Early puberty tied to obesity

New data published in Pediatrics bolster scientific evidence indicating that the onset of puberty is occurring at younger ages in girls, with results pointing to obesity as a strong predictor for early breast development.

“The impact of earlier maturation in girls has important clinical implications involving psychosocial and biologic outcomes,” study researcher Frank Biro, MD, of the division of adolescent medicine at Cincinnati Children’s Hospital Medical Center, said in a press release. “The current study suggests clinicians may need to redefine the ages for both early and late maturation in girls.”

BMI effect on pubertal onset

For their study, Biro and colleagues longitudinally followed 1,239 girls from the three puberty study sites of the Breast Cancer and the Environment Research Program (BCERP) — San Francisco Bay Area, Cincinnati and New York City — for a mean of 4.3 years from 2004 to 2011. They evaluated sexual maturity via a standardized method based on Tanner staging that used observation and palpation to evaluate breast development. Age at enrollment ranged from 6 to 8 years.

Results indicated that age at onset of breast development varied by several factors, including race/ethnicity, BMI and geographic location. Median ages at onset of breast stage 2 were 8.8 years for black girls, 9.3 years for Hispanic girls and 9.7 years for white and Asian girls. The finding that black girls experienced breast development at an earlier age than white girls is consistent with previous findings, according to the researchers.

However, regardless of race/ethnicity, BMI appeared to be the strongest predictor of age at onset of breast development. Girls with BMI greater than the 50th percentile were more likely to reach breast stage 2 compared with those with BMI less than the 50th percentile (P=.001 for trend), and girls with BMI in the 85th percentile or greater matured earlier than those with BMI less than the 85th percentile, according to the study findings. Additionally, BMI accounted for 14.2% of variance of all the covariates included in the researchers’ model for analysis.

Of those included in the study, 39% of black, 44% of Hispanic, 26% of white and 12% of Asian girls had a BMI in the 85th percentile or greater.

When compared with two large cross-sectional studies — Pediatric Research in Office Settings and National Health and Nutrition Examination Survey III — conducted 10 to 20 years ago, the researchers found that breast development occurred earlier among white girls but not black girls in the BCERP.

Despite the association between higher BMI and earlier onset of puberty, the exact mechanisms by which they are linked remains unclear and requires further study, the researchers wrote.

Early puberty not the ‘new normal’

In an accompanying commentary, Marcia E. Herman-Giddens, PA, MPH, DrPH, of the Gillings School of Global Public Health at the University of North Carolina at Chapel Hill, said the study’s findings add to the body of evidence showing that puberty is occurring at younger ages, but they also raise many questions, including the role that other factors besides obesity play in early puberty.

“Each individual girl is exposed to multiple factors in today’s environment, many not present decades ago, that may potentially influence her pubertal onset. Given that the exact trigger for pubertal initiation is still unknown, we can hardly fully understand the interactions of factors known to affect puberty, even with current sophisticated statistical modeling,” Herman-Giddens wrote.

Because of the detrimental psychosocial effects, however, Herman-Giddens said clinicians should not accept premature development as the “new normal” due to these study results, but emerging data on early puberty have at least spurred researchers to further investigate the potential causes, which is a major step forward.

“With each new study in the past 2 decades, we hope the age of ‘early puberty’ has bottomed out,” Herman-Giddens wrote. “When each ‘new study’ has been published, however, we find the trend toward early puberty has continued. Fortunately, we have moved beyond controversy about the data and are responding to the wake-up call.”

For more information:

Biro FM. Pediatrics. 2013;doi:10.1542/peds.2012-3773.

Herman-Giddens ME. Pediatrics. 2013;doi:10.1542/peds.2013-3058.

Disclosure: The researchers and Herman-Giddens report no relevant financial disclosures.