Association between apolipoprotein E gene polymorphism and the risk of multiple sclerosis: A meta-analysis of 6977 subjects

Epidemiological studies have evaluated the association between apolipoprotein E (ApoE) gene polymorphism and multiple sclerosis (MS) risk. However, the results remain conflicting. Therefore, in order to derive a more precise association of ApoE gene polymorphism with MS risk, we performed this meta-analysis. Systematic searches of electronic databases PubMed, Embase and Web of Science, as well as hand searching of the references of identified articles were performed. Twenty studies were identified, covering a total of 4080 MS cases and 2897 controls. The results showed evidence for significant association between ApoE ε2 mutation and MS risk (for ε2/ε4 versus ε3/ε3: OR = 1.74, 95% CI = 1.12–2.71, p = 0.01; for ε2 allele versus ε3 allele: OR = 1.16, 95% CI = 1.01–1.35, p = 0.04). In the subgroup analysis by ethnicity, the similar results were obtained among Europeans (for ε2/ε4 versus ε3/ε3: OR = 1.81, 95% CI = 1.14–2.87, p = 0.01; for ε2 allele versus ε3 allele: OR = 1.19, 95% CI = 1.02–1.38, p = 0.03). After excluding the outlier studies by observing Galbraith plot, marginal association was found between ApoE ε3/ε4 genotype and the protective factor for MS (for ε3/ε4 versus ε3/ε3: OR = 0.86, 95% CI = 0.75–0.99, p = 0.04). In summary, the present meta-analysis provides evidence that ApoE ε2 mutation is associated with MS risk. In addition, ApoE ε3/ε4 genotype appears to be a protective factor for MS.

► We performed a meta-analysis to derive a more precise estimation of the relationship.
► Our study has the potential to detect small effects in genetic association studies.
► Our study suggests that ApoE gene polymorphism is associated with MS risk.