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Kosmadopoulos A, Boudreau P, Kervezee L, Boivin DB. Circadian Adaptation of Melatonin and Cortisol in Police Officers Working Rotating Shifts. J Biol Rhythms 2024; 39:49-67. [PMID: 37750410 PMCID: PMC10785562 DOI: 10.1177/07487304231196280] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/27/2023]
Abstract
Misalignment of behavior and circadian rhythms due to night work can impair sleep and waking function. While both simulated and field-based studies suggest that circadian adaptation to a nocturnal schedule is slow, the rates of adaptation in real-world shift-work conditions are still largely unknown. The aim of this study was to evaluate the extent of adaptation of 24-h rhythms with 6-sulfatoxymelatonin (aMT6s) and cortisol in police officers working rotating shifts, with a special attention to night shifts. A total of 76 police officers (20 women; aged 32 ± 5.4 years, mean ± SD) from the province of Quebec, Canada, participated in a field study during their 28- or 35-day work cycle. Urine samples were collected for ~32 h before a series of day, evening, and night shifts to assess circadian phase. Before day, evening, and night shifts, 60%-89% of officers were adapted to a day schedule based on aMT6 rhythms, and 71%-78% were adapted based on cortisol rhythms. To further quantify the rate of circadian adaptation to night shifts, initial and final phases were determined in a subset of 37 officers with suitable rhythms for both hormones before and after 3-8 consecutive shifts (median = 7). Data were analyzed with circular and linear mixed-effects models. After night shifts, 30% and 24% of officers were adapted to a night-oriented schedule for aMT6s and cortisol, respectively. Significantly larger phase-delay shifts (aMT6s: -7.3 ± 0.9 h; cortisol: -6.3 ± 0.8 h) were observed in police officers who adapted to night shifts than in non-adapted officers (aMT6s: 0.8 ± 0.9 h; cortisol: 0.2 ± 1.1 h). Consistent with prior research, our results from both urinary aMT6s and cortisol midpoints indicate that a large proportion of police officers remained in a state of circadian misalignment following a series of night shifts in dim-light working environments.
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Affiliation(s)
- Anastasi Kosmadopoulos
- Centre for Study and Treatment of Circadian Rhythms, Douglas Mental Health University Institute, Department of Psychiatry, McGill University, Montreal, Quebec, Canada
- Appleton Institute for Behavioural Sciences, Central Queensland University, Adelaide, South Australia, Australia
| | - Philippe Boudreau
- Centre for Study and Treatment of Circadian Rhythms, Douglas Mental Health University Institute, Department of Psychiatry, McGill University, Montreal, Quebec, Canada
| | - Laura Kervezee
- Centre for Study and Treatment of Circadian Rhythms, Douglas Mental Health University Institute, Department of Psychiatry, McGill University, Montreal, Quebec, Canada
- Laboratory for Neurophysiology, Department of Cell and Chemical Biology, Leiden University Medical Center, Leiden, the Netherlands
| | - Diane B. Boivin
- Centre for Study and Treatment of Circadian Rhythms, Douglas Mental Health University Institute, Department of Psychiatry, McGill University, Montreal, Quebec, Canada
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Park SY, Lee HM, Kim J. The Number of Monthly Night Shift Days and Depression Were Associated with an Increased Risk of Excessive Daytime Sleepiness in Emergency Physicians in South Korea. Behav Sci (Basel) 2022; 12:bs12080279. [PMID: 36004850 PMCID: PMC9404949 DOI: 10.3390/bs12080279] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2022] [Revised: 08/08/2022] [Accepted: 08/08/2022] [Indexed: 11/24/2022] Open
Abstract
This study aimed to report the prevalence and identify the factors associated with excessive daytime sleepiness (EDS) among emergency physicians in South Korea. We analyzed the Korean Emergency Physicians Survey data from 15 January to 26 February 2021. EDS was evaluated using the Epworth sleepiness scale, and a score of 11 or more indicated the presence of EDS. We conducted univariable and multivariable logistic regression analyses to verify the associated factors. A total of 1307 participants responded to the survey, and the response rate was 61.3%. Nine hundred fifty-four participants were included in the study. Two hundred ninety-three participants were classified as the EDS group, and six hundred sixty-one were classified as the non-EDS group. The prevalence of EDS was 30.7% (95% confidence interval (CI), 27.8–33.6%). Monthly night-shift days (odds ratio (OR) 1.106, 95% CI 1.028–1.191) and depression (OR 2.635, 95% CI 1.799–3.861) were significantly associated with an increased risk of EDS, and fair sleep quality (OR 0.560, 95% CI 0.318–0.985) was associated with a decreased risk of EDS. Almost one in three emergency physicians in South Korea suffer from daytime sleepiness. The number of monthly night-shift days and depression were associated with an increased risk of EDS.
