Purpose: The relationships between lipids/lipoproteins and atherosclerosis were determined in African Americans and whites to assess the consistency of the relationship between these two groups. Differences could suggest varying biological, environmental, or life-style cofactors influencing development of atherosclerosis.
Methods: In the Atherosclerosis Risk in Communities Study, 2966 African Americans and 9399 whites had determinations of LDL, HDL, HDL2, and HDL3 cholesterol, triglycerides, apolipoprotein A1 and B, and lipoprotein (a). Carotid intimal-medial thickening (IMT) was measured using B-mode ultrasound imaging.
Results: The associations, using linear regression, between carotid IMT and LDL cholesterol, HDL cholesterol, and other lipid measurements were significantly weaker in African Americans than whites. Averaging men and women, a 1.034 mmol/L (40 mg/dl) difference in LDL cholesterol was associated with a 0.028 mm IMT difference in whites but a 0.019 difference in African Americans. Similarly, for HDL cholesterol, a 0.44 mmol/L (17 mg/dl) difference is associated wth 0.026 mm difference in carotid IMT in whites and 0.011 mm difference in African Americans. The associations are much weaker in African Americans than whites at the bifurcation and internal carotid, the carotid sites most prone to atherosclerosis. Analysis was done stratifying for risk factors that differ between African Americans and whites, but within most, the relationships remained substantially weaker in African Americans.
Conclusions: We have observed a statistically significant difference in the association between many lipids/lipoproteins and carotid IMT between African Americans and whites. Analysis of many potential cofactors have not provided an explanation for the weaker association. Although possible differences in prior levels of these lipids may provide one explanation for the finding, these results need confirmation in other studies.