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Introduction: New oral anticoagulants are non-inferior compared with warfarin regarding stroke prevention in atrial fibrillation, with similar or decreased risk of bleeding. However, it is unclear whether high TTR warfarin is as effective and safe as NOACs. Our objective was to investigate efficacy and safety of apixaban, dabigatran or rivaroxaban compared with warfarin in clinical practice.

Materials and methods: Nationwide retrospective cohort study based on Swedish quality registries. Atrial fibrillation patients initiated on apixaban, dabigatran, rivaroxaban or warfarin between 2013-01-01 and 2015-1231 were included. Main outcome measures were all-cause stroke and systemic embolism, all-cause stroke, ischemic stroke, hemorrhagic stroke; major bleeding, intracranial bleeding, gastrointestinal bleeding, other bleeding (fatal or requiring hospital care); all-cause mortality; myocardial infarction.

Results: The study included 64,382 patients corresponding to 81,176 treatment years. Of these, 37,174 patients were instituted on warfarin, 6574 on dabigatran, 8323 on rivaroxaban and 12,311 on apixaban. In warfarin treated patients, the time in therapeutic range was 71.4%. After propensity score matching, there was no significant difference in risk of stroke or systemic embolism between NOAC and warfarin treated patients. Hazard ratios for major bleeding events were 0.63(95% CI 0.52-0.75) for apixaban, 0.74(0.62-0.87) for dabigatran and 1.06(0.92-1.23) for rivaroxaban, compared with warfarin.

Conclusions: This study showed no difference between apixaban, dabigatran, or rivaroxaban compared to high TTR warfarin treatment regarding stroke prevention. However, fewer bleeding events were seen for apixaban and dabigatran, but not for rivaroxaban. Further studies are needed on the comparability of individual NOACs with respect to bleeding risks.