Apolipoprotein E gene polymorphism and the risk of subarachnoid hemorrhage: a meta-analysis of case-control studies.

Background: Studies investigating the association between the apolipoprotein E gene (APOE) polymorphism and the risk of subarachnoid hemorrhage (SAH) have reported inconsistent results. So we performed a meta-analysis to estimate the association between APOE polymorphism and SAH susceptibility.

Methods: Relevant studies published before 5 November 2015 were identified by searching PubMed, Embase, EBSCO, and ISI web of knowledge. The strength of relationship between the APOE gene and SAH susceptibility was assessed using odds ratio (OR) and corresponding 95 % confidence interval (95 % CI).

Results: A total number of six case-control studies including 638 SAH cases and 2,341 controls were identified. No association was found in dominant model or allele contrast genetic model (ε4 dominant model: OR = 1.06, 95 % CI = 0.91-1.25; ε3 dominant model: OR = 0.99, 95 % CI = 0.97-1.01; ε2 dominant model: OR = 0.99, 95 % CI = 0.78-1.25; ε4 versus ε3: OR = 1.14, 95 % CI = 0.96-1.35; ε4 versus ε2: OR = 1.07, 95 % CI = 0.90-1.28; ε3 versus ε2: OR = 1.00, 95 % CI = 0.96-1.04) for APOE polymorphism and SAH susceptibility. In the subgroup analyzed that was stratified by ethnicity, increased risk of SAH was found in Asian subjects when ε4 allele compared with ε3 allele (ε4 vs ε3, OR = 1.55, 95 % CI = 1.07-2.52).

Conclusions: Our meta-analysis suggested that there is no association between APOE polymorphism and SAH risk for overall population. Due to several limitations in the present study, well-designed epidemiological studies with large sample size among different ethnicities should be performed in the future.