FASTING INSULIN AND APOLIPOPROTEIN-B LEVELS AND LOW-DENSITY-LIPOPROTEIN PARTICLE-SIZE AS RISK-FACTORS FOR ISCHEMIC-HEART-DISEASE

Context.-Epidemiological studies have established a relationship betwe en cholesterol and low-density lipoprotein cholesterol (LDL-C) concent rations and the risk of ischemic heart disease (IHD), but up to half o f patients with IHD may have cholesterol levels in the normal range. O bjective.-To assess the ability to predict the risk of IHD using a clu ster of nontraditional metabolic risk factors that includes elevated f asting insulin and apolipoprotein B levels as well as small, dense LDL particles. Design.-Nested case-control study. Setting.-Cases and cont rols were identified from the population-based cohort of the Quebec Ca rdiovascular Study, a prospective study conducted in men free of IHD i n 1985 and followed up for 5 years. Participants.-Incident IHD cases w ere matched with controls selected from among the sample of men who re mained IHD free during follow-up. Matching variables were age, smoking habits, body mass index, and alcohol consumption. The sample included 85 complete pairs of nondiabetic IHD cases and controls, Main Outcome Measures.-Ability of fasting insulin level, apolipoprotein B level, a nd LDL particle diameter to predict IHD events, defined as angina, cor onary insufficiency, nonfatal myocardial infarction, anti coronary dea th. Results.-The risk of IHD was significantly increased in men who ha d elevated fasting plasma insulin and apolipoprotein B levels and smal l, dense LDL particles, compared with men who had normal levels for 2 of these 3 risk factors (odds ratio [OR], 5.9; 95% confidence interval [CI], 2.3-15.4). Multivariate adjustment for LDL-C, triglycerides, an d high-density lipoprotein cholesterol (HDL-C) did not attenuate the r elationship between the cluster of nontraditional risk factors and IHD (OR, 5.2; 95% CI, 1.7-15.7). On the other hand, the risk of IHD in me n having a combination of elevated LDL-C and triglyceride levels and r educed HDL-C levels was no longer significant (OR, 1.4, 95% CI, 0.5-3. 5) after multivariate adjustment for fasting plasma insulin level, apo lipoprotein B level, and LDL particle size. Conclusion.-Results from t his prospective study suggest that the measurement of fasting plasma i nsulin level, apolipoprotein B level, and LDL particle size may provid e further information on the risk of IHD compared with the information provided by conventional lipid variables.