While breast cancer commonly affects women over the age of forty-five, a quarter of all breast cancers are diagnosed in younger women, and these cancers tend to be more aggressive. A new study reported in the Journal of the National Cancer Institute has found that teenage girls who exercise regularly can reduce their risk of breast cancer in their early years of adulthood.
Researchers at Washington University School of Medicine tracked nearly 65,000 nurses ages 24 to 42 for six years. Women were asked detailed questionnaires about their physical activity dating back to age 12. During the six-year period, 550 women were diagnosed with breast cancer. This said, those women who were physically active in their teenage years were 23% less likely to develop breast cancer later in life. Women with the lowest incidence of breast cancer exercised vigorously for a minimum of 3¼ hours a week as teenagers.
Maruti SS, et al. (2008). A Prospective Study of Age-Specific Physical Activity and Premenopausal Breast Cancer. Journal of the National Cancer Institute, epub.