Psychosocial risk factors for adverse outcomes in patients with nonvalvular atrial fibrillation receiving warfarin

OBJECTIVE: Our goal was to establish whether psychosocial risk factors for nonadherence, previously identified as negative predictors of warfarin prescribing, are predictors of adverse events for patients with nonvalvular atrial fibrillation receiving warfarin. DESIGN. Retrospective cohort analysis. SETTING: Ohio Medicaid administrative database. PATIENTS: We studied Ohio Medicaid recipients with nonvalvular atrial fibrillation receiving warfarin to determine whether a history of substance abuse, psychiatric illness, or social factors (identified as conditions perceived to be barriers to adherence) are predictors of adverse events, including stroke, intracranial hemorrhage, and gastrointestinal bleeding. Multivariable risk ratios were calculated for each risk factor using Cox proportional hazards models. RESULTS: 9,345 patients were identified as having nonvalvular atrial fibrillation and receiving 2 or more warfarin prescriptions between 1997 and 2002. The event rates for the sample as a whole were 1.5 strokes, 0.7 intracranial hemorrhages, and 4.3 gastrointestinal bleeds per 100 person-years of follow-up. Subjects with substance abuse had the highest adjusted risk ratio, 2.4 (95% confidence interval [CI]: 1.4, 4.0) for an intracranial hemorrhage while receiving warfarin, followed by subjects with psychiatric illness, adjusted risk ratio of 1.5 (95% CI: 1.04, 2.1). Subjects with psychiatric illness also had an adjusted risk ratio of 1.4 (95% CI: 1.1, 1.7) for stroke. Patients in all 3 identified risk groups were at a significantly increased risk of gastrointestinal bleeding. CONCLUSION: Patients with nonvalvular atrial fibrillation treated with warfarin who have psychosocial risk factors for nonadherence have an increased risk of adverse events.