Stroke Risks of Females versus Males in Asian Patients with Atrial Fibrillation: A temporal trend analysis and a comparison of the CHA2DS2-VASc and CHA2DS2-VA stroke risk stratification scores.

Background: The 2024 European guidelines for atrial fibrillation (AF) recommended use of the sex-less CHA2DS2-VASc score (ie. CHA2DS2-VA) for stroke risk assessment, but this has been less well validated in Asian cohorts.

Objective: Our aim was to perform temporal analysis of stroke risks of AF females versus males in Taiwan, and to compare the performance of CHA2DS2-VASc versus CHA2DS2-VA scores.

Methods: We used Taiwan's National Health Database (2000-2021) to compare CHA2DS2-VASc and CHA2DS2-VA scores by 2-year intervals, assessing performance with net reclassification index (NRI), integrated discrimination improvement (IDI), and C-statistics.

Results: We analyzed 495,569 newly diagnosed, non-anticoagulated AF patients (44% women). Across calendar years, women consistently had higher ischemic stroke risks than men (incidence rate ratio (IRR) 1.13-1.26, all p<0.05). Among those with CHA2DS2-VA scores of 0-1, women had a lower stroke risk (score 0: IRR 0.81; score 1: IRR 0.88, both p<0.001). For scores 2-8, stroke risk was higher in women (IRR 1.04-1.11, all p<0.05). CHA2DS2-VASc significantly outperformed CHA2DS2-VA in NRI from 2000-2021 and in IDI from 2000-2015. C-statistics were slightly higher for CHA2DS2-VASc from 2000-2013 (p<0.05), but not significantly different after 2014 (p>0.05), suggesting comparable performance of the two scores in more recent years.

Conclusions: AF females have a higher stroke risk than males only in high CHA2DS2-VA score categories, suggesting female sex is more likely to be a risk modifier of stroke in AF. Retaining female sex as a component of the CHA2DS2-VASc score may improve the net reclassification for stroke events in Asian AF patients.