PHYSICAL ACTIVITY MAY DECREASE RISK OF BREAST CANCER DECADES LATER Study shows a modest protective effect of strenuous physical activity in both pre- and postmenopausal women INDIANAPOLIS – Physical activity may reduce the risk of breast cancer, particularly in women who have been consistently active through their lifespan, according to a study published in the February 2003 issue of Medicine & Science in Sports & Exercise®, the official scientific journal of the American College of Sports Medicine. Exercise, well known for its role in aiding and preventing cardiovascular disease, colon cancer, diabetes, and a score of other chronic diseases, may also benefit women by having a favorable effect on hormone levels, body weight, weight gain with age, and immune function. This study set out to examine the effect of physical activity, both in leisure time and occupational settings, on the risk of breast cancer in pre- and postmenopausal women. The strongest protective effect on breast cancer risk was observed among women who reported high levels of physical activity at least 20 years prior to menopause. “We were most interested in the relationship between the amount of leisure-time physical activity and the risk of breast cancer in women, particularly because so many jobs require us to be sedentary for a large portion of our day,” said lead author Joan M. Dorn, Ph.D. “This study also uniquely looked at factors over the lifespan to get a sense of how exercise in early life may later impact breast health, and how this may continue into adulthood.” Researchers at the University at Buffalo recruited a total of 1,550 women between the ages of 40 and 85, including 301 premenopausal women diagnosed with breast cancer (cases) and 316 premenopausal women without breast cancer (controls); and 439 postmenopausal cases and 494 postmenopausal controls. The women were interviewed within two months of the date of their diagnosis. The control groups were randomly selected from the community and also interviewed to ascertain personal histories and lifestyle characteristics, including nutrition and exercise habits. All interviews took place in participants’ homes with a trained nurse. Menopausal status was designated during the interview sessions. Women who were menstruating or who were no longer menstruating due to a hysterectomy or other medical intervention but had at least one functioning ovary and were younger than 50 were considered premenopausal. Women who were no longer menstruating due to natural menopause or other medical conditions were classified as postmenopausal. During the interview sessions, women were asked if they participated in any regular sport, physical activity, or strenuous exercise long enough to work up a sweat. They were then asked to estimate the number of months and hours engaged in this level of activity, as well as how many miles they walked for exercise, pleasure, or as a means of transportation in an average week, not including on the job or in housework. The questions were repeated for different time periods in the lifespan, specifically two, 10 and 20 years before the interview, and at age 16. The researchers compared this information to the reported levels of activity accrued in occupational and leisure settings. They then linked the total number of hours per year spent in strenuous activity to estimates of risks for breast cancer. The control groups’ total accumulation of strenuous physical activity was slightly higher than that of the women with breast cancer. Women who reported the highest levels of activity during the most distant time period questioned, 20 years before their current age and at age 16, showed an approximate 35-45 percent decrease in breast cancer risk. “The fact that physical activity was questioned at different periods in a women’s life, including adolescence, enabled us to examine the important question of whether there was a particular time in a woman’s life when exercise may be most beneficial,” said Dorn. “The studies on this are not conclusive, but our research shows modest reductions in the risk of breast cancer for nearly all time periods, with the strongest protective factor observed in women who were active 20 years prior to their enrollment in this study.” The American College of Sports Medicine is the largest sports medicine and exercise science organization in the world. More than 18,000 International, National and Regional members are dedicated to promoting and integrating scientific research, education and practical applications of sports medicine and exercise science to maintain and enhance physical performance, fitness, health and quality of life.

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