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Affiliation(s)
- Song Yi Park
- Department of Emergency Medicine, College of Medicine, Dong-A University, Busan 48114, Korea
| | - Hyung Min Lee
- Department of Emergency Medicine, Hallym University Sacred Heart Hospital, Anyang 14068, Korea
| | - Jiyoung Kim
- Department of Neurology and Sleep Disorder Center, Bio Medical Research Institute, Pusan National University Hospital, School of Medicine, Pusan National University, Busan 50612, Korea
- Correspondence: ; Tel.: +82-051-240-8687
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3
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Boivin DB, Boudreau P, Kosmadopoulos A. Disturbance of the Circadian System in Shift Work and Its Health Impact. J Biol Rhythms 2021; 37:3-28. [PMID: 34969316 PMCID: PMC8832572 DOI: 10.1177/07487304211064218] [Citation(s) in RCA: 74] [Impact Index Per Article: 24.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The various non-standard schedules required of shift workers force abrupt changes in the timing of sleep and light-dark exposure. These changes result in disturbances of the endogenous circadian system and its misalignment with the environment. Simulated night-shift experiments and field-based studies with shift workers both indicate that the circadian system is resistant to adaptation from a day- to a night-oriented schedule, as determined by a lack of substantial phase shifts over multiple days in centrally controlled rhythms, such as those of melatonin and cortisol. There is evidence that disruption of the circadian system caused by night-shift work results not only in a misalignment between the circadian system and the external light-dark cycle, but also in a state of internal desynchronization between various levels of the circadian system. This is the case between rhythms controlled by the central circadian pacemaker and clock genes expression in tissues such as peripheral blood mononuclear cells, hair follicle cells, and oral mucosa cells. The disruptive effects of atypical work schedules extend beyond the expression profile of canonical circadian clock genes and affects other transcripts of the human genome. In general, after several days of living at night, most rhythmic transcripts in the human genome remain adjusted to a day-oriented schedule, with dampened group amplitudes. In contrast to circadian clock genes and rhythmic transcripts, metabolomics studies revealed that most metabolites shift by several hours when working nights, thus leading to their misalignment with the circadian system. Altogether, these circadian and sleep-wake disturbances emphasize the all-encompassing impact of night-shift work, and can contribute to the increased risk of various medical conditions. Here, we review the latest scientific evidence regarding the effects of atypical work schedules on the circadian system, sleep and alertness of shift-working populations, and discuss their potential clinical impacts.
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Affiliation(s)
- Diane B Boivin
- Centre for Study and Treatment of Circadian Rhythms, Douglas Mental Health University Institute, Department of Psychiatry, McGill University, Montreal, QC, Canada
| | - Philippe Boudreau
- Centre for Study and Treatment of Circadian Rhythms, Douglas Mental Health University Institute, Department of Psychiatry, McGill University, Montreal, QC, Canada
| | - Anastasi Kosmadopoulos
- Centre for Study and Treatment of Circadian Rhythms, Douglas Mental Health University Institute, Department of Psychiatry, McGill University, Montreal, QC, Canada
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Færevik H, Hansen JH, Wiggen Ø, Sandsund M. Cognitive Performance During Night Work in the Cold. Front Physiol 2021; 12:768517. [PMID: 34925063 PMCID: PMC8678462 DOI: 10.3389/fphys.2021.768517] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2021] [Accepted: 11/12/2021] [Indexed: 11/13/2022] Open
Abstract
Objective: The objective of this study was to investigate how night work at low ambient temperatures affects cognitive performance (short-term memory and reaction time), skin- and core temperature, thermal comfort, sleepiness, and cortisol. We hypothesized that cognitive performance is reduced at night compared with daytime and worsened when exposed to low ambient temperatures. Method: Eleven male subjects were recruited to perform three tests in a climatic chamber at night and daytime: Night –2°C, Night 23°C and Day 23°C. Each test lasted 6 h. Cognitive performance (short-term memory and reaction time), skin- and core temperature, thermal sensation and comfort, cortisol levels and sleepiness were measured during the tests. Results: A lower mean skin temperature and corresponding lower thermal sensation were observed at Night –2°C compared to Day 23°C and Night 23°C. Night work caused increased sleepiness and lower cortisol levels, but was not affected by changes in ambient temperatures, thermal comfort, or skin temperatures. There was no effect of either day/night work nor ambient temperature on the short-term memory or reaction time test. Conclusion: Lower skin- and core temperature were observed at night when exposed to low ambient temperature (–2°C), but there was no effect on short-term memory or reaction time. Increased sleepiness and lower cortisol levels were observed at night compared to daytime and was not influenced by low ambient temperature at night. The result from this study suggests that cognitive performance (short-term memory and reaction time) is not adversely affected by night work when exposed to low ambient temperatures if adequate protective clothing is worn.
