Comparison between insulin resistance indices and carotid and femoral atherosclerosis: a cross-sectional population study

Abstract

Objectives: To investigate the association between commonly used insulin resistance indices and presence and extent of carotid and femoral atherosclerosis in a general population setting. Methods: Cross-­sectional analysis of 762 volunteers from the ongoing epidemiological Cyprus Study (46.6% male; mean age=60.5±10.2). (a) Carotid intima-­media thickness (IMTcc), (b) carotid and femoral atherosclerotic plaque presence, (c) total plaque area in the carotid/femoral bifurcations (sum of the largest plaques in each carotid/femoral bifurcation-­SPAcar/fem) and (d) total plaque area in both carotid and femoral bifurcations (sum of the areas of the largest plaques present in each of the four bifurcations-­SPA) were measured using ultrasound at baseline. The HOMA-­IR, QUICKI and McAuley indices as well as fasting insulin levels were estimated and their quartiles were used in linear and logistic regression analysis. Results: All insulin resistance indices studied were strongly associated with IMTcc (p<0.01for all) even after adjustment for age and sex and exclusion of diabetic subjects. However, when looking at plaque presence and size (i.e.area) only the HOMA-­IR and especially the McAuley indexwere associated with both carotid plaque presence (OR adj = 1.17; 95%CI=1.01 to 1.36; p=0.03 and OR adj = 0.86; 95%CI=0.74 to 0.99; p=0.04 respectively) and area(OR adj = 0.10; 95%CI=0.008 to 0.20; p=0.03 and OR adj = -­0.11; 95%CI=-­0.20 to -­0.009; p=0.03 respectively), after adjustment.The McAuley index remained a significant predictor of both carotid plaque presence and area even after exclusion of diabetic subjects (p=0.04). CONCLUSIONS: Our results show that while all indices were associated with carotid IMT, supporting a strong role for insulin resistance in intimal-­medial thickening, only the HOMA-­IR and especially the McAuley indexwere associated with both carotid plaque presence and area, after adjustment. This highlights the importance of including triglyceride levels in estimating the risk for atherosclerotic plaque in the carotids as well as the possible differences in determinants for atherosclerosis between arterial sites.