Studies in the processes of aging: Electroencephalographic findings in 400 elderly subjects

1. 1. Electroencephalograms were obtained on 400 subjects over the age of 60 as part of a project dealing with aging of the central nervous system. 2. 2. One hundred senile patients, without evidence of gross focal neurological disease revealed that 22 per cent had normal records with a preponderance of diffuse and mixed abnormalities. 3. 3. In 145 volunteers from the community without neurological disease, a high percentage of focal disturbances were found, and a gradient of decreasing EEG abnormality of all types was noted with higher socio-economic levels. Focal disturbances alone did not seem to cause psychological impairment. 4. 4. Psychological test data correlate diffuse and mixed EEG abnormalities with the greatest degree of psychological deterioration. 5. 5. Forty-five psychiatric patients with no evidence of brain damage revealed patterns of electroencephalographic abnormalities similar to the community group volunteers, 60 per cent of their records being normal. Diffuse fast wave disturbances were relatively more frequent among the abnormalities seen. 6. 6. Ninety-four neurological cases showed the expected low incidence in normal records and a heavy preponderance of focal disturbances. 7. 7. A gradient of decreasing normal records was noted in progressively older decades. Diffuse dysrhythmias which followed this trend were due to slow wave disturbances. The incidence of focal records did not appear to change in succeeding decades, but a definite increase in the proportion of severe foci was noted in progressively older decades. 8. 8. Diffuse fast wave disturbances were not frequent, and showed a tendency to decrease in older patients, as did the proportion of severe fast disturbances. No fast wave abnormalities were seen in patients over the age of 79. 9. 9. The high incidence of foci in this series could not alone be correlated with psychological test evidence of deterioration. When foci were associated with diffuse abnormalities, however, organic deterioration was definitely noted. Primarily left temporal foci were often clinically silent. The suggestion was made that hippocampal degenerations or beginning generalized vascular disease might be the cause. 10. 10. It was suggested that temporal foci could be more easily elicited using the vertex as a reference electrode, as well as keeping the ears “untied” and ungrounded. Also important was the use of the low-lying anterior temporal lead.