Authored by: Dr. Zulfiqar Bhutta, Co-director of the Center for Global Child Health, The Hospital for Sick Children, Toronto Link to Bio
The question as to whether investments in water, sanitation and hygiene (WASH) impacts nutrition outcomes, especially linear growth, has vexed researchers for a very long time.
The classic association of poor WASH conditions with high burdens of disease –especially diarrheal disorders – is well-recognized. For a long time the pathway to linear growth deceleration and stunting was thought to be due to repeated diarrheal episodes with associated nutrition penalty.
Careful longitudinal studies, however, determined that short duration diarrheal episodes usually did not lead to linear growth deceleration nor were diarrheal disease burdens clearly associated with stunting unless the episodes were prolonged or persistent. While several observational studies include ecological analyses of linear growth within DHS data sets (Speers et al, several analyses1) indicated that stunting was associated with poor WASH status, especially hygiene and sanitation, corresponding data from randomized trials and systematic reviews have been confusing to say the least. Despite this uncertainty, WASH interventions have remained a sacrosanct part of “nutrition sensitive” or indirect interventions outside of the health sector.
More recent cohort studies such as MalED2 also confirm the association of impaired linear growth with high burden of bacterial colonisation in the gut and possible “environmental enteric dysfunction”, an important features of early growth failure.
However, Dangour et al conducted a Cochrane review of available information from WASH trials in 2013 and concluded that the effect on linear growth was small.
More recently, two large cluster RCTs of WASH (and additional nutrition interventions) in Bangladesh, Kenya and Zimbabwe (Luby et al and Humphreys et al 2018/20193) failed to show any impact on linear growth in children under 5, again throwing open the question of the link between WASH and linear growth.
These findings from carefully conducted RCTs must however be considered with caution as they may not capture the full, “real life” benefits of WASH on health and nutrition that occur at scale and over time. To illustrate, the SHINE and WASH benefits investigators themselves recognize that the effect of such interventions may well relate to the quality of intervention and dose exposure.
An alternative means of assessing the potential relationship of WASH investments on linear growth might be from ecological studies in countries which have made progress across several domains (social determinants, education, female empowerment and economic development). Indeed, our Stunting Exemplars research suggests a clearer connection. In countries with poor baseline WASH and environmental conditions, especially sanitation, we are able to see the independent impact of WASH investments on linear growth (in addition to improved health and nutrition investments and those related to socioeconomic growth, food security and education). This provides further evidence to support investments in safe water, sanitary conditions, and personal hygiene measures as a cornerstone for improved health and nutrition outcomes.
Our overall analysis does suggest that benefits from WASH investments accrue across a range of outcomes, including linear growth and importantly influencing overall nutrition and human development outcomes. Additionally, looking beyond implications for linear growth alone, countries will continue to invest in clean, safe water, proper sanitation, and promotion of hygienic measures as a fundamental human right.
References:
- 1 Geruso, M., & Spears, D. (2018). Neighborhood sanitation and infant mortality. American Economic Journal: Applied Economics, 10(2), 125–162; Spears, D. (2013a). How much international variation in child height can sanitation explain? (Working paper). Princeton, NJ: Princeton University; Spears, D. (2013b). Policy lessons from the implementation of India’s total sanitation campaign. India Policy Forum, 9, 63–99.
- 2 Murray-Kolb LE, Rasmussen ZA, Scharf RJ, et al. The MAL-ED cohort study: methods and lessons learned when assessing early child development and caregiving mediators in infants and young children in 8 low- and middle-income countries. Clin Infect Dis. 2014;59 Suppl 4(Suppl 4):S261–S272. doi:10.1093/cid/ciu437
- 3 Luby SP, Rahman M, Arnold BF, et al. Effects of water quality, sanitation, handwashing, and nutritional interventions on diarrhoea and child growth in rural Bangladesh: a cluster randomised controlled trial. The Lancet Global Health. 2018;6(3). doi:10.1016/s2214-109x(17)30490-4