Abstract P628: Long-Term Risk of Ischemic Stroke Among Survivors of Non-Traumatic Subarachnoid Hemorrhage

Abstract

Background and Purpose: Non-traumatic subarachnoid hemorrhage (SAH) is associated with poor long-term functional outcomes, but the risk of ischemic stroke among SAH survivors is poorly understood. Methods: We performed a retrospective cohort study using claims data from Medicare beneficiaries from 2008-2015. The exposure was a diagnosis of SAH, while the outcome was an acute ischemic stroke. The exposure and outcomes were identified using previously validated ICD-9-CM diagnosis codes. We excluded patients with prevalent ischemic stroke at the time of SAH diagnosis and those which occurred in the first 90 days after SAH discharge to avoid inclusion of stroke occurring as a medical or procedural complication of SAH. We used Cox regression adjusting for demographics and stroke risk factors to evaluate the association between SAH and long-term risk of ischemic stroke. Results: Among 1.3 million Medicare beneficiaries, 3,171 (0.18%) were diagnosed with non-traumatic SAH. During a median follow-up of 5.3 years (interquartile range [IQR], 2.7- 6.7), the cumulative incidence of ischemic stroke was 92 per 1,000 patients per year among patients with SAH, and 21 per 1,000 patients per year in those without SAH. In multivariable Cox regression analysis, SAH was associated with an increased risk of ischemic stroke (hazard ratio, 2.6; 95% confidence interval, 2.4-2.8) as compared to beneficiaries without SAH. Conclusions: In a large, heterogeneous national cohort of elderly patients, we found that survivors of SAH had more than double the long-term risk of ischemic stroke as compared to those without SAH. SAH survivors should be closely monitored and risk stratified for ischemic stroke.