Access to clean water is often associated with the reduction of the incidence of diseases. How did you come to study the effects of clean water on growth in children?
Growth in children is known to be directly affected by two critical factors: food intake and incidence of disease. It is known that access to good quality water, improved sanitation and enhanced hygiene (WASH) practices lead to decreased levels of infectious disease in children. We were interested to know whether this decline in disease would lead to improvements in child growth.
How many children are affected by poor height growth? What are the long term impacts of stunting? Can it be reversed?
Approximately 165 million children under 5 years of age globally have very poor height growth – defined as stunted. The process of reduced height growth occurs mostly in the first 1,000 days of life (from conception to about 2 years of age); a period when children are particularly susceptible to the consequences of inadequate diets and poor environmental conditions.
Compared to children with normal height, very short children are at increased risk of becoming shorter adults, perform less well at school and have lower social and economic potential.
What did your research involve and what were your findings?
We conducted a systematic review of studies that evaluated the effect of WASH interventions on the growth of children. We searched online databases, grey literature sources and contacted subject experts and identified 14 studies conducted in low- and middle- income countries (Bangladesh, Ethiopia, Nigeria, Chile, Guatemala, Pakistan, Nepal, South Africa, Kenya and Cambodia) that provided data on the effect of WASH interventions on 9,469 children under 5 years of age. Five of the studies were cluster-randomised trials, whilst the remaining 9 were non-randomised studies.
We combined the five cluster-randomised controlled trials in a meta-analysis to estimate the overall effect of WASH interventions on growth in children. This analysis suggested that WASH interventions (specifically solar disinfection of water, provision of soap and improvement of water quality with an intervention time of 9 – 12 months) slightly but significantly increased the height of children under 5 years of age.
How did the effect of clean water vary depending on the age of the child?
As the effect of poor diet and high disease burden is greatest in young children (< 2 years of age), we conducted pre-specified sub-group analysis to identify if there was a difference in effect of WASH interventions in children under 2 years of age and those over 2 years of age. In this sub-group analysis, there was some suggestion that WASH interventions had a greater effect on height growth in young children. These sub-group analysis should be interpreted cautiously.
Why do you think that access to clean water reduced the prevalence of stunting in children under the age of five?
When we started the review we constructed a conceptual framework to inform our search strategy and identified both direct and indirect pathways linking WASH and child nutritional status. Direct pathways (diarrhoea, environmental enteropathy and worm infections) relate to the body’s ability to respond to infection or parasitic infection and the impact of these on nutritional status.
Indirect pathways, such as time taken to collect water at long distances from the home (taking time away from childcare) and purchase of water from water vendors (thereby using valuable financial resources that could be used to purchase food for children) relate more to the ability of families to provide safe and clean living environments for their children.
Our review focused on the direct pathways – i.e. the reduction of infectious disease. Studies have consistently shown that diarrhoea is an important infectious disease determinant of stunting with the odds of stunting at 24 months of age increasing with each diarrhoea episode before that age. We therefore hypothesised that if the main source of the diarrhoea (poor WASH practices) is removed there will be a long-term effect leading to better growth in children.
What impact does stunting have on the social and economic outcomes of developing countries?
Chronic undernutrition, manifested as stunting, reduces the social and economic potential of children, undermining their adult earnings by up to 10%, and in some countries potentially reducing the size of the economy by 11%.
Chronic undernutrition also has effects throughout the lifecycle as short mothers are at increased risk of cephalo-pelvic disproportion and obstructed labour, and are more likely to give birth to infants with lower birth weights. This relationship between maternal size and infant size acts to perpetuate the cycle of undernutrition and poverty.
What impact do you think this research will have on tackling the problem of stunting?
There is currently a strong international focus on nutrition-sensitive interventions – those that indirectly affect nutritional status by impacting either disease status or the quality and/or quantity of food intake. WASH practices are an example of nutrition-sensitive interventions and our finding that such interventions could have a significantly positive effect on stunting levels is very exciting for both the WASH and nutrition sectors.
This review is the first to evaluate the links between WASH practices and child nutritional status. Whilst we have found a significant improvement in height growth with improved water quality and handwashing practices, the duration of the intervention in the included studies was short none of the studies we included were considered to be of high methodological quality. There are several trials in progress, the results of which should inform these findings, but for now, we are delighted to contribute to the evidence base in this important area.
How was your research funded?
Our research was funded by the UK Department for International Development via a grant to the SHARE consortium (http://www.shareresearch.org/).
Were there any limitations of your study? What further research is needed?
None of the studies included in our review were of high methodological quality, and the trials included in our meta-analysis were of a short duration (9 – 12 months). In addition there was very little data collected on process and implementation factors such as compliance and cost of intervention.
There are several high-quality trials in progress which should inform the findings of our review.
Do you think access to clean water could be having additional benefits other than reducing stunting and the incidence of disease?
It is possible that improved access to clean water could have social and financial benefits for a family, such as more time spent with children, or more money available to spend on food. Our review did not evaluate these other potential benefits.
Where can readers find more information?
The full review can be found at this link: http://onlinelibrary.wiley.com/doi/10.1002/14651858.CD009382.pub2/abstract
A summary of the review (PDF) can be found here: http://ph.cochrane.org/sites/ph.cochrane.org/files/uploads/WASHReviewOnePageSummary.pdf
About Dr Alan Dangour
Alan is a senior lecturer and Registered Nutritionist with a background in biochemistry and biological anthropology.
Over the past 10 years, Alan’s primary research focus has been nutrition in older age, and he has conducted a series of trials to determine the effectiveness of nutrition interventions for the maintenance of health and function in later life.
Alan currently co-leads the Leverhulme Centre for Integrative Research on Agriculture and Health that conducts inter-sectoral research on: poverty and development; globalisation and food quality; sustainability, environment and climate change; food-borne and zoonotic diseases; and common metrics for agricultural research and evaluation.
Since January 2012 Alan has been seconded to the UK Department for International Development as a Senior Research Fellow in the Agriculture Team of the Research and Evidence Division.