Relationship between Apo E gene polymorphism and risk of different subtypes of mild cognitive impairment

Objective To explore the relationship between Apo E gene polymorphism and the risk of mild cognitive impairment(MCI) and its subtypes among the community elderly population.Methods A 1:2 matched nested case-control studyas conducted on the basis of a cohort of 2 207 individuals aged 60 and overith normal cognitive function in Guiyang city.According to the results of mini-mental state examination(MMSE) screening,the subjectsere selected based on the outcome at the end of a 3 years follow-up.All of the subjectsere genotyped for Apo Eith restriction fragment length polymorphism(RFLP)-PCR.The dataas analyzed by using fitted conditional logistic regressionith Cox regression model.Results During the 3 years follow-up,105 new cases of MCIere diagnosedith an estimated incidence density of 18.2 per 1 000 person-years.The cases included 74 amnestic MCIith an estimated incidence density of 12.9 per 1 000 person-years,and 31 non-amnestic MCIith an estimated incidence density of 5.4 per 1 000 person-years.Single-factor analysis showed that Apo E ε4 geneas a common risk factor to the incidence of total MCI and amnestic MCI(odds ratioOR=2.463,95% confidence intervalCI:1.372-4.433; OR=2.824,95% CI:1.375-5.876).Apo E ε2 gene increased the risk of non-amnestic MCI(OR=3.688,95% CI:1.140-11.930).While Apo E ε3 gene might reduce the incidence of non-amnestic MCI and total MCI(OR=0.478,95% CI:0.275-0.864; OR=0.380,95% CI:0.147-0.984).After adjustment for education and relevant vascular risk factors,Apo E ε4 alleleas still related to a significantly higher risk of total MCI,especially amnestic MCI(OR=2.686,95% CI:1.407-5.127; OR=2.743,95% CI:1.260-5.970).However,non-amnestic MCIas associatedith Apo E ε3 allele(OR=0.305,95% CI:0.103-0.899).Conclusion Apo E gene polymorphism had different effects on the incidence of subtypes of MCI among the elderly in community.Apo E ε4 gene is a common independent risk factor for total MCI and amnestic MCI.Conversely,Apo E ε3 allele may have protective effect on the occurrence of non-amnestic MCI.