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By: Harvard Health Publications
Women with breast cancer who walk three or more hours a week (or exercise more strenuously for shorter periods) have a lower risk of dying of breast cancer than those who exercise less. These are the findings of a study published in the Journal of the American Medical Association.
After adjusting for factors such as smoking and diet, the study authors found that exercise lowered the rate of recurrence no matter what size the cancer was when it was diagnosed. (Women whose cancers had spread to other parts of the body did not participate in the study.) Compared to women who walked less than three hours per week, those who walked three to five hours saw the greatest drop in mortality risk — a 50% reduction over 4–18 years.
In a seeming paradox, risk reduction was less striking in women who exercised more. For example, women who walked five to eight hours every week reduced their chance of dying by 44%. But the researchers doubt this means that longer or more vigorous workouts lower the chance of survival. Rather, they say, the women who exercised most vigorously may have been exercisers before their diagnosis and therefore would not have benefited as much. It’s also possible that women with a worse prognosis were more strongly motivated to exercise.
Why is exercise so effective in preventing recurrence and raising survival rates? According to Harvard Medical School assistant professor Dr. Michelle Holmes, an associate physician at Boston’s Brigham and Women’s Hospital and lead investigator of the study, physical activity may lower hormone levels, including estrogen and progesterone, thereby suppressing cancer growth and recurrence. Also, exercise decreases insulin resistance, a condition linked to breast cancer, in which sugar accumulates in the blood because muscle, fat, and liver cells don’t use insulin properly. Exercise also reduces the risk of weight gain, which is known to lower the survival rate of breast cancer patients.
Dr. Holmes emphasized that the study’s findings should be kept in perspective: “This is just one study, and we need others to confirm the results.” But, she adds, women with breast cancer have little to lose and perhaps much to gain from being active: “We already know that women with breast cancer who exercise have better mood, body image, and self-esteem. Now it appears that exercise may also help them avoid dying from breast cancer.”
Women with breast cancer who walk three or more hours a week (or exercise more strenuously for shorter periods) have a lower risk of dying of breast cancer than those who exercise less. These are the findings of a study published in the Journal of the American Medical Association.
After adjusting for factors such as smoking and diet, the study authors found that exercise lowered the rate of recurrence no matter what size the cancer was when it was diagnosed. (Women whose cancers had spread to other parts of the body did not participate in the study.) Compared to women who walked less than three hours per week, those who walked three to five hours saw the greatest drop in mortality risk — a 50% reduction over 4–18 years.
In a seeming paradox, risk reduction was less striking in women who exercised more. For example, women who walked five to eight hours every week reduced their chance of dying by 44%. But the researchers doubt this means that longer or more vigorous workouts lower the chance of survival. Rather, they say, the women who exercised most vigorously may have been exercisers before their diagnosis and therefore would not have benefited as much. It’s also possible that women with a worse prognosis were more strongly motivated to exercise.
Why is exercise so effective in preventing recurrence and raising survival rates? According to Harvard Medical School assistant professor Dr. Michelle Holmes, an associate physician at Boston’s Brigham and Women’s Hospital and lead investigator of the study, physical activity may lower hormone levels, including estrogen and progesterone, thereby suppressing cancer growth and recurrence. Also, exercise decreases insulin resistance, a condition linked to breast cancer, in which sugar accumulates in the blood because muscle, fat, and liver cells don’t use insulin properly. Exercise also reduces the risk of weight gain, which is known to lower the survival rate of breast cancer patients.
Dr. Holmes emphasized that the study’s findings should be kept in perspective: “This is just one study, and we need others to confirm the results.” But, she adds, women with breast cancer have little to lose and perhaps much to gain from being active: “We already know that women with breast cancer who exercise have better mood, body image, and self-esteem. Now it appears that exercise may also help them avoid dying from breast cancer.”
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