Physical Activity Linked to Lower Premenopausal Breast Cancer Risk
By Charles Bankhead
BOSTON, 15 may 2008-- Regular physical activity has been associated with a reduction in the risk of premenopausal breast cancer, according to data from the Nurses' Health Study II.
The association with exercise and the risk of premenopausal breast cancer joined previous epidemiological research that had linked exercise with a reduction in risk for breast cancer after menopause.
In the current study, premenopausal women who reported as little as 3.25 hours of physical activity weekly had a 23% reduction in breast cancer risk compared with women who were less active, found investigators at the Harvard School of Public Health.
Women reporting the most lifetime exercise versus those reporting the least showed about a 30% reduction in breast cancer risk in association with increased physical activity. Sonia S. Maruti, Sc.D., and colleagues reported in the May 13 issue of the Journal of the National Cancer Institute. Dr. Maruti is now with the Fred Hutchinson Cancer Research Center in Seattle.
"These results suggest that consistent physical activity during a woman's lifetime is associated with decreased breast cancer risk," said Dr. Maruti. "Unlike many risk factors for breast cancer, physical activity is an exposure that can be modified. This association, if found to be causal, has public health implications for prevention."
Numerous studies have demonstrated a favorable impact of physical activity on postmenopausal breast cancer. However, limited data had pertained to the effects of physical activity on breast cancer risk in premenopausal women.
The authors analyzed data on 64,777 premenopausal women in the Nurses' Health Study II. Initiated in 1989, the ongoing study includes biennial questionnaires to update information on lifestyle and changes in health status. Since 1997 study participants have been asked about their leisure-time activity from ages 12 to the present.
During six years of follow-up, 550 participants developed breast cancer. The strongest associations with physical activity were for total lifetime leisure-time activity. Women who reported 39 or more metabolic equivalent hours per week (MET-h/wk) of activity (equivalent to 3.25 hours of running or 13 hours of walking) had a relative risk of breast cancer of 0.77 (95% CI 0.64 to 0.93) compared with women reporting less activity.
Women reporting the highest lifetime total physical activity (≥54 MET-h/wk) had an age-adjusted breast cancer incidence of 136 per 100,000 person-years. In contrast, the lowest category of physical activity (<21 href="http://jnci.oxfordjournals.org/cgi/content/abstract/djn135" target="_blank">"A prospective study of age-specific physical activity and premenopausal breast cancer" J Natl Cancer Inst 2008; DOI: 10.1093/jnci/djn135.
By Charles Bankhead
BOSTON, 15 may 2008-- Regular physical activity has been associated with a reduction in the risk of premenopausal breast cancer, according to data from the Nurses' Health Study II.
The association with exercise and the risk of premenopausal breast cancer joined previous epidemiological research that had linked exercise with a reduction in risk for breast cancer after menopause.
In the current study, premenopausal women who reported as little as 3.25 hours of physical activity weekly had a 23% reduction in breast cancer risk compared with women who were less active, found investigators at the Harvard School of Public Health.
Women reporting the most lifetime exercise versus those reporting the least showed about a 30% reduction in breast cancer risk in association with increased physical activity. Sonia S. Maruti, Sc.D., and colleagues reported in the May 13 issue of the Journal of the National Cancer Institute. Dr. Maruti is now with the Fred Hutchinson Cancer Research Center in Seattle.
"These results suggest that consistent physical activity during a woman's lifetime is associated with decreased breast cancer risk," said Dr. Maruti. "Unlike many risk factors for breast cancer, physical activity is an exposure that can be modified. This association, if found to be causal, has public health implications for prevention."
Numerous studies have demonstrated a favorable impact of physical activity on postmenopausal breast cancer. However, limited data had pertained to the effects of physical activity on breast cancer risk in premenopausal women.
The authors analyzed data on 64,777 premenopausal women in the Nurses' Health Study II. Initiated in 1989, the ongoing study includes biennial questionnaires to update information on lifestyle and changes in health status. Since 1997 study participants have been asked about their leisure-time activity from ages 12 to the present.
During six years of follow-up, 550 participants developed breast cancer. The strongest associations with physical activity were for total lifetime leisure-time activity. Women who reported 39 or more metabolic equivalent hours per week (MET-h/wk) of activity (equivalent to 3.25 hours of running or 13 hours of walking) had a relative risk of breast cancer of 0.77 (95% CI 0.64 to 0.93) compared with women reporting less activity.
Women reporting the highest lifetime total physical activity (≥54 MET-h/wk) had an age-adjusted breast cancer incidence of 136 per 100,000 person-years. In contrast, the lowest category of physical activity (<21 href="http://jnci.oxfordjournals.org/cgi/content/abstract/djn135" target="_blank">"A prospective study of age-specific physical activity and premenopausal breast cancer" J Natl Cancer Inst 2008; DOI: 10.1093/jnci/djn135.
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