Black Women's Health Study (BWHS) shows exercise improves breast cancer risk for African American women
Regular exercise, including brisk walking, is associated with a decrease in the incidence of breast cancer in African American women. This recently published study found strong evidence linking physical exercise to a lower rate of breast cancer in African American women, a group in which previous evidence has been lacking.
In a large prospective study on the health of black women, the Black Women's Health Study (BWHS), researchers from Boston University's Slone Epidemiology Center in Massachusetts collected information about exercise habits, such as time spent exercising per week and type of exercise. They followed more than 44,000 African American women over a span of 16 years and observed whether they developed breast cancer. Their study was published in Cancer Epidemiology, Biomarkers & Prevention (2014; doi:10.1158/1055-9965.EPI-14-0448).
They found that women who exercised vigorously for seven or more hours each week were 25% less likely to develop breast cancer, compared to those who exercised less than 1 hour each week. Examples of vigorous activity include basketball, swimming, running, and aerobics. The results were similar if women walked briskly, but there was no benefit for walking at normal pace. The results did not differ by the estrogen receptor status of the breast cancer.
Breast cancer incidence was not associated with vigorous exercise at ages 30 years, 21 years, or in high school. Further, no significant association was found between breast cancer incidence and sitting for long periods at work or watching TV.
"Although expert review panels have accepted a link between physical exercise and breast cancer incidence, most study participants have been white women. This is the first large scale study to support that vigorous exercise may decrease incidence of breast cancer in African American women," said Lynn Rosenberg, ScD, professor of Epidemiology at Boston University School of Public Health and principal investigator of the Black Women's Health Study.