Background Geographical mapping of variations in the treatment and outcomes of a disease is a valuable tool for identifying inequity. We examined international and intranational variations in initiating oral anticoagulation (OAC)
therapy and clinical outcomes among patients with
atrial fibrillation (AF) in Nordic countries. We also tracked real-world trends in initiating OAC and the clinical outcomes. Methods We conducted a registry-based multinational cohort study of OAC-naive patients with an incident hospital diagnosis of AF in Denmark ( N = 61,345), Sweden ( N = 124,120), and Finland ( N = 59,855) and a CHA 2 DS 2 -VASc score of ≥1 in men and ≥2 in women between 2012 and 2017. Initiation of OAC
therapy was defined as dispensing at least one prescription between 90 days before and 90 days after the AF diagnosis. Clinical outcomes included
ischemic stroke,
intracerebral hemorrhage, intracranial
bleeding, other major
bleeding, and all-cause mortality. Results The proportion of patients initiating OAC
therapy ranged from 67.7% (95% CI: 67.5-68.0) in Sweden to 69.6% (95% CI: 69.2-70.0) in Finland, with intranational variation. The 1-year risk of
stroke varied from 1.9% (95% CI: 1.8-2.0) in Sweden and Finland to 2.3% (95% CI: 2.2-2.4) in Denmark, with intranational variation. The initiation of OAC
therapy increased with a preference for direct oral
anticoagulants over
warfarin. The risk of
ischemic stroke decreased with no increase in intracranial and intracerebral
bleeding. Conclusion We documented inter- and intranational variation in initiating OAC
therapy and clinical outcomes across Nordic countries. Adherence to structured care of patients with AF could reduce future variation.