Difference in Risk Factor profile for Abdominal Aortic Aneurysm and Thoracic Aortic Aneurysm.

Background: Previous studies suggest partly different risk factor profiles of thoracic aortic aneurysm (TAA) and abdominal aortic aneurysm (AAA), but prospective data are scarce.

Aim/objectives: The purpose of this prospective population-based case-control study was to investigate differences in risk factor profile between TAA and AAA.

Methods: Participants in two prospective population-based studies, the Västerbotten Intervention Project (VIP) and the Monitoring of Trends and Determinants in Cardiovascular Disease (MONICA) study, between 1986 and 2010 underwent cardiovascular risk assessments, including blood samples, oral glucose tolerance test, blood pressure readings and a self-reported health questionnaire. All individuals who were later diagnosed with TAA or AAA were identified. Age, sex, and time-matched controls were selected from the same cohorts, aiming at four controls / case. Adjusted odds ratios for potential risk factors for later diagnosis of TAA and AAA respectively, were estimated by multivariate conditional logistic regression analyses.

Results: From total 96,196 individuals with prospectively collected data in the VIP/MONICA cohort, a total of 236 individuals with AAA (181 men and 55 women) and 935 matched controls, and 168 individuals with TAA (115 men and 53 women) and 662 controls were included. The average age at baseline examination was 57.0 ± 5.7 years for AAA cases and controls, and 52.1 ± 8.8 years for TAA cases and controls. Mean time between baseline examination and diagnosis of AAA/TAA was 12.1 and 11.7 years respectively. There was a clear difference in risk factor profile between AAA and TAA. Smoking, hypertension and coronary artery disease were significantly associated with later diagnosis of AAA with highest adjusted odds ratio for a history of smoking (OR 10.3, 95% CI 6.3-16.8). For TAA, hypertension was the only positive risk factor (OR 1.7, CI 1.1-2.7), while smoking was not associated. Diabetes was not associated with either AAA or TAA, neither was self-reported physical activity.

Conclusions: In this prospective population-based case-control study risk factor profile differed between AAA and TAA. This suggests a partially different etiology for TAA and AAA.