The EEG in the normal elderly: a contribution to the interpretation of aging and dementia.

Forty-seven normal elderly, 16 normal subjects ranging from 40 to 60 years of age and 14 patients affected by primary dementia are studied. The EEG is recorded from different brain areas and analysed by FFT algorithm. Main results are: There is persistence of the regional distribution of the alpha frequency which is higher in occipital than in frontal leads in the normal elderly. Spectral composition in the same group keeps its typical profile with age. Alpha-dominant tracings form 68%. Values collected from the two hemispheres are similar. Therefore, no evidence is detected for a selective age effect on one side, either right or left. In the elderly group, a sex-linked difference is found. Women have less delta and more beta frequency. The opposite holds true in men. EEG slowing is typical of old age. However, in occipital leads the alpha frequency has an average of 9.46 Hz. Statistical comparison between the normal groups (middle aged vs. elderly) gives no significant results. Significant differences are seen when the normal elderly are compared with demented subjects. The data do not support the hypothesis of a continuum from aging to mental deterioration.