Rapid eye movement activity before spontaneous awakening in elderly subjects

Previous research in young subjects found that rapid eye movement (REM) density is higher in those REM phases which are followed by an awakening (REM-W) than in those preceding NREM (REM-N), suggesting a 'gating role' of REM sleep toward the awakening. It is not yet known whether this evidence is maintained in elderly subjects, who display, relative to young subjects, more awakenings, different sleep states from which the awakenings come (NREM in a high proportion of cases) and a general impairment of rapid eye movement activity (REMA). To investigate this issue, we have compared in three different age groups (young, old and 'old old' subjects) the features of REMA, including REM density and the amount and duration of REM bursts, between REM-W and REM-N. Whereas in the young REM density is higher in REM-W than in REM-N, this difference is already reduced in the old group and fully cancelled in the old old subjects. The evidence that old individuals spontaneously wake up despite the absence of an increase of REMA could imply that in the aged awakening is not preceded by an increase of the arousal level (expressed in REM sleep by the REMA). The similar duration of REM bursts for REM-W and REM-N in both groups of old subjects suggests that with age a marked impairment occurs in the organizational aspects of REMs, independently from the following state.