Atrial fibrillation, stroke, and anticoagulation in Medicare beneficiaries: trends by age, sex, and race, 1992-2010.

Background: We evaluated temporal trends in ischemic stroke and warfarin use among demographic subsets of the US Medicare population that are not well represented in randomized trials of warfarin for stroke prevention in nonvalvular atrial fibrillation (AF).
Methods and Results: One-year cohorts of Medicare-primary payer patients (1992-2010) were created using the Medicare 5% sample. International Classification of Diseases, Ninth Revision, Clinical Modification codes were used to identify AF and ischemic and hemorrhagic stroke; ≥ 3 consecutive prothrombin time claims were used to identify warfarin use. Ischemic stroke rates (per 1000 patient-years) decreased markedly from 1992 to 2010. Among women, rates decreased from 37.1 to 13.6 for ages 65 to 74 years, from 55.2 to 16.5 for ages 74 to 84, and from 66.9 to 22.9 for age ≥ 85; warfarin use increased 31% to 59%, 27% to 63%, and 15% to 49%, respectively. Among men, rates decreased from 33.8 to 11.7 for ages 65 to 74 years, from 49.2 to 13.8 for ages 75 to 84, and from 51.5 to 18.0 for age ≥ 85; warfarin use increased 34% to 63%, 28% to 66%, and 15% to 55%, respectively. Rates decreased from 47.0 to 14.8 for whites and 73.0 to 29.3 for blacks; warfarin use increased 27% to 61% and 19% to 52%, respectively. In all age categories, the thromboembolic risk (CHADS [congestive heart failure, hypertension, age ≥ 75 years, diabetes, stroke]) score was significantly higher among women (versus men) and blacks (versus whites).
Conclusions: Ischemic stroke rates among Medicare AF patients decreased significantly in all demographic subpopulations from 1992-2010, coincident with increasing warfarin use. Ischemic stroke rates remained higher and warfarin use rates remained lower for women and blacks with AF, groups whose baseline CHADS scores were higher.
(© 2014 The Authors. Published on behalf of the American Heart Association, Inc., by Wiley Blackwell.)