Children's Health Outcomes Associated with Access to Water, Sanitation and Hygiene (WASH): A Systematic Review of Empirical Gaps Related to Diarrhoea in Low- and Middle-Income Countries

Abstract

Sustainable Development Goal 3 (SDG 3) mandates global action to ensure healthy lives and promote well-being for all. However, child mortality in low- and middle-income countries (LMICs) remains alarmingly high due to inadequate access to clean water, hygiene, and sanitation. This systematic review critically examines empirical research linking water, sanitation, and hygiene (WASH) access to child health outcomes across LMICs, aiming to identify key empirical gaps related to diarrhoea, child development and stunting, and acute infections. A systematic literature review, conducted in June 2025 in accordance with PRISMA guidelines, searched databases including Taylor & Francis, EBSCOhost, and PubMed. Of 230 initial records, 48 empirical studies met the inclusion criteria of focusing on primary research examining children’s health outcomes. Data were analyzed thematically to categorize dependent variables and assess research trends. Findings revealed a disproportionate focus on diarrhoea, which accounted for 62.5% of all dependent variables, underscoring its enduring global health significance. Child development and stunting accounted for 29.17%, while acute infections were the least studied (8.33%), exposing substantial research gaps. Geographically, studies were heavily concentrated in Ethiopia (29.0%) and India (25.8%), followed by Bangladesh, Kenya, Nigeria, Senegal, South Africa, and Nepal. Most research targeted children under five (83.3%), highlighting their vulnerability. “Specific WASH Components” (e.g., water supply, sanitation, handwashing) emerged as the most common independent variables. Significant theoretical, methodological, and empirical gaps were identified: 92.6% of studies lacked explicit theoretical frameworks, most relied on cross-sectional designs, and 96.6% failed to examine mediating or moderating variables. These limitations hinder understanding of the causal pathways linking WASH to child health outcomes. Future research should adopt longitudinal designs, integrate theoretical and socio-cultural determinants, and systematically explore mediating mechanisms to strengthen causal inference and inform effective, context-specific policies supporting SDG 3 targets.