Background Prevalence of atrial fibrillation (AF) is increasing and now affects over 10% of individuals aged ≥80 years. Warfarin is effective in preventing thromboembolic events, but is substantially under–used in the elderly, and use of new anticoagulants at age ≥80 years is also limited. We determined the incidence and outcome of AF–related thromboembolic events at all ages in a population–based study and projected future event rates.

Methods We studied age–specific incidence and outcome of all AF–related incident strokes and systemic emboli from 2002–2012 in a population–based study in relation to premorbid use of warfarin. Future projections for incidence of AF–related strokes and systemic emboli were made based on predicted changes in population age and sex.

Results Among 3096 TIA, stroke or acute peripheral vascular events, there were 748 (24.2%) AF–related events, including 383 incident ischaemic strokes and 71 incident systemic emboli. Incidence increased steeply with age, with 272 (59•9%) events occurring at ≥80 years. Of 208 patients with incident events at age ≥80 years and known prior AF, 189 (90•9%) were not on warfarin. Among these cases, the premorbid CHADS2 score was ≥2 in 167 (88•4%), there was no documented contraindication to warfarin in 144 (76•2%), and of 99 patients who were independent prior to their event, 73 (73•7%) were dead or disabled at six months follow–up. Extrapolated to the UK population aged ≥80 years, 19,012 AF–related ischaemic strokes and 4189 systemic emboli would have been expected in 2010, increasing to 60,528 and 14,968 respectively by 2050, by which time 84% of all AF–related thromboembolic events will occur at age ≥80 years and 42.1% at ≥90 years.

Conclusion Numbers of AF–related ischaemic strokes at age ≥80 years are projected to treble by 2050, along with numbers of systemic emboli, unless rates of anticoagulation in older patients increase.