Measuring catch-up growth in malnourished populations

Chronic malnutrition during early childhood hinders growth and causes children to fall into a lower growth trajectory. In order to recover, children need to experience growth rates that are above the expected rate for their age. Several studies have analysed the extent of such catch-up growth by regressing adult height on early childhood height. In this paper, I show that these studies confuse catch-up growth with within-population convergence and are further plagued by a well-known statistical fallacy of regression-to-the-mean. This calls for a re-evaluation of the existing evidence. In the empirical part of the paper, I use data from the Philippines and the Kagera region in Tanzania to study catch-up growth. I find limited recovery in the Philippines cohort. In Kagera, almost 75 per cent of the children experience catch-up growth. The mean height-for-age z-score improves from -1.87 in early childhood to -1.20 by adulthood. Graphical analysis reveals that this catch-up growth takes place in puberty.