Lipoprotein (a) as a predictor of myocardial infarction in middle-aged men

Purpose: Whether serum lipoprotein (a) [Lp(a)] levels are an independent risk factor for coronary heart disease has been controversial. We have investigated its status in a prospective population survey, the Second Northwick Park Heart Study. Methods: We recruited 2,616 men 50 to 61 years old from nine primary care practices in the United Kingdom. Baseline serum Lp(a) levels were measured by enzyme-linked immunosorbent assay (ELISA) and were analyzed in 3 groups (<25th percentile, 25th to 75th percentile, and >75th percentile) to overcome the problem of some measurements falling below the threshold of the assay. Coronary end points included sudden cardiac death, acute myocardial infarction, silent myocardial infarction on the electrocardiogram, and coronary artery bypass surgery. Results: During a mean of 6 years of follow-up, 121 men had coronary events. In a multivariate analysis that also adjusted for fibrinogen, Apo-A1, Apo-B, and triglyceride levels, we identified several independent risk factors for coronary events, including cholesterol level (hazard ratio [HR] = 1.5 per SD 95% confidence interval [CI] 1.3 to 1.8), diabetes (HR = 4.1, 95% CI: 2.0 to 8.4), current versus never smoking (HR = 2.5, 95% CI: 1.5 to 4.1), diastolic blood pressure (HR = 1.4 per SD, 95% CI: 1.1 to 1.7), Apo-A1 (HR = 0.8 per SD, 95% CI: 0.6 to 0.9), age (HR = 1.3 per SD, 95% CI: 1.1 to 1.6), and Lp(a) (>26.3 mg/dL [75th percentile] versus <2.9 mg/dL [25th percentile], HR = 1.9, 95% CI: 1.1 to 3.3]. There was a statistically significant (P = 0.01) difference in risk between the three levels of Lp(a). Conclusions: We found that a high Lp(a) level was an independent predictor of the development of coronary heart disease in middle-aged men.