Continued Use of Warfarin in Veterans with Atrial Fibrillation After Dementia Diagnosis

Objectives To determine the effectiveness of warfarin in older adults with dementia. Design Retrospective cohort study. Setting Department of Veterans Affairs national healthcare system. Participants Veterans aged 65 and older (73% aged ≥75, 99% male, 91% white) who had been receiving warfarin for nonvalvular atrial fibrillation for at least 6 months, were newly diagnosed with dementia in fiscal year 2007 or 2008, and were not enrolled in Medicare Advantage (n = 2,572). Measurements The onset of dementia was defined according to International Classification of Diseases, Ninth Revision, code. Participants were followed for up to 4 years for persistence of warfarin therapy, anticoagulation control, major hemorrhage, ischemic stroke, and all-cause mortality. Results The average CHADS2 score was 3.3 ± 1.3. After a diagnosis of dementia, 405 individuals (16%) persisted on warfarin therapy. Unadjusted Cox proportional hazards analysis demonstrated a protective effect of warfarin in prevention of ischemic stroke (hazard ratio (HR) = 0.64, 95% confidence interval (CI) = 0.46–0.89, P = .008), major bleeding (HR = 0.72, 95% CI = 0.55–0.94, P = .02), and all-cause mortality (HR = 0.66, 95% CI = 0.55–0.79, P < .001). Using propensity score matching, the protective effect of continuing warfarin persisted in prevention of stroke (HR = 0.74, 95% CI = 0.54–0.996, P = .047) and mortality (HR = 0.72, 95% CI = 0.60–0.87, P < .001), with no statistically significant decrease in risk of major bleeding (HR = 0.78, 95% CI = 0.61–1.01, P = .06). Conclusion Discontinuing warfarin after a diagnosis of dementia is associated with a significant increase in stroke and mortality.