Age-related disturbances of the sleep-wake cycle can reflect ontogenetic changes in regulatory mechanisms underlying
normal and pathological aging, but the exact nature of these changes remains unclear. The present report is the
first attempt to apply principal component analysis to the electroencephalographic (EEG) spectrum to examine of whether
the observed age-related changes in the objective sleep measures can be linked to the opponent sleep-promoting and
wake-promoting processes. The EEG indicators of these processes - scores on the 1st and 2nd principal components of the
EEG spectrum, respectively - were compared in 15 older (57-74 years) and 16 younger (20-31 years) healthy volunteers.
The scores were calculated for non-REM sleep episodes which occurred during ten 75-min naps scheduled every 150 min
throughout a 40-h constant routine protocol. Both, a decrease of the 1st principal component score and an increase of the
2nd principal component score were found to contribute to such most obvious age-related modification of the sleep EEG
spectrum as attenuation of EEG slow-wave activity in older people. Therefore, we concluded that the normal aging process
can reflect both a weakening of the sleep-promoting process and a strengthening of the wake-promoting process, respectively.
Such bidirectional changes in chronoregulatory processes may explain why sleep of older people is characterized
by the few profitable and a number of detrimental features (i.e., a better ability to cope with daytime sleepiness and
sleep loss vs. difficulty of falling asleep, decreased total nighttime sleep, “lightened” and fragmentized sleep, unwanted
early morning awakenings, etc.).
Keywords: Circadian rhythms, EEG spectrum, normal aging process, principal component analysis, sleep homeostasis, sleep
disturbances, sleep-wake regulation, slow-wave activity.
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