The Effects on Subsequent Sleep of an Acute Restriction of Sleep Length

This experiment was designed to test the effects on subsequent sleep of a restriction in sleep length on the previous night. Eight male subjects were studied. After baseline recordings were made, sleep was restricted to either a period between 4-8 am or to a period between 6–8 am. On the night following the restriction of sleep the subjects retired at 11 pm and they were permitted to sleep ad lib in the morning. The restricted sleep periods resulted in differential sleep deprivation. Stages REM and 2 were markedly reduced whereas stages 3 and 4 showed little or no reduction in amount. There were significant reductions in sleep latencies and in the amount of lime spent in stages 0 and 1. The first 8 hrs of ad lib sleep following the 2 restricted sleep periods did not differ in any significant way from the 8 hrs of baseline sleep. When sleep was permitted to continue until the subjects awakened spontaneously, the sleep after the restriction of sleep to‘i hrs was significantly longer and displayed significantly more of stages REM and 2 when compared with the baseline ad lib sleep condition. The ad lib sleep period following the 4 hr condition showed similar changes although the differences were not statistically significant. The significant reductions in stages KEM and 2 during the restricted sleep periods were attributed to the effects of reduced steep length per se. The increases in sleep length and specifically the increases in stages REM and 2 during the ad lib sleep periods were attributed to a differential sleep “debt” accruing from restricted sleep length.