Global and regional trends in under-five diarrheal disease burden: impact of human development index and geographic disparities, 1990-2021.

Aim: In this study, global and regional trends between 1990 and 2021 were examined by sex, level of development, and geography, and projected to 2025.

Background: Diarrheal disease continues to be a leading cause of morbidity and mortality in children under the age of five (U5).

Methods: We assessed GBD 2021 data for U5 children in 204 countries, 21 regions, and 7 super-regions with joinpoint regression to analyze time trends, a hybrid ARIMA-ETS-ANN model to project prevalence and mortality until 2025, and longitudinal multilevel modeling to determine the effect of development level. Spatial clustering in 1990 and 2021 was assessed with Local Moran's I.

Results: In 2021, the global prevalence and mortality rates of diarrheal disease among children under five were 885.07 and 51.72 per 100,000 population, respectively. Between 1990 and 2021, global U5 mortality decreased by 80.4%, and prevalence by 71.8%. The heaviest burden remained in Sub-Saharan Africa (SSA) and South Asia (SA), though all super-regions experienced statistically significant decreases. Joinpoint regression across the entire interval (1990-2021) revealed significant overall reductions in mortality (AAPC -5.15; 95% CI: -5.19, -5.10) and prevalence (AAPC -3.98; 95% CI: -4.03, -3.94). Hybrid forecasts predict ongoing decreases through 2025, with prevalence reaching 631.3 and mortality 36.6 per 100,000 population worldwide. Multilevel models revealed steeper annual reductions in low- and medium-Human Development Index (HDI) nations, corroborated by significant time-HDI interaction terms (β=79.76 for prevalence; β=7.50 for mortality; both p<0.001), although such countries had a persisting higher absolute burden. Spatial analysis revealed enduring hotspots in SSA and SA in both 1990 and 2021, and the formation of new clusters in several high-income countries. Coldspots occurred primarily in high-income and island nations.

Conclusion: Significant global advancements have lessened the burden of diarrheal disease in U5 children; yet, ongoing disparities attributed to unsafe water, poor sanitation and hygiene, undernutrition, and low maternal education underscore the necessity for combined water, sanitation, and hygiene interventions, rotavirus immunization, and community-based health education in high-risk areas.