WASH and learn: a scoping review of health, education and gender equity outcomes of school-based water, sanitation and hygiene in low-income and middle-income countries

Abstract

School-age children in low-income and middle-income countries (LMICs) face health and educational challenges due to inadequate water, sanitation and hygiene (WASH) in schools (WinS). Evidence for the impact of WinS interventions is limited and inconsistent, and previous systematic reviews have faced challenges in synthesising data due to varied interventions, study designs and outcome measures, although most do not examine this variability in more detail. This scoping review identified 83 experimental studies from 33 LMICs measuring a primary or secondary health or educational outcome among pupils, published up to November 2023, using a systematic search of seven databases and searching of reference lists of previous systematic reviews and included articles. These included 65 studies (78%) not included in previous WinS reviews and encompassed 313 intervention effects across 14 outcome domains. Interventions comprised an array of WASH technologies and approaches, often combining infrastructure and behaviour change methods and frequently integrated with other school-based initiatives like deworming. 36 studies (43%) measured only behavioural or knowledge outcomes. Our comprehensive inventory of study outcomes identified 158 unique outcome measures, with 72% measured in exactly one study. Common outcomes included parasitic infections, anthropometric measures and school absence, but approaches to measurement varied widely even for similar outcomes. Only 7% of results were disaggregated by gender, limiting assessment of differential impacts. Our findings underscore the need for standardised outcome measures in WinS research incorporating a complete definition of the assessment and aggregation approach, greater attention to gender-specific impacts, and further exploration of modalities and functions of WinS interventions alongside novel meta-analysis methods to disentangle effects of diverse intervention components.

Keywords: Child health; Environmental health; Epidemiology; Hygiene; Review.

Figure 1. PRISMA flow diagram. PRISMA, Preferred Reporting Items for Systematic Reviews and Meta-Analyses.

Figure 2. Left: Venn diagram of interventions components compared across included studies. Right: outcomes assessed across three intervention arm categories. HWF, handwashing facilities.

Figure 3. Total non-unique outcomes measured and total intervention arm comparisons by outcome domain, across three intervention categories.

Figure 4. (A) Within-study relationship between number of health or educational outcomes and number of different outcome domains. Overlapping points separated by jitter effect. Studies measuring one or two outcomes in a single domain not labelled. Dashed line indicates one outcome per domain. (B) Within-study overlap between outcome domains, reporting number of studies measuring at least one outcome in both the horizontal and vertical domains. WASH, water, sanitation and hygiene.

Figure 5. (A) Total number of unique and non-unique outcomes by outcome domain (left) and disaggregation of results by gender at the outcome level (right). Right: non-unique outcomes by domain that were reported disaggregated by gender (solid bars) versus not disaggregated (lighter shading). *Out of six results—the three enrolment results for Freeman et al are already disaggregated by means of the gender parity in enrolment outcome and, therefore, not included in the denominator. (B) Disaggregation of study results by gender at the intervention level in the same 37 studies reporting treatment effects on health or educational outcomes. Number of intervention arm comparisons for which results were gender-disaggregated. ‘Full’: results for all health or educational outcomes were gender-disaggregated; ‘partial’: disaggregation of some outcomes; ‘tested’: study authors report conducting subgroup analysis or interaction tests by gender but did not report disaggregated results; ‘none’: no gender-disaggregated outcomes.