The Associated Press recently reported on a study alleging that American girls reach puberty earlier than commonly believed, with nearly half of black girls and 15 percent of white girls beginning to develop sexually by age 8.
The study, undertaken by Marcia Herman-Giddens of the University of North Carolina at Chapel Hill, raises what the AP says are “troubling questions about whether environmental estrogens, chemicals that mimic the female hormone estrogen, are bringing on puberty at an earlier age.”
Yet a review of the study’s methodology shows that there may be considerably less to the story than meets the eye. The study involved 17,000 girls ages 3 through 12. At age 8, 48.3 percent of the black girls and 14.7 percent of the white girls had begun developing breasts, pubic hair, or both. Menstruation occurred at age 12.16 in blacks on average and age 12.88 for whites.
As Herman-Giddens herself points out, the average age for menstruation for white girls has remained unchanged for 45 years, and it begins just four months earlier for black girls than it did 30 years ago. Improved nutrition and lower levels of poverty could well account for the earlier onset of puberty among blacks, Herman-Giddens acknowledged.
Moreover, the study shows a trend for black girls (who comprise just 9.6 percent of the sample), but not for whites. Rather than raising “troubling questions” about the effects of environmental estrogens, the study raises troubling questions about why the AP chose to draw premature conclusions from data which do not support the thrust of the story.
