Temporal trends in ischemic stroke and anticoagulation therapy for non-valvular atrial fibrillation: effect of diabetes

Background: Diabetes is an important risk factor for ischemic stroke in non-valvular atrial fibrillation (AF). The aim of the present study was to evaluate temporal trends in ischemic stroke and warfarin use among US Medicare patients with and without diabetes. Methods: In this retrospective cohort study, 1-year cohorts of patients with Medicare as the primary payer over the period 1992–2010 were created using the Medicare 5% sample (excluding patients with valvular disease and end-stage renal disease). International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) codes were used to identify AF, ischemic and hemorrhagic stroke, and diabetes; three or more consecutive prothrombin time claims were used to identify warfarin use. Results: Demographic characteristics of subjects in 1992 (n = 40 255) and 2010 (n = 80 314), respectively, were as follows: age 65–74 years, 37% and 32%; age >85 years, 20% and 25%; White, 94% and 93%; hypertension, 46% and 80%; diabetes, 20% and 32%; and chronic kidney disease, 5% and 18%. Among Medicare AF patients with diabetes, ischemic stroke decreased by 71% (1992–2010) from 65 to 19 per 1000 patient-years; warfarin use increased from 28% to 62%. Among patients without diabetes, ischemic stroke decreased by 68% from 44 to 14 per 1000 patient-years, whereas warfarin use increased from 26% to 59%. Approximately 38% of Medicare AF patients with diabetes did not receive anticoagulation in 2010. Conclusions: Ischemic stroke declined and warfarin use increased similarly in Medicare patients with and without diabetes. Ischemic stroke rates were consistently higher in diabetes patients, validating the inclusion of diabetes in risk calculators. The population of Medicare patients with diabetes who did not receive warfarin deserves future attention.