Modelling stunting in LiST: The effect of applying smoothing to linear growth data

Simon Cousens, Jamie L. Perin, Parul S Christian, Lee Shu Fune Wu, Sajid Soofi, Zulfiqar Bhutta, Claudio Lanata, Richard L. Guerrant, Aldo A.M. Lima, Kåre Mølbak, Palle Valentiner-Branth, William Checkley, Robert H Gilman, R. Bradley Sack, Robert E Black, Jean Hawes Humphrey, Neff Walker

Research output: Contribution to journalArticle

Abstract

Background: The Lives Saved Tool (LiST) is a widely used resource for evidence-based decision-making regarding health program scale-up in low- and middle-income countries. LiST estimates the impact of specified changes in intervention coverage on mortality and stunting among children under 5 years of age. We aimed to improve the estimates of the parameters in LiST that determine the rate at which the effects of interventions to prevent stunting attenuate as children get older. Methods: We identified datasets with serial measurements of children's lengths or heights and used random effects models and restricted cubic splines to model the growth trajectories of children with at least six serial length/height measurements. We applied WHO growth standards to both measured and modelled (smoothed) lengths/heights to determine children's stunting status at multiple ages (1, 6, 12, 24 months). We then calculated the odds ratios for the association of stunting at one age point with stunting at the next ("stunting-to-stunting ORs") using both measured and smoothed data points. We ran analyses in LiST to compare the impact on intervention effect attenuation of using smoothed rather than measured stunting-to-stunting ORs. Results: A total of 21,786 children with 178,786 length/height measurements between them contributed to our analysis. The odds of stunting at a given age were strongly related to whether a child is stunted at an earlier age, using both measured and smoothed lengths/heights, although the relationship was stronger for smoothed than measured lengths/heights. Using smoothed lengths/heights, we estimated that children stunted at 1 month have 45 times the odds of being stunted at 6 months, with corresponding odds ratios of 362 for the period 6 to 12 months and 175 for the period 12 to 24 months. Using the odds ratios derived from the smoothed data in LiST resulted in a somewhat slower attenuation of intervention effects over time, but substantial attenuation was still observed in the LiST outputs. For example, in Mali the effect of effectively eliminating SGA births reduced prevalence of stunting at age 59 months from 44.4% to 43.7% when using odds ratios derived from measured lengths/heights and from 44.4% to 41.9% when using odds ratios derived from smoothed lengths/heights. Conclusions: Smoothing of children's measured lengths/heights increased the strength of the association between stunting at a given age and stunting at an earlier age. Using odds ratios based on smoothed lengths/heights in LiST resulted in a small reduction in the attenuation of intervention effects with age and thus some increase in the estimated benefits, and may better reflect the true benefits of early nutritional interventions.

Original languageEnglish (US)
Article number778
JournalBMC Public Health
Volume17
DOIs
StatePublished - Nov 7 2017

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Growth Disorders
Growth
Odds Ratio
Mali

Keywords

  • Lives saved tool
  • Mixed effects modelling
  • Nutritional interventions
  • Stunting

ASJC Scopus subject areas

  • Public Health, Environmental and Occupational Health

Cite this

Modelling stunting in LiST : The effect of applying smoothing to linear growth data. / Cousens, Simon; Perin, Jamie L.; Christian, Parul S; Wu, Lee Shu Fune; Soofi, Sajid; Bhutta, Zulfiqar; Lanata, Claudio; Guerrant, Richard L.; Lima, Aldo A.M.; Mølbak, Kåre; Valentiner-Branth, Palle; Checkley, William; Gilman, Robert H; Sack, R. Bradley; Black, Robert E; Humphrey, Jean Hawes; Walker, Neff.

In: BMC Public Health, Vol. 17, 778, 07.11.2017.

