Exercise May Protect Women Against Colon Cancer

Long-term physical activity decreased colon cancer risk for postmenopausal women in California Teachers Study.

Los Angeles, Calif-Life-long physical activity may reduce colon cancer risk for postmenopausal women who have never used hormone therapy, a USC-led study suggests."Postmenopausal women who had never used hormone therapy and who exercised at least four hours a week had nearly a 50 percent reduction in their colon cancer risk," says Leslie Bernstein, professor of preventive medicine at the Keck School of Medicine of the University of Southern California. "Overall, the evidence is convincing that long-term moderate and strenuous physical activity reduces the risk for women not receiving menopausal hormones."Researchers analyzed data from a cohort of 120,147 women who were current or former California teachers and public school administrators between the ages of 22 and 84, and who had no history of colon cancer. The study-published this month in the Cancer Epidemiology Biomarkers & Prevention journal-began in 1995 and followed the women through 2002.Researchers collected information about exercise habits throughout the women's lives and used information from California's statewide comprehensive cancer registry to identify which women developed colon cancer. Over the course of the study, 395 participants were diagnosed with invasive colon cancer.In previous studies, the association between physical activity and reduced colon cancer risk was stronger in men than in women. In order to understand why women appeared to be benefiting less from regular exercise, researchers in the California Teachers Study divided participants into two groups: those who had taken hormone replacement therapy and those who hadn't."The issue was why the benefit to women was not as strong as expected," says Bernstein. "Most people hadn't looked at hormone therapy as a factor before."Hormone replacement therapy, which is often used to treat the symptoms of menopause, has been shown to reduce colon cancer risk in women, Bernstein says. For women who had taken hormone therapy, exercise didn't provide any additional benefit.While hormone therapy reduces the risk of colon cancer, it has also been associated with higher risks for other diseases such as breast cancer. With declining rates of hormone therapy use, physical activity offers a possible alternative for reducing women's colon cancer risk, the study suggests."Four hours of exercise a week provided the same benefit as taking hormones," Bernstein says. (Source: University of Southern California : April 2007.)