Frank M. Biro, M.D.; Susan M. Pinney, Ph.D.; Robert A. Hiatt, M.D., Ph.D.; Lawrence H. Kushi, Sc.D.; Mary S. Wolff, Ph.D.
University of Cincinnati; Mount Sinai School of Medicine, Michigan State University, University of California, San Francisco; Kaiser Foundation Research Institute
NIEHS Grants U01ES012770, U01ES012771, U01ES012800, U01ES012801, U01ES019435, U01ES019453, U01ES019454, U01ES019457, P01ES009584, P30ES006096, T32ES010957
Research that is part of the NIEHS Breast Cancer and the Environment Research Program found that breast development is occurring at an earlier age, and that earlier development was strongly associated with greater body mass index (BMI). Earlier than average maturation is a risk factor for obesity and hypertension, as well as breast, ovarian, and endometrial cancer.
From 2004 to 2011, the researchers followed girls in the San Francisco Bay Area, Greater Cincinnati, and New York City who were 6 to 8 years old when enrolled in the study. At regular intervals, trained and certified staff used Tanner staging to assess sexual maturity. They found that the age at onset of breast development (stage 2) varied by race/ethnicity, BMI at baseline, and geographical site. For African American, Hispanic, white non-Hispanic, and Asian participants, the median age at onset of breast stage 2 was 8.8, 9.3, 9.7, and 9.7 years, respectively. Girls with BMIs greater than 85th percentile reached breast stage 2 at younger ages.
Compared to data from studies conducted in the 1990s, white non-Hispanic girls are now maturing at younger ages while the maturation age for African American girls is similar to that found in the earlier studies.
Citation: Biro FM, Greenspan LC, Galvez MP, Pinney SM, Teitelbaum S, Windham GC, Deardorff J, Herrick RL, Succop PA, Hiatt RA, Kushi LH, Wolff MS. 2013. Onset of breast development in a longitudinal cohort. Pediatrics 132:1019-1027.