Stunting, defined as a low height for age z-score (HAZ), begins in the prenatal environment
leading to low birth weight and continues with growth faltering in the first 2 y of
life, after which it is generally irreversible. Although stunting prevalence has decreased
worldwide from 1990 to 2018, stunting continues to afflict 21.3% of children aged
<5 y worldwide (1). The burden of stunting falls almost entirely on low-income countries
as it is tied to poverty, an excess of childhood infections, and an inadequate diet.
The World Health Assembly (2) and the UN's Sustainable Development Goals (3) call
for a 40% reduction in childhood stunting by 2025 with the ultimate goal of eradicating
all childhood malnutrition. Although the destructive power of stunting is well known,
the actions which will operationalize its reductions are not. A several part series
on stunting in this issue of the American Journal of Clinical Nutrition (4–12) elucidates
factors and policies that allow for a robust decline in stunting, by using a mixed
method approach to identify how “exemplar countries” reduced stunting despite only
modest improvements in economic growth.
Stunting in childhood: an overview of global burden, trends, determinants, and drivers
of decline (4) is a systematic review of 89 studies from which basic, underlying,
and immediate determinants of stunting were identified. Basic determinants are: 1)
an asset index of household income and 2) parental education, particularly maternal
education. Underlying determinants are numerous: 1) sanitary disposal of stool, 2)
clean water, 3) bed nets, 4) vaccination coverage, 5) attendance of antenatal clinic
visits, 6) optimal breastfeeding practices, and 7) household food security. Immediate
stunting determinants are: 1) reduction in fertility, 2) birth spacing, 3) maternal
height, 4) infant birthweight, 5) dietary diversity, and 6) diarrhea incidence.
In order to understand how these determinants affected the stunting reduction in exemplar
countries, an in-depth analysis of quantitative and qualitative data was employed
(5). After potential exemplar countries that had a rapid decline in stunting relative
to their economic growth were identified, 5 countries were studied in-depth based
on a minimum population threshold of 5 million people and representation of different
global regions; Peru, the Kyrgyz Republic, Nepal, Senegal, and Ethiopia.
A quantitative data analysis of each country's Demographic and Health Surveys (DHS)
and Multiple Indicator Cluster Surveys (MICS), which are nationally conducted, standardized
household surveys collecting health and nutrition data, was performed to discern changes
in HAZ with respect to the basic, underlying, and immediate determinants. For each
country, HAZ kernel density plots showing population level shifts in HAZ over time
as well as changes in kurtosis, a measure of variability in the data, were prepared.
Descriptive analyses evaluated inequality of HAZ changes by wealth quintile, geographic
region, rural or urban setting, maternal education, and child gender. Victora curves,
which plot predicted HAZ by child's age in months for each country, determined the
critical ages of growth faltering as well as the maternal effect on HAZ at birth.
These data formed the basis of the multivariable analyses used to identify factors
that predicted an improvement in stunting.
Robust qualitative data from key stakeholders at the national, regional, and community
levels were collected to gain insight into the programmatic changes and contextual
factors associated with stunting reduction. These included surveys of community health
workers and teachers and focus groups with mothers. This qualitative data helped to
inform a timeline of key policies, programs, and practices that led to stunting reduction.
The most important data in this stunting project are the anthropometric measurements,
and thus great care was taken to assess their quality (6). A composite score was created
based on the proportion of collected data with incomplete demographic information
or anthropometric measurements, tendency for a digit to appear more often than by
chance, large differences in HAZ by month indicative of bias in age reporting, and
extreme/implausible values for HAZ and weight for height z-score (WHZ). The 5 countries
used for the analyses had high-quality anthropometric data, and this methodology is
a tool by which other datasets can be judged.
The next 5 articles of this series are in-depth country case studies for the 5 exemplar
countries, Peru, the Kyrgyz Republic, Nepal, Senegal, and Ethiopia (7–11). Baseline
stunting was 25–66% and the reduction over 16–25 years was 15 to 30 percentage points
(
Table 1
). Change in kurtosis in each HAZ kernel density plot was analyzed as a surrogate
for changes in the distribution of stunting across the population (Table 1). A decrease
in kurtosis suggests greater equity in stunting across determinant groups but could
also be a marker of greater precision in data collection. Therefore, separate equity
analyses were conducted to determine change in disparities among wealth quintile,
education level, rural/urban setting, and gender (Table 1). Among these exemplar countries
narrowing of the gap in stunting by maternal education and disparities between urban
and rural settings was consistently seen.
