Real-world Comparative Effectiveness of Apixaban Versus Vitamin K Antagonist

Inclusion Criteria: * NVAF will be defined as the occurrence of 2 or more inpatient or outpatient claims with ICD-9 427.31 as the diagnosis code at any time in the patient's data history prior to inclusion * Patients will be required to have 180 days of enrollment for the assessment of baseline characteristics * CHA2DS2-Vasc (C: Congestive heart failure; H: Hypertension; A2: Age ≥75 years; D: Diabetes mellitus; S2: prior Stroke or TIA or Thromboembolism; V: Vascular disease; A: Age 65-74 years; Sc: Sex category) score ≥2 during the 180 days prior to index apixaban use baseline period Exclusion Criteria: * Patients \<18 years of age * Patients with valvular AF (Atrial fibrillation) * Pregnancy * Malignant cancers * Transient cause of AF * Patients with VTE (Venous thromboembolism) (pulmonary embolism or DVT (Deep Vein Thrombosis)) * Patients with major surgery defined as hip or knee replacement * Prescriptions of OACs (Oral anticoagulants) (apixaban, warfarin, dabigatran, rivaroxaban) before index date * Prescription of more than one OAC on the index date * Patient with any of the events defined in the composite endpoint