To Örebro University

Background: It is still under debate whether patients with atrial fibrillation (AF) and a low risk of cerebral infarction would benefit from anticoagulation.

Objective: We aimed to assess whether younger patients with AF and lower CHA2DS2-VASc score would benefit from anticoagulation treatment.

Methods: In a retrospective, nationwide cohort study, using the Swedish national registries, 59981 hospitalized patients were identified with incident AF. After exclusion of 11548 patients because of warfarin use before the AF diagnosis, or death, emigration or stroke within 30 days of AF diagnosis, the remaining 48 433 patients, among whom 27166 patients had no warfarin treatment, were, after adjustment for age, sex and year of AF diagnosis, divided according to age, sex and CHA2DS2-VASc score 0, 1, 2 and ≥3 and included in a time-varying analysis of warfarin treatment versus no treatment. Patients were followed up to 48 months after the inclusion.

Results: In men <65 years and with a CHA2DS2-VASc score 2 or ≥3, the relative risk of having a stroke or cerebral infarction was lower when they received warfarin treatment, HR 0.35 (95% CI 0.18-0.69) and HR 0.37 (95% CI 0.23-0.59) respectively, as compared to HR 1.11 (95% CI 0.56-2.23) when the score was 1. Women younger than 65 years had a low relative risk when CHA2DS2-VASc score was ≥3 points, HR 0.31 (95% CI 0.16-0.59), as compared to HR 1.84 (95% CI 0.86-3.94) and HR 2.13 (95% CI 0.94-4.84) when the score was 2 and 1 respectively. The risk of intracranial bleeding was low and similar in all subgroups on anticoagulation except in the youngest men without risk factors.

Conclusion: Women and men <65 years had a beneficial effect of warfarin if they had two risk factors other than age and sex, without an increased risk of bleeding. Our results support prophylactic anticoagulation treatment in patients under 65 years and a CHA2DS2-VASc score ≥2, other than age and sex.