Cumulative sleep restriction and subsequent recovery sleep: Effects on subjective sleepiness, vigilance, and executive functions

Abstract

Objective: Cumulative partial sleep loss is more often practical eventually among aircrew. The sleep loss encountered on the weekdays is generally compensated by taking restorative sleep on the weekends. This study aimed to examine the subjective appreciation of sleepiness and cognitive performance pertaining to vigilance and executive functions during cumulative sleep restriction for a period of 05 days and then following 3 consecutive nights of recovery sleep. Material and Methods: In a repeated measures design, 14 healthy volunteers were longitudinally followed up twice on a day (morning and afternoon) on their subjective sleepiness (Stanford Sleepiness Scale), vigilance, and executive functions (Mackworth Clock Test and Stroop Test of Psychometric Evaluation Design for Aviators test battery, respectively) over a period of 5 days with 2 h of sleep restriction each night. These parameters were again assessed following 3 consecutive nights of restorative recovery sleep. Results: Subjective appreciation of sleepiness was significantly increased by accumulating sleep debt (F = 8.368, P < 0.001). Stroop Effect and Reaction Time did not show any significant changes; however, cumulative sleep loss significantly affected accuracy measures (F = 2.388, P = 0.04) and attention lapses (F = 2.816, P = 0.018). Following restorative sleep, the subjective sleepiness and accuracy scores did not show any significant difference from that of baseline. However, lapses continued to be significantly higher than the baseline values (P = 0.012). Conclusion: Cumulative sleep loss over a period of 5 days resulted in more sleepiness and a decrement in vigilance measures even though the executive functions remained intact. The persistence of attention lapses indicated incomplete recovery of vigilance functions following 3 days of restorative sleep.