Apolipoprotein E gene polymorphism and risk for coronary heart disease in the Chinese population: a meta-analysis of 61 studies including 6634 cases and 6393 controls

Abstract

Background: Numerous studies have evaluated the association between the apolipoprotein E (apoE) gene polymorphisms in coronary heart disease (CHD). However, the results remain uncertain. We carried out a meta-analysis to derive a more comprehensive estimation of the association in Chinese population.

Methods: Case-control studies in Chinese and English publications were identified by searching databases of PubMed, EMBASE, Web of Science, CNKI, CBM, Wanfang, VIP and hand searching of relevant journals and the reference lists of retrieved articles. Odds ratio (OR) and 95% confidence interval (CI) were applied to assess the strength of the associations. Subgroup analysis and sensitivity analysis were performed to explore the between-study heterogeneity.

Results: We finally identified 61 relevant studies which comprised 6634 case-patients and 6393 controls. The pooled OR for ε4 carriers was 96% higher than the ε3/3 genotype for CHD (OR, 1.96; 95% CI, 1.70 to 2.24; P<0.001). However, there was no evidence of statistically significant association between ε2 carriers and risk of CHD (OR, 1.02; 95% CI, 0.91 to 1.13; P = 0.729). In the subgroup analysis, different endpoints may partially account for the heterogeneity. No publication bias was found.

Conclusions: Our meta-analysis suggests that the apoE ε4 allele may be a risk factor for CHD in the Chinese population, however, ε2 allele has no significant association.

Figure 1. The flowchart of selection of studies.

Figure 2. Odds ratios for coronary heart disease in ε4 carriers versus population with the ε3/3 genotype of all 61 studies.

Size of the squares is proportional to the weight of the odds ratios; black circular dots indicate the odds ratios; horizontal lines represent the 95% CI. Dark hollow diamonds show the pooled estimates from the random-effects models (with 95% CI) and the fixed-effects model (with 95% CI).

Figure 3. Odds ratios for coronary heart disease in ε2 carriers versus population with the ε3/3 genotype of all 61 studies.

Size of the squares is proportional to the weight of the odds ratios; black circular dots indicate the odds ratios; horizontal lines represent the 95% CI. Dark hollow diamonds show the pooled estimates from the random-effects models (with 95% CI) and the fixed-effects model (with 95% CI).

Figure 4. The comparison of ORs between ε3/3 and all the other genotypes for coronary heart disease, based on 61 studies.

Size of data symbols is proportional to the inverse of the variance of odds ratios (ε3/3 is displayed with forced fixed size) and error bars represent 95% confidence intervals (CIs).