SAN ANTONIO – African-American women had half the risk of developing estrogen receptor–negative breast cancer if they exercised vigorously 3 hours per week, according to data from the Black Women’s Health Study.
The findings are based on nearly 20 years of follow-up on 44,704 women in the prospective, observational Black Women's Health Study. During this period, 1,377 subjects were diagnosed with invasive breast cancer, including 327 with ER-negative disease.
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Black women who exercised 3 hours or more per week had a 47% reduction in the risk of ER-negative breast cancer.
Black women who reported having engaged in vigorous exercise from high school onwards for a lifetime average of 3 hours or more per week had a 47% reduction in the risk of ER-negative breast cancer, compared with women exercising vigorously for less than 1 hour per week after adjusting for age, education, parity, and dietary pattern, Lucile Adams-Campbell, Ph.D., said at the San Antonio Breast Cancer Symposium.
Exercise proved unrelated to the risk of developing the generally more indolent ER-positive breast cancers in this population, said Dr. Adams-Campbell, professor of oncology at the Georgetown University Lombardi Comprehensive Cancer Center in Washington, D.C.
The inverse relationship between vigorous exercise and ER-negative breast cancer risk was statistically significant only among postmenopausal black women. In that population, the adjusted risk was reduced by 59% in participants with a lifetime average of at least 3 hours of exercise per week, compared with less than 1 hour.
The Centers for Disease Control and Prevention defines vigorous exercise as more than 6.0 metabolic equivalents (more than 7 kcal/min). Examples of activities through which this is readily accomplished include jogging, bicycling at more than 10 mph, or briskly walking uphill.
Dr. Adams-Campbell is a coleader of the ongoing Black Women’s Health Study, which aims to shed light on the elevated risks of hypertension, stroke, diabetes, lupus, and other diseases present in African-American women. The study is funded by the National Cancer Institute. Dr. Adams-Campbell reported having no relevant financial interests.