Regular moderate exercise is linked to lower breast cancer risk and improved survival. Ongoing physical activity reduces inflammation, lowers circulating estrogen and androgen levels, and induces beneficial changes in insulin levels and insulin-related pathways. There is also evidence that it might also boost immunity and favorably influence the regulation of tumor suppressor genes.

Several studies have reported that the reduction in breast cancer risk associated with regular sustained exercise is especially powerful for women who start exercising at a young age. Also, such pre-diagnostic physical activity improves survival outcomes even for women who eventually develop breast cancer. Now a new meta-analysis of previous studies has reported that women who are premenopausal or normal weight experience the strongest reductions in breast cancer risk from exercising.

Latest research finds breast cancer risk reduction depends on age and BMI

The study referenced at the beginning of this news story was designed to investigate the association between physical activity and risk of breast cancer by analyzing data from previous prospective studies. The authors analyzed data from 31 studies that included a total of 63,786 breast cancer cases. Overall, the risk of breast cancer was 12% lower among women engaging in regular physical activity compared to those who did not. The inverse association between physical activity and breast cancer risk was found among all subgroups analyzed.

When comparing activity due to work and non-work circumstances (including exercise, sports and household tasks), non-work related physical activity had a slightly higher risk reducing effect (13% risk reduction) than work related (10%). Stronger risk reductions were observed for women who were not overweight (BMI < 25) (28% risk reduction), premenopausal women (23%), and for hormone receptor negative (ER-/PR-) breast cancer (20%). The last result contradicts some studies that have reported that exercise preferentially reduces the risk of ER+/PR+ breast cancer.

The risk of breast cancer decreased by 2% for every 25 metabolic equivalent (MET)-hour/week increment in non-work related physical activity, 3% for every 10 MET-h/week (roughly equivalent to four hours per week of walking at a pace of 2 miles per hour or one hour per week of running at 6 miles per hour) in recreational activity, and 5% for every 2 hours per week in moderate/vigorous recreational activity. The authors conclude that physical activity can significantly reduce the risk of breast cancer.

Please see our article on exercise and breast cancer survival for more information.