Researchers writing in BMC Cancer say that post-menopausal women who engage in moderate or vigorous exercise have reduced risk of breast cancer.

Over 110,000 post menopausal women were asked to rate their level of physical activity at ages 15-18, 19-29, 35-39, and in the past 10 years. It was found, over 6.6 years of follow up, that women who engaged in more than 7 hours per week of moderate-to-vigorous exercise for the last ten years were 16% less likely to develop breast cancer than those who were inactive. However, no link was observed between breast cancer risk and physical activity in women who were active at a younger age.

“With an estimated 182,460 new cases diagnosed in the United States in 2008, breast cancer is recognized as the most common cancer affecting U.S. women,” says Dr. Tricia M Peters from the U.S. National Cancer Institute, Bethesda, Maryland, who headed up an international team of researchers.

Vigorous exercise has been hypothesized to reduce cancer risk for some time. However, this new study is one of the first prospective investigations to look at the importance of various intensities of exercise at different stages in an individual’s life.

Peters concludes, “Our findings could help inform the mechanisms of the physical activity-breast cancer relationship. With breast cancer still claiming so many lives, all the information of potential preventive measures we can get is vita.”

Article: Tricia M Peters, Steven C Moore, Gretchen L Gierach, Nicholas J Wareham, Ulf Ekelund, Albert R Hollenbeck, Arthur Schatzkin and Michael F Leitzmann, 'Intensity and timing of physical activity in relation to postmenopausal breast cancer risk: the prospective NIH-AARP Diet and Health Study', BMC Cancer (in press)