Physical Activity Linked to Reduced Breast Cancer

Results of a large new study by researchers at the American Cancer Society have added to mounting evidence suggesting that physical activity reduces breast cancer risk in postmenopausal women. Alpa Patel, Ph.D., and colleagues compared exercise and breast cancer status in 73,615 postmenopausal women taking part in in the CPS-II Nutrition Cohort study. Results showed that 9.2% women reported no recreational physical activity at the beginning of the study. Among those who said they were physically active, the average expenditure was equivalent to 3.5 hours per week of moderate walking. Among all the participants, 47% reported that walking was their only recreational activity. Physically active women tended to be leaner, more likely to maintain or lose weight during adulthood, more likely to drink alcohol, and less likely to currently smoke. They were also more likely to use postmenopausal hormone therapy and to have had a mammogram in the past year. Further analysis revealed that among those who reported walking as their only activity, those who walked for at least 7 hours per week had a 14% lower risk of breast cancer compared to those who walked 3 hours or less each week. Whilst the most active women had a 25% lower risk of breast cancer than the least active, a finding that is consistent with the majority of prior studies. Risk was not found to be linked to hormone receptor status, BMI, weight gain, postmenopausal hormone use, or sitting time. "Our results clearly support an association between physical activity and postmenopausal breast cancer, with more vigorous activity having a stronger effect," said Dr. Patel. "Our findings are particularly relevant, as people struggle with conflicting information about how much activity they need to stay healthy. Without any other recreational physical activities, walking on average of at least 1 hour per day was associated with a modestly lower risk of breast cancer. More strenuous and longer activities lowered the risk even more."