Study of the Use of Lipid Panels as a Marker of Insulin Resistance to Determine Cardiovascular Risk.

CONTEXT: When assessing the lipid panel, practical physicians tend to focus on the low-density lipoprotein cholesterol (LDL-c). However, an elevated triglyceride/high-density lipoprotein cholesterol (HDL-c) ratio, suggesting insulin resistance, also effectively predicts cardiovascular outcomes but requires different treatments than an elevated LDL-c. We tested whether high triglyceride/HDL-c ratios are associated with more risk than high LDL-c concentrations or other lipid markers of atherogenicity.

METHODS

We followed 103,646 members aged 50 to 75 years without cardiovascular disease or diabetes in a community health plan. Subjects were categorized as insulin sensitive or insulin resistant on the basis of triglyceride and HDL-c in the index year. The primary outcome was ischemic heart disease. The percentage of subjects with a primary outcome after 8 years was stratified by insulin category, lipid measures, and blood pressure. Hazard ratios (HR) for insulin resistance, LDL-c, age, sex, and the presence of hypertension were determined in a multivariate analysis.

RESULTS

Subjects with insulin resistance but lipid measures healthier than the median had worse outcomes than those who were insulin sensitive but had unhealthier lipid measures such as non-HDL-c and the ratios of total cholesterol/HDL-c and LDL-c/HDL-c. The HR for a 60 mg/dL increase in LDL-c was 1.14 (95% confidence interval [CI], 1.10-1.18); the HR for an LDL-c greater than 160 mg/dL was 1.19 (95% CI, 1.12-1.28). In contrast, the hazard ratio for having an insulin-resistant triglyceride/HDL-c ratio was 1.68 (95% CI, 1.57-1.80), compared with an insulin-sensitive ratio. There was no difference in outcomes between insulin-resistant but normotensive patients and insulin-sensitive but hypertensive patients.

CONCLUSION

Insulin resistance, as manifested by a high triglyceride/HDL-c ratio, was associated with adverse cardiovascular outcomes more than other lipid metrics, including LDL-c, which had little concordance. Physicians and patients should not overlook the triglyceride/HDL-c ratio.