Model fitting to early childhood length and weight data from the fels longitudinal study of growth

Length and weight data from 3 months to 6 years of age from 466 participants in the Fels Longitudinal Study of Growth were used to fit the Jenss non-linear growth curve. Six (1%) of the Fels participants had extremely outlying values for length parameters, and 20 (4%) had outlying values for weight parameters. The general pattern in the outliers is for average or below average size in infancy, followed by unusually rapid growth or weight gain in childhood. This outlier pattern is associated with significantly higher mean stature or weight at 18 years of age. The results for the majority of the participants are similar to those found in 229 children from the Harvard Growth Study, except for the non-linear intercept for length and the linear intercept for weight. Significant sex differences have not previously been reported for Jenss parameters, perhaps because previous applications have used much smaller sample sizes.