The effect of age on common carotid artery diameter is unclear for varying atherosclerosis risk levels.
Cross-sectional data from the Atherosclerosis Risk in Communities Limited Access Data set were used to estimate the association of age with B-mode ultrasound common carotid artery diameter for three atherosclerosis risk levels. Based on information from clinical examinations, B-mode ultrasounds, questionnaires, blood and other tests, participants were categorized into three groups: pre-existing disease (prevalent stroke and/or coronary heart disease), high risk group (no pre-existing disease, but prevalent diabetes, hypertension, plaques/shadowing, body mass index >= 30, current smoking, or hyperlipidemia), and a low risk group (no pre-existing disease, no plaques/shadowing, and no major elevated risk factors). Multivariable linear regression analyses modeled the common carotid artery diameter relationship with age.
Age was positively and significantly associated with common carotid artery diameter after risk factor adjustment in the overall sample, but age had a larger effect among persons with evidence of atherosclerosis (interaction p < 0.05). Each year of older age was associated with 0.03 mm larger diameter/year among persons with pre-existing disease, with 0.027 mm larger diameter/year in the high risk group, but only 0.017 mm/year among the low risk group. Results were qualitatively similar using plaques/shadowing status to indicate atherosclerosis severity.
The significant impact of age on common carotid artery diameter among low risk, middle-aged, black and white men and women suggests arterial remodelling may occur in the absence of identified risk factors. The significantly larger impact of age among persons with, compared to persons without identified atherosclerosis or its risk factors, suggests that arterial remodelling may be an indicator of exposure duration.
Because of its accessibility, the common carotid artery (CCA) is often evaluated using B-mode ultrasound to assess atherosclerosis severity 1-3. Ultrasound, animal, and anatomic studies indicate arterial diameters are associated with hemodynamic factors 4-7 and with vascular damage 8,9. Several studies have suggested that arterial wall area, or arterial diameter in conjunction with wall thickness, may provide useful information for understanding atherosclerosis progression, vascular injury, or vascular vulnerability 2,8,10-15.
However, the relationship between arterial wall thickness and diameter is not likely to be simple since both physiologic and pathological processes can contribute to diameter differences 13. For example multiple factors such as gender 16, physiologic response to shear stress17 as well as plaque characteristics 8,9 are known to be associated with arterial diameter. So, many factors could potentially impact the relationship between age and diameter. While many studies have evaluated associations of risk factors or vascular characteristics with arterial diameter 8,9,11,18-23, fewer studies have attempted to separate the effects of age and atherosclerosis on arterial diameter. The Bruneck study found that age was related to CCA diameter only in persons within the upper 50th percentile of wall thickness 11 while a small study of 69 male subjects screened for the absence of atherosclerosis and its risk factors found that diameter did increase significantly with age 13.
This study extends previous studies of B-mode ultrasound CCA by estimating optimal B-mode ultrasound right CCA diameters (interadventitial distances) within a low-risk subset from a bi-racial population sample of both men and women; by determining whether atherosclerosis severity measures were effect modifiers of the age-CCA diameter relationship; and by estimating the effect of age among diseased, high risk, and low risk populations from the same population sample.
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