Objective: To evaluate if 3-hydroxy-3-methylglutaryl CoA reductase reductase inhibitor use (statins) alters mammography measured breast density.
Methods: Cohort study of women ages 50 to 80 years with two mammography screenings. Changes in BI-RADS breast density between screenings was compared for nonusers, initiators, discontinuers, continuers, and any users of statins.
Results: Statin use was not associated with increases or decreases in breast density compared with nonusers after adjusting for age, body mass index, change in body mass index, hormone therapy use, and time between screenings. Cumulative days of statin use during the year before screening was not associated with changes in breast density in any of the groups of statin users. When hormone therapy users were excluded, any statin use was associated with an increase in breast density compared with nonusers (odds ratio, 1.2; 95% confidence interval, 1.0-1.5).
Conclusions: We found no association between statin use and change in breast density in general, but statin use may be associated with increases in breast density among nonusers of hormone therapy.