Protective effect of Apolipoprotein E epsilon 3 on sporadic Alzheimer's Disease in Chinese population: A Meta-Analysis

Introduction Alzheimer's disease (AD) is fastly becoming one of the most expensive, deadly and burdensome diseases in this century. It has the fastest growing disease burden in China. Apolipoprotein E (APOE) polymorphic alleles are generally considered to be the primary genetic determinant of AD risk: individuals with the E4 allele are at increased risk of AD compared to individuals with the more common E3 allele. The association intensity is different among different ethnic groups, so a separate meta-analysis of the Chinese population is needed. Methods We searched Chinese and English databases to sift through literature over the past 20 years. Data on the APOE genotype and AD were collected for correlation analysis. OR was calculated according to APOE allele and genotype. Publication bias analysis and sensitivity analysis were performed, and the main results were further verified by subgroup analysis. Results The 116 eligible studies enrolled 23396 AD patients and 25568 healthy controls. The study subjects covered at least 30 of the 34 provincial-level administrative regions (including Taiwan). Partial sex ratio: AD male/female: 10291/11240; Control male/female: 11304/12428, X2=0.122，P=0.727. Meta-analysis results of alleles showed that I2>50% and Q statistics were significant for all genotypes, so the random effect model was selected. The frequency of the ApoE ε4 allele in AD was higher than that in healthy controls, and the difference was statistically significant (OR=2.847, 95% CI=[2.611-3.101], PConclusion The results provide support for the protective effect of the ApoE ε3/ε3 in developing AD. Discussion This research is the most comprehensive meta-analysis of the correlation between APOE and AD in the Chinese population by analysing the distribution of the APOE gene in AD reported in the last 20 years. It was concluded that the APOE ε3 allele had a protective effect on sporadic AD in the Chinese population with great significance, and its protective effect was stronger than that of ε2.