Several studies have documented earlier onset of puberty in
girls over the past few decades. In a longitudinal study following more than
1,200 girls for seven years, researchers found those with higher BMI had
earlier onset of puberty, as measured by breast development, and that white
girls are entering puberty at younger ages than previously reported. The study,
“Onset of Breast Development in a Longitudinal Cohort,” in the December 2013
Pediatrics (published online Nov. 4), tracked girls in San Francisco,
Cincinnati and New York City. The age at onset of breast development varied by
race, BMI, and geographic location. In white, non-Hispanic girls, breast
development began at a median age of 9.7 years, which is earlier than
previously documented, according to the study authors. Black girls continue to
experience breast development earlier than white girls, at a median age of 8.8
years, compared to 9.3 years for Hispanic girls and 9.7 years for Asian girls.
However, BMI was a stronger predictor of puberty onset than race or ethnicity.
Study authors conclude the earlier onset of puberty in white girls is likely
due to greater obesity.
The American Academy of Pediatrics is an organization
of 60,000 primary care pediatricians, pediatric medical subspecialists
and pediatric surgical specialists dedicated to the health, safety and
well-being of infants, children, adolescents and young adults. For more
information, visit www.aap.org.