Young girls are maturing earlier, according to a study published in the September issue of Pediatrics, the official journal of the American Academy of Pediatrics.
The study was sponsored by the Breast Cancer and the Environment Research Centers (BCERC). The BCERC were established in 2003 in partnership with the National Institute of Environmental Health Science (NIEHS) and the National Cancer Institute (NCI) to better understand the role of genetics and environment as it relates to breast cancer development. Their efforts are focused on prepubertal and pubertal stages of development as epidemiological studies have indicated women with breast cancer have a younger age of menarche.
Researchers theorize that longer exposure to the hormones estrogen and progesterone during a woman’s lifetime may play a genetic role in breast cancer development. Rapidly developing breast tissue during puberty may also be more susceptible to environmental toxins.
To assess the age of onset of puberty, over 1,200 girls from 6 to 8 years were recruited for this study between 2004 and 2006. The young girls were from three U.S. cities – New York, Cincinnati and San Francisco. Participants were split evenly across racial/ethnic groups (33.7% White; 30.7% Black and 29.9% Hispanic). Less than 5 percent of participants were Asian. Researchers used stage of breast development and other measurements to determine the maturation level of participants.
At 7 years, about 15% of the girls had reached puberty. Black non-Hispanic girls had the highest rate of maturity (23.4%), followed by Hispanics (14.9%) and Whites (10.4%). Asian girls had the lowest rate at 2.2%. These rates were much higher compared to those reported in another study conducted over 10 years ago. In that study, at 7 years only 5.0% of White girls and 15.4% of Black non-Hispanic girls had reached puberty.
By 8 years, more than a quarter of girls had reached puberty, with the incidence by race similar to that seen in 7 year olds. Black girls had the highest rate of maturity (42.9%) followed by Hispanics (30.9%) and Whites (18.3%). Asian girls had the lowest rate at 13.6%.
Based on the study, researchers concluded that young girls are reaching puberty at younger ages than they did 10 to 30 years ago. Although traditionally Black and Hispanic girls have developed at younger ages, White girls are catching up. These results are consistent with other studies that have been conducted recently.
Researchers are not sure why young girls are maturing earlier. But, one explanation is the soaring obesity rate in children. Regardless of sex or ethnicity, a higher BMI is associated with earlier periods as body fat can produce sex hormones. Environmental factors could also play a role. Bisphenol-A (BPA), a chemical found in hard plastics and believed to have estrogenic effects, is pervasive in today’s environment.
The Bottom Line
As parents, it is important to teach our children at an early age how to eat healthy, nutritious meals to support their growth and development. Yet, another reason may emerge as new studies determine the relationship of excess body fat during puberty and the risk of women developing breast cancer later in life.