Apolipoprotein E polymorphism and Alzheimer's disease in eastern Finland.

Apolipoprotein E is a polymorphic protein defined by three alleles, epsilon 2, epsilon 3 and epsilon 4. An increased frequency of the epsilon 4 allele is associated with late-onset familial and sporadic Alzheimer's disease (AD). We studied 202 Finnish AD patients and 55 age- and sex-matched controls. AD patients were divided into four subgroups; sporadic early-onset, sporadic late-onset, familial early-onset and familial late-onset disease. We found no significant differences in the epsilon 4 allele frequency between the subgroups. However, all the subgroups differed in the frequency of epsilon 4 allele detection from the controls (P < 0.0001). In the late-onset patients, the age at onset decreased from 76 to 69 as the number of epsilon 4 alleles increased from 0 to 2.