Elevated carotid artery intima-media thickness levels in individuals who subsequently develop type 2 diabetes

Objective - We examined whether B-mode ultrasound - detected carotid artery intima-media thickness (IMT) was elevated before the onset of clinical diabetes. Methods and Results - The study population for these analyses included 1127 nondiabetic participants, 66 prediabetic participants, and 303 diabetic participants with a mean age of 49.8 years who participated in the Mexico City Diabetes Study, a prospective cohort study. Common carotid artery (CCA) and internal carotid artery (ICA) IMTs were measured bilaterally by B-mode ultrasound. Age- and sex-adjusted mean ICA and CCA IMTs were both significantly higher among prediabetic individuals {0.81 mm [95% confidence interval (CI), 0.75 - 0.88] and 0.72 mm [ 95% CI, 0.69 - 0.75], respectively} than in individuals who remained free of diabetes [0.71 mm ( 95% CI, 0.69 - 0.72) and 0.69 mm ( 95% CI, 0.68 - 0.69), respectively]. However, after adjustment for established cardiovascular risk factors, ICA IMT, but not CCA IMT, remained significantly higher among prediabetic individuals [ 0.81 mm ( 95% CI, 0.75 - 0.88) and 0.71 mm ( 95% CI, 0.68 - 0.74)] than in individuals who remained free of diabetes [ 0.71 mm ( 95% CI, 0.69 - 0.72) and 0.69 mm ( 95% CI, 0.68 - 0.70)]. Conclusions - The present study provides direct evidence at the vascular level that atherosclerosis levels are elevated before the clinical onset of diabetes.