LAUSR

BACKGROUND It is not known how medication adherence changes after hospitalization for a sentinel thromboembolic event. OBJECTIVE The purpose of this study was to examine the impact of hospitalization for ischemic stroke or thromboembolism on postdischarge adherence to oral anticoagulants in patients with atrial fibrillation. METHODS We conducted a quasi-experimental pre-post observational study using a large U.S. commercial insurance health care claims database. Adult patients with atrial fibrillation taking oral anticoagulants with a random hospitalization for a nonbleeding-related reason occurring after the first observed oral anticoagulant prescription fill, with no other admissions within the preceding and following 6 months, were identified in Optum Clinformatics (Eden Prairie, MN) from 2009 to 2016. Adherence was estimated by the proportion of days covered within 6 and 12 months before and after hospitalization. Difference-in-difference analysis using a generalized linear model was employed to compare pre- and post-hospitalization proportions of days covered (PDCs) by reasons for hospitalization (i.e., ischemic stroke or thromboembolism vs. other nonbleeding-related reasons), adjusting for imbalanced baseline characteristics. RESULTS Of the 21,400 individuals meeting inclusion criteria, 5.4% were hospitalized for ischemic stroke or thromboembolism and 94.6% for other nonbleeding-related reasons. Baseline characteristics were quite similar between groups, except for a few covariables such as age or CHA2DS2-VASc score. Minority race or ethnicity individuals had 0.7% lower overall PDC than whites (P = 0.006). After covariate adjustment, 6-month adherence declined by 1.1% less in individuals hospitalized for ischemic stroke or thromboembolism, compared with other nonbleeding reasons, although the difference was not statistically significant (P = 0.17). Similar results were observed for the 12-month window. CONCLUSION This real-world study suggests that more effective strategies are needed to improve adherence to oral anticoagulant, particularly after a thromboembolic event.