This study is to compare the risk of major bleeding among oral anticoagulant (OAC)-naïve non-valvular atrial fibrillation (NVAF) patients initiating treatment

Inclusion Criteria:

• Individuals greater than or equal to 20 years old as of the index date
• At least 1 diagnosis of NVAF prior to or on index date, identified by any medical records
• Newly treated with warfarin or apixaban between 01-Jan-2011 to 31-Dec-2016. The first warfarin or apixaban prescription date during the identification period will be designated as the index date

Exclusion Criteria:

• Patient's medical records indicating pregnancy during the follow-up period
• Patient's medical records indicating taking warfarin, apixaban, dabigatran, rivaroxaban, or edoxaban during the 6-months prior to the index date
• Had > 1 OAC prescription in the patient's medical records on the index date

Other protocol defined inclusion/exclusion criteria could apply

Patients' medical charts with newly initiating warfarin or apixaban within the identification period fulfilling the study eligibility criteria