Purpose: To investigate risk factors for stroke in patients initiating oral anticoagulants for atrial fibrillation in Norway and their association with receiving DOACs versus warfarin.
Methods: From nationwide registries, we identified naïve users initiating treatment with warfarin, dabigatran, rivaroxaban, or apixaban for atrial fibrillation from 2010 to 2015 in Norway. We studied temporal changes in the CHA2DS2-VASc score and its component risk factors. We used multiple logistic regressions to identify CHA2DS2-VASc risk factors associated with receiving DOACs versus warfarin in 2015.
Results: From 2010 to 2015, the yearly number of new oral anticoagulant users increased from 7588 to 13,344. All new users initiated warfarin in 2010, while 86% initiated a DOAC in 2015. The mean CHA2DS2-VASc score decreased from 3.2 (SD 1.7) to 3.1 (SD 1.6) in the same period. Vascular disease (0.56 [0.49-0.63]), congestive heart failure (OR 0.65 [95% CI 0.58-0.72]), and diabetes (0.83 [0.73-0.95]) decreased the odds of receiving DOACs instead of warfarin, and ischemic stroke/transient ischemic attack/arterial thromboembolism (1.31 [1.12-1.54]), age 65-74 (1.23 [1.06-1.43]), and female sex (1.22 [1.10-1.36]) increased it. Age ≥ 75 (reference age < 65) and hypertension had no impact.
Conclusions: The uptake of DOACs was rapid and spurred an increase in new users of oral anticoagulants for atrial fibrillation from 2010 to 2015 in Norway. The mean CHA2DS2-VASc score did not change substantially during this period. Vascular disease, heart failure, and diabetes were associated with initiation of warfarin, and previous stroke, age 65-74 and female sex with initiation of DOACs.
Keywords: Anticoagulation treatment; Atrial fibrillation; Risk factors; Stroke.