The natural history of vertebrobasilar artery (VBA) stenosis or occlusion remains understudied. >bold<>italic<Methods:>/italic<>/bold< Patients with diagnosis of ischemic stroke or transient ischemic attack (TIA) who were noted to have VBA stenosis based on computed tomography or magnetic resonance imaging or catheter-based angiogram were selected from Taiwan Stroke Registry. Cox proportional hazards model was used to determine the hazards ratio (HR) of recurrent stroke and death within 1 year of index event in various groups based on severity of VBA stenosis (none to mild: 0-49%; moderate to severe: 50-99%: occlusion: 100%) after adjusting for differences in demographic and clinical characteristics between groups at baseline evaluation. >bold<>italic<Results:>/italic<>/bold< None to mild or moderate to severe VBA stenosis was diagnosed in 6972 (66%) and 3,137 (29.8%) among 10,515 patients, respectively, and occlusion was identified in 406 (3.8%) patients. Comparing with patients who showed none to mild stenosis of VBA, there was a significantly higher risk of recurrent stroke (HR 1.21, 95% CI 1.01-1.45) among patients with moderate to severe VBA stenosis. There was a nonsignificantly higher risk of recurrent stroke (HR 1.49, 95% CI 0.99-2.22) and significantly higher risk of death (HR 2.21, 95% CI 1.72-2.83), among patients with VBA occlusion after adjustment of potential confounders. >bold<>italic<Conclusions:>/italic<>/bold< VBA stenosis or occlusion was relatively prevalent among patients with TIA or ischemic stroke and associated with higher risk of recurrent stroke and death in patients with ischemic stroke or TIA who had large artery atherosclerosis>bold<>italic<.>/italic<>/bold<.
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