Growing evidence that WASH investments can reduce stunting

New research is helping shed light on the connection between WASH and stunting and adding to the growing body of evidence indicating that WASH improvements can play a meaningful role in the global effort to reduce stunting.

For decades, researchers have struggled to pin down the murky relationship between WASH investments and stunting.

We spoke with child nutrition expert Dr Zulfiqar A. Bhutta, the Robert Harding Inaugural Chair in Global Child Health at the Hospital for Sick Children, Toronto, Co-Director of the SickKids Centre for Global Child Health, the Founding Director of the Institute for Global Health & Development, at the Aga Khan University, and an Exemplars in Global Health research partner, about what the latest research tells us about the impact of WASH improvements on childhood stunting rates.

Experts recognize that poor hygiene can serve as a pathway to stunting in a few ways. First, poor hygiene (which can be related to a variety of factors including lack of access to clean water or improved sanitation, high open defecation rates etc.) increases the likelihood of infection. This matters because infections require extra calories to fight – and that can deplete young children of the energy they need to grow. Second, poor hygiene can lead to diarrhea, which doesn’t allow for the full absorption of the nutrients children need to grow. Third, poor hygiene can lead to inflammation of different areas along the intestinal track, which, again, doesn’t allow for the full absorption of nutrients.

Based on these pathways, the global health community expected that interventions to improve WASH (by improving access to clean water, or improved sanitation, or reducing open defecation, etc.), would reduce the frequency of infections, diarrhea, and inflammation, and thereby improve the absorption of nutrients and reduce stunting.

However, three recent randomized control trials in Zimbabwe, Bangladesh, and Kenya tested the impact on stunting of both nutrition interventions (supplementation, counseling on breastfeeding and complementary feeding) and WASH interventions (improved pit latrines, handwashing stations, and chlorine water treatment). Across all three trials, nutrition interventions were significantly associated with increased growth while WASH interventions were not.

The studies’ findings prompted global health researchers to ask how good, robust studies could so obviously fly in the face of logic and a lot of other evidence. Global health researchers are now asking if these studies, which followed children over the course of two years, provided sufficient time to capture WASH related improvements to growth.

“What makes this so complicated is the multi-causal nature of stunting,” explained Dr. Bhutta. “The levers for improving a child’s growth include: maternal health, maternal diet, breastfeeding habits, complementary feeding habits, access to supplementation for both mother and infant, household level food security, diet, sanitation, women’s empowerment, or familial expectations for feeding and growth, to name just a few.” (for a full list, click here).

“Further, more than half a century after first identifying stunting as an indicator of long-term poor nutrition, we still have an incomplete understanding of the biological forces at work in stunting,” Dr. Bhutta added. “Some stunting is clearly caused by inadequate caloric intake – similar to wasting. At the same time, we see stunting in children who are overweight – which indicates that they are suffering, not from inadequate caloric intake, but from a lack of critical micronutrients.”

“Our research, with Exemplars in Global Health is helping clarify the relationship between WASH and stunting to help inform decision-makers in the health sector,” said Dr. Bhutta. “In five of the seven case exemplars in stunting reduction that we’ve identified and analyzed, WASH played a meaningful role in stunting reduction – especially when examining the impact of WASH over a 10-20 year period."

Dr. Bhutta outlined his team findings:

In Ethiopia, Exemplars in Global Health research partners, including Addis Ababa University, estimated that improvements to WASH were responsible for 17 percent of the country’s stunting reduction. Ethiopia’s community health workers prioritized raising awareness about the dangers of open defecation, as part of the Community Led Total Sanitation approach. The effort led to one of the largest declines in open defecation in the world. Between 2000 and 2017, the percentage of Ethiopians defecating in the open dropped from 79 to 22 percent. At the same time, the number of people with access to “improved” water sources doubled.

Nepal adopted Community Led Total Sanitation in 2003 and Exemplars in Global Health researcher partners, including Nepal Public Health Foundation, estimated that improvements to WASH were responsible for 12 percent of the country’s stunting reduction. In 1996, about 77 percent of households had no toilet. Twenty years later, that figure was just 15 percent—again, one of the largest declines in open defecation in the world. Partly as a result, diarrhea incidence declined from 20 to eight percent and acute respiratory infection incidence from 23 to two percent between 2001 and 2016.

Senegal privatized the water sector to improve access to clean water and the Exemplars in Global Health research partners, including Université Cheikh Anta Diop (University of Dakar), estimate that those improvements were responsible for 8 percent of the country’s stunting reduction. Between 1992 and 2017, access to an improved source of drinking water rose from 52 percent to 81 percent, piped water from 47 percent to 74 percent, and improved sanitation from 22 percent to 51 percent. Meanwhile, households not using a toilet facility fell from 40 percent to 13 percent.

In Uganda, WASH indicators have been steadily improving over time. Exemplars in Global Health’s systematic review found that access to piped water accounted for 4.5 percent of the stunting reduction and reduction in open defecation accounted for another 2.7 percent. Research partners, including Makerere University, found that access to improved sanitation increased from 4 percent in 2000 to 21 percent in 2016, while access to a basic drinking water source doubled from 22 percent in 2000 to 41 percent in 2016. Access to piped water also improved from 11 percent to 21 percent over the same period. Similar reductions in open defecation were observed, with the percentage engaging in this practice declining from 15 percent to 6 percent over the study period.

Exemplars in Global Health research in Pakistan demonstrates that all investments in WASH are not of equal value when it comes to reducing stunting. Research partners, including Aga Khan University, found that Pakistan focused on reducing open defecation and building latrines—a focus that was specifically encouraged by the targets included in the Millennium Development Goals (MDGs). Those investments had limited impact because, according to a 2018 World Bank report, Pakistan’s investments paid “little or no attention to fecal waste management or latrine quality, resulting in an unprecedented concentration of untreated fecal waste near human settlements.” So, while open defecation decreased by 74 percent in Khyber Pakhtunkhwa Province, by 65 percent in Punjab, and by 33 percent in Sindh, many of the newly constructed toilets in those regions flowed into open drains that then contaminated communities.

Nevertheless, in Pakistan, Exemplars in Global Health found that reductions in diarrhea incidence was the third most important factor for stunting decline, accounting for 10 percent of the total explained HAZ (height-for-age z score) change among children under-5 in good performing regions.

Exemplars researchers, including Universidad Peruana Cayetano Heredia and University of Central Asia, found that WASH was not a leading driver of stunting reduction in Peru and Kyrgyzstan. In Peru, open defecation rates were relatively low even at the start of the study period. And in Kyrgyzstan open defecation was non-existent during the study period. Other elements of WASH were also relatively high in these two geographies during the study period limiting their potential impact.

“Even if later research finds that WASH is important for stunting reduction in only limited circumstances such as very poor and contaminated settings, there are many other good reasons to invest in WASH, the foremost of which is a human rights perspective” said Dr. Bhutta. He added, “the World Health Organization estimates that every dollar invested in water and sanitation services brings a return of $4.30 in the form of reduced healthcare costs and greater productivity. That is a great return on investment.”