Effects of early water, sanitation, handwashing, and nutrition interventions on child development at school age: a follow-on study of a cluster-randomized trial in rural Bangladesh.

Publication date: Dec 01, 2025

A previous cluster-randomized controlled trial in Bangladesh found that individual or combined water, handwashing, sanitation, and nutrition interventions during pregnancy and after birth improved developmental outcomes of children at 1 and 2 years of age. In this study, we aimed to determine if these intervention effects were sustained for children at school age. Clusters of pregnant women were enrolled between May 31, 2012 and July 7, 2013 and block-randomized into chlorinated drinking water (W); improved sanitation (S); handwashing with soap (H); combined WSH; nutrition counseling and provision of lipid-based supplements (N); combined WSH + N, or a double-sized passive control arm (C) with no intervention visits (N = 5,551). The primary outcomes of the main trial after the 2-year intervention were 7-day diarrhea prevalence and length-for-age z-score, measured in 4,584 children of enrolled pregnant women. We conducted a post hoc, follow-up of all initially enrolled mothers and their children 5 years after intervention completion, when children were 7 years old. Primary outcomes were child cognition assessed using the Wechsler Pre and Primary Scale of Intelligence (WPPSI-IV), along with assessments of fine motor abilities, behavior, school achievement, and executive function; secondary outcomes were maternal mental health and stimulation in the home environment. We conducted intention-to-treat analyses using generalized linear models to calculate unadjusted and adjusted comparisons between each arm and the control group, accounting for block-level clustering. Between September 2019 and February 2021, we re-enrolled 4,175 households from all 720 original clusters, with the full set of child development assessments conducted on 3,833 children across 718 clusters. Children in the WSH + N, N, and S arms had improved cognitive scores on one or more domains compared to the control arm, with adjusted effect sizes between 0. 10 (95%CI: 0. 00, 0. 20) and 0. 15 (0. 03, 0. 27). Children in the W, H, N, WSH, and WSH + N arms demonstrated improved prosocial behaviors (adjusted effect sizes between 0. 20 (0. 07, 0. 33) and 0. 31 (0. 16, 0. 46)) and reduced difficult behaviors (adjusted effect sizes between -0. 15 (-0. 28, -0. 01) and -0. 31 (-0. 45, -0. 17)). No intervention effects were observed for fine motor, executive functioning, or school achievement outcomes. Maternal depressive symptoms were improved in the WSH + N, H, and N arms (adjusted effect sizes between -0. 14 (-0. 24, -0. 03) and -0. 21 (-0. 31, -0. 11)), and the stimulating home environment was improved in all intervention arms (adjusted effect sizes between 0. 17 (0. 01, 0. 33) and 0. 40 (0. 25, 0. 56)). Children whose families had higher wealth at baseline and those who were male tended to have larger effect sizes on the FSIQ. Data collection for this study was interrupted by a 6-month pause at the start of the COVID-19 pandemic. The main limitation of this study is loss to follow-up. At 7 years of age, we found small, sustained benefits of early water, sanitation, handwashing, and nutrition interventions on child cognitive and socioemotional outcomes, the stimulating home environment, and maternal mental health. Future work to determine the mechanisms underlying these intervention effects will further inform the design of early interventions to improve child health and development. Trial registration: Follow-up trial: ClinicalTrials. gov, NCT04443855. Original WASH-Benefits Bangladesh (WASH-B): ClinicalTrials. gov, NCT01590095.

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