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Reduce your breast cancer risk with exercise

Robin Wulffson MD's picture
breast cancer, risk, prevention, exercise, obesity

Physical activity has been reported to reduce breast cancer risk. However these studies have not adequately addressed relevant factors such as duration, intensity, and optimal time for exercise note the authors of a new study. Researchers affiliated with the University of North Carolina (Chapel Hill, NC), Columbia University (New York, NY), and Mount Sinai University (New York, NY) published a study evaluating factors related to exercise on June 25 in the journal Cancer.

The authors noted that, although physical activity reduces breast cancer risk, issues critical to providing clear public health messages remain to be elucidated. These include the minimum duration and intensity necessary for risk reduction and the optimal time period for occurrence, as well as subgroup effects, particularly with regard to tumor heterogeneity (type of tumor) and body size.

The study group was comprised of 1,504 women with breast cancer (in situ: 233; invasive: 1,271) and 1,555 controls whose ages ranged from 20 to 98 years). The subjects were enrolled in the Long Island Breast Cancer Study Project in Long Island, New York. The researchers investigated the relationship between recreational physical activity and breast cancer risk. They evaluated the joint effects of activity level, weight gain, and body size.

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In the study, only 131 case women and 137 control women lost weight after menopause; however, 525 case women and 436 control women gained weight after menopause. The researchers found a nonlinear (not a straight line increase) dose-response association between breast cancer risk and recreational physical activity during both the reproductive years and after menopause. Women who exercised 10 to 19 hours per week experienced the greatest benefit with an approximate 30% risk reduction. Minimal to no difference was observed regarding intensity of activity or hormone receptor status. (Some breast cancers have estrogen receptors while others do not.) Joint assessment of recreational physical activity, weight gain, and body size revealed that women with unfavorable energy balance profiles were at increased breast cancer risk. A significant relationship was found between recreational physical activity and adult weight gain. Among woman who were not physically active, a high weight gain during adulthood was associated with a 28% increased risk for breast cancer. Conversely, exercise did not appear to reduce the effects of weight gain; high gainers who reported high levels of physical activity did not reduce their risk of breast cancer.

The authors concluded that recreational physical activity at any intensity level during the reproductive and postmenopausal years have the greatest benefit for reducing breast cancer risk. Furthermore, substantial postmenopausal weight gain might eliminate the benefits of regular activity. They noted that their results were consistent with a number of other studies that examined the effect of physical activity on breast cancer risk; these studies reported an average 25% risk reduction.

Reference: Cancer

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