Banking sleep: Realization of benefits during subsequent sleep restriction and recovery

Objective: Determine whether sleep extension (a) improves alertness and performance during subsequent sleep restriction and (b) impacts the rate at which alertness and performance are restored by post-restriction recovery sleep. Design: Participants were randomly assigned to an Extended (10 h time in bed [TIB]) or Habitual TIB [mean (SD) hours = 7.09 (0.7)] sleep group for one week, followed by 1 Baseline (10 hours or habitual TIB), 7 Sleep Restriction (3 h TIB), and 5 Recovery Sleep nights (8 h TIB). Performance and alertness tests were administered hourly between 08:00-18:00 during all in-laboratory phases of the study. Setting: Residential sleep/performance testing facility. Participants: Twenty-four healthy adults (ages 18-39) participated in the study. Interventions: Extended vs. habitual sleep durations prior to sleep restriction. Results: Psychomotor vigilance task (PVT) lapses were more frequent and modified maintenance of wakefulness (MWT) sleep latency was shorter in the Habitual group than in the Extended group across the sleep restriction phase. During the Recovery phase, PVT speed rebounded faster (and PVT lapsing recovered significantly after the first night of recovery sleep) in the Extended group. No group differences in subjective sleepiness were evident during any phase of the study. Conclusion: The extent to which sleep restriction impairs objectively measured alertness and performance, and the rate at which these impairments are subsequently reversed by recovery sleep, varies as a function of the amount of nightly sleep obtained prior to the sleep restriction period. This suggests that the physiological mechanism(s) underlying chronic sleep debt undergo long-term (days/weeks) accommodative/adaptive changes.