A new study finds African American women derive similar breast cancer risk reductions associated with multiple births and breastfeeding as white women, but that recent trends may lead to a rising risk. The study appears June 7, 2004 in the online edition of CANCER, a peer-reviewed journal of the American Cancer Society. The full study will be available via Wiley InterScience, and will appear in the July 15, 2004 print issue.
The protective effects of reproductive factors against breast cancer have been well documented in white populations. Few studies have investigated whether these same factors can be applied to other races. Overall, African American women have lower risks of breast cancer. Existing data conflict on whether parity and lactation confer similar protection in African Americans and whites.
Led by Dr. Giske Ursin of the University of Southern California Keck School of Medicine in Los Angeles researchers compared the effects of parity and breastfeeding on the risk of breast cancer among white and African American women aged 35 to 64 years old in the National Institute of Child Health and Development Women's Contraceptive and Reproductive Experiences (CARE) study.
The authors found live births and breastfeeding lowered the risk of breast cancer for both races. The overall risk reduction from these reproductive practices was more pronounced among white women, although the differences between the groups were not statistically significant. Among women aged 35 to 49, the risk reduction of breast cancer per live birth was 13 percent for white women and 10 percent for African American women. Among women aged 50 to 64, the risk reduction was 10 percent for white women and 6 percent for African American women per live birth.
In addition, the data found the longer a woman breastfed, the lower her risk of breast cancer. This was applicable only to the younger women, with the protection most pronounced during the first five years after pregnancy.
The study also found that younger African American women were having fewer pregnancies than in the past and, more importantly, breastfed less often and for shorter duration than white women. If this trend continues, the authors write, "then this could result in a more rapid increase in breast cancer rates in this group than in whites."