The necessity of using direct measures of child development

More than half of the world's poor are children,1Fenz K Hamel K More than half of the world's poor are children.https://www.brookings.edu/blog/future-development/2019/06/20/more-than-half-of-the-worlds-poor-are-children/Date: 2019Date accessed: August 18, 2019Google Scholar and one crushing consequence of growing up in poverty is the subsequent loss of human potential.2McCoy DC Peet ED Ezzati M et al.Early childhood developmental status in low- and middle-income countries: national, regional, and global prevalence estimates using predictive modeling.PLoS Med. 2016; 13e1002034Crossref PubMed Scopus (197) Google Scholar A common metric used to quantify the effects of poverty on human capital is the use of child growth, or stunting, as a proxy measure for poor cognitive development.3Lu C Black MM Richter LM Risk of poor development in young children in low-income and middle-income countries: an estimation and analysis at the global, regional, and country level.Lancet Glob Health. 2016; 4: e916-e922Summary Full Text Full Text PDF PubMed Scopus (195) Google Scholar This crucially important approach allows researchers and advocates to push for government action. However, despite the standard assumption that improvements in growth lead to improvements in cognitive development, the associations between these two variables are not consistent. In two studies using data from multiple countries,4Sudfeld CR McCoy DC Danaei G et al.Linear growth and child development in low- and middle-income countries: a meta-analysis.Pediatrics. 2015; 135: e1266-e1275Crossref PubMed Scopus (199) Google Scholar, 5Tran TD Holton S Nguyen H Fisher J Physical growth: is it a good indicator of development in early childhood in low- and middle-income countries?.BMC Pediatr. 2019; 19: 276Crossref PubMed Scopus (4) Google Scholar child growth and cognitive development were associated, but findings differed by context (eg, associations ranged from non-existent in Barbados, Lebanon, and Moldova to r=0·36 in Nigeria)5Tran TD Holton S Nguyen H Fisher J Physical growth: is it a good indicator of development in early childhood in low- and middle-income countries?.BMC Pediatr. 2019; 19: 276Crossref PubMed Scopus (4) Google Scholar and child age (eg, associations were stronger for children aged 2 years or younger than for those older than 2 years).4Sudfeld CR McCoy DC Danaei G et al.Linear growth and child development in low- and middle-income countries: a meta-analysis.Pediatrics. 2015; 135: e1266-e1275Crossref PubMed Scopus (199) Google Scholar Furthermore, a large amount of variation in child development was unexplained by child length-for-age or height-for-age. In The Lancet Global Health, Elizabeth Prado, Leila Larson, and colleagues6Prado EL Larson LM Cox K Bettencourt K Kubes JN Shankar AH Do effects of early life interventions on linear growth correspond to effects on neurobehavioral development? A systematic review and meta-analysis.Lancet Glob Health. 2019; 7: e1398-e1413Summary Full Text Full Text PDF PubMed Scopus (39) Google Scholar add to this existing literature by doing a meta-regression of randomised trials done during pregnancy and with children aged 0–5 years to understand the shared versus independent intervention effects on linear growth and neurological development. Their approach differed from that of a typical meta-analysis in that the major inclusion criteria were based on reported outcomes rather than intervention type. Therefore, all interventions that reported child linear growth and outcomes on motor, cognitive (or mental), language, or social-emotional (or behavioural) development were included, which resulted in substantial heterogeneity in intervention type, context, and population. The meta-analysis included 75 studies with 122 comparisons between intervention and control groups and outcomes reported for 72 275 children. Prado and colleagues reported no overall association between intervention effects on growth and cognitive (β 0·18, 95% CI −0·36 to 0·72; p=0·51), language (0·12, −0·07 to 0·31; p=0·21), and motor development scores (0·23, −0·05 to 0·50; p=0·11), but found an association between effects on growth and social-emotional scores (0·23, 0·05 to 0·41; p=0·02). Among nutrition supplementation studies, Prado and colleagues found a significant association between effects on growth and cognitive (β 0·40, 95% CI 0·04–0·77; p=0·049) and motor (0·43, 0·11–0·75; p=0·01) scores. Using pooled analyses, the authors found a small pooled effect of nutrition interventions on both growth and development, and a larger pooled effect size of caregiving interventions on child development, but no corresponding effects on growth. A key message of Prado and colleagues’ study is that intervention effects on child growth and child development do not always co-occur, and this is important for researchers, practitioners, and policy makers alike. As the authors emphasise, the standard practice of using child growth as a proxy for intervention