Is the apoE4 allele an independent predictor of coronary events?

Abstract

Purpose: Although the apolipoprotein E genotype ϵ4 (apoE4) has been associated with high cholesterol levels, whether it is an independent predictor of coronary events is not certain. Subjects and Methods: We measured apoE genotypes in 730 participants in the Baltimore Longitudinal Study of Aging (421 men and 309 women, mean [± SD] age of 52 ± 17 years) who were free of preexisting coronary heart disease. A proportional hazards regression model was used to study the association between risk factors and the occurrence of coronary events, defined as angina pectoris, documented myocardial infarction by history or major Q waves on the electrocardiogram (Minnesota Code 1:1 or 1:2), or coronary death, adjusted for other risk factors, including total plasma cholesterol level. Results: The apoE4 allele was observed in 200 subjects (27%), including 183 heterozygotes and 17 homozygotes. Coronary risk factor profiles were similar in those with and without apoE4. Coronary events developed in 104 (14%) of the 730 subjects, including 77 (18%) of the 421 men during a mean follow-up of 20 years and 27 (9%) of the 309 women during a mean follow-up of 13 years. Coronary events occurred significantly more frequently in subjects with apoE4 (n = 40, 20%) than in those without this allele (64, 12%, P <0.05). In a multivariate model, apoE4 was an independent predictor of coronary events in men (risk ratio [RR]= 2.9, 95% confidence interval [CI]: 1.8 to 4.5, P <0.0001) but not in women (RR = 0.9, 95% CI: 0.4 to 1.9, P = 0.62). Conclusion: The apoE4 genotype is a strong independent risk factor for coronary events in men, but not women. The association does not appear to be mediated by differences in total cholesterol levels.