The prevalence of AF in a cohort of very old nursing home residents was 10%. Anticoagulation was prescribed in fewer than 50% of eligible cases despite high individual risk of stroke. Geriatric syndromes, especially falls and cognitive disorders, were the main reported contraindications for prescribing anticoagulants. Physicians caring for those residents wrongly thought that paroxysmal AF caused fewer thromboembolic events than permanent AF, which explains lower rates of anticoagulant prescription in individuals with paroxysmal AF.