Trends in mild, moderate, and severe stunting and underweight, and progress towards MDG 1 in 141 developing countries: a systematic analysis of population representative data

Abstract

Background: There is little information on country trends in the complete distributions of children's anthropometric status, which are needed to assess all levels of mild to severe undernutrition. We aimed to estimate trends in the distributions of children's anthropometric status and assess progress towards the Millennium Development Goal 1 (MDG 1) target of halving the prevalence of weight-for-age Z score (WAZ) below -2 between 1990 and 2015 or reaching a prevalence of 2·3% or lower.

Methods: We collated population-representative data on height-for-age Z score (HAZ) and WAZ calculated with the 2006 WHO child growth standards. Our data sources were health and nutrition surveys, summary statistics from the WHO Global Database on Child Growth and Malnutrition, and summary statistics from reports of other national and international agencies. We used a Bayesian hierarchical mixture model to estimate Z-score distributions. We quantified the uncertainty of our estimates, assessed their validity, compared their performance to alternative models, and assessed sensitivity to key modelling choices.

Findings: In developing countries, mean HAZ improved from -1·86 (95% uncertainty interval -2·01 to -1·72) in 1985 to -1·16 (-1·29 to -1·04) in 2011; mean WAZ improved from -1·31 (-1·41 to -1·20) to -0·84 (-0·93 to -0·74). Over this period, prevalences of moderate-and-severe stunting declined from 47·2% (44·0 to 50·3) to 29·9% (27·1 to 32·9) and underweight from 30·1% (26·7 to 33·3) to 19·4% (16·5 to 22·2). The largest absolute improvements were in Asia and the largest relative reductions in prevalence in southern and tropical Latin America. Anthropometric status worsened in sub-Saharan Africa until the late 1990s and improved thereafter. In 2011, 314 (296 to 331) million children younger than 5 years were mildly, moderately, or severely stunted and 258 (240 to 274) million were mildly, moderately, or severely underweight. Developing countries as a whole have less than a 5% chance of meeting the MDG 1 target; but 61 of these 141 countries have a 50-100% chance.

Interpretation: Macroeconomic shocks, structural adjustment, and trade policy reforms in the 1980s and 1990s might have been responsible for worsening child nutritional status in sub-Saharan Africa. Further progress in the improvement of children's growth and nutrition needs equitable economic growth and investment in pro-poor food and primary care programmes, especially relevant in the context of the global economic crisis.

Funding: The Bill & Melinda Gates Foundation and the UK Medical Research Council.

Figure 1

Flowchart of data sources, access, and inclusion NCHS=US Centres for Disease Control and Prevention National Center for Health Statistics. DHS=Demographic and Health Survey. MICS=Multiple Indicator Cluster Survey.

Figure 2

Trends in the cumulative distribution functions for HAZ (A) and WAZ (B) by region Each curve shows the cumulative proportion of children (y-axis) that lies below a given HAZ or WAZ level (x-axis). Therefore, the lower the curve, the better the nutritional status of the region. All distributions are compared with the WHO standards. We present the trends by country in the appendix (pp 90–231). HAZ=height-for-age Z score. WAZ=weight-for-age Z score.

Figure 3

Trends in HAZ and WAZ means and prevalences by region between 1985 and 2011 Shaded regions show the uncertainty interval. We present the trends by country in the appendix (pp 90–231). Prevalence of children with Z scores below −2 includes all children below this cutoff, including those with Z scores below −3. HAZ=height-for-age Z score. WAZ=weight-for-age Z score.

Figure 4

Number of children in the mild to severe parts of the HAZ and WAZ distributions, by region The number of children with Z scores below −1 includes all children below this cutoff, including those with Z scores below −2 and −3. Similarly, the number of children with Z scores below −2 includes all children below this cutoff, including those with Z scores below −3. HAZ=height-for-age Z score. WAZ=weight-for-age Z score.

Figure 5

Posterior probability of meeting the MDG 1 target Defined here as halving the prevalence of WAZ below −2 between 1990 and 2015 or reaching a prevalence 2·3% or lower if post-2000 trend continues. WAZ=weight-for-age Z score.