Internal Desynchronization of Circadian Rhythms and Tolerance to Shift Work

Abstract Introduction National reports of work-related injuries found the excess risk of work injury attributed to shift work to be significantly higher among women. The Working Time Society (WTS) concluded that male sex is one of the few factors that is “consistently associated with perceived or actual shift work tolerance”. However, it is unclear if physiological parameters are involved. Laboratory-controlled studies report sex differences in circadian rhythms (body temperature, melatonin). In sleep deprivation protocols, alertness and cognitive performances were affected by sex, menstrual cycle phase and hormonal contraceptives [HC] use. Nevertheless, field studies that compare male and female shift workers are scarce. Methods An observational study including 76 police officers working on patrol: 56 males and 20 females (11 using [HC], 6 not using [non-HC] and 3 with unknown use of hormonal contraception) aged 32.0 ± 5.3 years. Participants were followed throughout a month-long work cycle (1,457 morning, evening, night, or other shifts, plus rest days). They filled out time-stamped questionnaires (Samn-Perelli, KSS, Visual Analogue Scales, ~5/day; sleep and work-related information, ~1–2/day), completed 5-min Psychomotor Vigilance Tasks (PVT, ~2/day), and wore an actigraph to collect activity data. Linear mixed-effects models were used to analyze the effects of group, time awake and time-of-day on fatigue, sleepiness, alertness, mood and PVT measures. Results Self-reported measures and psychomotor performance significantly varied with time awake and time-of-day. Fatigue and sleepiness levels were significantly higher among female compared to male police officers, both with time awake and across the 24-h day. These variations were similar between non-HC females and the other groups. Compared to males, HC females were more fatigued and less alert, both with time awake and across the 24-h day, and sleepier with time awake. Having children at home did not explain these differences. Conclusion The results of this study expand our knowledge on the sex differences in the sleep and circadian physiology and demonstrate a critical effect of HC on women fatigue, sleepiness and alertness when working shifts. Sex and hormonal parameters must be considered in occupational medicine as well as in future laboratory and field studies on shift workers and circadian rhythms. Support (if any) IRSST, FRQS.

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The relation of age to the adjustment of the circadian rhythms of oral temperature and sleepiness to shift work

Applied Ergonomics ◽

10.1016/0003-6870(91)90137-7 ◽

1991 ◽

Vol 22 (6) ◽

pp. 424

Author(s):

M. Harma ◽

P. Knauth ◽

J. Ilmarinen ◽

H. Ollila

Keyword(s):

Circadian Rhythms ◽

Shift Work ◽

Oral Temperature

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Impacts of shift work on sleep and circadian rhythms

Pathologie Biologie ◽

10.1016/j.patbio.2014.08.001 ◽

2014 ◽

Vol 62 (5) ◽

pp. 292-301 ◽

Cited By ~ 146

Author(s):

D.B. Boivin ◽

P. Boudreau

Keyword(s):

Circadian Rhythms ◽

Shift Work

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Etudes comparées des rythmes circadiens et reflet actimétrique du sommeil de sportifs et de sédentaires en poste régulier de nuit

Canadian Journal of Applied Physiology ◽

10.1139/h03-062 ◽

2003 ◽

Vol 28 (6) ◽

pp. 831-887 ◽

Cited By ~ 11

Author(s):

Benoît Mauvieux ◽

Laurent Gouthière ◽

Bruno Sesboüe ◽

Damien Davenne

Keyword(s):

