Strenuous Living Reduces the Risk of Some Breast Cancers

Today’s Archives of Internal Medicine reported that women who participated in long term strenuous physical activity reduced their risk of invasive breast cancer by 20% and their risk of in situ breast cancer 31%. The study involved over 110,000 women in the California Teachers Study who were enrolled at 20 to 79 years of age and followed for 6-7 years. Previous studies had suggested a relationship between physical activity and breast cancer risk. Howevr, the present study employed a more robust prospective design in that physical activity levels were calculated at the time of enrollment and the women followed thereafter. The beneficial effects of exercise seemed to be specific to estrogen receptor negative forms of breast cancer. Strenuous activities were those such as swimming laps, aerobics, running or jogging. Protective effects were noted when these activities were performed more than 5 hours per week.