Apolipoprotein E polymorphism and age at onset of Alzheimer's disease in a quadriethnic sample

The relationship between the apolipoprotein E (ApoE) genotype and the risk for developing Alzheimer's disease (AD) or age at onset of AD is relatively well established in Caucasians, but less established in other ethnicities. We examined the association between the ApoE genotype and age at onset of AD in a quadriethnic group of community-dwelling AD patients.

AD patients were evaluated at 2 university-based outpatient memory disorder clinics. The ethnic distribution was as follows: Caucasians (n = 1,083), Hispanics (n = 55), African Americans (n = 84) and Koreans (n = 87). All were diagnosed with probable AD according to NINCDS-ADRDA diagnostic criteria.

After adjusting for ethnicity, the ε4 allele was significantly associated with earlier age at onset (p < 0.0001) for the combined group. Within ethnic groups, the effect of Apo ε4 on age at onset was significant in Caucasians (p < 0.0001) and African Americans (p < 0.05), but nonsignificant in Koreans (p = 0.43) and in the smaller Hispanic (p = 0.07) group.

The association between Apo ε4 and younger age at onset was significant in Caucasians and African Americans, where the ε4 allele was also most frequent. This study suggests that the impact of ApoE polymorphism on age at onset of AD may be different among distinct ethnic groups.