Objective: To explore whether traumatic brain injury (TBI) may be a risk factor for subsequent ischemic stroke.

Methods: Patients with any emergency department visit or hospitalization for TBI (exposed group) or non-TBI trauma (control) based on statewide emergency department and inpatient databases in California from 2005 to 2009 were included in a retrospective cohort. TBI was defined using the Centers for Disease Control definition. Our primary outcome was subsequent hospitalization for acute ischemic stroke. The association between TBI and stroke was estimated using Cox proportional hazards modeling adjusting for demographics, vascular risk factors, comorbidities, trauma severity, and trauma mechanism.

Results: The cohort included a total of 1,173,353 trauma subjects, 436,630 (37%) with TBI. The patients with TBI were slightly younger than the controls (mean age 49.2 vs 50.3 years), less likely to be female (46.8% vs 49.3%), and had a higher mean injury severity score (4.6 vs 4.1). Subsequent stroke was identified in 1.1% of the TBI group and 0.9% of the control group over a median follow-up period of 28 months (interquartile range 14?44). After adjustment, TBI was independently associated with subsequent ischemic stroke (hazard ratio 1.31, 95% confidence interval 1.25?1.36).

Conclusions: In this large cohort, TBI is associated with ischemic stroke, independent of other major predictors.