Girls Hitting Puberty Earlier, Study Says

The age of onset of puberty in girls continues to decline, according to a new study, which shows that the number of 7- and 8-year-old girls experiencing breast development is greater than it was even 10 years ago.

“What causes earlier onset of puberty isn’t entirely clear at this time, but we are looking closely at several different potential factors, including genes and environmental exposures, as well as how those two may interact with each other,” said lead author Frank Biro, MD, director of adolescent medicine at Cincinnati Children’s Hospital Medical Center and a professor of pediatrics at the University of Cincinnati (UC) College of Medicine, in a press release.

For the study, which is published in Pediatrics, Biro and colleagues observed 1,239 girls between the ages of 6 and 8 from the Cincinnati area, East Harlem, N.Y., and the San Francisco area. The researchers used various criteria of pubertal maturation, including the five stages of breast development known as the Tanner Breast Stages.

They found a higher prevalence of onset of breast development among girls at age 7 and 8, especially in white girls, compared to those observed in a study conducted more than 10 years ago and another study conducted 30 years earlier.

The study was conducted through the Breast Cancer and the Environment Research Centers, which were established by the National Institute of Environmental Health Science and the National Cancer Institute.