Impact of Intima–Media Thickness Progression in the Common Carotid Arteries on the Risk of Incident Cardiovascular Disease in the Suita Study

BACKGROUND: No prospective study of the relationship between intima–media thickness (IMT) progression and incident cardiovascular disease (CVD) has been performed. METHODS AND RESULTS: We studied 4724 participants (mean age: 59.7±11.9 years; without CVD at the baseline) who had carotid ultrasonographic measurement of IMT on both sides of the entire carotid artery area (ie, the entire scanned common carotid artery [CCA], carotid artery bulb, internal carotid artery, and external carotid artery areas for both sides) between April 1994 and August 2001. Carotid ultrasonographic follow‐up was performed every 2 years between April 1994 and March 2005 in 2722 of these participants, newly revealing 193 CCA plaques (maximum IMT in the CCA >1.1 mm). We followed up for incident CVD until December 2013. Statistical analyses were performed using a Cox proportional hazards regression model, evaluated using C statistics, and net reclassification improvement. During the 59 909 person‐years of follow‐up, we observed 221 strokes and 154 coronary heart disease events. CCA plaque and maximum IMT in the whole carotid artery area >1.7 mm were risk factors for CVD. CCA plaque presented an increased risk of CVD based on C statistics and the reclassification improvement of the current risk prediction model. After adding the new incident CCA plaques, during the 23 702 person‐years of follow‐up, 69 strokes and 43 coronary heart disease events occurred. The adjusted hazard ratios for incident CCA plaque were 1.95 (95% confidence interval, 1.14–3.30) in CVD and 2.01 (95% confidence interval, 1.01–3.99) in stroke. CONCLUSIONS: Maximum IMT in the CCA contributed significantly but modestly to the predictive power of incident CVD used in calculating traditional risk factors. This study provides the first demonstration that new progression of incident CCA plaque is a CVD risk.