AbstractBackgroundAtrial fibrillation (AF) associates with higher Alzheimer's disease (AD) and vascular dementia risks but the clinical implications have been scarcely investigated. We examined the association between AD or vascular dementia and adverse outcomes in AF patients.MethodsCohort study between January 2000 and 2017. AF patients were divided into two groups according to vascular dementia or AD, and balanced using propensity score matching (PSM). During 4‐years of follow‐up, incident intracranial hemorrhages (ICH), the composite of ischemic stroke/transient ischemic attack (TIA), hospitalizations, and all‐cause deaths, were recorded.ResultsTwo thousand three hundred seventy‐seven AF patients with dementia (1225 with vascular dementia, and 1152 with AD) were identified. Following a PSM, 615 patients were included in each cohort (i.e., 1:1) and all variables were well‐matched. After PSM, 22 (3.6%) patients with vascular dementia and 55 (8.1%) patients with AD had incident ICH during follow‐up (hazard ratio [HR]: 2.22, 95% confidence interval [CI]: 1.33−3.70, log‐rankp= 0.002). Overall, 237 (38.5%) patients with vascular dementia and 193 (31.4%) patients with AD, developed an ischemic stroke/TIA. The risk of ischemic stroke/TIA was 1.32‐fold higher in vascular dementia (HR: 1.32, 95% CI: 1.09−1.59, log‐rankp= 0.003). The risk of rehospitalization (HR: 1.14, 95% CI: 1.01−1.31), and mortality (HR: 1.25, 95% CI: 1.01−1.58) were also higher among AF patients with vascular dementia compared to AD.ConclusionsThe two forms of dementia in AF patients are associated with different prognosis, with AD being associated with a higher risk of ICH, and vascular dementia with a higher risk of stroke/TIA, hospitalization, and mortality.