Prevalence of and factors associated with diarrheal disease among under-five children in South and Southeast Asian communities: a systematic review and meta-analysis

Diarrheal disease remains a leading cause of childhood illness and death in South and Southeast Asia, yet region-wide syntheses of its prevalence are sparse. We conducted a systematic review and meta-analysis to estimate the pooled prevalence of diarrheal disease among children under five years in South and Southeast Asia, to describe its spatio-temporal and socioeconomic variation, and to identify factors associated with diarrheal disease. We searched five bibliographic databases (PubMed/MEDLINE, Embase, Scopus, Web of Science and Google Scholar) from January 2000 to December 2024. We included eligible studies that were cross-sectional, cohort (baseline), surveillance, or baseline randomised-trial data published in English and reported diarrheal disease prevalence among children under five years in South and Southeast Asian countries using the WHO definition. Prevalence was pooled by random-effects meta-analysis of logit-transformed proportions (REML) in R (v4.5.0), with subgroup analysis, meta-regression, sensitivity analyses and assessment of publication bias. The protocol was registered prospectively in PROSPERO (CRD42024623645). We assessed certainty of evidence using GRADE. Study quality was evaluated using the Joanna Briggs Institute (JBI) Critical Appraisal Checklist for prevalence studies. Thirty-three studies (1,036,975 children) were included. The pooled two-week prevalence of diarrheal disease was 13% (95% CI: 10–16%; 95% prediction interval: 3–42%), with extreme between-study heterogeneity (I² = 99.7%). Funnel plot asymmetry was present (Egger’s test p = 0.017), and trim-and-fill adjustment lowered the pooled estimate to approximately 10%; the true regional prevalence may therefore be closer to 10% than to the unadjusted 13%. Country-level estimates ranged from 5% in the Maldives to 44% in Nepal, but the estimates for Nepal, Bhutan, the Maldives and Timor-Leste each derive from a single study and are exploratory. Prevalence was 13% before, 16% during and 7% after the COVID-19 pandemic; the post-COVID estimate rests on only four studies and should be interpreted with caution. Pooled prevalence was lower in upper-middle-income (10%) than in lower-middle-income countries (13%), although confidence intervals overlapped, and higher in urban (17%) than rural (13%) settings. Hospital-based studies and consecutive or convenience sampling were associated with higher estimates. In pooled analyses based on two to five studies per factor, age 12–23 months (OR 2.00, 95% CI 1.81–2.20) and 24–35 months (OR 2.19, 95% CI 1.77–2.70) compared with younger infants, and maternal lack of education (OR 1.30, 95% CI 1.17–1.43) were associated with higher odds of diarrheal disease. The prevalence of diarrheal disease among children under five years is high in South and Southeast Asia, but disparities exist across geographic and socioeconomic characteristics. Extreme heterogeneity, possible publication bias and a predominantly cross-sectional evidence base limit the precision of the pooled estimate, and the associations identified should not be interpreted as causal. Age-targeted case management, maternal education, strengthened surveillance and integrated water, sanitation and hygiene (WASH) programmes are plausible priorities, and higher-quality, standardised prospective studies are needed. Not applicable.