Sleep stages preceding spontaneous awakenings in the elderly.

Spontaneous awakenings from sleep were studied in a group of 21 elderly subjects (mean age 69.29+/-3.02 years) free of neurological and somatic diseases. The prevalence of awakenings and the duration of waking bouts were analyzed with regard to the prior sleep state. The results showed an increased frequency of awakenings during Stage 2 NREM in the elderly, who wake out of Stage 2 NREM no less frequently than out of REM sleep. This trend is different from that observed in younger subjects (babies and young adults), where a clear prevalence of REM sleep awakenings has been reported. The duration of Stage 2 interrupted by awakening was shorter than Stage 2 followed by sleep. The duration of waking bouts did not differ according to the preceding sleep stage. It is suggested that the relative inability to sustain Stage 2 may be a mechanism which contributes to the difficulty of sleep maintenance in the elderly.