El Niño-Southern Oscillation and Diarrhea Risk among Young Children in Low- and Middle-Income Countries

Background: Diarrhea in children is a climate-sensitive disease that causes a large disease burden worldwide, while the impact of El Niño-Southern Oscillation (ENSO) remains unclear. Objectives: This study aimed to evaluate the diarrhea risk among children associated with ENSO in low- and middle-income countries. Methods: Individual data on 1,340,334 children under five years of age were collected from 53 low- and middle-income countries from the Demographic and Health Surveys Program during 2005-2019, including information on diarrhea, demographic characteristics, cluster location, water, sanitation, and hygiene (WASH). ENSO indexes (E and C index) were calculated with sea surface temperature through Empirical Orthogonal Function analysis. Teleconnection (τ^E and τ^C) of the locations where the cluster sites were located was calculated based on population-weighted temperature and total precipitation. For each location, ENSO exposure (El Niño and La Niña strength) were calculated by month-specific ENSO indexes and its teleconnection, respectively. A binomial generalized linear mixed-effects model was used to explore the association between ENSO exposure and diarrhea risk in children. Results: Odds ratios of diarrhea in children were 1.032 (95%CI: 1.025, 1.040) and 0.977 (95%CI: 0.971, 0.984) for each standard deviation increase in El Niño and La Niña strength, respectively. The effect size of El Niño was greater for children in rural areas [OR: 1.042 (95%CI: 1.033, 1.052)] and low-income households [OR: 1.047 (95%CI: 1.035, 1.060)]. The association between El Niño and diarrhea risk was stronger among those with unimproved toilet facilities and source of drinking water compared to those with improved conditions, while associations were similar by other WASH conditions, and La Niña showed similar results in the subgroup analyses. Discussion: This multicountry study indicates an association between ENSO and the diarrhea risk in children under five years globally. Our findings will benefit international prevention and control policy development for diarrhea in children to immediately reduce ENSO-related impacts.