Introduction: Carotid intima-media thickness (IMT) is increasingly used as a subclinical marker of cardiovascular disease. However, few studies have examined the association between IMT and incident coronary heart disease (CHD) and stroke in non-Westerners. We assessed the hypothesis that carotid atherosclerosis is a predictor of CHD and stroke events in a general urban Japanese population.
Methods: We studied 4,751 Japanese (2181 men and 2570 women, mean age 59.8 years, without stroke or CHD at the baseline) who completed a baseline survey and carotid atherosclerosis in the Suita Study, and were then followed for an average of 12.6 years. Carotid atherosclerosis was evaluated by high-resolution ultrasonography with atherosclerotic indexes of IMT in the common carotid artery (CCA) and the carotid artery bulb. Mean IMT was defined as the mean of the IMT of the proximal and distal walls for both sides of the CCA at a point 10 mm proximal to the beginning of the dilation of each carotid artery bulb. Max-CCA and Max-Bulb were defined as the maximum IMT in the CCA and bulb areas, respectively. We used adjusted Cox proportional-hazards models to compare the risk of CHD and stroke by use of mean and maximum carotid IMT in the CCA and bulb areas.
Results: During the follow-up, we documented 145 cerebral infarctions, 58 hemorrhagic strokes, 20 unclassified strokes, and 159 CHD. The adjusted hazard ratios (HRs; 95% confidence intervals [CI], P for trend [P trend]) in the fourth quartile (≥ 0.95 mm) of the mean IMT for strokes, cerebral infarction, and CHD were 3.13 (1.48-6.63, P trend = 0.002), 3.34 (1.33-8.37, P trend = 0.002), and 1.93 (0.96-3.88, P trend <0.0001), respectively, compared with the first quartile (<0.775 mm). The adjusted HRs (95% CI) in the fourth quartiles of Max-CCA (≥1.10 mm) and Max-BIF (≥1.55 mm) were 2.48 (1.10-5.62, P trend = 0.07) and 3.28 (1.40-7.69, P trend <0.0001) in stroke, 1.87 (0.75-4.659, P trend = 0.07) and 2.83 (1.05-7.63, P trend = 0.005) in cerebral infarction, and 3.07 (1.18-8.04, P trend <0.0001) and 6.01 (2.02-17.9, P trend <0.0001) in CHD, respectively, compared with the first quartiles (<0.9 mm).
Conclusions: Carotid IMT, especially Max-BIF was a strong predictor of stroke, cerebral infarction, and CHD in a Japanese urban general population.