Effects of a 25-h sleep deprivation on daytime sleep in the middle-aged

Our understanding of the mechanisms by which sleep deteriorates with age al most exclusively stems from comparisons of young and elderly subjects. The present study investigated the different effects of a 25-h sleep deprivatio n on the recovery sleep initiated in the morning (when circadian sleep prop ensity decreases) of young (20-39 y) and middle-aged subjects (40-60 y). Mi ddle-aged subjects showed a steeper increase in the duration of wakefulness during daytime recovery sleep than the young subjects. Slow-wave sleep (SW S) and EEG slow-wave activity (SWA: spectral power between 0.5-4.5 Hz) were potentiated in both groups following sleep deprivation. However, the rebou nd of SWS and SWA was significantly less pronounced in the middle-aged than in the young. This reduction in homeostatic recuperative drive in middle-a ged subjects might account for the decrease in their ability to maintain sl eep when they have to recuperate at an abnormal circadian phase. These resu lts helps to understand the increase in complaints related to shift work an d jet lag in the middle years of life. (C) 2001 Elsevier Science Inc. All r ights reserved.