Abstract:This study was undertaken to examine the effect of aging on sleep. All‐night sleep polygrams of 15 subjects in their 70's and 11 subjects in their 80's were recorded for three consecutive nights. The increase in stage wakefulness (SW) and the decrease in stage 2 (S2) were significant in the subjects in their 80's in comparison with those in their 70's (p<0.05, P<0.01, respectively). After the age of 70, slow wave sleep decreased in the earlier part of the night and REM sleep shifted to the earlier part of the night. These facts support the hypothesis that slow wave sleep and REM sleep compete with each othe