Plasma glucose within the normal range is not associated with carotid atherosclerosis: prospective results in subjects with normal glucose tolerance from the Bruneck Study.

OBJECTIVE

There is substantial evidence that glucose intolerance is associated with an increased risk of cardiovascular disease. However, it is not well established whether plasma glucose is independently related to atherosclerosis when glucose tolerance is normal and, if so, to which stage of the complex atherosclerotic process.

RESEARCH DESIGN AND METHODS

We prospectively examined the status of carotid arteries in 625 subjects aged 40-79 years who were randomly selected from the general population and had normal glucose tolerance (according to World Health Organization criteria) both at baseline and at 5 years of follow-up. All subjects had high-resolution echo-duplex evaluation of the common and internal carotid arteries (eight regions of interest on both sides) in 1990 and 1995 to detect the change in carotid status over time. The occurrence of new plaques in previously normal segments was termed "incident nonstenotic" or "early atherosclerosis," and the occurrence of stenosis in >40% of previously normal segments was termed "incident stenotic" or "advanced atherosclerosis." In addition, we evaluated the changes in the atherosclerosis score (the sum of all plaques) during the follow-up, and we measured intimal-medial thickening (IMT) in the common carotid artery in 1995. In all subjects, several candidate risk factors were assessed: sex, age, BMI, waist-to-hip ratio, glucose, HbA1c, insulin, urate, lipids, apolipoproteins A1 and B, blood pressure, lipoprotein(a), fibrinogen, antithrombin III, factor V Leiden mutation, ferritin, leukocyte count, smoking, alcohol intake, physical activity, and socioeconomic status. Fasting plasma glucose (FPG), plasma glucose 2 hr after the glucose load (2-h PG), and HbA1c concentrations in 1990 and 1995 were averaged in each subject to obtain an estimate of long-term glucose exposure of the arterial wall.

RESULTS

Linear or logistical regression analyses indicated that neither baseline glucose and HbA1c levels nor mean FPG, mean 2-h PG, or mean HbA1c in 1990 and 1995 were independently related to IMT, a 5-year change in the atherosclerotic score, incident nonstenotic (early) atherosclerosis, or incident stenotic (advanced) atherosclerosis. Likewise, subjects with FPG levels above the median and subjects in the new category of "impaired fasting glucose" did not have an increased occurrence or progression of atherosclerosis. All results were consistent before and after adjustment for other vascular risk factors and possible confounders.

CONCLUSIONS

These results suggest that plasma glucose levels within the normal range (<7.8 mg/dl both at FPG and 2-h PG) are not independently related to any stage of atherosclerosis.