Physical activity reduces the risk of breast cancer in premenopausal women. These results were recently published in the Journal of the National Cancer Institute.
The majority of breast cancers occur in postmenopausal women; however, if breast cancer does occur in a premenopausal woman, it tends to have a much worse prognosis. Recently, researchers have discovered that physical activity can reduce the risk of developing breast cancer among postmenopausal women, but the association between physical activity and breast cancer among premenopausal women remains unknown.
Researchers from several medical institutions in the United States recently evaluated data from the Nurses’ Health Study II, in which nearly 65,000 premenopausal women were involved. The study included a questionnaire evaluating variables that included physical activity habits. Physical activity habits were further specified to include age period (adolescence, adulthood, and lifetime) and intensity (strenuous, moderate, walking, and total) of physical activity levels beginning in 1997. Follow-up was 6 years.
• 550 premenopausal women developed breast cancer.
• Total leisure-time activity over the course of a participant’s lifetime had the greatest association with the risk of premenopausal breast cancer; most notably, high levels of physical activity between the ages of 12 and 22 years.
• Women who averaged 3.25 hours of running or 13 hours of walking per week had a 23 percent reduced risk of developing premenopausal breast cancer compared to women with less physical activity.
The researchers concluded that “Leisure-time physical activity was associated with a reduced risk for premenopausal breast cancer in this [group]. Premenopausal women regularly engaging in high amounts of physical activity during both adolescence and adulthood may derive the most benefit.” These results provide further evidence that physical activity reduces the risk of breast cancer.
Reference: Maruti S, Willett W, Feskanich D, Rosner B, Colditz G. A Prospective Study of Age-Specific Physical Activity and Premenopausal Breast Cancer. Journal of the National Cancer Institute. Early on-line publication May 13, 2008. DOI: 10.1093/jnci/djn135.
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