Background: No data exist on whether ischemic stroke admissions among patients with atrial fibrillation (AF) vary by day of the week.

Methods: The nationwide registry-linkage FinACAF study includes all patients with incident AF in Finland between 2007 and 2018. This analysis focused on patients who experienced their first-ever ischemic stroke. Hospital stroke admissions were categorized by day of the week, and a weekday-to-weekend ratio was calculated as the ratio of strokes on a weekday versus a weekend day.

Results: We identified 13 781 patients (mean age 79.2 years; 57.1% women) with AF admitted for ischemic stroke. Stroke admissions varied significantly by day of the week (p < 0.001), with the highest number occurring on Mondays (16.1% of all strokes), followed by a progressive decline over the week. Admission rates were notably higher on Monday and Tuesday, remained relatively stable from Wednesday to Friday, and decreased on Saturday and Sunday (11-12% of all strokes per day). The overall weekday-to-weekend ratio was 1.31 (95% CI 1.26-1.37) and was more pronounced in men than in women, as well as during the first half of the study period (2007-2012) compared to the latter half (2013-2018).

Conclusions: This nationwide cohort study demonstrates a clear day-of-the-week variation in hospital admissions for ischemic stroke among patients with AF, with fewer admissions on weekends than on weekdays. Promoting awareness of stroke symptoms and the importance of seeking timely care regardless of the day may represent a modifiable target to improve outcomes in patients with AF who experience stroke.

Keywords: Atrial fibrillation; circaseptan variation; stroke; weekday variation.