TABLE 1
Summary of quantitative data for 5 exemplar countries
1
Senegal
Kyrgyz Republic
Ethiopia
Nepal
Peru
Study period
1992–2017
1997–2014
2000–2016
1996–2016
2000–2016
Baseline stunting prevalence
25.0%
36.2%
51%
66%
31.3%
End stunting prevalence
17.7%
12.9%
32%
36%
13.1%
Stunting reduction over study period
15%
23.3%
19%
30%
18.2%
HAZ kernel density plots
Baseline average HAZ
−1.25 SD
−1.42 SD
−2.14 SD
−2.35 SD
−1.24 SD
End average HAZ
−0.97 SD
0.75 SD
−1.35 SD
−1.41 SD
−0.84 SD
Change in kurtosis
+0.54
+0.06
+0.04
+0.48
−0.93
Equity analysis: change in stunting between lowest/highest:
Wealth quintile
Widened (19.6% to 20.8%)
Narrowed (27% to 10%)
Widened (12% to 24%)
Widened (22.2% to 32%)
Narrowed (46% to 27%)
Education level
Narrowed (22.6% to 8.5%)
Narrowed (13% to –1%)
Narrowed (27% to 22%)
Narrowed (39% to 25%)
Narrowed (48% to 10%)
Urban/rural
Narrowed (16% gap to 10% gap)
Narrowed (8.5% to 1.6%)
Widened (13% to 16%)
Narrowed (13% to 10%)
Narrowed (30% to 18%)
Gender gap
No change
No change
No change
No change
No change
Growth curves
Birth length
No change (−0.4 SD to −0.4 SD)
Increased (−0.4 to 0.3 SD)
Increased (−0.4 to −0.1 SD)
Increased (−1.5SD to −0.6 SD)
No change (−0.5 to −0.6 SD)
Growth faltering 0–6 mo
Decreased
Decreased
Decreased
Decreased
Decreased
Growth faltering 6–23 mo
Decreased (−0.1 SD/mo to −0.06 SD/mo)
No change (−0.072 SD/mo to −0.073 SD/mo)
No change (−0.14 SD/mo to −0.13 SD/mo)
No change (−0.11 SD/mo to −0.081 SD/mo)
Decreased (−0.08 SD/mo to −0.03 SD/mo)
1
HAZ, height for age z-score.
Comparing the Victora curves, which plot predicted HAZ over child's age in months,
across the 5 countries demonstrated 2 patterns of stunting reduction. The intercept
on Victora curves is the birth length, which reflects prenatal factors, such as maternal
nutrition and health. The intercept for all exemplar countries in the early 1990s
was well below that of the international reference population. Ethiopia, Nepal, and
the Kyrgyz Republic improved the birth HAZ over the study period, reflecting improved
maternal nutrition and antenatal care. In contrast, there was no change in birth length
for Peru and Senegal. The 0–6 mo time frame generally reflects breastfeeding practices
and was a period of growth faltering in all countries initially. All countries demonstrated
reduction in growth faltering in the 0–6 mo range suggesting improvement in breastfeeding
and other practices. The 6–23 mo time frame reflects dietary practices and infectious
disease management as foods and water are introduced to the infant diet during this
time period. Peru and Senegal showed a dramatic reduction in growth faltering in the
6–23 mo time frame reflecting improved food security and disease prevention from improved
sanitation practices. In contrast, Ethiopia, Nepal, and the Kyrgyz Republic showed
much less improvement in growth faltering in the 6–23 mo time period. These data suggest
that there are multiple time periods that can serve as effective targets when attempting
to reduce stunting prevalence. All 5 exemplar countries reduced their stunting prevalence
but from this data it appears that Senegal and Peru accomplished this by preventing
growth faltering from 6–23 mo with no improvements in birth length, in contrast to
the other exemplar countries which accomplished stunting prevalence reduction via
marked improvements in birth length but no change in growth faltering at 6–23 mo (Table 1).
Determinants for the reduction in stunting were identified for each country by multivariable
analysis of the health survey data and by qualitative data collection from key stakeholders.
The multivariable models explained 72–100% of the improvement in mean HAZ depending
on the exemplar country. Senegal, Nepal, and the Kyrgyz Republic did not have national
data on food security, which likely contributed to the larger fraction left unexplained
by the multivariable model.
Although there were a few determinants of stunting reduction that were specific to
certain countries (e.g., migration from the mountainous regions in Peru; higher crop
yield in Ethiopia), there were many determinants that were important across all exemplar
countries (
Table 2
). The authors classified the determinants as nonhealth sector improvements and health
sector improvements (12). They found that nonhealth sector improvements, such as government
programs for poverty relief, maternal education, and agriculture changes accounted
for 36–70% (median 47%) of stunting reduction. Health sector changes such as maternal
and newborn health care, access to family planning/reduction in fertility, and maternal
nutritional status accounted for 20–64% (median 37%) of changes in HAZ. The qualitative
analysis identified key programs and policies that led to improvements in these sectors,
and the focus groups with mothers in the community confirmed which programs affected
change at the household level.
