluster and country, accounting for cross-cluster and cross-country differences.eTable 1. Severity Class of Flood Events Severity Definition

Large flood events
Causing substantial damage to structures or agriculture, loss of life, and/or having a reported interval of 1-2 decades since the occurrence of a similar event.
Very large flood events Having an estimated recurrence interval of more than 2 decades but less than 100 years, and/or having a local recurrence interval of 1-2 decades and impacting a vast geographic region exceeding 5000 square kilometers.

Extreme flood events
Characterized by an estimated recurrence interval surpassing 100 years.
Note: This classification method has been consistently adopted by the Dartmouth Flood Observatory.

eMethods 1 .
Collection of Temperature and Rainfall Data and Assessment of Drought

eFigure 1 .
Single Lag and Cumulative Lag Periods for the Interview Date in Relation to the Flood Start Date.On the interview date, mothers reported diarrhea occurrence during the two weeks before the interview.eFigure 6.Effect Modification of the Association Between Exposure to Floods and Risk of Diarrhea Among Children Under 5 by Roundtrip Time to Collect Water, by Cumulative Lag Period (N = 607 179).Statistically significant differences [p<0.05] in the association are marked with an asterisk).eFigure 7. Effect Modification of the Association Between Exposure to Floods and Risk of Diarrhea Among Children Under 5 by Place to Wash Hands, by Cumulative Lag Period (N = 585 304).Statistically significant differences [p<0.05] in the association are marked with an asterisk).

(1.01, 1.62) 1.57 (1.18, 2.09)
Flood Events That Children (Among All 639 250 Children in the Complete Data Series) Odds Ratios and 95% CIs for Associations Between Exposure to Floods and Risk of Diarrhea 5 eTable 2. Note: bold font represents statistically significant result.© 2023 Wang P et al.JAMA Pediatrics.