MOdélisation des Courbes de Croissance chez les Adolescents en fonction de la maturation biologique et de l’âge chronologique – MOCCA

Human growth is the set of changes that occur between fertilization and achievement of the full adult potential. Unique changes occur, and many adult features are acquired during adolescence. Events that have a major impact on maturation are triggered during this key growth period. The various models described in the international literature yield mean growth curves that do not faithfully reflect the growth of the individual patient, as age at puberty varies across individuals. As a result, these models are unreliable for monitoring or predicting physical characteristics at completion of puberty, because they do not take account pubertal criteria. An evaluation of growth based only on chronological age may be wrong or misleading, most notably in individual patients. These facts prompted us to develop an original research project for evaluating the growth of healthy male and female adolescents. Our approach is innovative in that we model longitudinal growth curves based on both pubertal stage and chronological age. These models distinguish three age-at-puberty situations: early puberty, puberty at the usual age, and delayed puberty. This research project will contribute to basic science by faithfully describing growth during the pubertal period via the development of new reference values. In fact, this is the first time that it is tried to establish growth curves taking into account the variability of the studied features with pubertal stage and chronological age. Our research project has three distinct but complementary phases. The first phase will consist in collecting the longitudinal data needed to develop the database. To this end, we will conduct a longitudinal study of male and female students attending schools in and around Soissons, near the Ile de France region of France. Initially, we will record 13 anthropometric variables; body-composition variables (fat-free mass, fat mass) measured using a portable ultrasound machine-based method for which an international patent has been requested; pubertal stage assessed on a four-level scale (puberty not started, early puberty, puberty well under way, and puberty completed); and a number of variables reflecting socioeconomic and cultural status. In the second phase, we will model the growth curves for girls and boys separately for the study variables according to three situations: early puberty, puberty at the normal age, and delayed puberty. This approach leads to an approximately 30% decrease in age variability at peak velocity, giving more accuracy in growth parameters at individual level. A specific study for body mass index (BMI : body weight [kg]/height [m]²) by total body fat (kg) will be developed during pubertal period is a major point in terms of public health for determining cutoffs and risks. A new reference standard could be developed according to the relationship between body fat mass and the BMI. In the third phase, we will use the pubertal growth curves thus obtained as an essential reference for monitoring the growth of elite athletes. In fact, as athlete morphology is an essential criterion at elite level, anthropometric data during pubertal period must be know for training improvement. Individual and mean profiles of athletes in each sport will be developed. We will predict the adulthood values of several variables, most notably the height of athletes in fields where height is of key concern at the highest level of competition. In practice, we will develop an interactive computer program called 'AUXO-Logi' that will integrate all our pubertal growth curves. This software will constitute a convenient tool for assessing changes in individual and mean anthropometric characteristics over time. By placing an individual on the reference curves derived from our models, the user will obtain valuable information on growth during the key period of pubertal development.