Supplementary Material for: Long-term risk of stroke after traumatic brain injury: A population-based medical record review study

ABSTRACT Objective To reliably inform secondary prevention strategies and reduce morbidity and mortality after traumatic brain injury (TBI), we sought to understand the long-term risk of stroke after TBI in patients aged 40 years and older in comparison to age- and sex-matched referents from a population-based cohort. Materials and Methods TBI cases in Olmsted County, Minnesota from January 1, 1985 to December 31, 1999 were confirmed by manual review, classified by injury severity and mechanism, and non-head trauma was quantified. Each TBI case was matched to 2 sex- and age-matched population-based referents without TBI and with similar severity non-head trauma. Records of cases and referents were manually abstracted to confirm stroke diagnosis. Stroke events during initial hospitalization for TBI were excluded. Results In total, 1,410 TBI cases were confirmed, 61% classified as Possible TBI (least severe, consistent with concussive), with the most common mechanism being falls. There were 162 stroke events among those with TBI (11.5%), and 269 among referents (9.5%). Median time to stroke from the index date for those with TBI was 10.2 years (Q1-Q3 5.2 – 17.8), and for referents 12.1 years (Q1-Q3 6.2-17.3), P = 0.215. All-severity TBI was associated with increased risk of stroke (HR: 1.32, 95% CI: 1.06–1.63, P = 0.011), but only Definite TBI (consistent with moderate-severe) was associated with significant risk (HR: 2.20, 95% CI: 1.04-4.64, P = 0.038) when stratified by severity. Discussion/Conclusion By confirming TBI cases, stroke diagnoses, and injury severity classification using manual review with levels of accuracy not previously reported, these results indicate moderate-severe TBI increases long-term risk for stroke. These findings confirm the need to regularly assess long-term vascular risk after TBI to implement disease prevention strategies.