Ischaemic and haemorrhagic stroke associated with non-vitamin K antagonist oral anticoagulants and warfarin use in patients with atrial fibrillation: a nationwide cohort study

BACKGROUND: Non-vitamin K antagonist (VKA) oral anticoagulants (NOACs) are widely used as stroke prophylaxis in non-valvular atrial fibrillation (AF), but comparative data are sparse. PURPOSE: To compare dabigatran, rivaroxaban, and apixaban vs. VKA and the risk of stroke/thromboembolism (TE) and intracranial bleeding in AF. METHODS: Using Danish nationwide registries (2011-15), anticoagulant-naïve AF patients were identified when initiating VKA or an NOAC. Outcomes were stroke/TE and intracranial bleeding. Multiple outcome-specific Cox regression was performed to calculate average treatment effects as standardized differences in 1-year absolute risks. RESULTS: Overall, 43 299 AF patients initiated VKA (42%), dabigatran (29%), rivaroxaban (13%), and apixaban (16%). Mean CHA2DS2-VASc (SD) score was: VKA 2.9 (1.6), dabigatran 2.7 (1.6), rivaroxaban 3.0 (1.6), and apixaban 3.1 (1.6). Within patient-specific follow-up limited to the first 2 years, 1054 stroke/TE occurred and 261 intracranial bleedings. Standardized absolute risk (95% CI) of stroke/TE at 1 year after initiation of VKA was 2.01% (1.80% to 2.21%). In relation to VKA, the absolute risk differences were for dabigatran 0.11% (-0.16% to 0.42%), rivaroxaban 0.05% (-0.33% to 0.48%), and apixaban 0.45% (-0.001% to 0.93%). For the intracranial bleeding outcome, the standardized absolute risk at 1 year was for VKA 0.60% (0.49% to 0.72%); the corresponding absolute risk differences were for dabigatran -0.34% (-0.47% to - 0.21%), rivaroxaban -0.13% (-0.33% to 0.08%), and apixaban -0.20% (-0.38% to - 0.01%). CONCLUSIONS: Among anticoagulant-naïve AF patients, treatment with NOACs was not associated with significantly lower risk of stroke/TE compared with VKA, but intracranial bleeding risk was significantly lower with dabigatran and apixaban.