Epidemiology of triglycerides, small dense low-density lipoprotein, and lipoprotein(a) as risk factors for coronary heart disease.

In addition to LDL cholesterol, triglyceride; small, dense LDL (LDL subclass phenotype B); and lipoprotein(a) are emerging as important risk factors for CHD. Elevated plasma levels of each of these risk factors have consistently been associated with increased risk of CHD in case-control studies of white patients. In prospective studies, however, the association between triglycerides and CHD is generally not independent of HDL cholesterol in multivariate statistical analyses. Although the data are scarce, studies in women show that triglycerides are a stronger risk factor for CHD in women than in men. Although no prospective studies of LDL subclass phenotype B have been reported, a number of potential atherogenic mechanisms may be responsible for the association with CHD seen in the case-control studies. Similarly, few prospective studies of lipoprotein(a) have been published, all in Scandinavian men. The observational studies generally show an association between elevated lipoprotein(a) and CHD in whites but not in blacks. Each of these risk factors also has a genetic component. Of the two familial forms of hypertriglyceridemia, FCH has been associated with familial CHD in two cross-sectional studies. LDL subclass phenotype B is inherited consistent with a single major gene effect, and candidate gene linkage studies are in progress to map the chromosomal location of this proposed gene. Finally, lipoprotein(a) levels are largely attributable to variation at the apo(a) locus on chromosome 6. Whether other genetic variations explain the lack of reported associations between lipoprotein(a) and CHD in black populations remains to be determined. Understanding of these "non-LDL" lipoprotein-related risk factors will provide important information for the development of new, effective intervention strategies for the prevention of CHD.