Physical activity's effect on breast cancer varies
NEW YORK (Reuters Health) - The results of a literature review of published studies confirm that while all women are likely to reduce their risk of breast cancer with regular physical activity, certain subgroups benefit more than others.
According to the report posted online by the British Journal of Sports Medicine, postmenopausal women and those with a normal body mass index (BMI) are among the groups that achieve the greatest risk reduction with physical activity. BMI is the ratio of height to weight.
The findings also indicate that certain activities influence the risk reduction more than others. For instance, recreational physical activity cut the risk of breast cancer to a greater extent than did work-related activity.
Dr. C. M. Friedenreich, from the Alberta Cancer Board in Calgary, Canada, and Dr. A. E. Cust, from the University of Melbourne in Australia, examined how the timing, type, and level of physical activity affects the breast cancer risk. Their literature search identified 62 studies.
Forty-seven of the 62 (76 percent) studies indicated there was an anti-breast cancer effect for increased physical activity, with typical risk reductions of 25 percent to 30 percent, the authors report. In 28 of 33 studies, they found evidence of a dose-response effect, which means more exercise correlated with more benefits.
In terms of activities, recreational activity, vigorous activity, and lifetime or later life activity provided the strongest reductions in breast cancer risk.
In addition to postmenopausal women and those with a normal BMI, other subgroups most likely to benefit from physical activity were non-white women, women who have given birth, and those without a family history of breast cancer.
Exercise also had a greater effect in reducing hormone receptor-negative tumors than hormone receptor-positive tumors, the findings indicate.
"Further observational epidemiological research is needed to clarify the biological mechanisms underling the association between physical activity and reduced breast cancer risk," Friedenreich and Cust conclude, "especially with regard to the type, duration and intensity of activity and to explain differences in population subgroup effects."
SOURCE: British Journal of Sports Medicine, May 12, 2008.
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What breastcancer.org says about this article…
Physical activity's effect on breast cancer varies
This study looked at the results of more than 60 research trials examining the link between breast cancer risk and exercise. One thing comes through loud and clear in all these studies: regular exercise can lower breast cancer risk by about 25% to 30%. The benefits of exercise were not the same for all women -- the type and amount of exercise affected the amount of risk reduction.
- Women who had a healthy weight to height ratio -- body mass index (BMI) -- got more benefits from exercise than women with a higher BMI. This could be because the protective effects of exercise were offset by the increase in risk associated with being overweight.
- Older, post-menopausal women; non-white women; women who have given birth; and women with no family history of breast cancer got more benefits from regular exercise.
- Exercise seems to lower the risk of hormone-receptor-negative breast cancer more than it lowers the risk of hormone-receptor-positive breast cancer.
- Vigorous recreational (not done at work) exercise, such as running, bike riding, swimming, etc., lowers breast cancer risk more than physical activity done during work.
- The more a woman exercised over her lifetime, the more her breast cancer risk was reduced.
Along with healthy diet and lifestyle choices, regularly doing moderately intense exercise during your lifetime is one the best steps you and ALL girls and women can take to help keep breast cancer risk as low as it can be. Regular exercise also helps keep your general health the best that it can be. No matter how old you are, it's never too soon or too late to get moving.
To learn more about how exercise and a healthy lifestyle can lower your risk of breast cancer, visit the Breastcancer.org Changes You Can Make to Lower Your Risk page.