Age-dependent association between heart failure and stroke risk in atrial fibrillation: a nationwide cohort study

Background Atrial fibrillation (AF) is a major cause of ischemic stroke (IS), and the risk varies among individuals depending on age and comorbidities. Although age is the most significant independent risk factor, it also appears to influence other risk factors—such as vascular disease and female sex—though data on how it impacts other key risk factors remain limited. Purpose Therefore, we conducted a nationwide retrospective cohort study to assess whether the association between heart failure (HF)—a well-established risk factor—and IS in AF patients is age-dependent. Methods The Finnish AntiCoagulation in Atrial Fibrillation (FinACAF) study includes all patients with AF in Finland from 2007 to 2018. Data were collected from healthcare registries encompassing all levels of care. Incidence rate ratios (IRRs) for stroke were calculated comparing patients with HF to those without HF across the entire age spectrum. Results We identified 229,565 patients with new-onset AF. The prevalence of HF increased progressively with age, reaching 4.3%, 8.8%, 11.0%, 15.2%, 26.1% and 38.7% in the respective age groups <50, 50-59, 60-69, 70-79, 80-89 and ≥90 years. The association between HF and IS was highest among younger patients and decreased with age, with a statistically significant interaction between age and IRR (p-value <0.001). The adjusted absolute rate difference between patients with and without HF remained stable, at approximately 1 event per 100 patient-years, across all age categories. Conclusion HF was more strongly associated with IS in younger patients than in older individuals with AF, highlighting the importance of considering HF in the decision-making regarding oral anticoagulation particularly in younger patients.