Research output: Contribution to journalArticle

Cousens, Simon ; Perin, Jamie L. ; Christian, Parul S ; Wu, Lee Shu Fune ; Soofi, Sajid ; Bhutta, Zulfiqar ; Lanata, Claudio ; Guerrant, Richard L. ; Lima, Aldo A.M. ; Mølbak, Kåre ; Valentiner-Branth, Palle ; Checkley, William ; Gilman, Robert H ; Sack, R. Bradley ; Black, Robert E ; Humphrey, Jean Hawes ; Walker, Neff. / Modelling stunting in LiST : The effect of applying smoothing to linear growth data. In: BMC Public Health. 2017 ; Vol. 17.
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abstract = "Background: The Lives Saved Tool (LiST) is a widely used resource for evidence-based decision-making regarding health program scale-up in low- and middle-income countries. LiST estimates the impact of specified changes in intervention coverage on mortality and stunting among children under 5 years of age. We aimed to improve the estimates of the parameters in LiST that determine the rate at which the effects of interventions to prevent stunting attenuate as children get older. Methods: We identified datasets with serial measurements of children's lengths or heights and used random effects models and restricted cubic splines to model the growth trajectories of children with at least six serial length/height measurements. We applied WHO growth standards to both measured and modelled (smoothed) lengths/heights to determine children's stunting status at multiple ages (1, 6, 12, 24 months). We then calculated the odds ratios for the association of stunting at one age point with stunting at the next ({"}stunting-to-stunting ORs{"}) using both measured and smoothed data points. We ran analyses in LiST to compare the impact on intervention effect attenuation of using smoothed rather than measured stunting-to-stunting ORs. Results: A total of 21,786 children with 178,786 length/height measurements between them contributed to our analysis. The odds of stunting at a given age were strongly related to whether a child is stunted at an earlier age, using both measured and smoothed lengths/heights, although the relationship was stronger for smoothed than measured lengths/heights. Using smoothed lengths/heights, we estimated that children stunted at 1 month have 45 times the odds of being stunted at 6 months, with corresponding odds ratios of 362 for the period 6 to 12 months and 175 for the period 12 to 24 months. Using the odds ratios derived from the smoothed data in LiST resulted in a somewhat slower attenuation of intervention effects over time, but substantial attenuation was still observed in the LiST outputs. For example, in Mali the effect of effectively eliminating SGA births reduced prevalence of stunting at age 59 months from 44.4{\%} to 43.7{\%} when using odds ratios derived from measured lengths/heights and from 44.4{\%} to 41.9{\%} when using odds ratios derived from smoothed lengths/heights. Conclusions: Smoothing of children's measured lengths/heights increased the strength of the association between stunting at a given age and stunting at an earlier age. Using odds ratios based on smoothed lengths/heights in LiST resulted in a small reduction in the attenuation of intervention effects with age and thus some increase in the estimated benefits, and may better reflect the true benefits of early nutritional interventions.",
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author = "Simon Cousens and Perin, {Jamie L.} and Christian, {Parul S} and Wu, {Lee Shu Fune} and Sajid Soofi and Zulfiqar Bhutta and Claudio Lanata and Guerrant, {Richard L.} and Lima, {Aldo A.M.} and K{\aa}re M{\o}lbak and Palle Valentiner-Branth and William Checkley and Gilman, {Robert H} and Sack, {R. Bradley} and Black, {Robert E} and Humphrey, {Jean Hawes} and Neff Walker",
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T1 - Modelling stunting in LiST

T2 - The effect of applying smoothing to linear growth data

AU - Cousens, Simon

AU - Perin, Jamie L.

AU - Christian, Parul S

AU - Wu, Lee Shu Fune

AU - Soofi, Sajid

AU - Bhutta, Zulfiqar

AU - Lanata, Claudio

AU - Guerrant, Richard L.

AU - Lima, Aldo A.M.

