Elsevier

Atherosclerosis

Volume 164, Issue 1, September 2002, Pages 89-94
Atherosclerosis

Carotid atherosclerosis, intima media thickness and risk factors—an analysis of 1781 asymptomatic subjects in Taiwan

https://doi.org/10.1016/S0021-9150(02)00017-5Get rights and content

Abstract

The aim of this study was to investigate the association of intima media thickness (IMT) and plaque with risk factors for atherosclerosis in asymptomatic subjects in Taiwan. Between 1998 and 2001, the study recruited 1781 asymptomatic subjects (1131 men and 650 women [mean age, 49 years; range 18–85 years]). These were examined by B-mode ultrasound to measure the IMT at the far wall of the common carotid artery (CCA) and the extent of plaque formation. A wide range of vascular risk factors including age, gender, smoking, body mass index, blood chemistry, and previous history were surveyed. The mean (±S.D.) IMT observed was 0.68 (±0.12) and 0.66 (±0.11) mm for men and women, respectively, (P=0.0008). The mean (S.D.) IMT of the CCA was 0.66 (±0.12) mm on the right side and 0.68 (±0.12) mm on the left side (P=0.0004). IMT increased with aging, according to the equation IMT=(0.005×age in years)+0.043. Higher IMT was associated with male gender, and IMT was greater in the left CCA. About 36.9% of subjects had carotid plaques. The percentage of plaque increased with aging. The plaque prevalence was positively associated with IMT. The value of IMT over the cut point of 0.68 mm correlated with obviously increased risk of carotid atherosclerosis. Age, systolic blood pressure and fasting blood sugar were independent risk factors related to both carotid atherosclerosis and thick IMT.

Introduction

High resolution B-mode ultrasound is a noninvasive method for examining the walls of peripheral arteries and provides measures of the carotid artery intima media thickness (IMT) and of plaques that may indicate early presymptomatic disease. IMT has been proposed as a quantitative index of atherosclerosis and has been shown to be positively associated with coronary heart disease and stroke [1], [2], [3], [4]. In healthy adults, IMT ranges from 0.25 to 1.5 mm, and values >1.0 mm are often regarded as abnormal [5], [6], [7]. However, the ‘normal’ range and ‘abnormal’ value and even the risk factors associated with abnormal IMT might vary considerably between different populations [7], [8], [9], [10]. Ultrasonographic diagnosis of increased IMT in one individual at risk of atherosclerosis might help to stratify the risk factor, to better justify the decision to treat and to follow the efficacy of preventive therapy such as that involving the use of antihypertensive, antiplatelet, or lipid-lowering drugs [11], [12], [13].

Though the pathologic characteristics of atherosclerotic plaque and IMT are quite different, both are related to generalized atherosclerosis, and to cerebral and cardiac ischemic symptoms [14], [15]. IMT and carotid plaques can be used for predicting and evaluating progression/regression of atherosclerosis and for predicting subsequent clinical complications [16]. So, the screening and detection of the risk factors for carotid plaques and IMT are quite important before symptoms or disease really develop. And the correlations between IMT and carotid plaque need to be clarified [8], [9].

The first aim of present study was to define the mean and range of IMT in the carotid arteries of young to old subjects. The second aim was to investigate the correlation between IMT and carotid plaque and to define the cut value of IMT associated with significant prevalence of plaque. The third aim was to identify the risk factors associated with thick IMT and carotid plaque in asymptomatic subjects in Taiwan.

Section snippets

Subjects

This study was performed between April 1998 and February 2001. A total of 1961 subjects who consulted En Chu Kong Hospital for their general physical check-up underwent carotid duplex examination. All subjects resided in northern Taiwan and were asked information about smoking behavior, alcohol consumption, and previous disease. Those who had suffered from symptomatic vascular disease such as stroke, transient ischemia, coronary heart disease, congestive heart failure and intermittent

Results

A total of 1781 subjects, 1131 men and 650 women, was examined (mean age, 49 years; range 18–85 years).

Discussion

Though the increase of IMT with age was described in several previous reports, the progression rates were quite varied [7], [9], [10], [18]. Longitudinal estimates of progression rate of CCA IMT in our subjects was 0.005 mm year, which was much less than the rate of 0.06 mm per year in Finnish men [18] and less than 0.01 mm per year in participants from US communities [7], and 0.02 mm per year in another population study [5]. Such variation is likely to be due to the methodological differences.

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