A study published online in BMC Cancer on October 1 of this year, conducted by the National Cancer Institute and the National Institutes of Health-AARP, found that postmenopausal women who did regular and frequent, moderate to vigorous exercise lowered their risk for breast cancer. This held true even for those women who had not exercised regularly in the past.

Many studies have shown that women who regularly had a high level of physical activity have a lower risk of getting postmenopausal breast cancer than do those women with a low level of physical activity, in some studies by as much as 20-40%.  In addition, prior studies have shown that women with breast cancer have a reduced risk of having it recur when they do regular exercise. This study, however, was the first to look at the specifics of the parameters of exercise (eg, how often and how vigorous) and of age at the time the exercise begins and their relationship to breast cancer risk.

The study was made up of 118,899 women, ages 50 to 71, who were followed for nearly 7 years.  Initially, these women were asked about their prior exercise regimens during four periods of their lives: ages 15-18; 19-29; 35-39; and the ten years just prior to the beginning of the study in 1995. They were also asked the number of hours exercised per week (from 1-7 hours), and how vigorous that exercise was (with specific examples of each level given) – from light to moderate to vigorous. During the 6.6 years that the women were followed, 4,287 breast cancers were diagnosed.

The study found that the risk of breast cancer was reduced by 16% in those women who did vigorous exercise (7 or more hours per week) in the ten years prior to the study when compared to those women who led sedentary lives. In women who did light exercise (less than 1 hour per week) in the decade before the study, there was no significant reduction in the risk for breast cancer.

Interestingly, the BMI (body mass index) of the study participants had little impact on the correlation between high levels of activity and breast cancer. This suggests that if you regularly do a moderate or vigorous level of exercise, you can lower your risk for breast cancer, no matter what your weight is.

Yet another reason we must get regular, frequent, and moderate-vigorous levels of physical activity in midlife and beyond. I’m convinced that I need to do it – are you?