Statins do not Increase the Rate of Bleeding Among Warfarin Users

Clinical significance of potential interaction between warfarin and statins is unclear. Our objective was to determine whether use of statins as a class or use of simvastatin modulates the rate of bleeding requiring hospitalization among new warfarin users. Using Finnish healthcare databases, we identified a cohort of 101,588 warfarin initiators between 1 January 2009 and 30 June 2012. By the end of 2012, these patients accumulated 92,695 person‐years of exposure to warfarin‐only and 60,253 years of exposure to warfarin‐with‐statin. The outcome was a composite of gastrointestinal, intracranial or other bleeding leading to hospitalization. A Poisson generalized estimating equation model was employed to estimate rate ratios (RR) and their 95% confidence intervals (CI) for exposure to warfarin‐with‐statin compared to warfarin‐only and to allow multiple episodes per patient and time‐dependent covariates. In multivariable models, we found no difference in the bleeding rate in association with exposure to any statin (multivariable‐adjusted RR = 0.98, 95% CI 0.89–1.07) or to simvastatin (RR = 1.01, 95% CI 0.91–1.11) with warfarin compared to exposure to warfarin‐only. We conclude that concomitant use of statins and warfarin was not associated with an increased rate of bleeding requiring hospitalization.