Nature and Science of Sleep (Feb 2022)
Timing of Sleep in the Break Between Two Consecutive Night-Shifts: The Effect of Different Strategies on Daytime Sleep and Night-Time Neurobehavioural Function
Abstract
Charli Sargent,1 Anastasi Kosmadopoulos,2 Xuan Zhou,3 Gregory D Roach1 1Appleton Institute for Behavioural Science, Central Queensland University, Wayville, SA, Australia; 2Centre for Study and Treatment of Circadian Rhythms, Douglas Mental Health University Institute, Department of Psychiatry, McGill University, Montreal, QC, Canada; 3Centre for Quantitative Genetics and Genomics, Aarhus University, Aarhus, DenmarkCorrespondence: Charli Sargent, Appleton Institute for Behavioural Science, Central Queensland University, PO Box 42, Goodwood, Wayville, SA, 5034, Australia, Tel +61 8 8378 4523, Email [email protected]: The aim of this study was to examine whether the timing of sleep in the break between consecutive night-shifts affects the quantity and quality of sleep obtained during the daytime and/or neurobehavioural function and self-perceived capacity during the night-time.Methods: Participants (n = 12, all male, aged 22.9± 5.2 y) completed three randomised, counterbalanced conditions in a sleep laboratory, consisting of two consecutive 12-hour night-shifts (18:00– 06:00) with 7 hours in bed in the break between shifts. The three conditions differed only in the timing of the sleep opportunities – immediate (07:00– 14:00), delayed (10:00– 17:00), split (07:00– 10:30 and 13:30– 17:00). Neurobehavioural function (attention, memory, throughput) and self-perceived capacity (sleepiness, alertness, fatigue, mood) were assessed at 2-hour intervals during the night-shifts.Results: Condition did not affect total sleep time (p = 0.465), but it did affect sleep onset latency (p < 0.001; W = 0.780; large effect), wake after sleep onset (p = 0.018; W = 0.333; moderate effect) and the amount of Stage N3 sleep (p < 0.001; η2=0.510; small effect). Compared to the immediate and delayed sleep conditions, the split sleep condition had less wake after sleep onset and more Stage N3 sleep; and compared to the delayed condition, the split sleep condition had longer latency to sleep onset. There was no effect of condition on measures of neurobehavioural function or self-perceived capacity during the second night-shift.Conclusion: None of the three sleep strategies examined here – immediate, delayed or split – are clearly superior or inferior to the others in terms of the capacity to sleep during the daytime or to work at night. Therefore, those who work consecutive night-shifts should employ the strategy that best suits their personal preferences and/or circumstances.Keywords: shift work, sleep duration, slow wave sleep, performance, sleepiness, split sleep