TABLE 2
Changes in potential determinants for reducing stunting prevalence over the study
period
Senegal
Kyrgyz Republic
Ethiopia
Nepal
Peru
Multivariable analysis for children under 5 y
Variability explained by multivariable model
72%
88.9%
110%
90.9%
109%
Nonhealth sector
Wealth index, 0–10
+0.91
1
+0.63
1
+0.85
1
+1.11
1
−0.23
1
Open defecation, % of population
−23.9%
—
−50.3%
1
−54.7%
1
−17.4%
Clean water, % of population
+25.2%
1
+9.61%
+14.9%
+13.6%
+7.7%
Maternal education, y
+1.69
1
+30%
+1.22
1
+3.63
1
+2.13
1
Duration of breastfeeding, mo
−2.2
−1.1
−3.17
1
−1.45
1
+0.55
1
Health sector changes
Respiratory illness prevalence, % under 5 y
−11.6%
−10.4%
−15.2%
−23.4%
−9.2%
Diarrhea prevalence, % under 5 y
−3.7%
−11.9%
−14.4%
−15.3%
−4.6%
1
Maternal BMI, kg/m2
—
+1.08
1
+0.62
1
+1.5
1
+1.51
1
Antenatal visits ≥4, % pregnant women
+43%
1
—
+21.3%1
+54.8%1
+26.8%1
Birthweight <2500 g, %
+3.2%
+0.58%
1
+5.36%
—
−1.9%1
Maternal age, y
+1
1
+0.77
1
−0.15
1
−1.2
1
+0.8
1
Fertility, children per mother
−0.77
1
−0.35
1
−0.24
1
−1.05
1
−0.65
1
1Significant determinants of height for age z-score change over time identified in
multivariable modeling.
From this 9-part stunting series, key drivers of stunting reduction were elucidated
using a robust mixed methods approach which can be applied to other low- and middle-income
countries (LMICs) aiming to reduce stunting prevalence. In all countries, factors
that were identified in the multivariable analysis as significant contributors to
stunting reduction were improvements in poverty, maternal education, maternal nutrition
status, good antenatal care, increase in maternal age, and reduction in fertility
(Table 2). Although a reduction in poverty, measured by change in wealth index, was
significant in all countries, exemplar countries were picked because their stunting
reduction was out of proportion to their economic gains. Therefore, the other factors
that were found to be significant across all countries should act as targets for other
countries aiming to reduce the burden of stunting. This body of work is important
as it can serve as a template for ways to reduce stunting burden in other countries.
Both by elucidating common factors between all 5 exemplar countries and by highlighting
the mixed methods approach, this body of work will allow other countries to study
the efficacy of their national programs on stunting reduction.
This in-depth analysis of 5 exemplar countries presents a road map for how to reduce
stunting prevalence. However, many LMICs struggle with a high burden of stunting and
have employed programs of their own to attempt to decrease the burden. This series
does not compare effective programs from the exemplar countries with similar but failed
programs in other countries. It would be helpful to contrast exemplar countries with
countries who have not been able to reduce their stunting prevalence in order to identify
what specific elements of the government and nongovernmental organizations programs
in exemplar countries allowed for success when compared to similar programs that are
applied worldwide with less impact.
Even within these 5 exemplar countries more contrasts could have been identified to
guide future programs. For example, 2 patterns emerged from the Victora curves, 1
pattern showing increases in birth length but similar growth faltering at 6–23 mo
and the other showing no changes in birth length but greater reduction of growth faltering
in the 6–23 mo range. This series does not contrast the programs that were rolled
out in each country to deliver these different patterns of stunting reduction which
would be helpful guidance for other countries looking to emulate their success.
Many countries implemented micronutrient supplementation programs over the course
of the study period, which are identified in literature reviews and qualitative analysis
of national and regional stakeholders as being important drivers for stunting reduction.
However, the actual effects of micronutrient supplementation on changes in HAZ were
not conducted in their quantitative analysis as the data on these programs was not
routinely collected in the national surveys. Finally, a cost-effectiveness analysis
would provide more information about which programs had the greatest impact for dollar
spent and would allow countries looking to emulate the exemplar country's stunting
reductions to know where best to focus their efforts and budget.
This body of work and future directions are especially important as the COVID-19 pandemic
is predicted to worsen malnutrition globally. It is estimated that the prevalence
of wasting could increase 10–50% causing an excess of ≤2 million child deaths (13).
The required self-isolation and country-wide lockdowns alongside the commensurate
change in focus of the health care system and worsening economic conditions will have
myriad downstream effects on health and nutrition, especially in LMICs (14). The disruption
to food supply chains coupled with decreases in household income will compound food
insecurity. Households will rely on less nutritious but easily accessible and cheaper
processed foods. The limited access to health care due to travel restrictions and
health center's shift in focus to COVID-19 will reduce access to family planning and
prenatal care. In addition, the reduced financial resources will disrupt the social
safety net and programs intended to identify and treat malnutrition. Globally, schooling
has been interrupted due to coronavirus concerns which prohibits school-based nutrition
initiatives in the short term and will also have long-term effects as maternal education
is tied with stunting reduction. Finally, water/sanitation/hygiene projects will be
put on hold during the pandemic but remain especially important in urban crowded settings
under lockdown as outbreaks of communicable diseases are common without adequate water
and sanitation. As the current pandemic is predicted to worsen malnutrition worldwide,
this body of work remains of paramount importance to guide countries as they work
to implement programs to mitigate the effects of the pandemic on their population.
In sum, it is possible for substantial reductions in stunting to be realized. In the
exemplar countries there was careful accounting for the local context, which allowed
for mobilization of existing resources. As with all great endeavors, champions are
required to overcome the natural entropic tendencies. Given the future dividends that
will accrue with reduced stunting, embrace of this sustainable development goal is
worthy wherever stunting exerts it scourge.