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.