Aging and changes in phasic events during sleep.

Changes in phasic events in the elderly are reviewed. Such phasic events may in part be determined by the macrostructure of sleep (sleep stages). Therefore, a brief description of sleep architecture and EEG morphology in the aged person is given. Second, there is a marked variability among individuals in the number of spindles and K-complexes and more so in older individuals than in younger. However, there is an overall decrease in these events with age. The characteristics of these events (amplitude, frequency content, and distribution) change simultaneously. Third, the number of rapid eye movement occurring during REM sleep decreases with aging, but important gender differences exist, in that women generally maintain a higher REM density. The degree of changes in phasic events might correlate with mental deterioration (sleep cognition theory), but physical factors might also be the underlying reason for the observed changes. Whether these changes are indicative of the individual's ability to maintain sleep remains to be determined.