Spectral analysis of EEG in Alzheimerʹs disease: Relation to apolipoprotein E polymorphism

Apolipoprotein E (ApoE) ε4 allele is a risk factor for late-onset Alzheimerʹs disease (AD) and proposed to have a direct impact on cholinergic function in AD. Slowing of the EEG is characteristic in AD and the cholinergic system has an important role in modulating EEG. Fifty-eight AD patients at the early stage of the disease and 34 age- and sex-matched controls were studied using the quantitative EEG recorded from T6-O2 derivation. AD patients were divided into two subgroups: a) according to the ApoE allele (2 ε, 1 ε4, and 0 ε4) and b) according to familial aggregation. AD subgroups did not differ in clinical severity or duration of dementia. The AD patients with the ε4 allele had higher relative theta amplitude and lower relative beta amplitude than controls and patients without the ε4 allele. The peak frequencies were lower in all AD subgroups compared to controls. In conclusion, we found a tendency towards more pronounced EEG slowing in AD patients carrying the ε4 allele. The minor differences in EEG may suggest differences in the degree of the cholinergic deficit in these subgroups.