effects on child development is not accurate or appropriate. Although in some contexts, stunting can be an indicator of social and environmental influences in early life, interventions designed to improve child growth outcomes might be grossly suboptimal when the desired intervention outcome is also improved child development. Among the examined studies that measured both development and growth, child development was more responsive to intervention effects than growth. Prado and colleagues report differential pooled effects of nutrition interventions on outcomes on the basis of supplementation type and timing and economic context, although they were not able to explore these issues in detail. This study was well designed and implemented and is a substantial and important addition to the existing literature. However, some key questions remain that still need to be answered. First, how do effects vary across subgroups? The study had vast heterogeneity in intervention types and details across all of the interventions included in the primary analysis, even within the nutrition and caregiving intervention subgroups. Differences included duration and intensity of the intervention, target population (eg, child age, sociodemographic factors, and baseline nutritional status), and broader country context (eg, economic, political, and cultural factors). Existing studies have shown differential effects of interventions for malnourished children compared with those for non-malnourished children,7Schroeder DG Pachón H Dearden KA Ha TT Lang TT Marsh DR An integrated child nutrition intervention improved growth of younger, more malnourished children in northern Viet Nam.Food Nutr Bull. 2002; 23: 50-58Crossref Google Scholar and nutrition intervention effects on growth have been shown to vary by income status.8Lassi ZS Das JK Zahid G Imdad A Bhutta ZA Impact of education and provision of complementary feeding on growth and morbidity in children less than 2 years of age in developing countries: a systematic review.BMC Pub Health. 2013; 13: S13Crossref PubMed Scopus (140) Google Scholar Furthermore, in the analyses reported here, children's age at assessment ranged from 6 months to 12 years, and effects were not disaggregated by age or gender, although previous studies have found varying effects when disaggregating by age and gender. Another question that emerges from the findings relates to pathways. Nutrition interventions might have direct effects on brain development and growth, whereas responsive caregiving might have indirect effects on child development through changing parental caregiving behaviours and maternal mental health, and no direct or indirect effects on child growth.9Prado EL Yakes Jimenez E Vosti S et al.Path analyses of risk factors for linear growth faltering in four prospective cohorts of young children in Ghana, Malawi and Burkina Faso.BMJ Glob Health. 2019; 4e001155Crossref PubMed Scopus (13) Google Scholar Better understanding the various pathways through which early life interventions affect child growth and development, either together or independently, would allow for the development of more targeted and effective interventions for vulnerable children. Prado and colleagues’ study clearly reinforces the idea that, wherever possible, direct measures of child development should be incorporated into research studies to avoid an overreliance on proxy measures. Multiple measures of child development exist and have been adapted, translated, modified, and used in low-income and middle-income countries.10Fernald LCH Prado E Kariger P Raikes A A toolkit for measuring early childhood development in low- and middle-income countries. World Bank, 2017https://openknowledge.worldbank.org/handle/10986/29000Date accessed: August 18, 2019Crossref Google Scholar Given the importance of measuring child development for programme assessment and population-level monitoring, an effort is underway to develop the Global Scale for Early Development, a reliable, easily interpretable tool that would allow for valid cross-national comparisons. More broadly, accurate measurement is crucial to generate information on progress and challenges in reaching development goals and can add to effective assessments of programmes and interventions to inform evidence-based policies to improve outcomes for children at risk. We declare no competing interests. Do effects of early life interventions on linear growth correspond to effects on neurobehavioural development? A systematic review and meta-analysisIn nutritional supplementation interventions, improvements in linear growth were associated with small improvements in child development, whereas nurturing and stimulation interventions had significant effects on child development but no effects on linear growth. The determinants of linear growth and neurodevelopment are only partly shared. To nurture thriving individuals and communities, interventions should specifically target determinants of neurodevelopment and not simply linear growth. Full-Text PDF Open Access