Etiology of Thoracic Aortic Aneurysms Most thoracic aortic aneurysms result from Atherosclerosis Risk factors for both thoracic aortic aneurysms and aortic dissections include prolonged hypertension, dyslipidemia, and smoking. Additional risk factors for TAAs include presence of aneurysms elsewhere in the body, infection, aortitis, and older age (peak incidence at age 65 to 70).