Validating the WWHLA growth model: a preliminary study utilizing serial height data of eight Zurich children.

In this study, we set out to validate the WWHLA growth model. We randomly selected eight children (four boys and four girls) who participated in the First Zurich Longitudinal Growth Study and fitted the model to their serial height growth data, using a computerized nonlinear least-squares technique. The results showed that the model provided an excellent fit to their data. The underlying trends of the height displacement, velocity, and acceleration curves were almost perfectly described, for the entire growth period from birth to maturity. The descriptive statistics obtained from fitting the model supported these results. In addition, student's t tests showed that all 14 model parameters differed from zero and were significant in describing the relationship between height and age in each child. From the growth curves of these children, we were able to easily discern and identify the six macroscopic growth processes (neonatal, infantile, early-childhood, mid-childhood, late-childhood, and pubertal) that were predicted by the model. The processes had properties that were similar to what we found in the earlier study. These are preliminary results, but they provide additional support for the WWHLA growth model and its use in describing linear growth curves in humans.