Diabetes Care, Vol 21, Issue 2 221-230, Copyright © 1998 by American Diabetes Association
U-shaped and J-shaped relationships between serum insulin and coronary heart disease in the general population. The Bruneck Study
E Bonora, J Willeit, S Kiechl, F Oberhollenzer, G Egger, R Bonadonna and M Muggeo
Department of Endocrinology and Metabolic Diseases, University of Verona Medical School, Italy.
OBJECTIVE: To evaluate the relationship existing between serum insulin and
coronary heart disease (CHD) in the general population. RESEARCH DESIGN AND
METHODS: In a cross-sectional survey on atherosclerosis and its risk
factors, 500 men and 500 women aged 40-79 years were randomly selected from
the population of Bruneck, Italy. Clinical, biochemical, and behavioral
risk factors of atherosclerosis were assessed in the 936 subjects who
participated in the study. Serum insulin was measured at fasting (n = 888)
and 2 h (n = 811, known diabetic subjects were excluded) after an oral
glucose load. CHD was ascertained by an abnormal electrocardiogram and/or a
history of angina or myocardial infarction. RESULTS: Subjects were
stratified according to serum insulin quintiles at fasting or 2 h after
glucose loading. After adjustment for sex, age, BMI, smoking, physical
activity, alcohol intake, and socioeconomic status (analysis of
covariance), cardiovascular risk factors clustered in subjects of the top
insulin quintile. Multiple logistic regression analysis, including sex and
age in model 1, sex, age, BMI, glucose tolerance, socioeconomic status, and
behavioral variables in model 2, or this set of variables together with
triglycerides and apoproteins A1 and B, fibrinogen, and blood pressure
status in model 3, revealed a significant association between high serum
insulin and CHD when median insulin quintile was used as the reference
class. Moreover, low serum insulin levels, such as those found in subjects
of the lowest quintile, were independently related to CHD. These results
were found either before (model 1) or after (models 2 and 3) adjusting for
several covariates. Consistent results were found in men and women, as well
as in younger and older subjects. CONCLUSIONS: Results of the present study
suggest that both hyperinsulinemia and "hypoinsulinemia" are independent
indicators of CHD. Furthermore, it is proposed that the relationship
between CHD and fasting insulin is U-shaped, whereas that between CHD and
postglucose insulin may be J-shaped.