Puberty occurring at younger ages among white girls

**Biro FM. Pediatrics.2010;126:e1-e8.**

Since 1997, the percentage of 7-year-old white girls who reached pubertal maturation has nearly doubled, according to data from a recent study.

Data published in a 1997 issue of Pediatrics demonstrated that at age 7, 5% of white participants had reached breast stage ≥2. Recent results from a multi-center study demonstrate an increase in that statistic: 10.4% of white girls attained breast stage ≥2 at 7 years (P<.001). In addition, the proportion of black non-Hispanic girls who reached breast stage ≥2 by age 7 was also higher compared with the 1997 results (23.4% vs. 15.4%; P=.09).

As part of the National Institute of Environmental Health Science and National Cancer Institute’s Breast Center and the Environment Research Centers, researchers examined assessment methods and maturation status for a multisite cohort of girls as old as 8 years. Together, they developed a pubertal maturation assessment, which defined onset of maturation as breast stage 2.

The study enrolled 1,239 girls aged 6 to 8 years from East Harlem, the greater Cincinnati metropolitan area and the San Francisco Bay area. The researchers measured baseline characteristics by interviewing caregivers and taking anthropometric measurements. Using logistic regression, they identified factors associated with pubertal maturation; they used linear regression to study factors associated with height velocity.

According to the researchers, 10.4% of white girls, 23.4% of black non-Hispanic girls and 14.9% of Hispanic girls reached breast stage ≥2 by age 7. By age 8, 18.3% of white girls, 42.9% of black non-Hispanic girls and 30.9% of Hispanic girls had reached breast stage ≥2. A higher BMI percentile, older age, black race and being from the New York or Cincinnati site were all associated with breast stage ≥2, according to the logistic regression model. In addition, pubertal status was the strongest predictor for height velocity, according to the linear regression model (P<.0039); Asian race was the only other significant predictive factor (P=.017).

“The ability to capture with reasonable accuracy the timing and tempo of pubertal breast maturation in this prospective study … should allow us to pool data for detecting associations between specific factors, including diet and environmental chemicals, with variations in patterns of pubertal maturation,” the researchers wrote.

Though various racial/ethnic and socioeconomic statuses were represented, the researchers acknowledge that this is not a nationally represented sample. In addition, site-specific differences in maturation at baseline suggest varying dietary patterns, chemical exposures and racial/ethnic differences. Therefore, further examinations using longitudinal observations and more information on exposure and diet are needed, the researchers noted.

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