Risk factors for abdominal aortic aneurysm: results of a case-control study

Abdominal aortic aneurysms (AAAs) have historically been considered to be a manifestation of atherosclerosis. However, there are epidemiologic and biochemical differences between occlusive atherosclerotic disease and aneurysmal disease of the aorta. A case-control study was performed to investigate risk factors for AAA at the two tertiary care hospitals in Winnipeg, Manitoba, Canada, between June 1992 and December 1995 to investigate risk factors for AAA. Newly diagnosed cases of AAA (n = 98) were compared with non-AAA controls (n = 102), who underwent ultrasound for indications similar to those of the cases. Compared with that for never smokers, the adjusted odds ratio (OR) was 2.75 (95% confidence interval (CI): 0.85, 8.91) for 1-19 pack-years, 7.31 (95% CI: 2.44, 21.9) for 20-34 pack-years, 7.35 (95% CI: 2.40, 22.5) for 35-49 pack-years, and 9.55 (95% CI: 2.81, 32.5) for 50 or more pack-years. Other factors significantly associated with AAA were male gender (OR = 2.68, 95% CI: 1.26, 5.73), diastolic blood pressure (OR per 10 mmHg = 1.88, 95% CI: 1.31, 2.69), and family history of AAA (OR = 4.77, 95% CI: 1.26, 18.1). There was an inverse association between diabetes mellitus and AAA (OR = 0.32, 95% CI: 0.12, 0.88). Neither clinical hypercholesterolemia nor serum levels of total cholesterol, low density lipoprotein cholesterol, and high density lipoprotein cholesterol was associated with AAA. The results of this study suggest that the risk factors for AAA differ from those for atherosclerosis and that atherosclerosis per se is not an adequate explanation as the cause of AAAs.