Associations between apolipoprotein E gene polymorphisms and Alzheimer’s disease risk in a large Chinese Han population

OBJECTIVE Apolipoprotein E gene (APOE) polymorphisms contributing to the risk of sporadic Alzheimer's disease (AD) have been identified for decades, but it has not been investigated in large AD samples of Chinese Han population. METHODS We performed a cross-sectional study to explore the effect of APOE polymorphisms on sporadic AD in 875 sporadic AD patients and 1,195 cognitive normal controls of Chinese Han. Genotyping of APOE was determined by multiplex amplification refractory mutation system polymerase chain reaction. RESULTS APOE ε3ε4 and ε4ε4 genotypes increased AD risk with dosage effect. The odds ratio (OR) of ε3ε4 was 1.89 and the OR of ε4ε4 was 15.64 compared with that of ε3ε3 in all the subjects. E2ε3 genotype decreased AD risk in all the subjects (OR=0.64), female subgroup (OR=0.57), and late-onset AD subgroup (OR=0.60). However, neither ε2ε2 nor ε2ε4 affected AD risk. About the age at onset (AAO), the influence of APOE ε4 was only exhibited in late-onset AD subgroup, with 1 year lower in ε4-positive ones than negative ones. Further analysis did not show the dosage effect of ε4 pertinent to AAO, though the AAO of ε4ε4 patients decreased by 2 years. E2 did not affect the AAO of AD. CONCLUSION APOE ε4 is a strong risk factor of AD risk in Chinese Han population, and APOE ε4ε4 genotype might be related to the AAO of late-onset AD.