The prevalence of atrial fibrillation (AF) is increasing in older patients faster than that of any other arrhythmia. AF is associated with increased morbidity and mortality. Data on AF in European populations are scarce. The aim of this study was to determine the prevalence and potential predictors of AF and to assess its impact on physical function and mortality in a representative sample of an Italian population >or=65 years of age. One thousand five hundred ninety-nine participants in the Pro.V.A. study, an observational cohort study of Italian subjects >or=65 years old, were assessed for health status, disability, and presence of AF at baseline and at a 4-year follow-up visit. After weighting, prevalence of AF at baseline was 7.4% and increased with advancing age. In subjects with AF, prevalences of stroke, coronary heart disease, peripheral artery disease, cognitive impairment, and physical disability were significantly higher (p <0.01) than in those without AF. In patients with AF, 34% had heart failure compared to 5.3% of those without AF (p <0.0001). In multivariate logistic regression, heart failure was associated with a fivefold risk of AF (odds ratio 5.09, 95% confidence interval 3.20 to 8.11). In Cox analysis, AF was an independent risk factor for mortality. After adjustment for potential confounders, the hazard ratio for mortality associated with AF was 1.47 (95% confidence interval 1.08 to 1.99). In conclusion, in subjects >or=65 years old, AF is strongly associated with heart failure, is an independent risk factor for mortality, and, in the presence of physical disability, could be considered a severity measurement of disability.