Forty years trends in timing of pubertal growth spurt in 157,000 Danish school children - PubMed (original) (raw)

Lise Aksglaede et al. PLoS One. 2008.

Abstract

Background: Entering puberty is an important milestone in reproductive life and secular changes in the timing of puberty may be an important indicator of the general reproductive health in a population. Too early puberty is associated with several psychosocial and health problems. The aim of our study was to determine if the age at onset of pubertal growth spurt (OGS) and at peak height velocity (PHV) during puberty show secular trends during four decades in a large cohort of school children.

Methods and findings: Annual measurements of height were available in all children born from 1930 to 1969 who attended primary school in the Copenhagen Municipality. 135,223 girls and 21,612 boys fulfilled the criteria for determining age at OGS and age at PHV. These physiological events were used as markers of pubertal development in our computerized method in order to evaluate any secular trends in pubertal maturation during the study period (year of birth 1930 to 1969). In this period, age at OGS declined statistically significantly by 0.2 and 0.4 years in girls and boys, respectively, whereas age at PHV declined statistically significantly by 0.5 and 0.3 years in girls and boys, respectively. The decline was non-linear with a levelling off in the children born between 1940 and 1955. The duration of puberty, as defined by the difference between age at OGS and age at PHV, increased slightly in boys, whereas it decreased in girls.

Conclusion: Our finding of declining age at OGS and at PHV indicates a secular trend towards earlier sexual maturation of Danish children born between 1930 and 1969. Only minor changes were observed in duration of puberty assessed by the difference in ages at OGS and PHV.

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Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Figure 1

Figure 1. Height velocity curves in 9 girls and 9 boys from the validation of the method.

Height velocity curves in a subset of 9 girls (A–I) and 9 boys (J–R) from the validation of the method. The complete set of measurements and the randomly selected annual measurements are illustrated with indications of age at onset and PHV judged by both visual and computerized methods independent of each other. Note Figure 1F and 1K, where ages at onset and PHV were not determined by computation. These children were recorded as having reached onset of pubertal growth and PHV, but the yearly measurement was too sparse to determine the pubertal growth. By looking at the complete set of measurements there was no doubt that all these children had reached onset and PHV and the interval censoring of these children was thus fully acceptable.

Figure 2

Figure 2. Trends in age at OGS and PHV.

Age at onset of pubertal growth spurt (Age at OGS) in boys (A) and girls (B), and age at peak height velocity (Age at PHV) in boys (C) and girls (D) according to year of birth. Curves are smoothed by 5-year intervals (e.g. 1930–1934, 1935–1939, 1940–1944 etc.) and presented with confidence intervals.

Figure 3

Figure 3. Validation of the method.

Correlation between manually determined and compute-based estimates of the age at OGS (as indicated by ▪) and at PHV (as indicated by x) in 20 girls (left panel) and 20 boys (right panel) with multiple height-measurements.

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