Atrial fibrillation (AF) is a risk factor for cerebrovascular diseases and can manifest as impaired cognitive function (ICF). ICF may be accompanied by various focal neurologic deficits (FNDs). This study evaluated cognitive function and the risk for ICF in patients aged >or=65 years hospitalized for any reason and grouped according to the presence of AF and/or FNDs. Data on 2,314 conscious patients aged >or=65 years (1,506 women) were analyzed. Physical examination, electrocardiography at rest, and the Mini-Mental State Examination were performed at admission. The median Mini-Mental State Examination score was 25 in patients without AF or FNDs (63.4%), 23 in those with AF alone (23.6%), 21 in those with FNDs alone (8.9%), and 18 in those with AF and FNDs (4.1%). On multivariate logistic regression (adjusted for age and gender), the risk for ICF was increased in patients with AF alone (p <0.0001), in those with FNDs alone (p <0.0001), and in those with AF and FNDs (p <0.0001). In conclusion, hospitalized patients aged >or=65 years with AF and/or FNDs at admission are at increased risk for ICF. The influences of AF and FNDs on the risk for ICF are independent of each other.