• Falling age of puberty in girls raises health, social concerns

    October 2010

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    For the past 20 years, the age of onset of puberty in girls has been falling. Now, new studies suggest the age of onset is continuing to drop among white and Latina girls. The news is cause for concern because of the possible link of early maturation to breast cancer as well as to social and emotional problems in young girls.

    Although there is yet to be a definitive answer, possible explanations for this phenomenon include a worldwide increase in obesity, high sugar and fat diets, lack of exercise and exposure to chemicals that disrupt endocrine. It is also unclear as to whether the age has stabilized or will continue falling. The National Institutes for Health places the norm for onset of puberty at 10 to 14 years.

    Girls in three areas studied

    A new multisite study, published in the journal Pediatrics, August 2010, looked at breast maturation and pubic hair development as indicators of maturation. It did not consider menstrual age.

    The study included 1,239 girls, ages 6 to 8, at three sites: East Harlem, greater Cincinnati metropolitan area and San Francisco Bay area. White, black and Hispanic girls each made up about 30 percent of the girls studied; 5 percent were Asian. The project was conducted at hospitals that are part of the Breast Cancer and the Environment Research Centers, which focus on the possible relationship between environmental exposures and breast cancer.

    The data, collected through interviews with caregivers and examinations by experts, revealed that, by age 7, 10.4 percent of the white, 23.4 percent of the black and 14.9 percent of the Latina girls had reached a stage of breast development marking puberty. The results were significantly higher than those from a landmark study in 1997 which showed that 5 percent of white girls entered puberty at age 7. The rates have apparently not changed for African-American girls. Hispanic girls were not included as a separate group in the 1997 study.


    “Early maturation in girls is associated with lower self-esteem and less favorable body image, as well as greater rates of eating problems, depression and suicide attempts.” 


    The Copenhagen Puberty Study, published in 2009 in Pediatrics, revealed similar results in European girls, although different methodologies were used. The researchers found significantly earlier breast development among girls born more recently.

    “Alterations in reproductive hormones and BMI did not explain these marked changes, which suggests that other factors yet to be identified may be involved,” they state.

    Risks of early puberty

    “Early maturation in girls is associated with lower self-esteem and less favorable body image, as well as greater rates of eating problems, depression and suicide attempts,” the authors of the American study write. They also point out that these girls are more likely to have sexual intercourse early and engage in risk-taking behaviors. There is also research that suggests early puberty leads to academic problems. “Health risks include greater risk for breast cancer and endometrial cancer,” they state. “Earlier maturation is also associated with hyper-insulinemia and elevated blood pressure.”

    Implications for future research

    The authors of the American study point out that they did not use a nationally representative sample of subjects nor did they look at development over time to account for environmental exposure, dietary differences or other factors related to race and ethnicity. Additionally, some subjects were selected because they had existing risks for early puberty. Also missing from this study is information about the onset of menstruation, which could indicate whether puberty has actually started.

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Page last updated: 5/23/2014 12:31:50 PM
  • What the news means for you

    Adolescents need to be educated about puberty

    Hatim A. Omar, MD, FAAP
    Pediatrics

    Wright, Heather, MDSince multiple sites were chosen for this more recent study, the researchers accounted for more variables, such as ethnicity, than the 1997 study did. They looked at Hispanic, African-American and Caucasian girls in different areas of the country. They have now proven what we physicians have been seeing every day in our practices.


    “Ten or 15 years ago I might have seen one or two girls a year who were menstruating by age 10. Now I see dozens.” 


    Ten or 15 years ago I might have seen one or two girls a year who were menstruating by age 10. Now I see dozens. The first indication that a girl is entering puberty is breast development; menarche is the culmination of that development and usually comes one to three years after breast development.

    Study benefits

    Part of the reason this study is important is that it should ease the anxiety of parents. In the past, if I saw a 7- or 8-year-old developing breasts, that would have been considered precocious puberty, which could be a symptom of some underlying pathology such as a tumor or glandular issue. Now, if there are no other symptoms, I can tell parents their daughter’s development is a normal variation.

    For the last 20 years or so, the average at which a girl started her period was 12. Now it’s 11.8 or 11.5 to 12 years of age, plus or minus four years. So that puts the age range from 8 to 16. Age 16 and above is not normal and would be considered late puberty, which could be related to genetics, endocrine factors, eating disorders or excessive involvement in sports.


    “There is also no clear evidence that girls who enter puberty early are more likely to have breast cancer. If they don’t have the genetic disposition to develop cancer, the age of puberty is probably irrelevant.” 


    Causes unclear

    The reasons for this trend in early puberty are unclear. There is just speculation at this point. Is it hormones in food or water? I can’t say with certainty either way. One thing that has changed in the last 20 years is that people are eating more high-fat foods. They’re also exposed to more sexual stimulation in the media. I have to presume both these issues have had some effect.

    Another change in foods is that we know animals and poultry are being raised to be fatter. So is it the fact that our kids are getting more calories and more fat or that there is something in the feed given animals that induces early puberty? We don’t know, but we do know that the start-up chemical for sex hormones is cholesterol.

    There is also no clear evidence that girls who enter puberty early are more likely to have breast cancer. If they don’t have the genetic disposition to develop cancer, the age of puberty is probably irrelevant.

    What parents can do

    Girls who enter puberty early are more likely to start sexual activity early and have more partners. You have a girl of 10 or 12 who physically looks like an 18-year-old. She’s having the same feelings as a mature woman, yet she’s mentally still a child, too young to make the right decisions. That’s why we need sex education and pregnancy prevention programs to start in the fifth grade.

    These girls are at greater risk of getting pregnant or contracting HPV, which can lead to cervical cancer. We know that 50 percent of kids will have sex before they enter the 10th grade. This is what we should be concerned about when we talk about early puberty.

    In research conducted at UK in 2003, we found that very few of the 409 adolescents we studied had adequate information about puberty and sexual issues. And most of them got that information after they had entered puberty. Boys were even less likely than girls to have been informed.

    Some parents fear that if we talk to kids about sex, they’re more likely to have sex. Actually, the opposite is true: The less you talk to them, the more likely they are to do it. They’re curious and everything they see around them is about sex. All they learn from their peers and from the Internet is that sex is fun. Nobody talks to them about the consequences. This is what we can change. We have to explain to them the consequences on their body, their brain, their academic progress. If we don’t talk to them, they’ll turn to their peers or to the Internet. It’s time to wise up and realize that knowledge is power.

    Dr. Omar is director of the UK HealthCare Young Parents Program and professor of pediatrics at the UK College of Medicine.

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