Why is it difficult to solve?
What challenges remain?
Globally, stunting has seen steady and significant decline over the past few decades, and there are a number of exemplars that prove rapid reduction is possible. Nevertheless, stunting rates remain stubbornly high in low-resource settings across the world where stunting-related programming has been absent or ineffective.
The uneven progress to date in resource-limited settings reflects two key issues:
- Gaps in understanding: There are important things about stunting that we still do not fully understand. These gaps in our knowledge remain despite ongoing research on the subject.
- Implementation challenges: The multi-factorial nature of stunting that makes it a useful indicator for overall health and well-being also makes it challenging to address. Policymakers often struggle to identify which drivers of stunting played a key role in their geographic areas. Delivering the required multi-sectoral response to the children who need it most is both politically and practically challenging.
Gaps in Understanding
For an issue so critical to our future, there remains robust debate among experts on basic facts. Recent research, for instance, has challenged longstanding assumptions on the impact of improved water and sanitation on child growth. Outside the limited setting of a randomized controlled trial, there remains even more uncertainty as to what types of programs work at scale across diverse and geographically dispersed nations.
Stunting is a statistical metric most useful in examining a whole population whose growth curves are shifted to the left, rather than diagnosing a particular individual. As such, while we have defined stunting as being two standard deviations in height-for-age Z-score (HAZ) below average, it is unclear whether or not this is the right cutoff from a biological perspective. Clinically, a child just above the stunting cutoff (considered “healthy”) may have the same health risks as a child just below the stunting cutoff.
More than half a century after first identifying stunting as an indicator of long-standing malnutrition, we still have an incomplete understanding of the biological forces that retard linear growth. Indeed, the clean lines of the WHO Median Growth Curve chart mask a lack of certainty. Some linear growth retardation is clearly caused by inadequate caloric intake – similar to wasting (which is based on a child’s weight for her height). At the same time, a lack of important micronutrients can also contribute to stunted growth in children. And we do not fully understand the relationship between linear growth retardation (measured through stunting) and other forms of malnutrition (e.g., anemia, wasting, overweight).
One of the most significant implications of stunting is its association with cognitive development. Stunted children often suffer from delayed mental development, which eventually leads to reduced cognitive abilities.1 At the individual level, stunted cognitive development correlates with poorer educational outcomes, lower wages, and a higher risk of living in poverty. For a nation, high stunting prevalence could mean reduced GDP (as much as 11 percent annually) and diminished ability to compete in the knowledge economy of the future.2
While there is still more work needed to further understand the specific relationship between stunting and cognitive development, it is clear that an association between stunting and delayed or impeded cognitive development exists. Difficulty measuring cognitive development, particularly in low-resource settings, hinders further research. And tracking cognitive development at the same time points as accurate linear growth measurements is an even bigger hurdle to clear.
We know a lot about what works to address the factors that lead to stunting. The 2013 Lancet Maternal and Child Nutrition Series paper, “Evidence-Based Interventions for Maternal and Child Nutrition,” identified ten effective nutrition interventions. At 90 percent coverage worldwide, these interventions could reduce the global stunting burden by an estimated one- fifth.3 Some countries have successfully implemented these interventions, in concert with broad social programs, to dramatically decrease national stunting prevalence.
However, incomplete understanding of the biology behind linear growth retardation and a still-developing evidence base around both nutrition-specific and -sensitive interventions has left policymakers with uncertainty around some interventions with the potential to improve childhood growth.
The correlation between water, sanitation, and hygiene (WASH) and stunting, though well documented across several large-scale studies, continues to puzzle researchers. While significant correlation has been identified between poor WASH and stunting in analyses of cross-sectional and observational data, WASH intervention trials have not demonstrated a positive impact on linear growth.
