Research shows converging evidence of the key role of open defecation in explaining child stunting in India
For two days, leading scholars of child height—economists, epidemiologists, nutritionists, and pediatricians—and government officials gathered at the Delhi School of Economics for a conference supported by the World Bank’s Water and Sanitation Programme to share research on an urgent question: why are children in India so short? Height is an important indicator of overall health and human development because the same good health that helps a child grow tall can also help her grow smart. In presentation after presentation at the conference, sanitation stood out as an important part of this puzzle.
India has exceptionally poor sanitation: the country accounts for 60% of the incidence of open defecation. Open defecation is an immense hardship for those who have no other practical option and an important issue of human dignity. The conference also presented striking convergence in the evidence showing open defecation as a key factor explaining widespread stunting in India.
As Nisha Malhotra, an economist at the University of British Columbia, summarized, “open defecation doesn’t go away"—meaning that there is essentially no way of analyzing data on Indian children’s height where open defecation does not emerge as a key factor explaining shortfalls in child growth. Work done by researchers from different disciplines using different methods produced similar conclusions.
Oliver Cumming, from the London School of Hygiene and Tropical Medicine, first laid the biological groundwork for the discussion. There are very plausible biological links between exposure to fecal pathogens and diseases like diarrhea, nematode infection (also known as worms), and environmental enteropathy (a disease of the small intestine that prevents nutrients from being absorbed by the body), and studies have shown that these diseases increase the odds of stunting. A recent meta-analysis by Alan Dangour and co-authors, which summarizes the results of all of the high-quality research available on water, sanitation, and hygiene interventions suggests that water quality interventions are effective in reducing stunting.
Nutritionists at the conference also showed that nutrition alone cannot explain stunting. A study by Zulfiqar Bhutta and co-authors, published in a recent Lancet series on nutrition, includes an analysis showing that if the 10 most effective nutrition interventions were scaled up to 90%, we would see only a 20% reduction in stunting. Maternal and child nutrition are certainly very important for child health, but the research conducted by Purnima Menon of the International Food Policy Research Institute (IFPRI) has shown that the combined impact of nutritional interventions and proper sanitation in India is more effective than either one individually.
From the economic literature, Jeffrey Hammer and Manisha Shah, economists from Princeton University and University of California, Los Angeles (UCLA), respectively, presented evidence from two randomized-controlled trials (RCTs). Researchers love RCTs because they randomly assign treatment, and thus overcome many of the selection biases that plague other types of studies. Both studies, conducted in Maharashtra and Indonesia, show causal evidence that improved sanitation increases average child height.
The link between sanitation and child health outcomes across countries at the population level was also examined. An international comparison by Dean Spears shows that countries where many people defecate in the open are the same countries where the most children are stunted and the average child is shortest. Another international comparison, by Diane Coffey, shows that countries where many people defecate in the open are the same countries where children have the lowest hemoglobin levels on average. Hemoglobin is affected by diseases caused by fecal pathogens, and is an important measure of health because it is a marker of anemia. Two other studies, by Payal Hathi and myself, look at Bangladesh and Cambodia in particular and find that the regions where sanitation improved the most over time were the same regions where child height improved the most over time. The effects of open defecation in these studies do not go away even when the analyses consider other factors that may matter for child height. While one cannot infer causality from these non-experimental studies, they are notably consistent with the findings from the experimental, epidemiological, and nutritional literatures.
There has been much public debate recently about why children in India are shorter than children in other places. One takeaway from the conference is that many parts of children’s environments matter: disease, pollution, poor feeding practices. But what is also clear from the research is that sanitation is an important part of what explains variation in child height, and that the reason why sanitation explains a lot of stunting in India is precisely because it is so bad here. Improving sanitation has been shown to reduce stunting, so perhaps open defecation is the lowest-hanging fruit of India’s stunting puzzle.
So now what? The question still remains as to how to actually improve sanitation, and researchers should now focus their attention there. The Total Sanitation Campaign was far from perfect in its outcomes and implementation. So what could be done differently? Why do many of the latrines built remain unused? What are the cultural norms surrounding sanitation practices in India? What kinds of policies would stimulate behavioural change and bring about a reduction in open defecation? What are the supply-side problems in implementing sanitation programs, and how can we minimize leakage? These are the kinds of questions that the research community should now be focusing on.