Carotid atherosclerosis and relation to growth of infrarenal aortic diameter and follow-up diameter: the Tromsø Study.

OBJECTIVES: This research aims to study how carotid atherosclerosis is related to growth of infrarenal aortic diameter and aneurysmal formation. DESIGN: Population-based follow-up study. MATERIALS AND METHODS: At baseline, ultrasound examination of the carotid artery and the abdominal aorta was performed in 4241 persons from a general population with no evidence of abdominal aortic aneurysm (AAA). The burden of atherosclerosis was assessed as carotid total plaque area (TPA). After a mean follow-up of 6.3 years, a new ultrasound examination was performed and measurements of the aortic diameter and carotid TPA were repeated. The effects on aortic diameter progression, follow-up diameter and risk for AAA were assessed in multiple linear and logistic regression models according to carotid TPA, adjusted for known risk factors. RESULTS: When analysing AAA as a dichotomous variable, a borderline association between atherosclerosis and AAA could be demonstrated. When modelling aortic diameter as a continuous variable, a 1-SD increase in 5 years' carotid plaque area (ΔTPA) was associated with a 0.12-mm growth in infrarenal aortic diameter (standard error (SE) 0.04) and a 0.20-mm wider aorta at follow-up (SE 0.06). No independent relation was seen for baseline atherosclerosis. CONCLUSIONS: Carotid plaque progression was positively related to growth in infrarenal aortic diameter and aortic diameter at follow-up. Whether this co-variation between plaque growth and aortic diameter growth is causally related or independent events is still an open question.

Diameter of the infrarenal aorta as a risk factor for abdominal aortic aneurysm: the Tromsø Study, 1994-2001.

OBJECTIVES: We aim to study whether the diameter of the non-aneurysmatic infrarenal aorta influences the risk for abdominal aortic aneurysm (AAA) and whether the larger diameter in men can explain the male predominance in AAA. DESIGN: This is a population-based follow-up study. MATERIALS AND METHODS: In 4265 men and women with a normal-sized aorta in 1994-1995, 116 incident cases of AAA were diagnosed 7 years later. The risk of an incident AAA was analysed in a multiple logistic regression model according to baseline maximal infrarenal aortic diameter, adjusted for known risk factors. RESULTS: Compared with subjects with aortic diameter in the 21-23 mm bracket, men and women with a diameter <18mm and > or =27mm had an adjusted odds ratio (OR) of 0.30 (95% confidence interval (CI): 0.10-0.88) and 4.22 (95% CI: 1.94-9.19), respectively, for an incident AAA. When adjusted for age and baseline aortic diameter, male sex was not statistically significantly associated with the incidence of AAA (OR=1.45, 95% CI: 0.93-2.30, P=0.10). CONCLUSIONS: Increased baseline diameter of the infrarenal aorta was a highly significant, strong and independent risk factor for developing an AAA. The larger aortic diameter in men than in women may be the most important explanation for the higher AAA risk in men.