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The relationship between wasting and stunting: a retrospective cohort analysis of longitudinal data in Gambian children from 1976 to 2016

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Summary of research¹

Each year, around 800,000 deaths in children under five years of age are in part attributable to wasting; 60% of which are attributable to severe wasting. In addition, over one million child deaths are attributable to stunting, although this association remains poorly understood. Even though progress is being made in decreasing undernutrition in low- and middle-income countries, stunting and wasting during childhood continue to burden people in the poorest regions in the developing world. Although both forms of undernutrition occur together in children in many contexts and may co-occur in the same child (referred to as “concurrence”), wasting and stunting are often considered separately with respect to how they are managed clinically and programmatically and how they are researched. The rationale behind this conceptual separation of stunting and wasting in terms of etiology and programming has been questioned in several recent reviews and publications (Briend, Khara and Dolan, 2015; Khara and Dolan, 2014). These publications highlight outstanding gaps in understanding the interrelationship between these two forms of undernutrition as a result of insufficient examination of data; in particular from longitudinal cohorts.

The authors of this paper contribute to filling this gap by describing the interrelationships between wasting and stunting in children under two years old through a retrospective cohort analysis, based on growth-monitoring records spanning four decades from clinics in rural Gambia. Three broad research questions were tested: 1) is wasting a risk factor for stunting, and vice versa? 2) does the season of birth influence future wasting and stunting;? and 3) are there gender differences in growth deficits in the Gambia? Anthropometric data collected at scheduled infant-welfare clinics between May 1976 and September 2016 were converted to z-scores, comprising 64,342 observations on 5,160 subjects (median: 12 observations per individual). Children were defined as “wasted” if they had a weight-for-length z-score (WLZ) <–2 against the WHO reference and “stunted” if they had a length-for-age z-score (LAZ) <–2.

Results reveal that prevalence of wasting and stunting were high in this population. The prevalence of stunting increased with age, peaking at 37% (girls) and 39% (boys) at 24 months of age. Wasting showed an early decline in the first three months (reflecting a period of positive weight gain in the months immediately postpartum), followed by a peak at around one year of age (18% in boys, 12% girls). The prevalence of children with concurrence peaked at 9% in boys and 5% in girls, also at around one year of age. Infants who were wasted in the first wet season of their life were more likely to be wasted in their second wet season, even after controlling for recovering during the intervening dry season (OR:3.2; 95% CI:2.3, 4.4).

Infants born at the start of the annual wet season (July–October) showed early growth faltering in WLZ, putting them at increased risk of subsequent stunting. Time-lagged observations show that being wasted was predictive of stunting (OR: 3.2; 95% CI: 2.7, 3.9), even after accounting for current stunting. The reverse also holds: children currently stunted are 1.5 times more likely to be wasted three months later, even after accounting for currently wasting status. Boys were more likely to be wasted, stunted, and concurrently wasted and stunted than girls, as well as being more susceptible to seasonally-driven growth deficits.

This analysis highlights several key issues of relevance to our understanding of the relationship between wasting and stunting in early childhood. First, in this highly seasonal, rural environment with high rates of exclusive breastfeeding, there is a seasonally-driven risk among young infants of poor growth. This indicates the need to provide more targeted support to breastfeeding mothers and increase attention to infant feeding during periods of seasonal stress. Second, results demonstrate that being wasted leads to increased risk of subsequent stunting. This suggests that stunting is in part a biological response to previous episodes of being wasted and that stunting may represent a deleterious form of adaptation to more overt undernutrition (wasting). Stunted children are not just short, but are children who were earlier more seriously malnourished and who are survivors of a composite process. Third, children who are wasted in one wet season are more likely to be wasted in a subsequent wet season even after recovery, suggesting a continued vulnerability across seasons. Further understanding is needed of related physiologic mechanisms and environmental factors. Fourth, and consistent with much of the global literature, boys are more likely to be wasted or stunted or to have concurrent wasting and stunting; all of which convey added risk of mortality. There is a need to understand this gender difference in vulnerability so that the policy and practice communities can take this into account.

Results indicate that, where there are levels of wasting and stunting of public health significance in a given context, there are compelling reasons for both treatment and prevention interventions to consider wasting and stunting jointly and with awareness of the relation between them. The separation of the wasted infant/child and the stunted infant/child in terms of policies, programmes and research risks opportunities being missed to detect and intervene to prevent both forms of undernutrition in this highly-vulnerable population group. The attainment of World Health Assembly and other global targets remains a very strong global and country-level intent, but these targets will not be achieved where approaches to infant and child undernutrition remain siloed.

Endnotes

¹Simon M Schoenbuchner, Carmel Dolan, Martha Mwangome, Andrew Hall, Stephanie A Richard, Jonathan C Wells, Tanya Khara, Bakary Sonko, Andrew M Prentice, Sophie E Moore. The relationship between wasting and stunting: a retrospective cohort analysis of longitudinal data in Gambian children from 1976 to 2016. The American Journal of Clinical Nutrition, Volume 110, Issue 2, August 2019, Pages 498–507, https://doi.org/10.1093/ajcn/nqy326

References

Briend A, Khara T, Dolan C. Wasting and stunting–similarities and differences: policy and programmatic implications. Food Nutr Bull 2015;36(1 Suppl):S15–23.

Khara T, Dolan C. Technical Briefing Paper: Associations between wasting and stunting, policy, programming and research implications. Oxford, UK: Emergency Nutrition Network; 2014.

Reference this page

The relationship between wasting and stunting: a retrospective cohort analysis of longitudinal data in Gambian children from 1976 to 2016. Field Exchange 61, November 2019. p26. www.ennonline.net/fex/61/cohortanalysisgambia

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