To obtain a better understanding on the comparative effectiveness of apixaban versus VKA (Vitamin K antagonist) for stroke prevention in patients with NVAF (Non-valvular atrial fibrillation) in a real-life setting.

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

Patients with non-valvular atrial fibrillation (NVAF)