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Ageing is known to be accelerated by risk-factors. The continuity between normal and pathological ageing is still quite disputed. Concerning cerebral ageing, the use of statistical methods on electroencephalographic (EEG) parameters appeared to be interesting. In this study, three different groups of elderly subjects were examined by EEG: normal subjects without neurological nor cardiac disease, subjects with Alzheimer-dementia (AD) and cardiac patients without cerebral clinical signs. Stepwise discriminant analysis showed that EEG-parameters discriminating normal subjects from cardiac patients were different from those discriminating AD-patients from normal. Furthermore, AD-patients could be well-discriminated from elderly cardiac patients.

It is a widely accepted that normal ageing hardly modifies basal rythms: alpha frequency remains occipital, symmetrical, and reactive when eyes are opened. There is probably a frequency decrease, but this is hard to determine individually in the absence of longitudinal studies. In any event, alpha frequency never drops below 9 cycles per second until after 80 years of age. Localized and mostly left-sided temporal abnormalities in normal subjects have been noted several times in the literature. However, these pose the problem of early detection of brain damage in patients with hypertension, heart of pulmonary disease. Therefore, further EEG studies on normal and pathological cerebral ageing should investigate clinically well-defined populations.