Our final dataset for HAZ and WAZ included 628 country-years, comprising anthropometric measurements of more than 7·7 million children (; appendix pp 15–46
), providing an average of 4·5 years of data per country or territory. Data availability ranged from 1·1 years per country in Oceania to 6·8 in south Asia. 543 (86%) of these 628 country-years were nationally representative (appendix p 87
). 126 of 141 countries, with greater than 99% of the total population, had at least one data source; of these, 111 had at least two. Each country in south Asia and sub-Saharan Africa had at least one data source.
Flowchart of data sources, access, and inclusion
When all 141 developing countries in our analysis were taken together, children's anthropometric status improved between 1985 and 2011 but did not reach optimum nutritional status as envisioned by the WHO growth standards (). In 1985, global (ie, all countries in our analysis) mean HAZ was −1·86 (95% uncertainty interval −2·01 to −1·72) and WAZ was −1·31 (–1·41 to −1·20; ), representing a world where children were on average near the moderate stunting threshold (Z score of −2); these values improved to a mean HAZ of −1·16 (–1·29 to −1·04) and a mean WAZ of −0·84 (–0·93 to −0·74) in 2011. 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; PPs of being true decreases >0·999).
Trends in the cumulative distribution functions for HAZ (A) and WAZ (B) by region
Trends in HAZ and WAZ means and prevalences by region between 1985 and 2011
Despite this improvement, in 2011, 314 (296 to 331) million children younger than 5 years had HAZ below −1. Just greater than half of these children (170 [154 to 186] million) had HAZ below −2. 258 (240 to 274) million children had WAZ below −1, less than half (110 [94 to 126] million) of whom had WAZ below −2. 37% of all children with mild-to-severe stunting and 46% with mild-to-severe underweight lived in south Asia (). Sub-Saharan Africa had the second largest number, a position that had belonged to east and southeast Asia in 1985.
Number of children in the mild to severe parts of the HAZ and WAZ distributions, by region
Sub-Saharan Africa experienced a period of increasing undernutrition until the late 1990s, when anthropometric status began to improve (panel 1
). With large uncertainty, HAZ might have worsened slightly and WAZ might have improved only slightly in Oceania. Height for age and weight for age improved in all other regions. The largest improvements were in south Asia and east and southeast Asia (), with mean HAZ increasing by about 0·4 per decade and mean WAZ by about 0·25 per decade (PPs >0·99). Although Asia outperformed other regions in absolute gains, southern and tropical Latin America not only started with the best nutritional status but also had the largest relative decline in prevalences, with 39–44% declines per decade in moderate-and-severe stunting and underweight; the reductions in the severe tail were even larger.
Panel 1. Children's nutrition: a tale of three continents (and four countries)
In 1985, Burkina Faso, Brazil, China, and Ghana had mean height-for-age Z scores (HAZ) ranging from −1·34 to −1·67 and prevalences of moderate-and-severe stunting that ranged from 34% to 40%, with China faring slightly worse than the other three countries (appendix pp 88–89
). Over the subsequent 26 years, they had very different trajectories in children's nutritional status and growth. Brazilian and Chinese children experienced large improvements throughout the period such that, by 2011, mean HAZ had reached −0·33 to −0·42 and the prevalence of moderate-and-severe stunting was 9–13% (figure appendix 1
, appendix pp 90–231
). By contrast with these success stories, nutritional status of children in Burkina Faso worsened for over a decade before improving slowly after the late 1990s. As a result, children's nutritional status in 2011 was only slightly better than it had been 26 years earlier, and was much worse than those of children in Brazil and China. These three countries exemplify the experiences of their respective regions, and the regionalisation of child undernutrition. Yet some countries like Ghana, one of Africa's best governed nations with strong commitment to agriculture and nutrition, defied the negative trends of the late 1980s and 1990s in sub-Saharan Africa and achieved steady, although slow, improvements.
Even in these countries with moderately rich data it is hard to identify the precise contributions of specific determinants of trends, perhaps because children's growth is multifaceted and affected by a complex, dynamic, and interactive array of social, environmental, nutritional, and health-care determinants.19,20
The existing evidence collectively suggests that improving children's anthropometric status requires enhancing nutrition, the living environment, and health care for the poor through equitable economic development, maternal education, and pro-poor agriculture, food, and health-care policies and programmes.
