Investigation of the effectiveness of a split sleep schedule in sustaining sleep and maintaining performance

Abstract

Shift work is common in today's society, and is associated with negative health outcomes, and accidents and incidents. These detrimental effects can be primarily attributed to sleeping and working at an adverse circadian time. The aim of this study was to examine whether a split sleep schedule is as effective as a consolidated day shift or night shift schedule for maintaining performance and sustaining sleep. Fifty-three healthy male volunteers (mean ± SD age = 26.51 ± 4.07 years) underwent a randomized three condition study design. A split sleep condition involving two 5-h sleeping opportunities in 24 h [time in bed (TIB) 0300 h-0800 h and 1500 h-2000 h] was compared to a 10-h consolidated nighttime sleep (TIB 2200 h-0800 h) and 10-h consolidated daytime sleep (TIB 1000 h-2000 h). All participants underwent a baseline period of 10 h of nocturnal time in bed (TIB) followed by a 5-d simulated workweek spent in one of the three conditions. Polysomnography, psychomotor vigilance task, digit-symbol substitution task and subjective state were assessed. During the 5-d simulated workweek, participants in the nighttime sleep condition slept the most (total sleep time per day (TST) 8.4 h ± 13.4 min), followed by the split sleep condition (TST 7.16 h ± 14.2 min) and the daytime sleep condition (TST 6.4 h ± 15.3 min). Subjective sleepiness was highest in the daytime sleep condition and lowest in the nighttime sleep condition. No significant differences in performance were observed between the conditions. Compared to a nighttime consolidated sleep opportunity or split sleep, placement of a consolidated sleep opportunity during the day yielded truncated sleep and increased sleepiness. Further research in real-world situations is warranted to fully assess the efficacy of alternative split sleep schedules for improving safety and productivity.

A systematic review of the sleep, sleepiness, and performance implications of limited wake shift work schedules

“…Eight of the studies identified in this review used a within-subject's design (18,22,23,25,29,(36)(37)(38), ten a between-subject's design (17,24,26,27,30,31,34,35,39,40), and four employed a mixed within-and between-subjects design (19,28,32,33). Seventeen studies were field-based (17-19, 22, 24-32, 34-37) and five used laboratory simulations (23,33,(38)(39)(40).…”

“…Five studies examined 8 hours-on/8 hours-off roster schedules, all of which were conducted with Australian train drivers (22,25,29,36,37), five examined 6 hours-on/6 hours-off shift schedules, predominantly in ship bridge officers and offshore fleet workers (17,23,30,34,39), and nine examined 4 hours-on/8 hours-off shift schedules all among maritime watch keepers (17, 26-28, 30-33, 35). The remaining LWSW studies employed less common schedules.…”

“…Only primary, peer-reviewed articles published in English were included, while studies examining pharmacological interventions were excluded. From this search, we identified 22 papers which examined LWSW (17)(18)(19)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(32)(33)(34)(35)(36)(37)(38)(39)(40), two pairs of which overlap (25,29,36,37), leaving a total of 20 independent studies. The identified studies are summarized in table 1.…”

Sleep and performance in simulated Navy watch schedules

“…1) did not adversely affect total sleep duration. In another simulated shift work study, split sleep was associated with reduced sleep efficiency as compared to consolidated sleep (Jackson et al, 2014). However, this effect becomes negligible under conditions of sustained sleep restriction (Mollicone et al, 2007), as is more typical in operational settings.…”

21st International Symposium on Shiftwork and Working Time: The 24/7 Society – From chronobiology to practical life

“…In the same context, Jackson et al (2014) split evenly into two sleep periods, with two conditions in which sleep was consolidated into a single period (either daytime consolidated sleep and or nighttime consolidated sleep), to determine the effects of the sleep patterns on sleep, performance and subjective state. Overall, participants in the nighttime and split sleep conditions obtained significantly more total sleep time than participants in the daytime sleep condition.…”