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.