Risk of Stroke in Atrial Fibrillation According to Sex in Patients Aged Younger Than 75 Years: A Large-Scale, Observational Study Using Real-World Data

Background: It is unclear whether women have a higher risk of stroke than men. This study aimed to clarify the effects of a sex difference on the risk of ischaemic stroke in patients with atrial fibrillation (AF).

Methods: Health check and insurance claims data were used of people who were aged <75 years from 2005 to 2017 in Japan. Patients with AF who were not on anticoagulation therapy were identified. After excluding patients with artificial valves (n=28), haematological disease (n=1,124), aged ≤20 years (n=207), and taking anticoagulant therapy (n=11,848), 9,733 remained for inclusion into the study. The primary outcome was hospital admission due to ischaemic stroke.

Results: Of the 9,733 participants, 7,079 (72.7%) were men. The mean age of women (54.4 years) was significantly higher than that of men (53.2 years). During a mean 2.5-year follow-up period, 143 ischaemic stroke events occurred. Female sex was not associated with ischaemic stroke (adjusted hazard ratio [95% confidence interval]: 1.13 [0.78-1.66]). When stratified using the CHA₂DS₂-VASc score, the annual incidence of ischaemic stroke was similarly low among women with a CHA₂DS₂-VASc score of 1 (0.8%) and men with a score of 0 (0.7%). The incidence of ischaemic stroke increased with a CHA₂DS₂-VASc score of 2 in women and 1 in men.

Conclusions: In this large-scale, real-world study of patients with AF, the risk of ischaemic stroke among those aged <75 years was comparable between women and men. These findings are consistent with the current guidelines, which do not recommend anticoagulant therapy for women with no other risk factors (CHA₂DS₂-VASc score of 1).