Clarifying the Risk of Aortic Aneurysm Development
October 15, 2024
By Michael H. Crawford, MD
SYNOPSIS: A large, cross-sectional study of adults by aortic computed tomography angiography has shown that aortic aneurysms (AAs) are more frequent in men than women. While increasing age and body surface area were common risk factors for AA, hypertension was associated with thoracic AA, and hypercholesterolemia and smoking were risk factors for abdominal AA.The sex-specific prevalence and relative importance of cardiovascular risk factors in the development of thoracic and abdominal aortic aneurysms (TAAs and AAAs) are unclear. Thus, investigators from the Copenhagen General Population Study (CGPS) studied these questions in the > 10,000 Danes enrolled since 2003 in the CGPS.
Since 2012, participants aged 40 years or older were offered a computed tomography angiogram (CTA) of the aorta. Excluded were those with a bicuspid aortic valve or previous aortic surgery. A self-reported questionnaire was used to assess risk factors for atherosclerosis. Aortic diameter measurements were the largest one in each of the three regions: ascending thoracic, descending thoracic, and abdominal. TAAs were defined as a maximum diameter of the ascending aorta of ≥ 4.5 cm and descending ≥ 3.5 cm. AAAs were an abdominal aorta maximum diameter of ≥ 3.0 cm.
The study population consisted of 11,294 individuals who had a thoracic CTA, of whom 7,442 (66%) had an abdominal CTA. The median age of the population was 62 years, 56% were women, 36% had hypertension, 51% were current or former smokers, and 66% had hypercholesterolemia. The prevalence of AAs in the study population overall was 2%: 4% in men and 0.7% in women (P < 0.001). In men, AAAs were the most frequent (3.5%), followed by ascending aorta (3%) and descending aorta (1.2%). In women, ascending aorta location was most frequent (0.9%), followed by AAAs (0.3%) and descending aorta (0.1%).
On multivariable analysis, AAs were independently associated with male sex, increasing age, and body surface area (BSA). TAAs were associated with hypertension (odds ratio [OR], 2.0; 95% confidence interval [CI],1.5-2.8). AAAs were associated with hypercholesterolemia (OR, 2.4; 95% CI ,1.6-3.6) and smoking (OR, 3.2; 95% CI, 1.9-5.4). When adjustments for BSA were made, aortic size index was associated with an increased risk of AAs at all locations, which suggests that the higher risk of AAs in men probably is not a result of their larger size.
The authors concluded that subclinical AAs are four times more common in men than women and increasing age and BSA are risk factors for AAs in all locations. Hypertension is a risk factor for TAAs, and hypercholesterolemia and smoking are risk factors for AAAs.
Commentary
As causes of death in the general population, AA dissection and rupture only account for about 1% of deaths. However, the mortality of these events is about 85%, even with intervention. AAs have been called the silent killers because most are asymptomatic and, even when symptomatic, the symptoms usually are nonspecific pain. Thus, screening for AAs is worth considering.
Since AAAs are more common in older Caucasian men who smoke cigarettes, most public health guidelines recommend a one-time screening for AAA in such individuals. Studies have shown that such screening reduces mortality and is cost effective. This CGPS study was designed to further refine our knowledge of who is at risk for AAs.
Smaller retrospective studies have identified several potential risk factors: Caucasian ethnicity, male sex, older age, smoking, family history of AA, and atherosclerosis. However, their relative importance and their relationship to traditional risk factors for atherosclerosis (hypertension, hyperlipidemia, diabetes) is unclear.
The CGPS investigators showed that hypertension was a risk factor for TAA and hypercholesterolemia was a risk factor for AAA. Smoking was a risk factor for descending TAA and AAA, or so-called thoracoabdominal AA. Interestingly, diabetes appeared to decrease the risk of AAA (OR, 0.1; 95% CI, 0.02-0.9).
The authors suggested that this could be the result of the treatment of diabetes reducing the risk of atherosclerosis or the anti-inflammatory properties of some medications used to treat diabetes. Their data suggest that perhaps hypertension and hypercholesterolemia, in addition to smoking in older men, could justify screening. Women are more complicated. They have a lower prevalence of AA, but their rupture rates are four times higher. It is unknown if screening is cost effective in women.
There are limitations to this study. The clinical data were determined by questionnaires. There was no information on family history or the presence of systemic inflammatory diseases that could cause aortitis. It was largely a Caucasian population, which is appropriate considering the higher risk of AA in such individuals, but the results may not apply to other racial or ethnic groups.
The major strengths of this study are its large size and almost equal proportions of men and women. Until newer guidelines emerge, perhaps we should pay more attention to opportunistic screening when at-risk patients are undergoing CTA for other reasons.
Michael Crawford, MD, is Professor of Medicine, Lucy Stern Chair in Cardiology, University of California, San Francisco.