Women who engage in physical activity are less likely to develop breast cancer, a new report says.
The researchers, Dr. Christine M. Friedenreich of the Alberta Cancer Board and Dr. A.E. Cust of the University of Melbourne, analyzed data from 62 studies that investigated the link between exercise and breast cancer. They found that overall, women who were the most physically active had about a 25 per cent reduced risk of developing the disease versus women who were the least active.
Even though vigorous, recreational exercise was linked to the greatest reduction in risk, moderate activity, work-related activity and household chores all lowered the risk for breast cancer.
"There's now convincing evidence that physical activity is a means of reducing the risk of breast cancer and, because this is a modifiable lifestyle risk factor, this is something that people actually have control over," Friedenreich told CTV.ca.
"This is something that people can incorporate into their daily lives because it's activity that they can do occupationally, in the household or recreationally and it will have benefits beyond breast cancer. It will have benefits for all kinds of chronic disease."
The findings are published in the online edition of the British Journal of Sports Medicine.
The report showed that family history of breast cancer did not change how physical activity impacted breast cancer risk.
However, physically active women who had a low body-mass index (BMI) had a greater reduction in their risk for breast cancer versus women with a higher BMI. As well, post-menopausal women who exercised had their risk reduced more so than pre-menopausal women.
Exercise did not reduce breast cancer risk among obese women.
More study needs to be done to evaluate how exercise reduces breast-cancer risk. However, it could be that it reduces inflammation in the body, reduces levels of hormones that are linked to breast cancer development or has an impact on the DNA damage that can result in a variety of diseases.
As well, Friedenreich is currently working on a study whereby women are following vigorous exercise regimens so researchers can measure their impact on breast cancer.
"What we're trying to do is come up with more refined exercise prescriptions that you can actually give to people to say, 'to reduce your breast cancer risk, this is the frequency, duration and intensity of activity that you need to do.'"