As a result of these trends, the regions' HAZ and WAZ distributions were reordered between 1985 and 2011. South Asia had the single worst nutritional status in 1985. By 2011, its HAZ distribution was similar to those of sub-Saharan Africa and Oceania, which had experienced periods of deterioration or stagnation (). South Asia's WAZ did not catch up with other regions, but the difference with sub-Saharan Africa became smaller. At the other extreme, southern and tropical Latin America maintained its position as the best-nourished developing region, and increased its advantage compared with the Andean and central Latin America and Caribbean region and the central Asia, Middle East, and north Africa region. Improvements in southern and tropical Latin America slowed down after 2000, especially for mean. East and southeast Asia's strong performance led to its HAZ surpassing those of the central Asia, Middle East, and north Africa region and the Andean and central Latin America and Caribbean region.
The most undernourished country-years were in Bangladesh in the 1980s, when mean HAZ was as low as −2·7 and WAZ as low as −2·4; nearly three-quarters of children had HAZ below −2; more than a third were severely stunted; and about two-thirds were underweight (appendix pp 88, 89
). Although children's anthropometric status improved in most countries (appendix pp 90–231, 233–239
), height for age and weight for age remained very low in some places in 2011: children in Burundi, Yemen, Timor-Leste, Niger, and Afghanistan had HAZ means below or close to the −2 cutoff for moderate stunting (figure appendix 1
). About half of children in these countries were moderately or severely stunted. Mean WAZ was −1·5 or less in Timor-Leste, Bangladesh, Niger, India, and Nepal, with one-third or more of children moderately or severely underweight (figure appendix 2
). At the other extreme, children in Chile, Jamaica, and Kuwait had HAZ distributions indistinguishable from a well-nourished population in 2011, with means between 0·01 and 0·04. Similarly, 25 countries, mostly in the Latin America and Caribbean region and the central Asia, Middle East, and north Africa region, had WAZ means that surpassed the WHO standards, with the highest WAZ mean and lowest underweight prevalence in Chile.
HAZ probably deteriorated in 17 countries between 1985 and 2011, nearly all in sub-Saharan Africa and Oceania (appendix pp 230–239
); most had large uncertainties, but the PPs for the observed deteriorations were 0·90 in Côte d'Ivoire and Niger. The largest improvement in children's height was in China, followed by smaller improvements in six other Asian countries, Brazil, and Tunisia; in these countries mean HAZ increased by 0·35–0·51 per decade, all with PPs of 0·99 or greater. WAZ improvements varied less across countries, ranging from possible worsening in Somalia, Burkina Faso, Central African Republic, Zimbabwe, Côte d'Ivoire, and Madagascar to improvements of 0·25 or greater per decade in Brazil and some countries in Asia and Middle East, all with PPs of 0·98 or greater. Mirroring these, underweight prevalences declined by a third or more per decade in 21 countries, nearly halving each decade in Brazil.
In most countries, changes in moderate-and-severe stunting or underweight prevalences between 1985 and 2011 were statistically indistinguishable from those we expected had the whole HAZ and WAZ distribution shifted by as much as its median (appendix p 232
). In other words, reductions in prevalence were generally because of overall improvements in population nutrition versus interventions targeting children at high risk. In some countries, especially in the Latin America and Caribbean region, however, prevalence declined more than expected from the improvement in the population median—ie, an inequality-reducing change in the distribution.
Despite improvements, the probability that developing countries as a whole will meet the MDG 1 target is less than 0·05 if post-2000 trends continue. The probability ranged from virtually zero in sub-Saharan Africa to close to 1 in the two Latin America and Caribbean regions. 27 countries in the Latin America and Caribbean region, the central Asia, Middle East, and north Africa region, and east and southeast Asia have probabilities of 0·80 or greater, with probability close to 1·0 in Chile, Brazil, Mexico, and China. Another 34 countries had probabilities between 0·50 and 0·80, leaving 80 countries with less than a 50% chance of reaching this target (). Only six countries in sub-Saharan Africa had probabilities of 0·50 or greater, with the highest chances of success in Ghana and Angola.
Posterior probability of meeting the MDG 1 target