Abstract 8293: Atrial Fibrillation and Stroke in the General Medicare Population: a Fifteen Year Perspective (1992-2007)
Introduction: Non-valvular atrial fibrillation (AF) is a major cause of stroke in the elderly, and anticoagulation is indicated in these pts. Due to changing demography of the US population (“graying of America”), AF prevalence and characteristics of AF pts may have changed over time. Temporal trends in warfarin therapy potentially reflect evolving evidence-based practice patterns and pt characteristics.
Methods: We searched the 5% Medicare database (n ∼ 1.8 million pts/cohort yr) to identify AF pts (no ESRD, age 65+) in 1992-2007. We used Medicare claims to count ischemic and hemorrhagic strokes after the AF diagnosis. We used 3+ prothrombin time (PT/ INR) claims as a surrogate for warfarin use (a previously validated method). For each year's cohort, we calculated the rate of stroke events (per time at risk) and warfarin use within the cohort. CHADS2 risk scores and contra-indications to warfarin use were derived from diagnosis codes.
Results: The prevalence of AF within the elderly Medicare population grew from 3% in 1992 (n= 40,094; 37% age 65-74, 44% 75-84, 20% 85+; 44.7% male, 94.1% white, 4.1% black) to 7% in 2007 (n= 72,615; 31% age 65-74, 45% 75-84, 24% 85+; 47.7% male, 93.7% white, 3.7% black). The percent of pts at “high” risk for stroke (CHADS2 score >2) rose from 20% to 28%. Warfarin use progressively increased from 27% in 1992 to 63% in 2007, despite increase in warfarin contra-indications from 32 to 42%. The Figure details stroke rates and warfarin use over time.
Conclusion: Progressively more elderly AF pts have received warfarin therapy from 1992 to 2007. The characteristics of AF pts receiving warfarin have changed over time, reflecting temporal changes in practice patterns. The 15 yr decline in ischemic strokes (with no change in hemorrhagic stroke) is temporally co-incident with increasing warfarin use. Newer oral anti-coagulants without PT/INR monitoring requirements may further increase the number of elderly AF pts receiving therapeutic anti-coagulation.
- © 2011 by American Heart Association, Inc.