Background and Purpose— Bleeding risks from combined antiplatelet-warfarin therapy have not been well-described in clinical practice. We examined antiplatelet therapy among warfarin users and the impact on major bleeding rates.

Methods— Retrospective cohort analysis of persons discharged on warfarin after an atrial fibrillation admission using data from Medicare’s National Stroke Project. Data included Medicare claims, enrollment information, and medical record abstracted data. Logistic regression and Cox proportional hazards models were used to predict concurrent antiplatelet use and hospitalization with a major acute bleed within 90 days after discharge from the index AF admission.

Results— 10 093 warfarin patients met inclusion criteria with a mean age of 77 years; 19.4% received antiplatelet therapy. Antiplatelet use was less common among women, older persons, and persons with cancer, terminal diagnoses, dementia, and bleeding history. Persons with coronary disease were more likely to receive an antiplatelet agent. Antiplatelets increased major bleeding rates from 1.3% to 1.9% (P=0.052). In the multivariate analysis, factors associated with bleeding events included age (OR, 1.03; 95% CI, 1.002 to 1.05), anemia (OR, 2.52; 95% CI, 1.64 to 3.88), a history of bleeding (OR, 2.40; 95% CI, 1.71 to 3.38), and concurrent antiplatelet therapy (OR, 1.53; 95% CI, 1.05 to 2.22).

Conclusions— Although concerns about increased bleeding risk with combined warfarin-antiplatelet therapy are not unfounded, the risk of bleeding is moderately increased. The decision to use concurrent antiplatelet therapy appears to be tempered by cardiac and bleeding risk factors.