Upwards of six hours of strenuous activity each week could reduce your risk of invasive breast cancer by as much as 23%. A recent survey of more than 15,000 women showed that exercise has a lifelong protective effect against invasive breast cancer.
The survey was of women between the ages of 20 and 69 living in Wisconsin, New Hampshire and Massachusetts. During structured telephone interviews, researchers questioned almost 8,000 women without breast cancer, more than 1,500 survivors of non-invasive breast cancer, and more than 6,000 survivors of invasive breast cancer.
The women were asked about their physical activity, occupation, family history of breast cancer, menopausal status, and body mass index.
A reduction in risk for women who exercised was apparent whether the physical activity took place early in life, in postmenopausal years, or in the recent past.
Source: Cancer Epidemiology Biomarkers & Prevention