Age development and sex differences of various EEG elements in healthy children and adults--quantification by a...

The EEGs of 1416 healthy subjects aged 6-39 years were recorded and 1 min of background activity from Fp1, C3 and O1, was analyzed by a computerized wave form recognition method. Age development and sex differences of various EEG elements, which are employed in a conventional clinical EEG assessment, were statistically analyzed. The age developments of alpha and theta showed regional differences and were the most rapid in O1 and the slowest in C3. The delta amplitude, theta amplitude, theta continuity and percentage time of theta with an amplitude of 30 microV or more, which are important in a clinical EEG assessment, reached a stable level at 18-21 years of age in the 3 leads. The percentage time, amplitude and continuity of alpha in the 3 leads reached a stable level at 22-25 years of age. Including the low voltage theta in Fp1 and C3, all of the EEG elements reached the stable adult level at 26-29 years of age. Since there was a large interindividual variability in these age developments, the regression curves of the 10th and 90th percentiles of these EEG elements can be considered as quantitative standards for clinical EEG evaluation. As for sex differences, the percentage alpha time and alpha continuity were greater in males than in females after adolescence. The percentage theta time in Fp1 and C3 was greater in females than in males during childhood. The percentage beta time was higher in females than in males at all ages. But overall, these sex differences were minor compared with the differences associated with age developments of the EEG elements.