Poor hygiene can serve as a pathway to stunting in a number of ways. It increases the likelihood of infection, which demands a higher caloric intake to power an active immune system. Fecal-oral infection can cause diarrhea, which impedes the ability to fully digest food and extract vital nutrients. Finally, repeated diarrheal infection can inflame the small intestines, which chronically inhibits nutrient absorption. The condition, called environmental enteric dysfunction (EED) or environmental enteropathy (EE), is widespread among children and adults in low- and middle-income countries.4,5
However, while WASH conditions are regularly cited as strong independent risk factors for poor linear growth, they might also be confounded by other household indicators or elements of the study (e.g., contact frequency between promoters / participants and habit adoption). As a result, it is challenging to draw causal inferences around WASH effects on childhood stunting.
Despite these clear pathways, three randomized control trials recently conducted in Zimbabwe,6 Bangladesh,7 and Kenya8 to assess the impact of WASH interventions on linear growth. All three found no association between the two, stumping researchers.9 The rigorous trials tested large numbers of children in rural areas. The trials tested both nutrition interventions (supplementation, counseling on breastfeeding and complementary feeding) and WASH interventions (improved pit latrines, handwashing stations, and chlorine water treatment). Across all three trials, nutrition interventions were significantly associated with increased growth among children. WASH interventions, as implemented in these trials, were not.
|3,686 children||4,584 children||6,583 children|
Height and hemoglobin at 18 months
|Height and diarrhea at 24 months||Height and diarrhea at 24 months|
|Measurement timepoints||12 and 32 weeks gestation; 1,3,6,12,18 months postnatal||1 year of age, 2 years of age||1 year of age, 2 years of age|
|Nutrition intervention||Daily lipid-based nutrient supplement (LNS) 6-18 months + counseling on improved complementary feeding (breastfeeding counseling in all four arms as standard of care)||Daily lipid-based nutrient supplement 6-24 months + counseling on improved breastfeeding & complementary feeding practices||Daily lipid-based nutrient supplement 6-24 months + counseling on improved breastfeeding & complementary feeding practices|
|Uptake of nutrition interventions||High||High||High|
|Impact of nutrition interventions on child height||Statistically significant improvement||Statistically significant improvement||Statistically significant improvement|
|WASH interventions||Improved pit latrine (built to Govt. of Zimbabwe standard), handwashing stations, chlorine water treatment, child play area||Improved pit latrine, handwashing stations, chlorine water treatment, child potty & scoop||Improved pit latrine, handwashing stations, chlorine water treatment, child potty & scoop|
|Uptake of WASH interventions||High||High||High|
|Impact of WASH interventions on child height||None||None||None|
Despite the findings of these three studies, the debate over the impact of WASH interventions on growth continues. One hypothesis is that since the studies only observed participants through 18 to 24 months after the interventions, they may have missed the impact. Researchers have posited that WASH interventions may require more widespread geographic implementation to take effect or a longer timeline to evaluate impact. Additionally, only a limited set of WASH interventions was tested; the study therefore did not evaluate the impact of different (possibly more effective) interventions (e.g., food hygiene interventions). Further research is required for us to make sense of these findings and consider implementing WASH interventions differently.
Micronutrient supplementation at scale
As outlined in the Lancet nutrition series of 2013, micronutrient supplementation for women and children and/or fortification of food could be effective in reducing stunting. Included in the Lancet’s top ten nutrition specific interventions are the following:
- Maternal balanced energy protein supplementation (for fetal development)
- Multiple micronutrient supplementation in pregnancy (for fetal development)
- Vitamin A administration
- Preventive zinc supplementation in children aged 6–59 months
However, the efficacy of these micronutrient interventions at scale has varied widely. While some interventions (e.g., vitamin A supplementation)10 have achieved high coverage and effectiveness, others have been observed as having mixed results (e.g., iron/folic acid,11 zinc10), and still others have failed to scale effectively (e.g., calcium).12
While nutrition supplementation may work in theory, assessment of its impact at scale has proven difficult. Supplementation interventions have been difficult to scale to nationwide levels. Among other issues, measurement of program coverage and compliance has also been inconsistent within and across countries.
