Research has increasingly examined the relationship between diet, lifestyle, and breast cancer risk, including the role of physical activity.
Data from 90,509 women participating in the E3N cohort study were analyzed to evaluate the relationship between physical activity and breast cancer incidence. The study was published in Cancer Epidemiology, Biomarkers & Prevention (2006; 15(1):57–64). Participants were between 40 and 65 years of age at baseline and were followed for 12 years. Frequency and intensity of physical activity were assessed through questionnaires. During the follow-up period, 3,424 cases of breast cancer were diagnosed.
The investigators reported an inverse association between physical activity and breast cancer risk. Women who reported engaging in vigorous recreational physical activity for more than five hours per week had a relative risk of 0.62 compared with women who reported no recreational physical activity.
Physical activity has also been studied in relation to breast cancer survival. Research published in Cancer (October 15, 2006) analyzed data from women aged 20 to 54 years who had been diagnosed with breast cancer. Participants were asked to report how often they engaged in moderate or vigorous exercise at age 13, age 20, and during the year prior to diagnosis.
The study found that women who exercised regularly in the year before diagnosis had higher survival rates compared with sedentary women. This association was particularly evident among women who were overweight, defined as having a body mass index greater than 25.
Women in the most physically active quartile during the year prior to diagnosis were more than 20% more likely to survive compared with those in the least active quartile. Among overweight women, those in the most active group were approximately 30% more likely to survive than their least active counterparts. Levels of physical activity earlier in life did not appear to have a significant effect on survival outcomes.
