Factors related to the choice of warfarin for treating newly diagnosed nonvalvular atrial fibrillation are associated with safety outcomes during anticoagulation: A new‐user, active‐comparator, retrospective cohort study

Warfarin is often chosen for older patients with multiple comorbidities characterized by reduced renal function, which is associated with a higher risk of major bleeding and mortality. These high-risk patients seem to have a poor prognosis regardless of the type of anticoagulant used. Thus, safe anticoagulant therapy remains a challenge for such patients.