Data for: A modified Michaelis-Menten equation estimates growth from birth to 3 years in healthy babies in the US

Background: Standard pediatric growth curves cannot be used to impute missing height or weight measurements in individual children. The Michaelis-Menten equation, used for characterizing substrate-enzyme saturation curves, has been shown to model growth in many organisms including nonhuman vertebrates. We investigated whether this equation could be used to interpolate missing growth data in children in the first three years of life and compared this interpolation to several common interpolation methods and pediatric growth models.
Methods: We developed a modified Michaelis-Menten equation and compared expected to actual growth, first in a local birth cohort (N=97) and then in a large, outpatient, pediatric sample (N=14,695).
Results: The modified Michaelis-Menten equation showed excellent fit for both infant weight (median RMSE: boys: 0.22kg [IQR:0.19; 90%<0.43]; girls: 0.20kg [IQR:0.17; 90%<0.39]) and height (median RMSE: boys: 0.93cm [IQR:0.53; 90%<1.0]; girls: 0.91cm [IQR:0...., Sources of data: Information on infants was ascertained from two sources: the STORK birth cohort and the STARR research registry. (1) Detailed methods for the STORK birth cohort have been described previously. In brief, a multiethnic cohort of mothers and babies was followed from the second trimester of pregnancy to the babies’ third birthday. Healthy women aged 18–42 years with a single-fetus pregnancy were enrolled. Households were visited every four months until the baby’s third birthday (nine baby visits), with the weight of the baby at each visit recorded in pounds. Medical charts were abstracted for birth weight and length. (2) STARR (starr.stanford.edu) contains electronic medical record information from all pediatric and adult patients seen at Stanford Health Care (Stanford, CA). STARR staff provided anonymized information (weight, height and age in days for each visit through age three years; sex; race/ethnicity) for all babies during the period 03/2013–01/2022 followed from bi..., Example R code for fitting weight and/or height data with the MME equation is shown in the MME_growth_fitting.RMD file.
This file was written to fit the supplied STARR dataset. However, it can be adapted to alternative data. The HTML version of this file is available as well, in case viewing the script without opening it in R is desired. R_sessionInfo.txt contains the R software version, as well as the versions of the packages included in the code. See the methods section of the manuscript for the description of the starting parameters for the nls() function., # Data for: A modified Michaelis-Menten equation estimates growth from birth to 3 years in healthy babies in the US

## Description of the data and file structure

Data for this study include, per baby: sex, age in days, and, over time, weight in Kg and height in cm. Each baby had at least 5 visits. Our goal was to fit each baby’s data to a curve as described by a modified Michaelis-Menten equation, allowing interpolation of missing weight or height values. Among the subset of all infants who had 7 well-baby visits in the  first year of life, and 12 visits over 3 years, we further explored the minimum number of, and which, data points were necessary for good fit. Finally, among babies with 5 time points in year 1, and 2 in both year 2 and year 3, we examined whether weight or height data early in life could predict growth in later months.

To meet anonymization guidelines, we are providing only STARR data, including sex, age and jittered weight and height (for STORK data, STARR race/e...