Most research on exercise and breast cancer risk suggests that doing regular, moderate, aerobic exercise can reduce the risk of breast cancer after menopause. But the affect of exercise on breast cancer risk in younger women has been less clear.
The large study reviewed here looked at the relationship between breast cancer risk in premenopausal women and exercise starting at age 12. The researchers found that the more time a woman exercised, the more her breast cancer risk went down. They also found that regular exercise between ages 12 and 22 contributed the most to the reduction in risk. It didn't matter what type of exercise the girls and women did -- the exercise just needed to be moderately intense:
Either type of exercise lowered breast cancer risk by 23%.
While you can't control some of the things that affect breast cancer risk, such as your genes, you can make a number of diet, exercise, and lifestyle choices that can lower your risk of breast cancer. It's ideal if you can start making these choices -- including regular exercise -- in childhood. But if you didn't then, it's never too late to start. Whatever your age, do all that you can to keep your breast cancer risk as low as it can be. And while you're at it, coach your daughters, nieces, and the other girls and young women in your life to make healthy choices today that can lower their risk of breast cancer tomorrow.
NEW YORK (Reuters Health) - Premenopausal women who spend much of their leisure time in physical activities, especially during adolescence and early adulthood, are less likely to develop breast cancer than their more sedentary counterparts, according to a report in the Journal of the National Cancer Institute.
Prior research has linked physical activity with a reduced risk of breast cancer in postmenopausal women, but whether this also applies to younger premenopausal women was unclear, lead author Dr. Sonia S. Maruti, from the Fred Hutchinson Cancer Research Center in Seattle, and colleagues explain.
To address this question, the researchers determined whether physical activity at a particular age or intensity were needed to a see a reduction in risk. The analysis involved 64,777 premenopausal women enrolled in the Nurses' Health Study II who were surveyed regarding leisure-time physical activity from age 12 to their current age.
Overall, 550 subjects developed breast cancer after 6 years of follow-up, the report indicates.
Physical activity was inversely associated with breast cancer risk, the authors found. The strongest association was with total leisure-time physical activity rather than with activity during a certain age period or of a particular intensity. Still, activity between 12 and 22 years of age contributed most to the reduction in risk.
The investigators found that the amount of activity needed to a achieve a 23-percent reduction in risk was roughly equivalent to 3.25 hours of running or 13 hours of walking per week, the report shows.
In women with the highest level of physical activity, the rate of breast cancer was 136 cases per 100,000 persons per year, while in the young women with the activity lowest level, the rate of breast cancer was 194 cases per 100,000 persons per year.
"These results suggest that consistent physical activity during a woman's lifetime is associated with decreased breast cancer risk," the authors conclude. "This association, if found to be causal, has public health implications for prevention."
SOURCE: Journal of the National Cancer Institute, May 21, 2008.
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