Time trends in atrial fibrillation-related stroke during 2001-2020 in Sweden: a nationwide, observational study.

Background: Great efforts have been made to improve stroke prevention in atrial fibrillation (AF) patients. Meanwhile, incidence of AF is increasing, which may affect the share of AF-related stroke on all strokes. We aimed to examine the temporal trends in the incidence of AF-related ischemic stroke between 2001 and 2020, if it varied by use of novel oral anticoagulant drugs (NOAC), and if the relative risk of ischemic stroke associated with AF changed over time. Methods: Data from the total Swedish population aged ≥70 years during the period 2001-2020 were used. Annual incidence rate (IR) was calculated for overall and AF-related ischemic stroke which was defined as first-ever ischemic stroke with AF diagnosed up to 5 years before, on the same day, or within 2 months after the stroke event. Cox regression models were performed to examine if the hazard ratio (HR) between AF and stroke changed over time. Findings: While IR of ischemic strokes declined during 2001-2020, IR of AF-related ischemic stroke remained stable between 2001 and 2010 but showed a consistent decline between 2010 and 2020. The HR of ischemic stroke within 3 years from an AF diagnosis came down from 2.39 (95% confidence interval: 2.31-2.48) to 1.54 (1.48-1.61) over the study period, which was largely explained by a substantial increase in the use of NOAC among AF patients after 2012. Yet, by the end of 2020, 24% of all ischemic strokes had a preceding or concurrent AF diagnosis, which is slightly higher than in 2001. Interpretation: Even though both the absolute and relative risk of AF-related ischemic stroke declined over the past 20 years, every fourth ischemic stroke in 2020 still had a preceding or concurrent AF diagnosis. This represents a great potential for future gains in stroke prevention among AF patients. Funding: Swedish Research Council and Loo and Hans Osterman Foundation for Medical Research.