A longitudinal quantitative EEG study of Alzheimer's disease: relation to apolipoprotein E polymorphism.

Apolipoprotein E (apoE) sigma4 allele is a risk factor for late-onset Alzheimer's disease (AD) and is proposed to have an 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. QEEG was recorded from 31 AD patients at the early stage of the disease and after a 3-year follow-up. AD patients were divided into subgroups according to the apoE sigma4 allele (2sigma4, 1sigma4 and 0sigma4). AD subgroups did not differ in clinical severity or duration of dementia. The AD patients carrying the sigma4 allele had more pronounced slow-wave activity than AD patients without the sigma4 allele, although the progression rate did not change. The differences in EEG may suggest differences in the degree of the cholinergic deficit in these subgroups.