Childhood diarrhoeal illness may be underestimated in national health surveys

Katie Overbey, Kellogg Schwab and Natalie Exum

For children in low-income countries, diarrhoea remains a major cause of death and can lead to long-term health consequences. Accurate estimates of childhood diarrhoeal illness are crucial to evaluating the success of campaigns to defeat diarrhoea and improve health in countries where the burden of diarrhoea is high.

In our study, recently published in the IJE, we found that caregivers may underestimate diarrhoeal diseases in children aged under 5 years when asked to recall whether the children had diarrhoea in the previous 2 weeks. Compared with a 1-week recall period, there was a consistent underestimation of the prevalence of diarrhoea across five countries in sub-Saharan Africa.

Our analysis pooled over 80,000 household surveys from two similarly administered nationally representative surveys that use different recall periods for ascertaining caregiver-reported diarrhoea: Performance Monitoring and Accountability 2020 (PMA2020), which uses a 1-week recall; and the Demographic and Health Surveys (DHS), which use a 2-week recall. The PMA2020 survey was designed to be methodologically similar to the DHS in almost every aspect, and the two surveys are ideal for comparison of this important outcome. We found a childhood diarrhoea period prevalence of 21.4% using the 1-week-recall PMA2020 data, compared with a potentially underestimated 16.0% when using the 2-week-recall DHS data.

The finding that fewer diarrhoea episodes are identified when using a longer recall period initially appears counterintuitive. Researchers frequently use 2-week recall periods to try to identify a greater number of cases. However, in places where diarrhoea is common, a longer recall period may lead to caregivers forgetting more diarrhoea events. It may be easier for caregivers to remember diarrhoeal symptoms in only the past 7 days, which is a standard unit of time in many cultures, and this might have led to greater accuracy from the PMA2020 data.

A contributing factor to childhood diarrhoea is high faecal contamination due to lack of water and sanitation infrastructure in communities. As countries make investments to improve sanitary conditions, accurate measures of diarrhoeal disease will be important to track health outcomes. We found that children under 12 months of age were at greatest risk of diarrhoeal diseases and that lack of access to safely managed sanitation facilities in the household was the greatest risk factor for infection. A risk factor analysis using the 1-week recall PMA2020 data determined that improved sanitation reduced the odds of diarrhoeal disease, while access to improved drinking water did not.

Consistent with previous work, our findings underscore the importance of prioritising investments in sanitary infrastructure. Comprehensive investments in toilet construction and safe management of faeces will be important to improve the health of children and communities. Equally important is ensuring those toilets are used and changing individual behaviours to end open defecation.

More work is also needed to determine the optimal recall period for childhood diarrhoea in national health surveys. An ideal comparison would include the same question asked twice in the same survey – one question using a 2-week period and another using 1 week. It is important to further improve outcome measures for childhood diarrhoea to assist health ministries as they make large-scale efforts to defeat diarrhoea as a leading cause of childhood deaths.

Read more:

Overbey KN, Schwab KJ, Exum NG.Comparison of 1-week and 2-week recall periods for caregiver-reported diarrhoeal illness in children, using nationally representative household surveys. Int J Epidemiol 2019; Mar 25. https://doi.org/10.1093/ije/dyz043.


Katie Overbey is a PhD candidate in the Department of Environmental Health and Engineering at the Johns Hopkins University Bloomberg School of Public Health. Her research focuses on the fate and transport of norovirus in food, water and the environment.

Kellogg Schwab, PhD, is the Abel Wolman Professor in Water and Public Health in the Department of Environmental Health and Engineering at the Johns Hopkins University Bloomberg School of Public Health and Director of the JHU Water Institute. His research focuses on water reuse and infectious diseases around the world.

Natalie Exum, PhD, is an assistant scientist in the Department of Environmental Health and Engineering at the Johns Hopkins University Bloomberg School of Public Health and Deputy Director of the JHU Water Institute. She is also the Senior Technical Advisor for Water, Sanitation and Hygiene (WASH) for PMA2020’s mobile health data collection platform. Her research focuses on environmental faecal contamination and childhood enteric infections.

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