Can belonging to certain ethnic groups be associated with early puberty? Apparently so.
A study published recently in Pediatrics shows that those in some ethnic groups are more likely to go through puberty earlier than those in other groups. The study followed more than 1,200 girls in the U.S., who were from various ethnic backgrounds, for seven years, whose ages ranged from six to eight at the study's start.
The researchers found that the median age for the start of breast development—considered a key marker for puberty—for white non-Hispanic girls was 9.7 years, which is earlier than previous studies have found. For African Americans and Hispanics, however, the median ages were 8.8 and 9.3 respectively, a significant difference from that of the white girls.
But why should we care about early puberty? According to study co-author Julianna Deardorff, Ph.D., an assistant professor of maternal and child health at the UC Berkeley School of Public Health, early puberty has been linked to depression, body-image issues and substance use at a younger age. When these girls become adults, they are at higher risk for cardiovascular diseases, breast cancer and cervical cancer.
Like previous researchers, these scientists found that the girls in the study who were overweight—as determined by their Body Mass Indexes, or BMIs— were more likely to go through puberty earlier than normal. As the authors wrote, "The obesity epidemic appears to be a prime driver in the decrease in age at onset of breast development in contemporary girls."
But these researchers determined the sexual maturity of the study subjects by carefully monitoring their breast development. This method, which negated the need to estimate the start of the girls's breast development, has not been used often because it requires hands-on physical examinations of the breasts. “One reason this study is unique is that we have very good data on when girls began their breast development. By palpating the breasts, we were able to distinguish breast tissue from fat,” says Deardorff.
Some experts think that early puberty in certain groups may be related to genetic differences. But others suggest it's likely due to differences in socioeconomic status and environmental factors (such as lack of access to healthy food), which we need more research on. In fact, Deardorff and her research team are now finishing work on another study on early puberty, and she expects results to confirm that much of the variance between ethnic groups is related to both high BMI and low socioeconomic status.
For Deardorff, these differences in early puberty are a marker of inequity. For example, obesity is much more prevalent among African American and Mexican American adolescents than in non-Hispanic whites in the US. And data from the National Center for Health Statistics shows that in recent years, obesity rates have increased more significantly in African American boys and girls than in Caucasians.
The take-home: While we are seeing earlier puberty across all ethnic groups, studies like Deardorff’s drive home the fact that African American and Hispanic girls in the U.S. are at higher risk.
“We really need to pay attention to this as a social justice issue,” Deardorff says.
I couldn’t agree more.