The effects of acute sleep restriction and extension on sleep efficiency

This study employed a repeated measures design to assess the relationship between sleep efficiency and time-in-bed (TIB). Fourteen subjects underwent three TIB conditions: (5 hour, 8 hour, and 11 hour), which were presented in a Latin Square design. Subjects slept a total of six nights (two nights per condition) while being monitored by a wrist actigraph to determine sleep time. Sleep efficiencies (sleep time/TIB) were analyzed with a two-way repeated-measures ANOVA. The main effect of night was not significant. The main effect of TIB and the interaction of nights and TIB were significant. In the 11-hour condition, sleep efficiency fell from night one to night two, and on night two both the 5-hour and the 11-hour conditions were significantly different from the 8-hour condition. Analysis of total sleep time (TST) yielded the same results with the addition of a significant night-to-night difference in the 5-hour condition. It was concluded that sleep efficiency systematically changes with an extension or restriction of TIB from 8 hour.