Age-dependent changes in sleep EEG topography.

OBJECTIVE: To assess age-related topographic changes in the sleep electroencephalogram (EEG). METHODS: The sleep EEG records of young (mean age, 22.3 years) and middle-aged (mean age, 62.0 years) healthy men were compared. The EEG was obtained from 3 bipolar derivations (frontal-central (FC), central-parietal (CP), and parietal-occipital (PO)) along the antero-posterior axis. RESULTS: The total sleep time, sleep efficiency, stage 2 and slow wave sleep (SWS) were lower in the middle-aged group, while sleep latency, stage 1 and wakefulness after sleep onset were higher. Spectral analysis documented the age-related reduction of EEG power in non-REM sleep (0.25-14 Hz), and REM sleep (0.75-10 Hz). However, the reduction was not uniform over the 3 derivations, but was most pronounced in the anterior derivation (FC) in the theta (both sleep states) and high-alpha/low-sigma bands (non-REM sleep). CONCLUSIONS: These changes can be interpreted as age-related shifts of power from the anterior (FC) towards the middle derivation (CP). Aging not only reduces power in the sleep EEG, but causes frequency-specific changes in the brain topography. The results are consistent with the notion of sleep as a local process