2.6. Association of plasma lipids and lipoproteins with coronary artery disease

Elevated LDL cholesterol and apo B concentrations are associated with an increased risk of coronary artery disease (Lipid Research Clinics Program 1984a, Multiple Risk Factor Intervention Trial Research Group 1986, Canner et al. 1986, Frick et al. 1987, Maher et al. 1997). Conversely, HDL is consid­ered to be antiatherogenic, and elevated serum HDL cholesterol levels are associated with a reduced coronary risk (Gordon et al. 1989). A high total cholesterol-HDL chole­sterol ratio is postulated to be a good marker of the other risk-factors for CAD: hypertension, diabetes, smoking and AMI, suggesting that the decrease in HDL cholesterol might be a secondary phenomenon (de Backer et al. 1998, Luria et al. 1991). The role of elevated plasma triglycerides as a risk factor for CAD is controversial, because, although significant in univariate analyses, the triglycerides are usually eliminated by HDL in multivariate statistical tests (Lechleitner et al. 1990, Austin 1991).

Coronary artery disease manifests about ten years later in life in women than in men. One of the preventive mechanisms has been postulated to be the lower triglyceride and higher HDL cholesterol levels in women than in men, which difference becomes less marked after menopause, when the LDL cholesterol levels of women rise (Thompson 1996). Family histories of coronary artery disease and hypertension are more prevalent in women than in men with angiographically verified coronary artery disease, and diabetes is more prevalent in women with CAD than in women with normal coronary arteries (Sullivan et al. 1994). In women, triglycerides have been reported to be an independent CAD risk factor (Nieminen et al. 1992). Premature onset of CAD in men is postulated to be associated with a genetically determined trait characterised by abnormalities in the metabolism of tri­glyceride-rich lipoproteins and HDL (Richards et al. 1989, Criqui et al. 1993), the trait being more apparent in female than in male relatives of patients with coronary artery disease.