Study Finds Earlier Onset of Puberty in Girls

Monday, August 09, 2010

The age of onset of puberty in girls continues to decline.

A new study shows that the number of 7- and 8-year-old girls who have breast development is greater than that indicated in studies conducted 10 to 30 years earlier.

“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,” says Frank Biro, M.D., director of adolescent medicine at Cincinnati Children’s Hospital Medical Center and the study’s lead author.

The study is published online in the Aug. 9 issue of Pediatrics, the journal of the American Academy of Pediatrics.

The study was conducted through the Breast Cancer and the Environment Research Centers, which were established in 2003 by the National Institute of Environmental Health Science and the National Cancer Institute.

Previous studies have shown a link between an earlier age of menarche (first menstrual period) and an increased risk of breast cancer.

Dr. Biro and his colleagues studied over a period of time 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 well-established criteria of pubertal maturation, including the five stages of breast development known as the Tanner Breast Stages.

The researchers 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 Breast Cancer and the Environment Research Centers include the University of Cincinnati, the Fox Chase Cancer Center in Philadelphia and collaborators at University of Alabama Birmingham and Mount Sinai School of Medicine, Michigan State University, and the University of California San Francisco Comprehensive Cancer Center and Kaiser Permanente Northern California and Zero Breast Cancer. The epidemiology programs were established to conduct studies in pre- and early puberty girls, in recognition of puberty as a potential window of susceptibility for breast cancer.

The study was funded by a grant to the University of Cincinnati from the National Institutes of Health. Dr. Biro is a professor of pediatrics at UC.

About Cincinnati Children’s

Cincinnati Children’s Hospital Medical Center is one of just eight children’s hospitals named to the Honor Roll in U.S. News and World Report’s 2010-11 Best Children’s Hospitals. It is ranked #1 for digestive disorders and highly ranked for its expertise in pulmonology, cancer, neonatology, heart and heart surgery, neurology and neurosurgery, diabetes and endocrinology, orthopedics, kidney disorders and urology. Cincinnati Children’s is one of the top two recipients of pediatric research grants from the National Institutes of Health. It is internationally recognized for quality and transformation work by Leapfrog, The Joint Commission, the Institute for Healthcare Improvement, the federal Agency for Healthcare Research and Quality, and by hospitals and health organizations it works with globally. Additional information can be found at

Contact Information

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