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Vol. LXIII, No. 2
January 21, 2011

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Brisk Walking Reduces Risk of Breast Cancer, NCI-Funded Study Indicates
Dr. A. Heather Eliassen said, “The overall findings on the link between breast cancer risk and walking were really very encouraging.”

Dr. A. Heather Eliassen said, “The overall findings on the link between breast cancer risk and walking were really very encouraging.”

Lace up those Nikes, ladies—it’s never too late to get on the right track in the quest to deter a major killer.

Findings from a long-term National Cancer Institute-supported study of middle-aged women strongly suggest that brisk walking for nearly an hour most days of the week appreciably reduces the risk of breast cancer.

Prevention and early detection of breast cancer are paramount in the fight against the disease, which will afflict one in 8 women during their lifetime. Around 200,000 cases of breast cancer were diagnosed in 2010 and of these, nearly 40,000 women will succumb to the malady, NCI estimates. Breast cancer is the second leading cause of cancer mortality in women.

While factors such as proper nutrition, exercise and a healthy lifestyle are thought to possibly minimize the risk of developing breast cancer, little is known about how much exercise or what types of activity have the greatest effect. Also, since most cases of breast cancer occur in middle to later life, it is critical to know how exercise affects breast cancer for postmenopausal women. Little data existed prior to this analysis.

Walking has long been considered both beneficial and safe for almost all men and women. The risks are minimal and, when performed regularly, physical activity is thought to confer multiple health benefits including lowering risk of heart disease and stroke, maintenance of blood pressure, weight control, bone strengthening, improved insulin sensitivity, reduction of anxiety/ stress, heightened mood and perhaps even a reduced risk of cognitive decline and dementia. But what about its role in preventing or lessening risk of breast cancer? The findings from this longitudinal protocol, where walking was the primary activity, are noteworthy.

Dr. A. Heather Eliassen and her colleagues from Brigham and Women’s Hospital and Harvard Medical School analyzed two decades of self-reported data from questionnaires filled out by more than 95,000 postmenopausal women participating in the Nurses Health Study, a long-running protocol that began in 1976. Women were between ages 30 and 55 when the study began. Of that number, nearly 4,800 developed breast cancer.

“The overall findings on the link between breast cancer risk and walking were really very encouraging,” Eliassen said. “What we found was that women who walked briskly for about an hour on most days of the week were able to reduce their risk of breast cancer by some 15 percent. And even women who were less active until menopause, but began walking around mid-life, lessened their risk by about 10 percent. This is a very notable finding.”

She explained that her team was fortunate in that many participants in the trial were walkers. Meanwhile, women who ran, played tennis or engaged in other types of physical activity also saw some decreases in breast cancer risk, but the reduced risk was not as robust as that experienced by fervent walkers, according to the analysis.

Eliassen pointed out that while many or most risk factors for breast cancer (e.g., family history) are not modifiable, “physical activity is certainly something we can all do, even in mid-life if you’ve never been active before.”

With walking, she added, there’s no need to join a gym or buy special equipment. “In this day and age when breast cancer is on the minds of so many women, we find that physical activity can have an impact on risk,” Eliassen said, “and I find that quite heartening.”

Although the underlying mechanism for the reduced breast cancer risk from walking is not fully understood, one leading theory is that walking and exercise in general reduce the amount of circulating blood estrogen, which in turn may discourage tumor formation. In addition, activity helps with weight control; less body fat may also inhibit tumor growth. The role of insulin sensitivity—how the body responds to the rise and fall of blood glucose—may be another factor. Exercise has been shown to improve this metabolic feature and could affect the etiology of breast cancer, experts believe.

Eliassen noted that the most active, regular walkers analyzed in the Nurses Health Study were strolling at a rate of about 3 miles per hour.

The findings were reported in the Oct. 25, 2010, issue of the Archives of Internal Medicine. NIHRecord Icon

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