Association of Aortic Aneurysms and Dissections With Subarachnoid Hemorrhage

Background-It is uncertain whether aortic diseases, such as aneurysm and dissection, are associated with intracranial aneurysm formation and aneurysmal subarachnoid hemorrhage (SAH). Methods and Results-We used data on claims between 2008 and 2015 from a nationally representative 5% sample of Medicare beneficiaries. Our exposure variable was hospitalization with an unruptured or ruptured aortic aneurysm or aortic dissection. The outcome was nontraumatic SAH. Variables were ascertained by International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM), diagnosis codes. Survival statistics were used to calculate incidence rates. Cox proportional hazards analysis was used to examine the association between aortic aneurysm/dissection and SAH while adjusting for demographics, vascular risk factors, and Charlson comorbidities. Among 1 781 917 beneficiaries, 32 551 (1.8%) had a documented aortic aneurysm or dissection. During 4.6 +/- 2.2 years of follow-up, 2538 patients (0.14%) developed a nontraumatic SAH. The incidence of SAH was 9 (95% CI, 7-11) per 10 000 patients per year in those with aortic aneurysm/dissection compared with 3 (95% CI, 3-3) per 10 000 patients per year in those without aortic aneurysm/dissection. After adjustment for demographics, stroke risk factors, and Charlson comorbidities, patients with aortic aneurysm/dissection faced an increased risk of SAH (hazard ratio, 1.4; 95% CI, 1.02-1.9; P=0.04). Conclusions-In a nationally representative sample of Medicare beneficiaries, aortic aneurysm/dissection was associated with an increased risk of nontraumatic SAH.