Apolipoprotein E Polymorphisms And Parkinson's Disease With Or Without Dementia:A Meta-analysis

Objective: A large number of case-control studies have repeatedly investigated the association between apolipoprotein E(APOE)polymorphisms with Parkinson's disease(PD)and Parkinson's disease dementia(PDD).However,the results are not consistent.This meta-analysis aimed to evaluate the relationship of APOE polymorphisms and PD,PDD risk.Methods: We searched for studies published on PubMed,Web of Science,WanFang Data(in Chinese)and CNKI(in Chinese)from inception to November 2016.Additionally,studies were identified by manual search of references of original articles or review studies on this topic.Case-control studies that reported part or complete APOE genotype and allele frequencies data were included.The data were extracted according to the inclusion and exclusion criteria,and the quality of included studies was evaluated.The pooled odds ratios(ORs)with 95% confidence intervals(95% CIs)were calculated using RevMan 5.3 soft-ware.Publication bias and sensitivity analysis were also assessed.Results: 39 studies involving 6453 PD cases,which included 461 PDD cases,and 6855 controls were included in this meta-analysis.The results showed APOE ?3 was a protective factor for PD(OR=0.90,95%CI: 0.81-0.99,P=0.04),while APOE ?2 and ?4 had no significant differences with PD risk in the largest crowd(?2: OR=1.03,95%CI: 0.94-1.13,P=0.49;?4: OR=1.01,95%CI: 0.94-1.08,P=0.82).However,after ruling out positive family history and dementia,the results were not similar.Homozygous APOE ?2/?2,?3/?3,?4/?4 would not affect the outcome.But in Asians subgroups,the APOE ?4 was shown to be a risk factor for PD(OR=1.22,95%CI: 1.01-1.46,P=0.04).Additionally,APOE polymorphisms were significantly associated with PDD risk both in the largest crowd(?2: OR=1.16,95%CI: 0.83-1.64,P=0.38;?3: OR=0.72,95%CI: 0.58-0.89,P=0.003;?4: OR=1.46,95%CI: 1.12-1.88,P=0.004)as well as in Chinese subgroups.Conclusions: The APOE ?3 allele appears to cause a lower prevalence of PD in the largest crowd,and the ?4 allele is associated with a higher prevalence of PD in Chinese subgroups.The APOE?4 allele is a risk factor for PDD,while the ?3 allele is a protective factor.