Schaefer JK, et al. - In a registry-based cohort study of 3,688 propensity score-matched patients prospectively followed up at anticoagulation clinics, researchers assessed the occurrence and results of adding aspirin to warfarin in those with no clear therapeutic indication for combination therapy. In this study, 37.5% of participants were taking a combination of warfarin and aspirin with no clear therapeutic indication for aspirin. At 1 year, patients receiving combination warfarin and aspirin vs those receiving warfarin only had higher overall bleeding rates, major bleeding, emergency department visits for bleeding, and hospitalizations for bleeding. A combination of warfarin and aspirin therapy was related to higher bleeding and similar observed rates of thrombosis vs warfarin monotherapy.