IMPAIRED GLUCOSE-TOLERANCE, TYPE-2 DIABETES, AND CAROTID WALL THICKNESS - THE INSULIN-RESISTANCE ATHEROSCLEROSIS STUDY

OBJECTIVE - To assess whether people with impaired glucose tolerance ( IGT) exhibit an increased risk of atherosclerosis as measured by the t hickness of the carotid artery. RESEARCH DESIGN AND METHODS - We exami ned the relationship between glucose tolerance status and subclinical atherosclerosis in the Insulin Resistance Atherosclerosis Study (IRAS) . The IRAS is an epidemiological study of 1,625 Hispanic, African-Amer ican, and white men and women, with approximately equal numbers of sub jects with normal glucose tolerance (NGT), IGT, and type 2 diabetes as assessed by an oral glucose tolerance test. Half of those with diabet es were previously unaware of their condition and were defined as havi ng new diabetes. Persons using insulin were excluded, The intima-media thickness (IMT) of the common carotid artery (CCA) and internal carot id artery (ICA) was measured as an index of subclinical atherosclerosi s using B-mode ultrasonography, RESULTS - Adjusted for demographics an d smoking, CCA-IMT increased most notably at the level of established diabetes (802, 822, 831, and 896 mu m for NGT, IGT, new diabetes, and established diabetes, respectively). Adjustment for coronary heart dis ease (CHD) risk factors, which tended to worsen across glucose toleran ce category, further minimized the slightly graded relationship. The r elationship with the ICA-IMT was steeper and again suggested that the increased wall thickness is associated with diabetes, not with IGT, Th e relationship between glucose tolerance category and IMT was similar in men and women, CONCLUSIONS - We observed considerably greater IMT a mong persons with established diabetes but no significant increase in persons with IGT. These data suggest that the increased risk of CHD ob served in persons with diabetes may largely develop after the onset of overt diabetes.