Growth tracks in pre-pubertal children

The present investigation characterizes common growth tracks in pre-pubertal children. Growth tracks denominate areas of probability within which subsequent measurements of the body height (or body height SDS) of a healthy individual will predominantly be found. Growth tracks are defined over several years and they are insensitive to the timing of measurements. The concept of growth tracks was developed to improve separating aberrant patterns from normal growth. Longitudinal data on height were obtained from six large national growth studies, performed at Berkeley, USA, Jena, Germany, Lublin, Poland, Paris, France, Prague, Czech Republic and Zurich, Switzerland with a total of 515 healthy boys and 532 healthy girls. Four hundred and two series of annual height measurements were available in pre-pubertal boys (aged 3-11 years), 416 series in pre-pubertal girls (aged 3-10). Body height was converted into height SDS. Thereafter, average personal height SDS was determined, and subtracted from height SDS, resulting in individual series of residual height SDS. These were sorted by cluster analysis and distributed into groups (clusters) according to similarity or dissimilarity (squared difference). We identified similar clusters, and named them 'growth tracks'. We found five pre-pubertal male growth tracks, each containing between 4 and 37% of the boys. Twenty boys could not be assigned to either one of the five tracks. Very similar results were obtained in girls, with five pre-pubertal growth tracks also, each containing between 3 and 50%. Twenty-three individuals grew irregularly and could not be assigned. Growth tracks are narrow, with an average width between 12.1 and 14.8% of the SD of body height. Most children exhibited almost horizontal height SDS patterns. Others showed linearly declining, rising, or intersection -shaped patterns. None of the patterns were predominantly found in particularly short or tall children. Preliminary data support the practical advantages of the concept of growth tracks.