Data from racially and ethnically diverse US boys are needed to determine ages of onset of secondary sexual characteristics and examine secular trends. Current international studies suggest earlier puberty in boys than previous studies, following recent trend in girls.
Two hundred and twelve practitioners collected Tanner stage and testicular volume data on 4131 boys seen for well-child care in 144 pediatric offices across the United States. Data were analyzed for prevalence and mean ages of onset of sexual maturity markers.
Mean ages for onset of Tanner 2 genital development for non-Hispanic white, African American, and Hispanic boys were 10.14, 9.14, and 10.04 years and for stage 2 pubic hair, 11.47, 10.25, and 11.43 years respectively. Mean years for achieving testicular volumes of ≥3 mL were 9.95 for white, 9.71 for African American, and 9.63 for Hispanic boys; and for ≥4 mL were 11.46, 11.75, and 11.29 respectively. African American boys showed earlier (P < .0001) mean ages for stage 2 to 4 genital development and stage 2 to 4 pubic hair than white and Hispanic boys. No statistical differences were observed between white and Hispanic boys.
Observed mean ages of beginning genital and pubic hair growth and early testicular volumes were 6 months to 2 years earlier than in past studies, depending on the characteristic and race/ethnicity. The causes and public health implications of this apparent shift in US boys to a lower age of onset for the development of secondary sexual characteristics in US boys needs further exploration.
Comments
Earlier puberty in boys and rising prostate cancer incidence
Herman-Giddens et al report that the observed mean age of puberty in boys today is 6 months to almost 2 years earlier than in older studies dating back to 1970. At that time, 11.5 to 11.75 was the mean age of puberty in whites. Herman-Giddens et al found a current mean age of 10.1 in whites. The study of Herman-Giddens et al corroborates research on girls, whose breasts develop earlier than in the past. Herman-Giddens et al note that the public health implications need further exploration. (1)
One public health implication may be increased prostate cancer incidence, since early menarche is a risk factor for breast cancer.(2) The prostate cancer incidence has risen from 95 per 100,000 in 1975 to 250 per 100,000 in 1991. Although long-term incidence data indicate a decrease in prostate cancer since 2000, delay-adjusted rates in the most recent time period have increased from 155 (per 100,000) in 2005 to 171 in 2007. (3) Moreover, the long term trend is definitely upward.
Herman-Giddens et al did not analyze weight extensively, but the heaviest boys were entering puberty earlier. It is unclear if weight gain precipitated puberty or was a consequence. In girls adiposity is a risk factor for early menarche and breast cancer.(4) In any event, increasing childhood obesity is detrimental to health, and continued efforts are needed to combat it. (5)
Reference List
1. Herman-Giddens ME, Steffes J, Harris D, Slora E, Hussey M, Dowshen SA, et al. Secondary Sexual Characteristics in Boys: Data From the Pediatric Research in Office Settings Network. Pediatrics. 2012.
2. Kelsey JL, Gammon MD, John EM. Reproductive factors and breast cancer. Epidemiol Rev. 1993;15:36-47.
3. Siegel R, Ward E, Brawley O, Jemal A. Cancer statistics, 2011: the impact of eliminating socioeconomic and racial disparities on premature cancer deaths. CA Cancer J Clin. 2011;61:212-236.
4. Rosenfield RL, Lipton RB, Drum ML. Thelarche, Pubarche, and Menarche Attainment in Children With Normal and Elevated Body Mass Index. Pediatrics. 2009;123:84-88.
5. Ebbeling CB, Pawlak DB, Ludwig DS. Childhood obesity: public- health crisis, common sense cure. Lancet. 2002;360:473-482.
Conflict of Interest:
None declared
Also public health perspective
The acceleration of the maturity of children is a phenomenon the humanity watch with different degree of attention for at least 100 years. This process is coincided with the enormous increase of longevity. It is quite simple to conclude that the acceleration of maturity is the positive process, that acceleration is in some way reflect the welcome changes. Unfortunately, some data invite us to the cautious approach.
In the cross-sectional studies it was shown, that the very health cadets, selected for military training, are 'younger' than population by their blood variables.[1] Later in the cohort study it was shown that subjects who has the blood parameters more 'mature', i.e. advanced further from the adolescent values to the adult ones, are the subjects who earlier develop the chronic conditions.[2]
The situation with accelerated development of children in this sense is quite similar to the situation with overweight: while prevalence of overweight is increasing in parallel to the longevity of the population, in the cohort analysis the overweight subjects develop chronic conditions earlier. I believe that new cohort studies and/or new analysis of the data from the cohorts needed to understand the fine interactions of these processes. Reference List
(1) Spaulding S, Pate JC, Crum JW. Age difference in hematological parameters of young adults: A study of the United States Corps of Cadets. Milit Med 1978; 143(10):700-702.
(2) Vlassov VV. Changes in blood hemoglobin concentration of middle- aged healthy men. Milit Med 1999; 164(4):311-315.
Conflict of Interest:
None declared