At age 60, 1 in 25 Americans have AFib. At age 80+, this increases to nearly 1 in 10.
Prevalence of Diagnosed Atrial Fibrillation in Adults: National implications for rhythm management and stroke prevention: the AnTicoagulation & Risk Factors in Atrial Fibrillation (ATRIA) study. JAMA. 2001; 285(18). http://jama.jamanetwork.com/article.aspx?articleid=193807