on June 29, 2006
Published online before print June 29, 2006, doi: 10.1161/01.STR.0000230607.07928.17
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Submitted on April 28, 2006
From the Departments of Neurology (K.L., D.C.A.) and Medicine (A.J.C., C.A.H.), Hennepin County Medical Center, University of Minnesota, Minneapolis, Minn (K.L., D.C.A.); and the Chronic Disease Research Group, Minneapolis Medical Research Foundation, Minneapolis, Minn (C.A.S., A.J.C., C.A.H.). * To whom correspondence should be addressed. E-mail: cherzog{at}cdrg.org.
Background and Purpose--Clinical trials have illustrated warfarin’s protective effect on stroke risk in patients with atrial fibrillation (AF). The current study investigated temporal trends in AF prevalence, warfarin use, and its relation to stroke risk in Medicare patients with AF from 1992 to 2002. Methods--The Medicare 5% sample for 1992 to 2002 was used to create 1-year cohorts of patients with Medicare as primary payer throughout the year. International Classification of Diseases, Ninth Revision, Clinical Modification codes were used to identify AF, ischemic and hemorrhagic stroke, and comorbid conditions. A previously validated surrogate measure, prothrombin/international normalized ratio claims, was used to identify warfarin use. Cox proportional hazards regression was used to examine time to stroke with warfarin use as a time-dependent variable. Results--Among Medicare patients aged Conclusions--This analysis represents an observational validation of stroke prevention in AF trials. The significant increase in warfarin use among patients with AF illustrates diffusion of trial evidence into clinical practice.
Accepted on May 23, 2006
Atrial Fibrillation and Stroke in the General Medicare Population. A 10-Year Perspective (1992 to 2002)
Kamakshi Lakshminarayan MD, PhD;
65 years, AF prevalence increased from 3.2% in 1992 to 6.0% in 2002 with higher prevalence in older subsets of the study population. Among patients with AF, warfarin use increased significantly (P
0.001) for each year examined, from 24.5% in 1992 to 56.3% in 2002. Stroke rates per 1000 patient-years declined from 46.7 in 1992 to 19.5 in 2002 for ischemic stroke but remained fairly steady for hemorrhagic stroke (range, 1.6 to 2.9). Time-to-event modeling confirmed a protective association of warfarin against ischemic stroke among Medicare patients with AF.
Key words: atrial fibrillation • Medicare • warfarin
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