Ischemic stroke in low risk patients with atrial fibrillation: a nationwide, registry-based cohort study

Abstract

Abstract Background Despite the good evidence on the prevention of ischemic stroke in high risk patients with atrial fibrillation (AF), the knowledge in AF patients without any cardiovascular risk factors is still limited and the treatment has been highly questioned. Methods We linked data from Swedish health registers to identify all patients with AF but without any previous cardiovascular comorbidity. The risk of ischemic stroke was investigated by using Cox regression models and patients with AF compared with two controls without AF, matched for age and sex. Results Altogether, 229,613 patients with AF and 457,332 matched controls without AF were included in the study; 44.4% of the population were women. Both the 1-year and the 5-year risk to develop ischemic stroke was higher in patients with AF compared to their matched controls without AF, hazard ratio (HR) of 3.7 (95%, confidence interval (CI) 3.5–3.8) and 2.5 (95%, CI 2.5–2.6) respectively. According to the age groups, patients with age of 35 to 49 years had the highest risk to develop ischemic stroke within the first year after AF diagnosis, HR 8.3 (95%, CI 4.0–17.1). Women with AF had 4.4 times higher risk to develop ischemic stroke (HR 4.4, CI 4.2–4.7) compared to matched women without AF. Conclusions In this large, register-based, nationwide cohort study, we found that the 1-risk and 5-year risk to develop ischemic stroke was significantly higher in patients with AF but without any cardiovascular risk factor for stroke, compared to matched controls without AF. Women and middle-aged patients with AF carried the highest risk to develop ischemic stroke indicating the need of further research on risk stratification despite traditional factors. Funding Acknowledgement Type of funding sources: Public hospital(s). Main funding source(s): The Swedish state and The Swedish Research Council