Abstract WP94: Emphysema: A Potential Risk Factor for Ruptured Cerebral and Aortic Aneurysms

Background: Whether emphysema is associated with the development and rupture of cerebral and abdominal aortic aneurysms is unclear. Methods and Materials: We performed a retrospective cohort study using outpatient and impatient claims data from a nationally representative 5% sample of Medicare beneficiaries > 66 years of age. Our predictor variable was emphysema and our outcome was a hospitalization for aneurysmal subarachnoid hemorrhage (SAH) or ruptured aortic aneurysm. All predictors and outcomes were defined using previously reported International Classification of Diseases, 9 th Revision, Clinical Modification ( ICD-9-CM ) diagnosis code algorithms. Survival statistics were used to calculate incidence rates and Cox regression was used to measure the association between emphysema and outcomes while adjusting for demographics and previously reported risk factors for aneurysm rupture: hypertension, diabetes, and tobacco and alcohol use. Results: We identified 133,337 patients with emphysema and 1,484,760 patients without emphysema. Over a mean follow-up period of 4.3 (+/-1.9) years, we identified 5,396 cases of aneurysm rupture, 477 of which occurred in patients with emphysema. The annual incidence of aneurysm rupture was 159 (95% confidence interval [CI], 146-174) per 100,000 in patients with emphysema and 74 (95% CI, 72-76) per 100,000 in patients without emphysema. After adjusting for demographics and other risk factors, emphysema was independently associated with aneurysm rupture (hazard ratio [HR], 1.6; 95% CI, 1.4-1.8). In secondary analyses, emphysema was associated with both aneurysmal SAH (HR, 1.4; 95% CI, 1.2-1.6) and ruptured aortic aneurysm (HR, 2.1; 95% CI, 1.7-2.5). Conclusion: Patients with emphysema faced an increased risk of developing SAH and aortic aneurysm rupture. This finding is consistent with the hypothesis that protease/anti-protease imbalance, which is seen in emphysema, may play a role in vessel wall weakening and the development and rupture of aneurysms.