Objective: Although small, dense low-density lipoprotein (LDL) has been implicated in atherogenesis and coronary heart disease (CHD) events, little is known about possible racial differences in LDL particle size. This study was designed to examine racial differences in the prevalence of small, dense LDL among 159 African-American and 477 White siblings of persons with premature (<60 years of age) CHD.
Methods and results: This study examined fasting levels of total cholesterol, LDL cholesterol, high-density lipoprotein cholesterol, apolipoprotein B (ApoB), apolipoprotein A-1, and triglycerides, as well as factors known to be associated with small, dense LDL, including age, sex, obesity, hypertension, and diabetes. Relative LDL particle size was defined by the LDL cholesterol to ApoB ratio. Direct measurement of LDL particle size was obtained by proton NMR spectroscopy in a subset of 64 siblings. Despite similar levels of total and LDL cholesterol, White siblings were more likely to have low LDL cholesterol to ApoB ratios, indicative of atherogenic small, dense LDL, compared with African-American siblings. Multiple logistic regression analysis predicting the presence of LDL cholesterol/ApoB < or = 1.0 demonstrated that race (P = .009), triglyceride level (P = .0001), and diabetes (P = .02) were independent predictors, controlling for age and all other variables. Direct measurement of LDL particle size by NMR spectroscopy supported these findings.
Conclusion: These findings provide the first known evidence that White individuals from a population at high risk for premature CHD have a greater probability of having a preponderance of small, dense LDL particles than do African Americans, independent of triglyceride levels, and despite comparable levels of total and LDL cholesterol.