(HealthDay News) — Exercise may be a potentially modifiable risk factor for breast cancer in African-American women, according to a study published online August 7 in Cancer Epidemiology, Biomarkers & Prevention.

Lynn Rosenberg, ScD, from Boston University, and colleagues utilized prospective data from 44,708 participants (aged ≥30 years at baseline) of the Black Women’s Health Study to assess vigorous exercise and walking in relation to incidence of breast cancer. Invasive breast cancer (1,364 patients), estrogen receptor-positive (688 patients) cancer, and estrogen receptor-negative (405 patients) cancer were evaluated.

The researchers found that vigorous exercise at baseline was inversely associated with overall breast cancer incidence (P=0.05), with an incidence rate ratio of 0.74 for at least seven hours/week vs. less than one hour/week. Estrogen receptor status did not affect the association. Similar reductions in risk were seen with walking for at least seven hours/week and vigorous exercise. There was no association between breast cancer incidence and vigorous exercise at age 30, age 21, or in high school. There was also no association between incidence and sitting for long periods at work or watching television.

“High levels of vigorous exercise or brisk walking may be associated with a reduction in incidence of breast cancer in African-American women,” the authors write.

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