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Girls are beginning puberty at younger age, study finds

For more than a decade scientists have been debating whether girls are entering puberty at earlier ages — and, if so, what might be causing it.

A study published today in the journal Pediatrics raises the issue yet again. A team of researchers from across the country report that girls — particularly white girls — are more likely today to begin developing breasts at age 7 or 8 than they were in the 1990s.

Specifically, the study (which involved 1,200 girls) found that 10.4 percent of 7-year-old white girls had begun to develop breasts. This compares to 5 percent in a similar 1997 study.

The current study also found that 23.4 percent of black girls had begun to develop breasts at age 7 — but that percentage hadn’t shifted significantly (statistically speaking) from 1997.

This trend isn’t just happening in the U.S. Last year, Danish researchers reported that the average age for breast development in their country had dropped from 10.88 to 9.86 within a 15-year period from the early 1990s to the mid-2000s.

As the authors of today’s Pediatrics study point out, these findings have significant physical and psychological health ramifications for girls. Other research has found that earlier maturation is associated with lower self-esteem, increased risk of eating problems, depression and suicide attempts. Girls who experience a “precocious puberty” (as it’s called in the medical world) are also more likely to start having sex at a younger age than their peers.

Furthermore, early puberty — particularly an early menarche (first menstrual period) — is associated with an increased risk of type 2 diabetes in adulthood and with breast cancer. The girls in this study are going to be followed for another five years to determine if they also begin menstruating at an earlier average age than past generations.

What might be causing girls to be experiencing earlier maturation? The two main suspects are the rising incidence of childhood obesity (overweight girls tend to enter puberty earlier) and exposure to endocrine disruptors, chemicals that are known to disrupt the body’s endocrine, or hormone, system.

A study published in April found an association between a high exposure (determined by urine samples) to three common classes of chemicals — phenols, phthalates and phytoestrogens — and early breast development.

All studies have their limitations, of course, and this current Pediatrics one is no exception. As the authors point out, their study was not nationally representative and did not take into account such factors as dietary patterns and exposure to chemicals.

Furthermore, not all scientists agree on what’s the ideal age for entering puberty.

For two good synopses of the new study and the research that led up to it, read Todd Neale’s report in MedPage Today and Denise Grady’s in the New York Times. (Grady’s report also includes a good summary of the controversy surrounding this topic.)

For guidelines on how to avoid exposing your daughters (and sons) to endocrine disruptors, download (for free) the various “Smart” publications from the Minnesota-based Institute for Agriculture and Trade Policy. You’ll be surprised at how many of these chemicals are in foods and products your family eats and uses every day.

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Comments (1)

  1. Submitted by Bill Gleason on 08/09/2010 - 11:30 am.

    As noted by the author, endocrine disruptors are likely culprits.

    Phthalate esters are particularly suspect and evidence has been around for some time of premature sexual development in girls in Puerto Rico and unusually high serum concentrations of phthalate esters.

    For a leading reference see:

    http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2556932/

    Identification of phthalate esters in the serum of young Puerto Rican girls with premature breast development.

    This was published in 2000 and further evidence is accumulating in favor of problems with these compounds.

    It should also be noted that abnormal testicular development in young boys also may be linked to phthalate esters.

    What to do? Someone should be looking very hard into the use of more biocompatible plasticizers, e.g. esters of citric acid, a compound found normally in human metabolism.

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