Prevalence and associations of abdominal aortic aneurysm detected through screening

Background: Independent risk factors for abdominal aortic aneurysm (AAA) have not been clearly defined in multivariable analyses of large patient populations. Objective: To identify factors that are independently associated with AAA and to determine the prevalence of previously unrecognized AAA in defined demographic and risk groups. Design: Cross-sectional screening study. Setting: 15 Department of Veterans Affairs medical centers. Participants: 73 451 veterans who were 50 to 79 years of age and had no history of AAA. Measurements: The results of ultrasonographic screening for AAA and a prescreening questionnaire were analyzed using multiple logistic regression. Results: An AAA of 4.0 cm or larger was detected in 1031 participants (1.4%). Smoking was the risk factor most strongly associated with AAA; the odds ratio (OR) for AAAs of 4.0 cm or larger compared with normal aortas (infrarenal aortic diameter < 3.0 cm) was 5.57 (95% Cl, 4.24 to 7.31). The association between smoking and AAA increased significantly with the number of years of smoking and decreased significantly with the number of years after quitting smoking. The excess prevalence associated with smoking accounted for 78% of all AAAs that were 4.0 cm or larger in the study sample. Female sex (OR, 0.22 [Cl, 0.07 to 0.68]), black race (OR, 0.49 [Cl, 0.35 to 0.69]), and presence of diabetes (OR, 0.54 [Cl, 0.44 to 0.65]) were negatively associated with AAA. A family history of AAA was positively associated with AAA (OR, 1.95 [CI, 1.56 to 2.43]) but was reported by only 5.1% of participants. Other independently associated factors included age, height, coronary artery disease, any atherosclerosis, high cholesterol levels, and hypertension. Conclusions: Abdominal aortic aneurysm is associated with multiple factors. Smoking was the risk factor most strongly associated with AAA and may be responsible for most clinically important cases of previously undiagnosed AAA.