Maternal health and fertility
It was not until the late 2000s that global evidence clarified the link between reduced fertility, increased birth spacing, prevention of adolescent births, and reduced intergenerational transfer of child stunting. As a result, fertility-related interventions remain underrepresented in nutrition policies today.
However, we now know that fully 20 to 30 percent of stunting occurs in utero. This intrauterine growth restriction accounts for the intergenerational aspect of stunting (and increases other health risks, including low birthweight).13
This intergenerational cycle starts in the mother’s childhood when she becomes stunted and does not reach her full growth potential. As she grows into a teenager and then an adult, often still poorly nourished, she is more likely to give birth to babies that are small and poorly nourished from the start. Years of slow and delayed growth follow. And the cycle of stunting begins once more.
Pregnancy in adolescence exacerbates intrauterine growth restriction; teenage girls who become pregnant stop growing as nutrients get diverted to their fetuses. Reducing the number of adolescent pregnancies thus represents a significant opportunity for progress against stunting. Each year an estimated 10 million girls below the age of 18 are married.14 Adolescent pregnancies are associated with health complications beyond stunting: a 50 percent increased risk of stillbirths and neonatal deaths, and increased risk of low birthweight.15,16 Low birthweight is associated with a greater risk of stunting.
Even in adulthood, decreased fertility and increased birth spacing can serve as levers to reduce stunting and interrupt the intergenerational cycle of stunting (although more evidence is needed). Both factors diminish the toll that pregnancy and childbirth take on women’s bodies. Women with fewer children more widely spaced in age have more energy and resources to devote to each child, both in the womb and after birth. Other interventions in maternal health – antenatal care and attendance at birth by skilled providers, for example – increase contact between women and health workers, thereby increasing the likelihood that they will learn and adopt best practices in caring for their own health and nutrition and that of their children.
Still, many governments and healthcare providers continue to underestimate the importance of family planning, maternal health, and maternal nutrition during pregnancy and post-partum. Part of the challenge is that addressing these drivers-access to birth control, reducing child marriage, improving pregnant and lactating women’s access to good quality foods, and women’s access to prenatal care-often involves challenging deeply held customary beliefs that are difficult to tackle.
Challenges in even identifying stunting exist in almost every geographical area. In low-resource settings, stunting is even harder to recognize. In such settings, children often have poor access to the health care required to diagnose stunting. Newborns may not be measured, or their birth date may not be documented, complicating later efforts to measure their growth. Children often do not visit health care providers regularly or see physicians and nurses who do not record height.
Even when a child is born in a health facility with a skilled health care provider, precisely measuring the length at birth of a newborn can be extremely difficult. Weight tends to be a more important focus due to the importance of identifying low birthweight, which is also a risk factor for stunting.
Beyond difficulty measuring anthropometry of newborns and children, most governments also measure other key drivers of stunting inconsistently if at all. Important underlying factors, including maternal and household-level diet (both quality and caloric intake) and food security, household-level disposable income, women’s empowerment, and complementary feeding habits are poorly measured or not measured at all. Indicators around dietary intake and feeding frequency are especially challenging to measure in multipurpose surveys like the Demographic and Health Surveys (DHS), although some recent surveys have started to attempt this. Accurate, representative data on coverage and quality of nutrition-specific interventions, such as education around breastfeeding and complementary feeding and micronutrient supplementation and fortification, is even more lacking.
The implications of inadequate data are significant for policy makers. Many governments do not know if their interventions are making an impact. Are they reaching those most in need? If yes, are the interventions working? Data on coverage and quality of interventions remains scarce, even in many countries with robust nutrition programs.
