BACKGROUND Recent studies suggest that traumatic brain injury(TBI)is a risk factor for subsequent ischemic stroke,even years after the initial insult.The mechanisms of the association remain unclear.The presence of traumatic subarachnoid hemorrhage(t SAH)may mediate the effect of TBI on long-term stroke risk,as it has previously been linked to short-term vasospasm and delayed cerebral ischemia.METHODS Using administrative claims data,we conducted a retrospective cohort study of acute care hospitalizations.Patients discharged with a first-recorded diagnosis of t SAH were followed for a primary diagnosis of stroke.They were matched to patients with TBI but not t SAH.Cox proportional hazards modeling was used to assess the association between t SAH and stroke while adjusting for covariates.RESULTS:We identified 40 908 patients with TBI(20 454 patients with t SAH)who were followed for a mean of 4.3+1.8 years.A total of 531 had an ischemic stroke after discharge.There was no significant difference in stroke risk between those with t SAH(1.79%;95%confidence interval[CI]1.54%-2.08%)versus without t SAH(2.12%;95%CI 1.83%-2.44%).The same pattern was found in adjusted analyses even when the group was stratified by age-group or by proxies of TBI severity.CONCLU-SIONS:Our findings do not support a role of t SAH in mediating the association between TBI and protracted stroke risk.Further study is required to elucidate the mechanisms of long-term increased stroke risk after TBI.
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