Objective: To test the hypothesis that use of lipid-lowering drugs reduces the risk of breast cancer in older women.
Methods: This was a multicenter prospective cohort study conducted at four community-based clinical centers in the United States, including 7528 Caucasian women, mean age 77 years. The main outcome measure was incident breast cancer confirmed by medical record and pathology reports identified over an average of 6.8 years (244 cases).
Results: The use of lipid-lowering drugs was reported by 576 women (7.7%). The age-adjusted incidence of breast cancer was 3.1/1000 person-years among statin users, 1.4 among women using other lipid-lowering agents, and 5.0 among nonusers. After adjustment for age and body weight, the relative risk (RR) of breast cancer among statin users was 0.28 (95% confidence intervals [CI] 0.09-0.86), and among women who used other lipid-lowering drugs, it was 0.37 (95% CI 0.14-0.99) in comparison to nonusers. The combined group of lipid-lowering drug users had a 68% reduction in the risk of breast cancer (95% CI 32%-85%). Further adjustment for hormone use, family history of breast cancer, mammography use, or other risk factors did not alter the results.
Conclusions: Older women who use lipid-lowering drugs may have a reduced risk of breast cancer. Given the widespread use of statins in older women, these results could have a large public health impact. However, these findings need confirmation in other prospective studies, as they were based on a small number of breast cancer events.