Stunting, or impaired child growth due to undernutrition, has multiple negative health effects, making it a top global health priority. The current benchmark for classifying stunting assumes a universal model of growth with height-for-age z-score (HAZ) cutoffs set by the WHO . However, this universal model may hide hotspots of stunting if populations differ in HAZ in ways that are independent of undernutrition. We assess the potential magnitude of this bias by decomposing variation in HAZ from 1, 406,609 children from 63 low- and middle-income countries into two components ; 1) a component shaped by environmental inputs, poverty, infectious disease, inadequate sanitation, and healthcare access, and 2) a country-specific basal starting point that is independent of such inputs. After removing the effects of numerous environmental inputs, we find that different countries have reliably and substantially different basal starting points in average HAZ scores (a range of 1.7 SD) . These country-specific starting points, which we define as basal HAZ, are not associated with key indicators of undernutrition (e. g., infant mortality and average calorie deficit). By contrast, average increases in HAZ above a country's starting point, which we define as accrued HAZ , show strong correlations with these same variables, suggesting that low accrued HAZ captures standard definitions of stunting as impaired growth due to undernutrition. Using these two components, we show how universal cutoffs can underestimate stunting in specific world regions (e.g., sub-Saharan Africa and the Caribbean), where children in even very deprived situations start off taller . As stunting is a high priority global health problem , standards that are sensitive to such population variation in healthy growth should improve efforts to target those most vulnerable to childhood undernutrition.
Background: Stunting-or impaired child growth due to undernutrition-has multiple negative health effects, making it a top global health priority. The current benchmark for classifying stunting assumes a universal model of growth with height-for-age z-score (HAZ) cutoffs set by the World Health Organization . However, this model may hide hotspots of stunting if populations differ in HAZ in ways that are independent of undernutrition. We examine how universal cutoffs can underestimate stunting in specific regions around the world. Methods: Using a non-linear multi-level model, we decompose variation in height-for-age z-scores (HAZ) from 1, 430,986 children across 63 countries into two components : 1) "accrued HAZ" shaped by environmental inputs-undernutrition, infectious disease, inadequate sanitation, and 2) a country-specific "basal HAZ" independent of such inputs. We validate these components by assessing their associations with key indicators of undernutrition. We then re-estimate stunting prevalence with population-sensitive cutoffs based on the estimates of these two components. Results: Basal HAZ differs reliably across countries (range of 1.6 SD) and is independent of measures of undernutrition. By contrast, accrued HAZ captures stunting as impaired growth due to deprivation. Population-sensitive estimates suggest that universal cutoffs can miss 1 in 5 children in specific world regions , where children have greater basal heights. Conclusion: Current universal cutoffs may miss stunting in populations with taller basal HAZ . As stunting is a high priority in global health , standards that are sensitive to population variation in healthy growth should improve efforts to target those most vulnerable to childhood undernutrition.
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Stunting, or
Background: Stunting-or
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undernutrition, has
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WHO
World Health Organization
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universal
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assess the potential magnitude of this bias by decomposing variation in HAZ
examine how universal cutoffs can underestimate stunting in specific regions around the world. Methods: Using a non-linear multi-level model, we decompose variation in height-for-age z-scores (HAZ)
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406,609 children from
430,986 children across
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low- and middle-income
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;
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a component
"accrued HAZ"
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inputs, poverty,
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healthcare access, and
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basal starting point that is
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After removing the effects of numerous environmental inputs, we find that different countries have reliably and substantially different basal starting points in average HAZ scores (a range of 1.7 SD) . These country-specific starting points, which we define as basal HAZ, are not associated with key indicators of undernutrition (e. g., infant mortality and average calorie deficit).
We validate these components by assessing their associations with key indicators of undernutrition. We then re-estimate stunting prevalence with population-sensitive cutoffs based on the estimates of these two components. Results: Basal HAZ differs reliably across countries (range of 1.6 SD) and is independent of measures of undernutrition.
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average increases in HAZ above a country's starting point, which we define as accrued HAZ , show strong correlations with these same variables, suggesting that low accrued HAZ captures standard definitions of
accrued HAZ captures
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undernutrition. Using these two components, we show how
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underestimate stunting in
miss 1 in 5 children in
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(e.g., sub-Saharan Africa and the Caribbean), where children in even very deprived situations start off taller
, where children have greater basal heights. Conclusion: Current universal cutoffs may miss stunting in populations with taller basal HAZ
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