Temporal Trends of Ischemic Stroke Risk in Patients With Incident Atrial Fibrillation Before Anticoagulation

Atrial fibrillation (AF) is a major risk factor for ischemic stroke (IS), but whether the magnitude of this risk has changed over time is unknown. This study sought to investigate temporal trends in IS rates in patients with incident AF before oral anticoagulant agent (OAC) therapy. The nationwide FinACAF (Finnish Anticoagulation in Atrial Fibrillation) study covers patients with AF at all levels of care in Finland from 2007 to 2018. A 4-week quarantine period from AF diagnosis was applied, and only follow-up time without OAC therapy was included. Incidence rates of IS were computed in 4-year intervals in relation to sex and non-sex CHA DS -VASc (ie, CHA DS -VA) score values. In total, 129,789 patients with new-onset AF were identified (49.2% women; mean age: 71.4 ± 14.5 years). Between the calendar year intervals of 2007-2010 and 2015-2018, the patients' mean CHA DS -VA score increased from 2.5 to 3.0, and concurrently the overall IS rate decreased by 25% from 36.7 to 27.6 events per 1,000 patient-years. This trend was driven by a 32% decrease of IS rate in women, particularly among those with higher age and CHA DS -VA scores. The IS rate in patients with a CHA DS -VA score of 1 was 8.2 events per 1,000 patient-years and remained stable across the study period. The initial IS risk in AF patients, before the initiation of OAC therapy, has decreased by 25% between 2007 and 2018 despite an increase in both age and stroke risk scores. The decrease has been most pronounced in older women with high stroke risk scores.