What's up with catch‐up? No evidence of population‐level catch‐up growth in children under 5 years of age when using height‐for‐age difference (HAD) instead of height‐for‐age z‐scores (HAZ)

Abstract

Studies conducted in past decades showed little or no population‐level linear catch‐up growth (defined as reductions in absolute height deficit) in children after 2 y of age. Recent studies, however, have reported catch‐up growth in groups of children using height‐for‐age z‐scores (HAZ). We assessed whether population‐level catch‐up growth is found when height‐for‐age difference (HAD; child's height compared to standard in cm) is used instead of HAZ.Using data from Demographic and Health Surveys (DHS), Young Lives (YL), and the Consortium on Health‐Oriented Research in Transitional Societies (COHORTS), we compared changes in HAD and HAZ in populations of children between 2 and 5 y. We show that HAZ is inappropriate to measure changes in linear growth as populations of children age because they are constructed using SDs from cross‐sectional data, which increase with age. Using HAD, we find not only an absence of population‐level catch‐up growth, but a continued deterioration reflected in a decrease in mean HAD between 2 and 5 y; HAZ shows either no change (DHS) or an improvement in mean HAZ (YL, COHORT) as groups of children age.We show no evidence of population‐level catch‐up in children between 2 to 5 y when using HAD. The continued widening of the height deficit after 2 y does not challenge the current focus on the first 1,000 days, but raises questions regarding prevention of continued deterioration and the potential of children to benefit from nutrition interventions after 2 y of age.Funded by the CGIAR Research Program on Agriculture for Nutrition and Health (A4NH), led by IFPRI.