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BMI, physical activity may be linked to breast cancer risk
Phipps AI. Cancer Epidemiol Biomarkers Prev. 2011;20:1-10.
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Postmenopausal women with higher BMI were at a 35% to 40% increased risk for triple-negative and ER-positive breast cancer, according to study results.
Researchers from several sites in the US aimed to determine associations between body size, physical activity and triple-negative disease risk in 155,723 women enrolled in the Women’s Health Initiative.
Women were evaluated for current BMI and BMI in earlier adulthood, waist and hip circumference, waist-hip ratio and recreational physical activity. In the final analysis, the researchers examined the role of these factors in 307 triple-negative breast cancers and 2,610 ER-positive breast cancers.
Women in the highest BMI quartile had a 1.35-fold (95% CI, 0.92-1.99) increase in risk for triple-negative breast cancer compared with women in the lowest BMI quartile. For ER-positive breast cancer, the highest BMI quartile was linked to a 1.39-fold (95% CI, 1.22-1.58) increase in risk compared with the lowest quartile.
Positive associations also were observed between waist and hip circumference and risk for ER-positive breast cancer (P=.01 for both measures). There were no links between triple-negative breast cancer risk and waist and hip circumference.
Women in the highest tertile of recreational physical activity were at a reduced risk for triple-negative breast cancer compared with women who reported no activity (HR=0.77; 95% CI, 0.51-1.13). A similar trend was observed for ER-positive breast cancers for the highest rates of physical activity compared with no physical activity (HR=0.85; 95% CI, 0.74-0.98).
The median follow-up duration was 7.9 years.
“The biological mechanisms underlying these similarities are uncertain and these modest associations require further investigation,” the researchers wrote. “If confirmed, these results suggest potential ways postmenopausal women might modify their risk of both ER [positive] and triple-negative breast cancers.”
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