The rates of early puberty for girls have doubled in a little more than a decade, a new study of girls between 6 and 8 years old finds.
Some 10 percent of 7-year-old white girls were developing breasts compared to 5 percent more than 10 years ago, researchers found. For young black girls, early maturation was seen in 25 percent of 7-year-olds, also an increase from previous studies.
The results come from a study of more than 1,000 girls in three American cities. Researchers at the Cincinnati Children's Hospital who led the work say the rise in early puberty is linked to the rise in obesity in U.S. children, but they also say environment and genetics may be factors.
The results were just published online by the journal Pediatrics.
Previous studies have shown a link between an earlier age for the start of menstruation and an increased risk of breast cancer. Researchers also noted that earlier maturation of girls is associated with lower self-esteem, and greater rates of depression, eating problems and suicide attempts.
Dr. Marcia E. Herman-Giddens, a researcher at the University of North Carolina, Chapel Hill, told the New York Times that if there is an ideal age when girls should reach puberty, no one knows what it is.
And that's been the case all the while that the age of puberty has been declining. Thirteen years ago, Herman-Giddens remarked that no adequate studies on norms for the age of puberty had been done. A study she led at the time found that by age 8, 48 percent of black girls and 15 percent of white girls showed signs of puberty.