Lots of published evidence shows girls are reaching puberty earlier, and this is now generally accepted, but until now, there hasn't been as much research on whether today's boys are also showing a similar tendency.
AAP researchers designed and carried out the study through hundreds of pediatricians all over the US who belong to the AAP Pediatric Research in Office Settings (PROS) network and contribute data for research on children's health.
Data from this same PROS network was used in a large study that in 1997 showed US girls were reaching puberty earlier.
Parents and Doctors Need to KnowThe data for this latest study covers more than 4,100 boys, and was recorded by 212 pediatricians carrying out well-child care in 144 practices in 41 states.
American boys appear to be reaching puberty at a younger age, with African-American boys entering puberty earlier than white or Hispanic boys.
"All parents need to know whether their sons are maturing within the contemporary age range, but, until now, this has not been known for US boys."
To assess puberty in boys, pediatricians measured two features: genital and pubic hair, and testicular enlargement, both standard indicators of start of puberty.
The results showed that puberty onset was happening some 6 months to two years earlier than it was several decades ago, according to records from that time.
Ethnic DifferencesOverall, African-American boys are more likely to enter puberty earlier than white or Hispanic boys.
Across three ethnic groups, pediatricians recorded the earliest stage of puberty as 10.14 years in non-Hispanic white boys, 9.14 years in non-Hispanic African American boys and 10.4 years in Hispanic boys.
The authors write:
"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."