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We’re grateful to our colleagues Hugh Sharma Waddington, Sarah Bick, Sandy Cairncross and Edoardo Masset (LSHTM) for their work on this rigorous systematic evidence on the impacts of water supply, sanitation and hygiene (WASH) interventions on mortality. This title has previously been published in PLOS Medicine. The version here is slightly abridged for audience accessibility, with kind permission of the authors. 

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Around 2 million children globally die each year due to preventable causes like diarrhoea and respiratory illness. Many of them die because they lack access to WASH amenities. Every single one of these deaths is an avoidable tragedy. Each death leaves a family bereaved. One devastated grandfather visited a school each day in Burkina Faso to provide an update on the progress of a baby. The baby subsequently died, causing the grandfather to cry in anguish: “cela n’aurait pas dû!” (this should not have happened!)

Such tragedies inspire us to respond to the un-met need for rigorous evidence about the impacts of health and environmental interventions on childhood mortality, which comprises the vast majority of the global infectious disease burden. But in practice, measuring mortality accurately is very difficult to do in intervention studies. There must a large enough sample be collected of children who have died, which is very difficult to do in any single study. It is also ethically problematic for those who wish to design prospective intervention studies (trials). In the field of WASH, for example, this would require researchers to sit on their hands and wait for the most severely ill children to die, rather than providing live-saving oral rehydration or health care. Early studies therefore had to be done retrospectively using observational methods. One such study in metropolitan Brazil required enumerators to visit all households in a neighbourhood and ask mothers or carers to tell them whether their children had died in the past year, and then seek a comparable household nearby where children had survived beyond age 5. Unfortunately, this methodology is unlikely to generate reliable estimates of the impact of WASH improvements on mortality.

So, what can be done to estimate unbiased effects of WASH interventions on childhood mortality in low-income contexts? One answer lies in evidence synthesis, by combining data from multiple intervention studies, which individually could not measure mortality as a primary outcome. LSHTM researchers have been able to systematically collect mortality data from randomised trials and other studies that have estimated the impacts of WASH interventions in low-income contexts. The data compiled includes 2,600 deaths in low-income contexts that have previously been reported on in research publications, but which had remained unanalysed until now.

LSHTM researchers found answers to longstanding questions about how to prevent childhood mortality, and present the first rigorous estimates of the impact of interventions providing improved WASH to households on mortality in childhood. They discovered that:

• When people have more water to wash in, they are able to wash properly, which significantly improves the survival chances of their children, reducing deaths due to diarrhoea, respiratory illness and undernutrition by around one-third.
• When sanitation is available to the majority of people in a community, it lessens infection transmission due to children’s interactions with faeces from open defaecation, reducing diarrhoea mortality in childhood by around one-half.

The approach used in this study, which is applicable to many other topics in international development and global health, is reliant on journals ensuring study authors use agreed reporting standards, which urgently need to be improved in development economics. In a very real sense, this research supports arguments for more funding to be made available in order to supply ‘vulnerable’ populations – such as those aged under five – with clean, safe water, particularly in sub-Saharan Africa and parts of South Asia. Ultimately, it supports demands for justice.