Abstract 134: Effect of Warfarin Adherence on the Mortality After Ischemic Stroke: A Nationwide Multicenter Cohort Study

Abstract

Background and purpose: Warfarin is one of the most important prevention drugs against ischemic stroke. Factors influencing on warfarin adherence in patients with atrial fibrillation have been investigated. However, few studies have elaborated on the significance and related factors of warfarin adherence in patients with ischemic stroke or transient ischemic attack (TIA). Methods: A total of 46,219 patients with ischemic stroke or TIA were enrolled from October 2007 through December 2011 in Clinical Research Center for Stroke as a nationwide project in Korea. The morality information of all patients was based on computerized searches of death certificate data from the “Statistics Korea” of the Korean National Statistical Office, and the whole drug information was obtained from the Health Insurance Review Assessment and Review Service in Korea. Among them, warfarin was prescribed for 5,660 patients over 6 months. Warfarin adherence was defined as % adherence = (n of days’ supply) / (actual n of days to refill) х 100. Nonadherence was defined as < 80% adherence. We censored the mortality data on 31 December 2012. Results: From 5,660 patients using warfarin over 6 months, 801 patients (14.2%) were included in nonadherence group. The factors related to nonadherence for warfarin ware theses: old age, increased stroke severity, and the presence of diabetes or hyperlipidemia. Based on Cox regression analysis, compared with good adherence group, the adjusted hazard ratio (HR) of the nonadherence group for all-cause of mortality were 1.46 (95% confidence interval, 1.24 – 1.72) after controlling old age, stroke severity, and the presence of diabetes, hypertension, hyperlipidemia, and smoking. The presence of diabetes also predicted all-cause death after stroke independently in patients using warfarin over 6 months (adjusted HR, 1.28 ; 95% confidence interval, 1.10 – 1.49). Conclusion: Our study demonstrated that nonadherence for warfarin is independent predictor of all-cause death after ischemic stroke or TIA from nationwide multicenter follow-up study. The related factors to nonadherence for warfarin were old age, increased stroke severity, and the presence of diabetes or hyperlipidemia.