EEG characteristics of healthy adults living at higher elevations.

EEG data from 400 healthy adult volunteers in the Xining area (with an altitude of 2260 meters) are summarized to show changes in indices of waves, frequencies and amplitude. Analysis and observations were made for tests of eyes open-close, acoustic stimulation and hyperventilation. Differences in EEGs were compared between males and females of various age groups, and between adults living at the higher elevations in Xining and those living on the plains in the Beijing area (altitude 40 meters). Comparisons showed that EEG characteristics of healthy adults at the higher altitude were: an increase in the incidence of abnormality, a decrease of alpha indices, an increase in the number of slow waves, the appearance of spikes and sharp waves, and a reduction in the level of sensitivity to activation tests.