Abstract P321: Insulin Resistance is Associated with Incident Coronary Heart Disease but Not Stroke Among African Americans: The Jackson Heart Study

Abstract

Background: The association between the homeostasis model assessment for insulin resistance (HOMA-IR) and CVD varies by race/ethnicity and is often non-existent or weaker in African Americans (AAs). Triglyceride levels (110-149 mg/dl) below the current metabolic syndrome threshold are associated with insulin resistance in AAs, suggesting that the McAuley index (MA index ), based on insulin and triglycerides, may predict CHD and stroke better than HOMA-IR. We investigated this association in the Jackson Heart Study, a large longitudinal cohort of AAs. Methods: Insulin resistance was estimated for 3565 participants without diabetes and CVD at baseline using the MA index (exp [2.63-0.28 In(insulin in mU/l) - 0.31 In(triglycerides in mmol/l)]) and its association with incident CHD and stroke (composite outcome) was compared against that of the HOMA-IR index. A lower MA index and higher HOMA-IR are indicative of insulin resistance. Cox regression analysis was used to estimate adjusted hazard ratios (HR) for incident CHD and stroke, individually and as a composite. Results: There were 158 events (89 CHD-only, 58 stroke-only, and 11 CHD/stroke) over a median follow-up of 8.4 years. After adjustment for demographic factors, the risk of the composite outcome decreased with each SD increase in the MA index (HR 0.80; 95% CI: 0.67 - 0.96), with no attenuation following further control for CHD and stroke risk factors. When considered individually, the MA index was associated with CHD (HR 0.71, 95% CI: 0.55 - 0.92), but not stroke (HR 0.96, 95% CI: 0.74 - 1.25) risk. The log(HOMA-IR)-CHD association was comparable to that observed with the MA index (Table 1). For both indices, an association was present in men, but not in women (P interaction = 0.01 and 0.2 for log(HOMA-IR) and MA index , respectively). Conclusions: The performance of the MA index in predicting CHD and stroke risk in AAs is comparable to the widely used HOMA-IR index. Our findings suggest a role of insulin resistance in CHD but not stroke risk in this population.