What are most abdominal aortic aneurysms caused by?

Most abdominal aortic aneurysms (AAAs) are caused by atherosclerosis—a hardening and narrowing of the arteries due to a buildup of plaque that contains fat, cholesterol, calcium, and other substances. Other factors that can contribute to the development of AAAs include: age, male gender, smoking, family history of AAAs, high blood pressure, and type 2 diabetes.