Moving towards transformational WASH
Authors: Karen Levy, Joseph N S Eisenberg
Journal: The Lancet Global Health (2019)

The observational reanalysis by Amy Pickering and colleagues (August, 2019)1Pickering AJ Null C Winch PJ et al.The WASH Benefits and SHINE trials: interpretation of WASH intervention effects on linear growth and diarrhoea.Lancet Glob Health. 2019; 7: e1139-e1146Summary Full Text Full Text PDF PubMed Scopus (89) Google Scholar of controls in the WASH Benefits trials and the Sanitation, Hygiene, Infant Nutrition Efficacy (SHINE) trial is a compelling reminder that observational studies are susceptible to confounding bias. However, we should not discount the value of observational studies in global health research, because ethical and logistical issues often limit the feasibility of randomised control trials (RCTs) and observational studies are a requisite precursor to trials. More importantly, RCTs have their own, inherit limitations. When the adoption of interventions is perfect, RCTs have the power to examine causality. Uptake is often imperfect, however, meaning an intention-to-treat analysis will bias an effect towards the null.2Brown J Hayashi MAL Eisenberg JNS The critical role of compliance in delivering health gains from environmental health interventions.Am J Trop Med Hyg. 2019; 100: 777-779Crossref PubMed Scopus (5) Google Scholar This tendency can be seen in the WASH Benefits and SHINE trials, in which Bangladesh—the site with the highest frequency of contact between behaviour change promoters and participants—had more evidence of effects than the other sites. Thus, although an observational study might overestimate the effect, an RCT might underestimate it. The true causal estimate usually lies somewhere in between the estimates produced by the two approaches. Causal graph analysis is one promising approach to take advantage of both RCT and observational designs to make causal inferences.3Pearl J An introduction to causal inference.Int J Biostat. 2010; 6: 7Crossref Scopus (212) Google Scholar As noted by Pickering and colleagues,1Pickering AJ Null C Winch PJ et al.The WASH Benefits and SHINE trials: interpretation of WASH intervention effects on linear growth and diarrhoea.Lancet Glob Health. 2019; 7: e1139-e1146Summary Full Text Full Text PDF PubMed Scopus (89) Google Scholar the external validity of RCTs is low. RCTs often do not fully capture heterogeneity within a community or represent the target population of interest.4Sanson-Fisher RW Bonevski B Green LW D'Este C Limitations of the randomized controlled trial in evaluating population-based health interventions.Am J Prev Med. 2007; 33: 155-161Summary Full Text Full Text PDF PubMed Scopus (293) Google Scholar Although the WASH Benefits and SHINE trials were large and well conducted with consistent findings across the sites, all three studies were carried out in rural locations. Thus, the extent to which the results of these trials applies to the 68% of the global population expected to live in urban areas by 2050 is unclear.5UN Population Division of the Department of Economic and Social AffairsWorld urbanization prospects: the 2018 revision. United Nations, New York2018Google Scholar Finally, RCTs are only applicable for some kinds of interventions. Community-scale interventions, for example, are more challenging to study using RCT methodology.4Sanson-Fisher RW Bonevski B Green LW D'Este C Limitations of the randomized controlled trial in evaluating population-based health interventions.Am J Prev Med. 2007; 33: 155-161Summary Full Text Full Text PDF PubMed Scopus (293) Google Scholar This challenge is why the evidence base from water, sanitation, and hygiene (WASH) trials is heavily weighted towards household-level and compound-level interventions, with few studies evaluating community-scale interventions. We agree with the WASH Benefits and SHINE teams' collective conclusion that "radically more effective" interventions than the household-level interventions implemented in these trials are needed to reduce faecal contamination in the domestic environment.1Pickering AJ Null C Winch PJ et al.The WASH Benefits and SHINE trials: interpretation of WASH intervention effects on linear growth and diarrhoea.Lancet Glob Health. 2019; 7: e1139-e1146Summary Full Text Full Text PDF PubMed Scopus (89) Google Scholar If the public health community is truly interested in implementing and rigorously evaluating community-scale efforts towards "transformational WASH", we cannot limit ourselves to randomised trials. By not appreciating the power of the observational study, we risk getting a robust answer to the wrong question. When the world is full of more than just nails, we would be wise to have tools in our toolbox other than hammers. We declare no competing interests. The WASH Benefits and SHINE trials: interpretation of WASH intervention effects on linear growth and diarrhoeaChild stunting is a global problem and is only modestly responsive to dietary interventions. Numerous observational studies have shown that water quality, sanitation, and handwashing (WASH) in a household are strongly associated with linear growth of children living in the same household. We have completed three randomised efficacy trials testing improved household-level WASH with and without improved infant and young child feeding (IYCF) on stunting and diarrhoea in Bangladesh, Kenya, and Zimbabwe. Full-Text PDF Open AccessMoving towards transformational WASHAs noted by the Lancet Commission on pollution and health,1 the anthropogenic release of chemicals from industry and agriculture and the breakdown of consumer waste constitutes a major threat to water and global public health. Chemical pollution is severe and increasing in developing countries, where chemical substances are produced, used, and disposed of in an unregulated manner. The global public health consequences of pollution are similar to or greater than those of widespread infectious diseases, such as HIV/AIDS, tuberculosis, and malaria. Full-Text PDF Open AccessMoving towards transformational WASH – Authors' replyWe agree with Karen Levy and Joseph Eisenberg that observational studies of water, sanitation, and hygiene (WASH) interventions with carefully designed counterfactuals can play a valuable role in generating evidence on effectiveness, particularly in urban settings. Randomised controlled trials for community-level WASH infrastructure interventions are not always feasible in urban settings, because of the political and logistical constraints of defining treatment and control groups; strong observational designs could help fill the gap. Full-Text PDF Open Access