Physical Activity Associated With Increased Survival Rate Among Women With Breast Cancer

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Physical Activity Associated With Increased Survival Rate Among Women With Breast Cancer

A recent study published in the May 25, 2005, issue of the Journal of the American Medical Association (JAMA) shows that women diagnosed with breast cancer who engage in regular physical activity have an increased rate of survival over those who don't exercise.

According to the researchers, previous studies have shown a positive correlation between exercise and an improved quality of life following a breast cancer diagnosis, but few studies have addressed exercise and survival rates. The study examined the physical activity of 2,987 female registered nurses in the Nurses' Health Study who were diagnosed with stage I, II, or III breast cancer between 1984 and 1998. Participants were followed until June 2002 or death, whichever came first.

Physical activity was assessed using metabolic equivalent task (MET) hours. Three MET-hours equal walking at an average pace of 2 to 2.9 mph for one hour, and categories of MET-hours per week were classified as less than 3; 3 to 8.9; 9 to 14.9; 15 to 23.9; and 24 or more. Beginning in 1986, at least two years following diagnosis, the participants were asked about the amount of time they spent engaged in specific physical activities during the prior year, then asked about the amount of time spent participating in the physical activities. Physical activity was assessed again in 1988, 1992, 1994, 1996, 1998, and 2000.

Results: Compared with women who engaged in physical activity fewer than 3 MET-hours per week, the adjusted relative risk of death from breast cancer was 20% lower for 3 to 8.9 MET-hours per week of physical activity; 50% lower for 9 to 14.9 MET-hours per week; 44 % lower for 15 to 23.9 MET-hours per week; and 40% lower for 24 MET-hours per week or more. The absolute unadjusted risk of death reduction was 6% at 10 years for women who engaged in 9 MET-hours per week or more, compared with women who engaged in fewer than 3 MET-hours per week. The researchers also discovered that physical activity was particularly beneficial to women with hormone-responsive tumors.

"Women who engaged in an amount of physical activity equivalent to walking 1 or more hours per week had better survival compared with those who exercised less than that or not at all," the researchers wrote. "The maximal benefit occurred among women who performed the equivalent of walking 3 to 5 hours per week at an average pace (2-2.9 mph) with little evidence of increased benefit for more exercise," they added.

Holmes MD, Chen WY, Feskanich D, et al. Physical activity and survival after breast cancer diagnosis. JAMA May 25, 2005;293(20):2479-2486.