Insight into human pubertal growth by applying the QEPS growth model

Abstract

BackgroundComputerized mathematical models describing absolute and relative individual growth during puberty in both cm and standard deviation (SD)-scores are lacking. The present study aimed to fill this gap, by applying the QEPS-model that delineates mathematically the specific pubertal functions of the total growth curve.MethodsStudy population used was the individual growth curves of the longitudinally followed cohort GrowUp1974 Gothenburg (n = 2280). The QEPS-model describes total height as (T)otal-function: a combination of four shape-invariant growth functions, modified by time-scale and height-scale parameters: a (Q)uadratic-function for the continuous growth from fetal life to adulthood; a negative (E)xponential-function adds the rapid, declining fetal/infancy growth; a (P)ubertal-function the specific pubertal growth spurt; a (S)top-function the declining growth until adult height. A constructed variable, MathSelect, was developed for assessing data-quality. CIs and SD-scores for growth estimates were calculated for each individual.QEPS-model estimates used for pubertal growth; from the T-function: onset of puberty as minimal height velocity (AgeT ONSET); mid-puberty as peak height velocity (AgeT PHV); end of puberty as height velocity decreased to 1 cm/year (AgeT END); duration of different intervals and gain (AgeT ONSET–END and Tpubgain); from the P-function: onset of puberty, estimated as growth at 1% or 5% (AgeP1 , AgeP5); mid-puberty as 50% (AgeP50) and PHV (AgeP PHV); end of pubertal growth at 95 or 99% (AgeP95, AgeP99); duration of different intervals and pubertal gain (Ppubgain; P max); from the QES-function: gain (QESpubgain) . ResultsApplication of these mathematical estimates for onset, middle and end of puberty of P-function, QES-function, and T-function during puberty showed: the later the onset of puberty, the greater the adult height; pubertal gain due to the P-function growth was independent of age at onset of puberty; boys had higher total gain during puberty due to P-function growth than to QES-function growth; for girls it was reversed.ConclusionsQEPS is the first growth model to provide individualized estimates of both the specific pubertal growth function and the total growth during puberty, with accompanying SD-scores and Cis for each individual. These QEPS-derived estimates enable more in-depth analysis of different aspects of pubertal growth than previously possible.Electronic supplementary materialThe online version of this article (doi:10.1186/s12887-017-0857-1) contains supplementary material, which is available to authorized users.

Nordic populations are still getting taller – secular changes in height from the 20th to 21st century

“…For the longitudinal GrowUp 1974 cohort, we were able to compare the presently used method of PHV for estimating the impact of the material used, different subgroups of the cohort, as an estimation of impact of using the available mixture of semi-longitudinal and cross-sectional data from the other countries. For boys, the PHV became 0.5 year earlier (data not shown), whereas compared with other methods, 0.2 year earlier PHV (9,17).…”

“…Growth data were obtained from the GrowUp 1974 and 1990 Gothenburg cohorts (7,9,10,(14)(15)(16)(17), and publications of present and past national growth reference material for Sweden (9,(18)(19)(20), Denmark (13,21), Finland (11,22,23) and Norway (12,24,25) in the last four decades. For Sweden, data on adult heights of the parents of study participants were available for three of the studies (9,14,18,26).…”

Estimating secular changes in longitudinal growth patterns underlying adult height with the QEPS model: the Grow Up Gothenburg cohorts

“…A mathematical selection tool was used in both study cohorts to restrict the sample to those individuals with serial measurements at all age periods, together with visual growth curve analysis to select individuals with growth data of high quality. 20,23 The 1974 study cohort included data from 2280 healthy individuals (1139 girls) born in Sweden (Supplemental Table S1). The 1990 study cohort included data from 1901 healthy individuals (929 girls) born in Sweden (Supplemental Table S1).…”

“…The more traditional measure of the middle of puberty, age at PHV, was calculated from the total growth curve (AgeTPHV). 20 The duration of growth during puberty was calculated as the time from AgeP5 to AgeP95.…”

“…19 Thanks to the specific pubertal growth function (P), it is possible to mathematically estimate the onset, middle, and end of pubertal growth, thus enabling a more detailed evaluation of growth during puberty than that which has been previously possible. 20 The aim of this study was to evaluate secular changes in growth patterns during growth phases from birth to adulthood, and the resulting adult heights in two Swedish cohorts born in 1974 and 1990, with use of growth functions from the QEPS model.…”