Measuring catch-up growth in malnourished populations

Background and aim: Numerous recent studies measure catch-up growth by regressing adult or pre-adolescent height on early childhood height. Using simple statistical theory and data from a healthy and well-nourished population, this paper shows that these tests are uninformative about the extent of catch-up growth. The study also provides new empirical evidence on pubertal catch-up growth using longitudinal data for rural Tanzania. Subjects and methods: The 1970 British Cohort Study is used to demonstrate the flaws in the recent literature using regression techniques to study catch-up growth. The data for the empirical analysis come from the Kagera Health and Development survey-a longitudinal study spanning two decades. The final sample includes 540 children whose heights are measured in early childhood and in adulthood. Catch-up growth is measured as the change in height-forage z-score over time. Results: The mean HAZ-score in the cohort improves from -1.86 in early childhood to -1.20 in adulthood. Without catch-up growth, children would have been 4.5-5 centimetres shorter adults. Graphical analysis shows that most of this catch-up growth takes place in puberty. Conclusion: Catch-up growth after early childhood is possible. Puberty seems to offer an opportunity window for recovery.