AU - Mølbak, Kåre

AU - Valentiner-Branth, Palle

AU - Checkley, William

AU - Gilman, Robert H

AU - Sack, R. Bradley

AU - Black, Robert E

AU - Humphrey, Jean Hawes

AU - Walker, Neff

PY - 2017/11/7

Y1 - 2017/11/7

N2 - Background: The Lives Saved Tool (LiST) is a widely used resource for evidence-based decision-making regarding health program scale-up in low- and middle-income countries. LiST estimates the impact of specified changes in intervention coverage on mortality and stunting among children under 5 years of age. We aimed to improve the estimates of the parameters in LiST that determine the rate at which the effects of interventions to prevent stunting attenuate as children get older. Methods: We identified datasets with serial measurements of children's lengths or heights and used random effects models and restricted cubic splines to model the growth trajectories of children with at least six serial length/height measurements. We applied WHO growth standards to both measured and modelled (smoothed) lengths/heights to determine children's stunting status at multiple ages (1, 6, 12, 24 months). We then calculated the odds ratios for the association of stunting at one age point with stunting at the next ("stunting-to-stunting ORs") using both measured and smoothed data points. We ran analyses in LiST to compare the impact on intervention effect attenuation of using smoothed rather than measured stunting-to-stunting ORs. Results: A total of 21,786 children with 178,786 length/height measurements between them contributed to our analysis. The odds of stunting at a given age were strongly related to whether a child is stunted at an earlier age, using both measured and smoothed lengths/heights, although the relationship was stronger for smoothed than measured lengths/heights. Using smoothed lengths/heights, we estimated that children stunted at 1 month have 45 times the odds of being stunted at 6 months, with corresponding odds ratios of 362 for the period 6 to 12 months and 175 for the period 12 to 24 months. Using the odds ratios derived from the smoothed data in LiST resulted in a somewhat slower attenuation of intervention effects over time, but substantial attenuation was still observed in the LiST outputs. For example, in Mali the effect of effectively eliminating SGA births reduced prevalence of stunting at age 59 months from 44.4% to 43.7% when using odds ratios derived from measured lengths/heights and from 44.4% to 41.9% when using odds ratios derived from smoothed lengths/heights. Conclusions: Smoothing of children's measured lengths/heights increased the strength of the association between stunting at a given age and stunting at an earlier age. Using odds ratios based on smoothed lengths/heights in LiST resulted in a small reduction in the attenuation of intervention effects with age and thus some increase in the estimated benefits, and may better reflect the true benefits of early nutritional interventions.

AB - Background: The Lives Saved Tool (LiST) is a widely used resource for evidence-based decision-making regarding health program scale-up in low- and middle-income countries. LiST estimates the impact of specified changes in intervention coverage on mortality and stunting among children under 5 years of age. We aimed to improve the estimates of the parameters in LiST that determine the rate at which the effects of interventions to prevent stunting attenuate as children get older. Methods: We identified datasets with serial measurements of children's lengths or heights and used random effects models and restricted cubic splines to model the growth trajectories of children with at least six serial length/height measurements. We applied WHO growth standards to both measured and modelled (smoothed) lengths/heights to determine children's stunting status at multiple ages (1, 6, 12, 24 months). We then calculated the odds ratios for the association of stunting at one age point with stunting at the next ("stunting-to-stunting ORs") using both measured and smoothed data points. We ran analyses in LiST to compare the impact on intervention effect attenuation of using smoothed rather than measured stunting-to-stunting ORs. Results: A total of 21,786 children with 178,786 length/height measurements between them contributed to our analysis. The odds of stunting at a given age were strongly related to whether a child is stunted at an earlier age, using both measured and smoothed lengths/heights, although the relationship was stronger for smoothed than measured lengths/heights. Using smoothed lengths/heights, we estimated that children stunted at 1 month have 45 times the odds of being stunted at 6 months, with corresponding odds ratios of 362 for the period 6 to 12 months and 175 for the period 12 to 24 months. Using the odds ratios derived from the smoothed data in LiST resulted in a somewhat slower attenuation of intervention effects over time, but substantial attenuation was still observed in the LiST outputs. For example, in Mali the effect of effectively eliminating SGA births reduced prevalence of stunting at age 59 months from 44.4% to 43.7% when using odds ratios derived from measured lengths/heights and from 44.4% to 41.9% when using odds ratios derived from smoothed lengths/heights. Conclusions: Smoothing of children's measured lengths/heights increased the strength of the association between stunting at a given age and stunting at an earlier age. Using odds ratios based on smoothed lengths/heights in LiST resulted in a small reduction in the attenuation of intervention effects with age and thus some increase in the estimated benefits, and may better reflect the true benefits of early nutritional interventions.

KW - Lives saved tool

KW - Mixed effects modelling

KW - Nutritional interventions

KW - Stunting

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