While child stunting prevalence has declined in most low- and middle-income countries, equity gaps have persisted within nations. Gaps between population subgroups, particularly between the richest and poorest wealth quintiles, have actually increased in many low-income countries over the last twenty years.17 Height continues to vary significantly among children based on level of maternal education, residence (urban or rural), ethnicity, and by other sociodemographic groupings. Some exemplar countries have started to resolve these inequalities through data-driven targeting of marginalized populations with specific interventions or by broadly attempting to raise the status of vulnerable groups. Doing so can be challenging from an execution perspective, as well as for social and political reasons.
Stunting Prevalence by Wealth Quintile Over Time in Ethiopia
It is only recently that globally applicable growth standards, based on studies of child growth across ethnicities and nationalities, have been developed and used consistently. In many places, the WHO Child Growth Standards remain controversial.
Some activists have argued against international growth standards entirely, citing the idea that some groups are genetically predisposed to be shorter than others. They maintain that holding all children to the same growth standards and therefore labelling children from certain groups “stunted” is inaccurate.18 In addition to being scientifically incorrect, this sentiment can easily become justification for inaction. If policymakers do not believe that global measures of stunting apply to their people, they are less likely to intervene to reduce stunting.
Likewise, we have only recently appreciated the role of maternal health in contributing to poor child growth. The age of a mother, her height and body mass index (BMI), and the length of time between pregnancies each has an important influence on her child’s height. Governments have been slow to act on these lessons and develop programs to educate women, increase access to family planning, and improve maternal care.
While global understanding of the drivers of long-standing child malnutrition have improved, we need not look far to see the effect that incomplete science has had on policy interventions. Until recently, donors seeking to improve childhood nutrition invested significant funding in food supplementation and distribution efforts. Though food supplementation and distribution had other benefits (e.g., keeping children in school), these programs tended to reach children too late in their lives to make a catalytic difference in growth trajectories. Waiting until children were old enough to attend school to intervene meant missing the critical “first 1,000 days” from before conception to a child’s second birthday.
Stunting, driven by a wide array of disparate factors, is often seen as a long-term barometer of the general well-being of a given society. The more we learn about stunting, the clearer it becomes that these disparate drivers demand strong governance, political commitment, and collaboration across sectors to address.
An effective government will typically excel at both developing evidence-based strategies (e.g., incorporating the latest scientific findings into policy; adapting global recommendations for local epidemiology, population dynamics, and cultural features) and executing them. Effective implementation requires the following, among others:
- Communication, continuity, and incentives across various levels of government and in far-flung geographies
- Prioritization and targeting of particularly vulnerable population subgroups and regions
- Regular and frequent monitoring and evaluation, as well as adaptation of tactics based on new information or changes on the ground
- Sustained and adequate funding
In practice, because most governments do not have ministries of nutrition. Instead, they must forge partnerships and structures for collaboration across ministries of education, public works, agriculture, health, sanitation, and others to develop and implement effective responses to stunting. Collaboration of this sort, across ministries, has rarely been governments’ strong suit (with some exceptions like Peru).
Multi-sectoral programs also present financing challenges. Government funding is often earmarked by ministry rather than policy priority. Sharing and tracking funding across departments to address a joint priority comes with myriad management challenges.
While it is possible to overcome these challenges through operational excellence alone, high-level political commitment, ideally supported by a head of state, can galvanize a government and nation to achieve more in the fight against childhood stunting. In Peru, for instance, the President’s commitment to reducing stunting prevalence by nine percent within five years compelled ministries to work together and provincial and local governments to implement national-level policies. Similarly, Senegal’s Cellule de Lutte Contre la Malnutrition (Coordination Unit for the Fight Against Malnutrition; CLM), housed within the Prime Minister’s office, had the political backing to convene key stakeholders and generate support across sectors for a national-level nutrition strategy.
- 1Prendergast AJ, Humphrey JH. The stunting syndrome in developing countries. Paediatrics and International Child Health. 2014;34(4):250-265. doi:10.1179/2046905514Y.0000000158. https://www.tandfonline.com/doi/pdf/10.1179/2046905514Y.0000000158?needAccess=true.
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