To the Editor We read with interest the study by Hernandez et al1 regarding the risk of bleeding with dabigatran vs warfarin in patients with atrial fibrillation (AF). Using the Medicare population, the authors reported that dabigatran was associated with an increased risk of major bleeding compared with warfarin (hazard ratio [HR], 1.58; 95% CI, 1.36-1.83). In contrast, both the RE-LY randomized controlled trial2 and a recent observational study by Graham et al3 (also using the Medicare population) did not observe an increased risk of major bleeding with dabigatran compared with warfarin (HR, 0.93; 95% CI, 0.81-1.07, and HR, 0.97; 95% CI, 0.88-1.07, respectively).