Earlier Puberty in Danish Girls

A 15-year study of young girls in Denmark found that the average age of breast development has fallen by a full year compared to girls studied in the early 1990s.
The findings, published this month in the journal Pediatrics, add to a growing body of evidence that the timing of puberty is changing, possibly related to environmental exposure to endocrine-disrupting chemicals that mimic estrogen in the body.
While the conventional wisdom has long been that girls today mature sooner than their counterparts from earlier generations, the issue remains a source of debate in the scientific community. […]
The average age for breast development among the current generation of girls was 9.86 years, compared to an average age of 10.88 years among the children studied in the early 1990s. While it has long been speculated that an increase in childhood obesity could explain earlier breast development, the difference in breast development remained significant even after controlling for body mass index, according to the study.
It’s important to note that while puberty, in the form of early breast development, appeared to be starting sooner in the Danish girls, the average age of menarche did not change as quickly. In the study, the average age of menstruation in the girls studied between 2006 and 2008 began only three-and-a-half months earlier compared to the girls studied from 1991 to 1993. This suggests that the age at which girls fully mature hasn’t changed much in the past 40 years, but because puberty starts earlier, the duration of puberty is longer than for past generations. […]
While historical shifts in puberty appear largely due to improved health and living conditions, the more recent changes in earlier breast development are more worrisome. Studies have documented that a number of chemicals may act as endocrine disruptors and have estrogenic effects on the body.
The study’s lead author, Dr. Lise Aksglaede of Copenhagen University Hospital, said it’s not clear why onset of puberty has appeared to change in such a short amount of time among the Danish school girls. […]

More at The New York Times