Background: Atrial fibrillation (AF) and dementia are largely prevalent and incident in progressively older subjects, suggesting a link between the two conditions. While in the general population there are several findings supporting a causal relationship between AF and dementia, it is unclear whether or not this association is still present in individuals aged 80 and older. Results: So far, the few studies that analysed this issue did not provide enough evidence supporting the causative role of AF in increasing the risk of cognitive decline or dementia in patients aged 80 and older. Conversely, a relevant role of optimal anticoagulation control in determining a significant reduction in the risk of cognitive decline is suggested, in AF subjects aged 80. years or older. Conclusions: Further data, coming from population-based studies specifically investigating very old individuals and based upon large samples and comprehensive cognitive assessments, are needed to fully elucidate the relationship between AF and dementia in very old individuals.