Circadian adaptation to night shift work is associated with higher REM sleep duration

Iona Z Zimberg; Suzanne Ftouni; Michelle Magee; Sally A Ferguson; Steven W Lockley; Shantha M W Rajaratnam; Tracey L Sletten

doi:10.1016/j.sleh.2023.08.024

Circadian adaptation to night shift work is associated with higher REM sleep duration

Sleep Health. 2024 Feb;10(1S):S112-S120. doi: 10.1016/j.sleh.2023.08.024. Epub 2023 Oct 31.

Authors

Iona Z Zimberg¹, Suzanne Ftouni¹, Michelle Magee¹, Sally A Ferguson², Steven W Lockley³, Shantha M W Rajaratnam⁴, Tracey L Sletten⁵

Affiliations

¹ Turner Institute for Brain and Mental Health and School of Psychological Sciences, Monash University, Melbourne, Victoria, Australia.
² Central Queensland University, Appleton Institute, Goodwood, South Australia, Australia.
³ Division of Sleep and Circadian Disorders, Departments of Medicine and Neurology, Brigham and Women's Hospital, Boston, Massachusetts, USA; Division of Sleep Medicine, Harvard Medical School, Boston, Massachusetts, USA.
⁴ Turner Institute for Brain and Mental Health and School of Psychological Sciences, Monash University, Melbourne, Victoria, Australia; Division of Sleep and Circadian Disorders, Departments of Medicine and Neurology, Brigham and Women's Hospital, Boston, Massachusetts, USA; Division of Sleep Medicine, Harvard Medical School, Boston, Massachusetts, USA.
⁵ Turner Institute for Brain and Mental Health and School of Psychological Sciences, Monash University, Melbourne, Victoria, Australia. Electronic address: tracey.sletten@monash.edu.

PMID: 37914630
DOI: 10.1016/j.sleh.2023.08.024

Abstract

Objective: To investigate the influence of the degree of circadian adaptation to night work on sleep architecture following night shift.

Methods: Thirty four night workers (11 females; 33.8 ± 10.1years) completed a simulated night shift following 2-7 typical night shifts. Participants completed a laboratory-based simulated night shift (21:00-07:00 hours), followed by a recovery sleep opportunity (∼09:00-17:00 hours), recorded using polysomnography. Urinary 6-sulphatoxymelatonin (aMT6s) rhythm acrophase was used as a marker of circadian phase. Sleep duration and architecture were compared between individuals with aMT6s acrophase before (unadapted group, n = 22) or after (partially adapted group, n = 12) bedtime.

Results: Bedtime occurred on average 2.16 hours before aMT6s acrophase in the partially adapted group and 3.91 hours after acrophase in the unadapted group. The partially adapted group had more sleep during the week before the simulated night than the unadapted group (6.47 ± 1.02 vs. 5.26 ± 1.48 hours, p = .02). After the simulated night shift, both groups had similar total sleep time (partially adapted: 6.68 ± 0.80 hours, unadapted: 6.63 ± 0.88 hours, p > .05). The partially adapted group had longer total rapid eye movement sleep duration than the unadapted group (106.79 ± 32.05 minutes vs. 77.90 ± 28.86 minutes, p = .01). After 5-hours, rapid eye movement sleep accumulation was higher in the partially adapted compared to the unadapted group (p = .02). Sleep latency and other stages were not affected by circadian adaptation.

Discussion: Partial circadian adaptation to night shift was associated with longer rapid eye movement sleep duration during daytime sleep, highlighting the influence of entrainment between the sleep-wake cycle and the circadian pacemaker in night workers. The findings have important implications for sleep and subsequent alertness associated with shift work.

Keywords: Circadian; Melatonin; REM; Shift work; Sleep.

MeSH terms

Circadian Rhythm
Female
Humans
Melatonin*
Shift Work Schedule*
Sleep Duration
Work Schedule Tolerance

Substances

Melatonin