Apolipoprotein E epsilon 4 allele frequency and age at onset of Alzheimer's disease

The age distribution of the epsilon 4 allelic form of the apolipoprotein E gene ( APOE) was investigated in 630 patients with Alzheimer's disease ( AD) with onset age ranging from 35 to 90 years. Overall, mean age at onset in APOE epsilon 4 allele bearers was significantly later than that in nonbearers. However, when stratified into early onset AD (EOAD) and late onset ( LOAD) groups, mean age at onset in EOAD cases bearing APOE epsilon 4 allele was later than that in those EOAD cases without epsilon 4 allele, whereas in LOAD mean age at onset in cases bearing APOE epsilon 4 allele was earlier than in those without epsilon 4 allele. When analysed by decade, it was observed that 37% of the total number of APOE epsilon 4 allele bearers, and 43% of total number of cases with APOE epsilon 4/epsilon 4 genotype fell into the 60 - 69 years age class. Hence, APOE epsilon 4 allele frequency, at 0.44, was highest in the 60 - 69 years age class, progressively decreasing either side of this age group. APOE epsilon 4 allele therefore has its maximum impact between onset ages of between 60 and 70 years. Copyright (C) 2007 S. Karger AG, Basel.