- Among postmenopausal women with normal BMI (18.5-24.9 kg/m2) participating in the Women's Health Initiative (WHI), the highest (vs lowest) level of whole-body fat is associated with an 89% increase in breast cancer risk.
Why this matters
- BMI does not distinguish between adiposity and muscle mass.
- Normal BMI categorization may not be the best proxy for breast cancer risk in postmenopausal women.
- Prospective cohort (N=3460) of postmenopausal women in the WHI with normal BMI who underwent body fat measurement using dual-energy X-ray absorptiometry (DXA).
- Funding: Breast Cancer Research Foundation; Conquer Cancer Foundation; NIH; others.
- After a median follow-up of 16 years, women with the highest (vs lowest) quartile of whole-body fat had an 89% increase in invasive breast cancer risk (aHR, 1.89; 95% CI, 1.21-2.95).
- Women with the highest (vs lowest) quartile of trunk fat mass had an 88% increase in invasive breast cancer risk (aHR, 1.88; 95% CI, 1.18-2.98).
- Somewhat higher risks were found for estrogen receptor-positive breast cancer, with corresponding aHRs of 2.21 (95% CI, 1.23-3.67) and 1.98 (95% CI, 1.18-3.31), respectively.
- Observational design.
- Findings limited to postmenopausal women.