Circadian Rhythm ◽

Circadian Rhythms ◽

Sleep Quality ◽

Shift Work ◽

Physical Training ◽

Night Shift ◽

Circadian Variation ◽

Night Work ◽

Sedentary Subjects

The aim of this study was to show the resistance and persistence of the circadian rhythm of temperature (T°) and the sleep quality of athletic subjects and sedentary subjects engaged in night work, and attempt to explain the mechanisms that influence these differences. The effects of night work on biological rhythms have been studied extensively in the past few years. The contradictory situations for the night workers irrefutably affect their biological systems. Individuals with high amplitudes in their circadian rhythms have been found to be more tolerant to shift work and this results in a greater stability of circadian rhythms. This seems beneficial in coping with frequent rhythm disturbances. The physical training program seems to improve several mechanisms of the human biological system: amplitudes of circadian rhythms were increased and the circadian rhythm period was more resistant to an environment extreme (night work, shift work, sleep deprivation, or jet lag). To test this hypothesis, athletes and sedentary subjects who were engaged in regular night work were selected in the PSA Peugeot Citroën Automobiles Group in French Normandy country. The circadian rhythm of the T° for both groups was studied with a specific methodology and with extensive spectral analysis, especially the spectral elliptic inverse method. Study models of the rhythm of the T° were determined and the characteristic parameters were exposed. A complementary actigraphic study showed the physical training program's effects on the sleep quality. The results revealed a large stability in the rhythm of circadian variation of T° for the athletes: the amplitude was still large but for the sedentary subjects the amplitude of the T° decreased and it was difficult to adjust a period on the rhythm of T°. The stability and persistent quality of the athletes' circadian rhythm was confirmed. We observed that the actigraphic sleep was greater for athletes than for sedentary subjects, and the acrophase time for the athletes was later than for the sedentary subjects during the night shift. Key words: circadian rhythm of temperature, actimetry, sleep quality, exercise, night work, methodology of rhythms analysis

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Genomic heterogeneity affects the response to Daylight Saving Time

10.1101/2021.03.10.434637 ◽

2021 ◽

Author(s):

Jonathan Tyler ◽

Yu Fang ◽

Cathy Goldstein ◽

Daniel Forger ◽

Srijan Sen ◽

...

Keyword(s):

Circadian Rhythms ◽

Shift Work ◽

Mental Health Problems ◽

Multiple Time ◽

Physical And Mental Health ◽

Daylight Saving Time ◽

Circadian Misalignment ◽

Daylight Saving ◽

The One ◽

External Time

ABSTRACTCircadian rhythms drive the timing of many physiological events in the 24-hour day. When individuals undergo an abrupt external shift (e.g., change in work schedule or travel across multiple time zones), circadian rhythms become misaligned with the new time and may take several days to adjust. Chronic circadian misalignment, e.g., as a result of shift work, has been shown to lead to several physical and mental health problems. Despite the serious health implications of circadian misalignment, relatively little is known about how genetic variation affects an individual’s ability to shift to abrupt external changes. Accordingly, we use the one-hour advance from the onset of daylight saving time (DST) as a natural experiment to comprehensively study how individual heterogeneity affects the shift of sleep-wake rhythms in response to an abrupt external time change. We find that individuals genetically predisposed to a morning tendency adjust to the advance in a few days, while genetically predisposed evening-inclined individuals have not shifted. Observing differential effects by genetic disposition after a one-hour advance underscores the importance of heterogeneity in adaptation to external schedule shifts, and these genetic differences may affect how individuals adjust to jet lag or shift work as well.

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Simulated shift work disrupts maternal circadian rhythms and metabolism, and increases gestation length in sheep

The Journal of Physiology ◽

10.1113/jp277186 ◽

2019 ◽

Vol 597 (7) ◽

pp. 1889-1904 ◽

Cited By ~ 6

Author(s):

Kathryn L. Gatford ◽

David J. Kennaway ◽

Hong Liu ◽

David O. Kleemann ◽

Timothy R Kuchel ◽

...

