Boys in USA, like girls, showing signs of early puberty

Michelle Healy, USA TODAY | USATODAY

American boys are showing signs of starting puberty six months to two years earlier than they did 30 to 40 years ago, finds new research out today.

The new study found signs of puberty in white boys — genital and pubic hair growth and early testicular development — at 10.14 years old, more than a year earlier than in a classic British study of white boys in 1969 (11.60 years). And African-American boys in the new study showed signs of puberty even earlier, at 9.14 years old; Hispanic boys did at 10.40 years old.

The new findings follow widely accepted research documenting earlier physical maturation among U.S. girls, and are in line with other research finding earlier puberty onset among boys in Denmark, Sweden, Great Britain, Italy and China, according to the study in November's Pediatrics. It was released today at the American Academy of Pediatrics' annual meeting in New Orleans.

There has been considerable research on the start of puberty in girls, "but boys have not been studied nearly as much," says Marcia Herman-Giddens, an adjunct professor at the University of North Carolina School of Public Health in Chapel Hill, and lead author of both the new study and a landmark 1997 study on girls.

The findings do not come as a complete surprise, she says, noting similar findings in a recent longitudinal study on boys and puberty, and recent growth data showing boys achieving their mature height earlier. "They can't do that without entering puberty earlier."

For the study, researchers analyzed data on 4,100 boys ages 6 to 16 collected from 144 pediatric offices in 41 states. It was designed to report only physical changes and not hormonal, social or psychological changes associated with puberty.

Earlier puberty seen in boys, just like in girls Researchers have found signs of puberty in American boys up to two years earlier than previously reported _ age 9 on average for blacks, 10 for whites and Hispanics. (Oct. 20)

That African-American boys were more likely to start puberty earlier than whites or Hispanics "is consistent with the data for girls as well," says pediatrician Frank Biro, director of adolescent medicine at Cincinnati Children's Hospital Medical Center. Biro, who studies early maturation in girls, was not involved in the new study.

It's "a gross oversimplification" to assume differences in onset of puberty are related only to genetic differences between racial and ethnic groups, he says. "Race and ethnicity incorporate a lot of different factors, some of them genetic, some of them cultural." Dietary habits and socioeconomic issues, for example, can be significant, he adds.

The research did not look at what caused the onset of earlier puberty, but authors say that "current environmental factors, including exposure to chemicals, changes in diet, less physical activity and other modern lifestyle changes and exposures, may be related."

Whatever the cause, the outcome has consequences, says Herman-Giddens: "They're going to be interested earlier in sexual activity and other behaviors associated with adolescence that may be high-risk behaviors."

Their brains, however won't necessarily be prepared to follow their bodies. "Their brains are taking their own sweet time to mature," she says.

"Kids who mature physically at a younger age tend to be placed in situations that are consistent with how they look, which is older than they really are," says assistant professor of human development Jane Mendle, director of the Adolescent Transitions Lab at Cornell University, Ithaca, N.Y.

But "just because a child looks mature doesn't mean he is necessarily ready for the social and emotional challenges, which come along with that level of maturity."