According to the journal Pediatrics, American girls are hitting puberty earlier than ever. In a study profiling 1,239 girls between the ages 6-8, researchers found that about 15% of the girls participating in the study, which was conducted in 2010, reached puberty by age 7. Scientists are not entirely sure of the reason girls are maturing at such a young stage, but they believe several factors, including obesity and environmental toxins, could be involved. Whereas girls in the U.S. typically used to reach puberty around age 10 or 11, the age at which girls today begin to menstruate and develop breasts has been dropping quickly. The early onset of puberty has “shortened the childhood of girls by about a year and a half” over the last 30 years, according to Sandra Steingraber, who wrote a report on precocious puberty in 2007.
Young girls whose bodies mature their brains face serious health risks, according to Marcia Herman-Giddens, an adjunct professor at the University of North Carolina-Chapel Hill. Early onset puberty raises the risks of girls dealing with depression, alcohol and drug abuse, and self-injurious tendencies such as eating disorders and attempted suicide. Later in life, the odds of breast and uterine cancers are significantly elevated due to the fact that they will have been exposed to estrogen for a longer period of time.
The effect of obesity on young girls has been explored as a reason for early onset puberty. In the past generation, boys and girls alike “have become less connected to nature and, in many ways, less free,” according to Chris Feudtner, a pediatrician at Children’s Hospital of Philadelphia. Children are less active than previous generations, and as a result are heavier; according to the Center for Disease Control and Prevention, 30% of America children are overweight or obese. Dr. Luigi Garibaldi, a professor of pediatrics and clinical director or pediatric endocrinology at Children’s Hospital of Pittsburgh, believes obesity has a role to play in precocious puberty. Garibaldi points out that in the 1700s, girls didn’t begin to menstruate until they were around 17 or 18, largely due to malnutrition. Dr. Frank Biro, the director of adolescent medicine at Cincinnati Children’s Hospital and the lead author of the study, also believes obesity is a critical factor in early onset puberty. Research has shown that children who are overweight have higher levels of leptin, a hormone that regulates appetite and is produced in fat cells. Although leptin is not solely responsible for starting puberty, research has suggested that puberty cannot start without the presence of leptin.
Environmental toxins have also been blamed for triggering early puberty. Numerous chemicals, which can be found in pesticides, household cleaners, and plastic products, can interfere with the hormone system. Bisphenol A (also known as BPA), an estrogen-like chemical found in numerous plastic and metal consumer products, has drawn the attention of scientists after it was discovered that BPA has caused early puberty in animals. There is speculation that BPA can cause early puberty in young girls. As with other chemicals, the effects of BPA are not entirely understood, although BPA is increasingly present in the population- according to the CDC, 90% of Americans have BPA in their bodies.
Several other factors contributing to early puberty are being examined by researchers. The rate of premature infants, which have increased by 18% since 1990, may be a contributing factor. Babies who were born early or at a low birth weight play “catch-up growth,” which could eventually lead to being overweight, according to Steingraber. Rapid weight gain initiated by prematurity makes children less sensitive to insulin, which increases their chance of developing diabetes. It is also possible that genetics play a factor; studies have shown that black girls consistently hit puberty earlier than white girls. This is attributed to the fact that black girls generally have higher levels of insulin and leptin, which, as previously mentioned, may influence the onset of puberty. In the study published in Pediatrics, 23% of the black girls studied had started puberty by age 7, compared to 10% of white 7-year-olds.
In an effort to further research the causes of precocious puberty, the National Institutes of Health is funding research to examine the effects of environmental causes on young girls. Dr. Frank Biro, who is involved with the study, will be working with other researchers to test more than 1,200 girls for exposure to chemicals. The National Children’s Study will be conducting similar research on 10,000 children from before birth to age 21 to assess the effects of environmental influences.