Keyword(s):

Circadian Rhythms ◽

Shift Work ◽

Gestation Length

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Assessment of the Relationship between Sleep Disorders and Circadian Type in Nurses with Shift and Daytime Work

Journal of Sleep sciences ◽

10.18502/jss.v5i1.4568 ◽

2020 ◽

Author(s):

Lahya Afshari Saleh ◽

Amir Rezaei Ardani ◽

Ehsan Rafeemanesh ◽

Pegah Kheradmand

Keyword(s):

Circadian Rhythms ◽

Sleep Disorders ◽

Shift Work ◽

Sleep Problems ◽

Work Group ◽

Severity Index ◽

Teaching Hospitals ◽

Cross Sectional ◽

Significant Difference ◽

Circadian Type

Background and Objective: Chronotypes vary in different people, and the daily function outside of the framework of this rhythm can affect the quality of work. This study aimed to investigate the association between sleep disorders and chronotypes among the shift and day work nurses. Materials and Methods: This cross-sectional study was performed among nurses in two teaching hospitals in Mash-had, Iran, during 2016-2017. A total of 180 randomly-selected nurses were divided into shift work and day work groups. Participants completed demographic information form, Circadian Type Inventory (CTI), Insomnia Severity Index (ISI), Epworth Sleepiness Scale (ESS), Beck Anxiety Inventory (BAI), and Beck Depression Inventory (BDI). Results: A total of 180 female nurses (90 participants in each group) with a mean age of 35.62 ± 4.07 years were stud-ied. The prevalence of rigid circadian rhythm in the day work group (93.3%) was significantly (P = 0.004) higher than shift work group (78.9%). However, the groups did not show any significant difference regarding the languid/vigorous (LV) index of the CTI (P = 0.080). There was a significant difference in the mean score of CTI between individuals with rigid and flexible circadian rhythms in the shift work group (P = 0.021). Conclusion: In the present study, although there was no association between circadian type and sleep problems includ-ing insomnia and daytime sleepiness in shift work nurses, we observed the capability of coping with working in the rotating shifts in nurses with flexible circadian rhythms.

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The Relation of Age to the Adjustment of the Circadian Rhythms of Oral Temperature and Sleepiness to Shift Work

Chronobiology International ◽

10.3109/07420529009056979 ◽

1990 ◽

Vol 7 (3) ◽

pp. 227-233 ◽

Cited By ~ 18

Author(s):

Mikko Haurmau ◽

Peter Knauth ◽

Juhani Ilmarinen ◽

Hannu Ollila

Keyword(s):

Circadian Rhythms ◽

Shift Work ◽

Oral Temperature

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Melatonin phase shifts human circadian rhythms in a placebo-controlled simulated night-work study

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.00135.2001 ◽

2002 ◽

Vol 282 (2) ◽

pp. R454-R463 ◽

Cited By ~ 63

Author(s):

Katherine M. Sharkey ◽

Charmane I. Eastman

Keyword(s):

Circadian Rhythms ◽

Shift Work ◽

Phase Shifts ◽

Night Work ◽

Phase Shifting ◽

Jet Lag ◽

Work Study ◽

Temperature Minimum ◽

Sleep Schedule ◽

Dim Light

There has been scant evidence for a phase-shifting effect of melatonin in shift-work or jet-lag protocols. This study tested whether melatonin can facilitate phase shifts in a simulated night-work protocol. Subjects ( n = 32) slept in the afternoons/evenings before night work (a 7-h advance of the sleep schedule). They took melatonin (0.5 mg or 3.0 mg) or placebo before the first four of eight afternoon/evening sleep episodes at a time when melatonin has been shown to phase advance the circadian clock. Melatonin produced larger phase advances than placebo in the circadian rhythms of melatonin and temperature. Average phase advances (±SD) of the dim light melatonin onset were 1.7 ± 1.2 h (placebo), 3.0 ± 1.1 h (0.5 mg), and 3.9 ± 0.5 h (3.0 mg). A measure of circadian adaptation, shifting the temperature minimum enough to occur within afternoon/evening sleep, showed that only subjects given melatonin achieved this goal (73% with 3.0 mg, 56% with 0.5 mg, and 0% with placebo). Melatonin could be used to promote adaptation to night work and jet travel.

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