Are Nutrition Interventions Effective Past the First Thousand Days?
Good nutrition during the first thousand days in the life of a child, from conception to the second birthday, is critical to allow children to reach their physical and cognitive potential. Nutrition interventions tend to focus on this window of opportunity to prevent permanent growth failure and mental development, as it was thought that interventions conducted later would not be effective. Today in the Journal of the American Medical Association, Friedrich published a short note to remind readers of some recent research that found that improving nutrition up to at least 8 years of age could still have a beneficial effect on growth and cognition.
The recent evidence was based on the Young Lives study, published by Crookston and co-workers. This is a study being conducted in four developing countries (Ethiopia, India, Peru and Vietnam) over a period of 15 years that is tracking the health and development of around 12,000 children. The authors looked at whether changes in stunting status between the ages of one and eight years had an effect on cognitive development. Stunting occurs due to chronic lack of nutrition, including total calorie deficits, low protein intakes, low intake of particular nutrients such as zinc, and disease that can increase food requirements or decrease food intakes. To measure stunting, the height-for-age z-score was used; this compares the current height of the child with the average height of children of the same age. If children are much shorter than average, in the bottom 5th percentile for their age, they are considered to be stunted. Four categories of children were identified:
(1) Children who were not stunted at both 1 and 8 years of age (never stunted)
(2) Children who were stunted at 1 year of age but not at 8 years of age (recovered)
(3) Children who were not stunted at 1 year of age but were stunted at 8 years of age (faltered)
(4) Children who were stunted at both 1 and 8 years of age (persistently stunted)
There were differences in rates of stunting between countries. Vietnam had the lowest proportion of persistently stunted children (11%) and the highest proportion of never-stunted children (71%), while Ethiopia had the lowest proportion of never-stunted children (52%) and India had the highest proportion of persistently stunted children (17%). The height-for-age z-score indicated that the average child in all four countries was more than one standard deviation below what would be expected for their age.
The concept of “school overage” was used in the article. This is a measure of whether children are more than one year behind the expected school grade for their age. For example, if an 8 year old had normally entered school at 5 years of age, this child would have completed 3 grades of school by their 8th birthday. If in fact the child had attended less than 2 years of school they would be considered to have a school overage. In the study, rates of school overage were highest in Ethiopia (19%) and lowest in Peru (5%).
The authors found that children that were persistently stunted were more likely to have school overage than those that were never stunted. Children who had faltered growth were also more likely to have school overage, but those who had recovered did not have overage compared to never stunted children. In mathematics, stunted children received the lowest grade, followed by recovered, faltered and never-stunted children. Similar trends were also seen for measures of vocabulary and reading comprehension.
The results of this study show that catch-up growth after infancy improves outcomes compared to children that remain stunted, although children who were stunted at any time point measured performed worse than children that were never stunted. The first thousand days are important. Catch-up growth beyond the second birthday can still be beneficial, however, in recovering some of the cognitive and developmental potential lost due to stunting.
Friedrich MJ. For Malnourished Infants, Deficits Reversible After 2 Years of Age. JAMA. 2014;311(7):666. doi:10.1001/jama.2014.1053.
Crookston BT, Schott W, Cueto S, Dearden KA, Engle P, Georgiadis A, et al. Postinfancy growth, schooling, and cognitive achievement: Young Lives. The American Journal of Clinical Nutrition. 2013;98(6):1555-63. http://dx.doi.org/10.3945/ajcn.113.067561