Introduction: Carotid intima-media thickness (IMT) has been increasingly a subclinical marker for cardiovascular disease (CVD). However, no study has examined the association between IMT and mortality in non-Western peoples. We assessed the hypothesis that carotid IMT was a predictor for mortality in a general Asian population.
Methods: We studied 5,330 Japanese individuals (mean age 59.8 years, without CVD at the baseline) who completed a baseline survey and carotid atherosclerosis in the Suita Study, and were then followed for 13.7 years on average. Carotid IMT was evaluated by high-resolution ultrasonography with atherosclerotic indexes of IMT in the common carotid artery (CCA) and carotid artery bulb (Bulb). Mean CIMT and BIMT were defined as the averages of the IMT of both proximal and distal walls for both sides of the CCA at points 10 mm proximal and 5 mm distal, respectively, to the beginning of the dilation of each Bulb. Max-CIMT and BIMT was defined as the maximum IMT in the CCA and Bulb scanned areas, respectively. The risks of all-cause mortality across carotid IMT were compared by the use of Cox proportional-hazards models adjusting for age, sex, body mass index, hypertension, total and HDL cholesterol, antihyperlipidemic drug use, diabetes mellitus, smoking and drinking status.
Results: In 72,923 person-years of follow-up, we documented 972 all-cause mortality (including 66 strokes and 233 CVD). The adjusted hazard ratios (HRs, 95% confidence intervals, CIs) for all-cause mortality and stroke were 1.11 (1.06-1.18) and 1.01 (0.81-1.25), 1.07 (1.05-1.09) and 1.10 (1.00-1.20), 1.04 (1.02-1.07) and 1.06 (0.95-1.17), and 1.04 (1.03-1.05) and 1.06 (1.01-1.11) with 0.1 mm increases in mean-CIMT, mean-BIMT, Max-CIMT, and Max-BIMT, respectively. The adjusted HRs (95% CIs) in the 4th quartiles of mean-CIMT (≥0.95 mm), mean-BIMT (≥1.15 mm), Max-CIMT (≥1.10 mm), and Max-BIMT (≥1.55 mm) for all-cause mortality were 2.05 (1.45-2.91), 1.57 (1.08-2.28), 2.02 (1.27-3.22), and 2.11 (1.38-3.23), compared with their 1st quartiles (<0.775 mm, <0.85 mm, <0.85 mm, and <0.90 mm), respectively.
Conclusions: Carotid IMT is a strong predictor for all-cause. Especially, Mean- and Max-BIMT are good predictors for stroke mortality in general Asian population.