BACKGROUND AND AIMS A recent European trial found that in frail elderly patients with atrial fibrillation (AF), switching from well-managed warfarin to direct oral anticoagulants (DOACs) was associated with higher bleeding risk. This study aimed to evaluate the safety and effectiveness of switching from warfarin to DOACs in frail elderly Asian AF patients.

METHODS The Korean national claims database was used to identify AF patients aged ≥75 years who were prescribed warfarin between January 2013 and August 2015, had Hospital Frailty Risk Score ≥ 5, and experienced no major bleeding or thromboembolic events during this period. To evaluate the effect of switching from warfarin to a DOAC, a time-varying approach based on anticoagulant exposure was applied. The primary outcome was major bleeding. Secondary outcomes included thromboembolic events, net clinical outcome (NCO; composite of major bleeding and thromboembolic events), and all-cause death.

RESULTS Among 12 461 patients, 9112 patients remained on warfarin, whereas 3349 switched to DOACs at least once. During a total follow-up of 11 842 person-years, DOAC treatment was associated with higher risks of major bleeding (hazard ratio 1.36, 95% confidence interval 1.01-1.81), thromboembolic events (1.61, 1.30-2.00), NCO (1.58, 1.29-1.94), and all-cause death (1.20, 1.02-1.42). In various subgroup analyses, DOAC treatment tended to show higher risks of all outcomes compared with warfarin treatment.

CONCLUSIONS In frail elderly Asian AF patients stably maintained on warfarin, switching to DOACs was associated with higher risks of adverse clinical events, suggesting the need for careful consideration before routine switching.