Micro and macro perspectives in auxology: findings and considerations upon the variability of short term and individual growth and the stability of population derived parameters

Abstract

The present paper links the two most contrasting aspects of auxology, and addresses the apparent discrepancy between the variability and pulsatility of short term individual growth, and the stability of population derived parameters. When body stature is measured at monthly intervals, an irregular incremental pattern becomes obvious, with a number of large scale components such as series of prepubertal and pubertal growth spurts, seasonal influences on height gain, and influences of the psychosocial and economic background. When measurement intervals decrease, the patterns of stature increment appear even more irregular, and a number of short scale components become apparent, that are distinct from measurement error. Observations are presented that suggest growth being a pulsatile, a periodic, a saltatory, respectively a chaotic event as suggested by some recent studies in animals and in human newborns. Accurate measurements of the lower leg at intervals of 24 hours support the idea of short term growth being characterized by chaotic series of ‘mini growth spurts’ that occur at intervals of approximately 4–9 days. The amplitude of mini growth spurts ranges between 2 and some 10 mm, and also growth velocity of each spurt varies considerably so that one spurt needs between less than one and up to several days for completion. The very opposite of the variability of individual growth was found in populations. A meta-analysis of 40 male and 51 female European and US American growth studies revealed an almost uniform general pattern of average stature increment during the last 100 years. An additional analysis of stature variation of very large Japanese and Czechoslovakian growth surveys, with all together more than 23 000 000 measurements, and more than 500 000 German preschool and school measurements, suggested similar uniformity in the standard deviation of stature.