This is a retrospective non-intervention observational study to evaluate the difference in safety and effectiveness between apixaban and warfarin using a database provided by Medical Data Vision Co. Ltd. (MDV Co. Ltd.). Eligible patients will be extracted from the database and allocated to the pre-defined cohorts based on the actual age, age of NVAF diagnosis and types of anticoagulant therapy.~Patient characteristics will be balanced by an Inverse probability of treatment weighting (IPTW) method, and risk of stroke/SE (primary effectiveness endpoint) and major bleeding (primary safety endpoint) will be compared.
The objective of this study is to investigate safety and effectiveness of apixaban compared to warfarin in very elderly patients with Non-valvular atrial fibrillation (NVAF). In addition to the absolute age, effects on higher age-related risk factors on relative risk of apixaban to warfarin is also investigated through subgroup analyses.