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 thickness of the carotid artery.


METHODS
We examined 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-American, and white men and women, with approximately equal numbers of subjects with normal glucose tolerance (NGT), IGT, and type 2 diabetes as assessed by an oral glucose tolerance test. Half of those with diabetes were previously unaware of their condition and were defined as having new diabetes. Persons using insulin were excluded. The intima-media thickness (IMT) of the common carotid artery (CCA) and internal carotid artery (ICA) was measured as an index of subclinical atherosclerosis using B-mode ultrasonography.


RESULTS
Adjusted for demographics and smoking, CCA-IMT increased most notably at the level of established diabetes (802, 822, 831, and 896 microm for NGT, IGT, new diabetes, and established diabetes, respectively). Adjustment for coronary heart disease (CHD) risk factors, which tended to worsen across glucose tolerance category, further minimized the slightly graded relationship. The relationship with the ICA-IMT was steeper and again suggested that the increased wall thickness is associated with diabetes, not with IGT. The relationship between glucose tolerance category and IMT was similar in men and women.


CONCLUSIONS
We observed considerably greater IMT among persons with established diabetes but no significant increase in persons with IGT. These data suggest that the increased risk of CHD observed in persons with diabetes may largely develop after the onset of overt diabetes.
Wagenknecht
L E
LE
Department of Public Health Sciences, Wake Forest University School of Medicine, Winston-Salem, North Carolina 27157, USA. lwagenkn@rc.phs.wfubmc.edu
D'Agostino
R B
RB
Haffner
S M
SM
Savage
P J
PJ
Rewers
M
M
D000328:Adult; D001741:Black or African American / Q000706:statistics & numerical data; D000368:Aged; D001161:Arteriosclerosis / Q000209:etiology; D044383:Black People; D001786:Blood Glucose / Q000378:metabolism; D002339:Carotid Arteries / Q000473:pathology*; D003327:Coronary Disease / Q000453:epidemiology; D003924:Diabetes Mellitus, Type 2 / Q000473:pathology*; D005260:Female; D005951:Glucose Tolerance Test; D006630:Hispanic or Latino / Q000706:statistics & numerical data; D006801:Humans; D007328:Insulin / Q000097:blood; D007333:Insulin Resistance; D008297:Male; D008875:Middle Aged; D012307:Risk Factors; D012907:Smoking; D044465:White People / Q000706:statistics & numerical data
D001786:Blood Glucose; D007328:Insulin