© 2002 by the American Diabetes Association, Inc.
Is Insulin Sensitivity a Causal Intermediate in the Relationship Between Alcohol Consumption and Carotid Atherosclerosis?The Insulin Resistance and Atherosclerosis Study
1 Department of Public Health Sciences, Wake Forest University School of Medicine, Winston-Salem, North Carolina OBJECTIVEA J-shaped association has been demonstrated between alcohol consumption and atherosclerosis. Insulin resistance, also a risk factor for atherosclerosis, has been shown to have a similar J-shaped association with alcohol intake. This raises the question of whether insulin sensitivity (SI) is a causal intermediate in the alcohol-atherosclerosis relationship. RESEARCH DESIGN AND METHODSThe Insulin Resistance Atherosclerosis Study was a multicenter cohort study designed to investigate relationships among SI, risk factors for cardiovascular disease, and carotid artery atherosclerosis. Using regression analysis, we tested whether adjustment for SI attenuated the alcohol-atherosclerosis relationship observed at baseline. RESULTSA J-shaped association was observed between alcohol consumption and common carotid artery intimal medial thickness. The protective aspect of the alcohol-atherosclerosis relationship was attenuated by 25% after the adjustment for SI. However, an interaction was observed between alcohol consumption and glucose tolerance (GT) status. In comparison with never drinkers, all levels of alcohol consumption were associated with less atherosclerosis in participants with normal GT status. Participants with impaired GT status (but not diabetes) demonstrated a J-shaped alcohol-atherosclerosis association. All levels of alcohol consumption were associated with more atherosclerosis in participants with diabetes. CONCLUSIONSSI may be a causal intermediate at protective levels of alcohol intake, but an alcohol-GT interaction precluded a definitive conclusion. Moderate alcohol consumption may increase the risk of atherosclerosis in people with diabetes. These findings contrast with previous reports and do not support current recommendations regarding moderate alcohol consumption in people with diabetes. More research is needed to clarify this issue.
Abbreviations: CCA, common carotid artery GT, glucose tolerance ICA, internal carotid artery IMT, intimal medial thickness IRAS, Insulin Resistance Atherosclerosis Study SI, insulin sensitivity.
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