The importance of serum lipoprotein (a) as an independent risk factor for premature coronary artery disease in middle-aged black and white women from the United States

Objective. To determine the association of serum levels of lipoprotein (a) (Lp(a)) with coronary artery disease (CAD) in relation to other risk factor variables in black and white women. Design. Retrospective case-control study. Setting. Community of Bogalusa, Louisiana and Cardiac Catherization Laboratory at the Medical Center of Louisiana, New Orleans, USA. Subjects. The study included 47 female cases (52% black; mean +/- SD age: 50.8 +/- 6.3 years) with confirmed myocardial infarction (MI) or at least 75% blockage of one or more major epicardial coronary arteries determined by angiography, and 55 controls (60% black; mean +/- SD age: 49.6 +/- 7.9 years) with no high grade obstructive lesion (<50% blockage) and no history of CAD. Main outcome measures. Lipoprotein variables, homocysteine, body mass index and cigarette smoking. Results. In the whole group, mean values of Lp(a), total cholesterol, low-density lipoprotein cholesterol (LDL-C), apolipoprotein B (apoB) and very-low-density lipoprotein cholesterol (VLDL-C) were higher (P < 0.05-0.0001) and apoA-I was lower (P < 0.05) in cases than in controls. The multivariate logistic regression analysis showed elevated levels of Lp(a) (>500 mg L-1) and LDL-C (>3.36 mmol L-1) as strong independent risk factors, with odds ratios (with 95% confidence intervals) of 13.6 (4.00-46.30) and 4.64 (1.31-16.49), respectively. ApoA-I, with an odds ratio of 0.11 (0.02-0.64), was a protective factor only at high levels (>53.6 mu mol L-1). Between races, significant odds ratios were noted in the black women for Lp(a) (OR = 15.98; P < 0.01) and LDL-C (OR = 7.69; P < 0.05) and in the white women for only Lp(a) (OR = 15.23; P < 0.01). Conclusions. Lp(a) is an important risk factor for CAD both in black and in white women.