Correlation between Apolipoprotein E polymorphism and age at onset of Alzheimer's disease in a Chinese Han population

Abstract

To investigate the correlation between the ApoE genotype and age at onset in a cohort of hospital-based AD patients of Han population in China. All cases were consecutive probable AD patients from the Memory and Cognitive Impairment Clinic of Peking Union Medical College Hospital from 1999 to 2010. They were all Han ethnicity. They were divided into two groups according to age at onset (AAO): early onset AD (EOAD, AAO < 65 years) and late onset AD (LOAD, AAO ≥ 65 years). DNA was extracted and ApoE was genotyped by polymerase chain reaction-restriction fragment length polymorphism analysis. The linkage between ApoE polymorphism and AAO of AD were analyzed by one-way ANOVA. AAO of all cases (n = 495) was (69 ± 10) years, of EOAD (n = 149) was (58 ± 5) years and of LOAD (n = 346) was (74 ± 6) years. ApoEε4(+) genotypes were not associated with AAO of EOAD [ε4-/-: (57 ± 5) years, n = 90; ε4+/-: (59 ± 5) years, n = 50; ε4+/+: (59 ± 5) years, n = 9; F = 0.99, P = 0.38], while they were significantly associated with AAO of LOAD [ε4-/-: ( 75 ± 6) years, n = 189; ε4+/-: (73 ± 6) years, n = 138; ε4+/+: (71 ± 5) years, n = 19; F = 6.51, P = 0.002]. As for all ApoE genotypes, AAO of LOAD reduced gradually in a way as follows: ε2/3 > ε3/3 > ε3/4 > ε2/4 > ε4/4. There was great correlation between AAO and ApoE polymorphism in LOAD without dementia family history, whereas no correlation in LOAD with dementia family history. ApoE genotypes carrying at least one ε4 allele maybe significantly lower AAO of LOAD in a dose-dependent manner whereas no such correlation in LOAD with dementia family history.