Aortic Aneurysms

Abdominal Aortic Aneurysms Human Studies The incidence of abdominal aortic aneurysms (AAA) is increasing in the elder population. Independent risk factors for AAA include not only aging but also male and smoking, whereas some risk factors such as hypertension and hypercholesterolemia have not been consistently demonstrated to be independent risk factors. There are several recent population studies that have enhanced or extended insights into risk factors for AAA or associations with AAA. The ARIC study (Atherosclerosis Risk in Communities) is a 24-year prospective study recruited 15 792 participants. Tang et al evaluated lifetime risk and risk factors for AAA in this large cohort. Smoking is not only the most prevalent risk factor but also a lifetime risk for AAA in men. Higher plasma low-density lipoprotein or total cholesterol is also associated with increased risk for AAA. Inflammation is apparent during the initiation and development of AAA in animal models. Inflammatory cell types and markers have also been detected in human AAA. Psoriasis and asthma have profound inflammatory responses. A previous systematic review and meta-analysis has shown an association between psoriasis and AAA. Recently, retrospective cohort studies using Danish populations reported that psoriasis and asthma were associated with higher risk for AAA. Animal studies have provided consistent evidence that the renin–angiotensin system plays a critical role in development of AAA. There is also evidence from a retrospective human study that inhibition of angiotensin-converting enzyme in the renin–angiotensin system prevents progression of AAA. In Danish nation-wide registries (1995–2011), Kristensen et al found that administration of either angiotensin-converting enzyme inhibitors or angiotensin receptor blockers was associated with reduction of mortality in patients with AAA. Human studies have demonstrated that diabetes mellitus is associated with lower risk for AAA. Experimentally, hyperglycemia attenuates development of AAA in elastase or angiotensin II (AngII)–induced AAA. Hemoglobin A1c reflects an average of blood glucose concentrations within an extended interval of ≈3 months. Using the participant information collected from the VIVA (Viborg Vascular) randomized screening trials of the Central Denmark Region, Kristensen et al reported that growth rates of AAA were inversely associated with concentrations of hemoglobin A1c. This study provides insights that long-lasting elevated blood glucose concentrations impair progression of AAA in humans.