Background: Recent large randomized controlled trials have shown that novel oral anticoagulants (NOACs) are at least as effective as warfarin for risk reduction of stroke in patients with non-valvular atrial fibrillation (NVAF) and are associated with similar or lower rates of bleeding. The study aim was to compare major bleeding risk among untreated NVAF patients to those initiating apixaban, dabigatran, rivaroxaban or warfarin