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Affiliation(s)
- Hilde Færevik
- SINTEF Digital, Department of Health Research, Trondheim, Norway
| | | | - Øystein Wiggen
- SINTEF Digital, Department of Health Research, Trondheim, Norway
| | - Mariann Sandsund
- SINTEF Digital, Department of Health Research, Trondheim, Norway
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Wei T, Li C, Heng Y, Gao X, Zhang G, Wang H, Zhao X, Meng Z, Zhang Y, Hou H. Association between night-shift work and level of melatonin: systematic review and meta-analysis. Sleep Med 2020; 75:502-509. [PMID: 33022488 DOI: 10.1016/j.sleep.2020.09.018] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/14/2020] [Revised: 09/09/2020] [Accepted: 09/17/2020] [Indexed: 11/27/2022]
Abstract
BACKGROUNDS Night-shift workers are exposed to nocturnal light and are more prone to circadian rhythm disorders. Although night-shift work is thought to be associated with the decrease in melatonin secretion, studies have shown inconsistent results. METHODS This systematic review and meta-analysis studied the association between night-shift work and melatonin levels. Pubmed and Embase databases were used for literature searching. The pooled standardized mean differences (SMDs) and 95% confidence intervals (CIs) were used to compare the differences between night-shift workers and the controls. RESULTS Thirty-three studies reported in 25 articles (1845 night-shift workers and 3414 controls, mean age 45.12 years) were included after a systematic literature review. Data of circulating melatonin levels and its metabolites, 6-sulfatoxymelatonin (aMT6s) in urine were collected for meta-analysis. The results showed that the first morning-void aMT6s level in night-shift workers was significantly lower than in day workers (SMD = -0.101, 95% CI = -0.179 to -0.022, P = 0.012). The level of mean 24-h urinary aMT6s was lower in night-shift workers than day workers (SMD: -0.264, 95% CI: -0.473 to -0.056, P = 0.013). Among fixed night-shift workers, the level of circulating melatonin, as well as first morning-void aMT6s was lower than that of day workers. CONCLUSION Our findings indicate that experience of night-shift work is associated with suppression of melatonin production, especially among fixed night-shift workers.
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Affiliation(s)
- Tao Wei
- School of Medicine, Shandong First Medical University & Shandong Academy of Medical Sciences, Taian 271016, China
| | - Cancan Li
- School of Public Health, Shandong First Medical University & Shandong Academy of Medical Sciences, Taian 271016, China
| | - Yuanyuan Heng
- School of Public Health, Shandong First Medical University & Shandong Academy of Medical Sciences, Taian 271016, China
| | - Xiang Gao
- Department of Otolaryngology, Head and Neck Surgery, Beijing TongRen Hospital, Capital Medical University, Beijing 100730, China
| | - Guimei Zhang
- School of Medicine, Shandong First Medical University & Shandong Academy of Medical Sciences, Taian 271016, China
| | - Huachen Wang
- School of Medicine, Shandong First Medical University & Shandong Academy of Medical Sciences, Taian 271016, China
| | - Xuan Zhao
- School of Public Health, Shandong First Medical University & Shandong Academy of Medical Sciences, Taian 271016, China
| | - Zixiu Meng
- School of Public Health, Shandong First Medical University & Shandong Academy of Medical Sciences, Taian 271016, China
| | - Yanbo Zhang
- The Second Affiliation Hospital of Shandong First Medical University, Taian 271016, China.
| | - Haifeng Hou
- School of Public Health, Shandong First Medical University & Shandong Academy of Medical Sciences, Taian 271016, China; School of Public Health and Management, Binzhou Medical University, Yantai 264003, China.
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Application of a Limit-Cycle Oscillator Model for Prediction of Circadian Phase in Rotating Night Shift Workers. Sci Rep 2019; 9:11032. [PMID: 31363110 PMCID: PMC6667480 DOI: 10.1038/s41598-019-47290-6] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2018] [Accepted: 06/17/2019] [Indexed: 12/21/2022] Open
Abstract
Practical alternatives to gold-standard measures of circadian timing in shift workers are needed. We assessed the feasibility of applying a limit-cycle oscillator model of the human circadian pacemaker to estimate circadian phase in 25 nursing and medical staff in a field setting during a transition from day/evening shifts (diurnal schedule) to 3-5 consecutive night shifts (night schedule). Ambulatory measurements of light and activity recorded with wrist actigraphs were used as inputs into the model. Model estimations were compared to urinary 6-sulphatoxymelatonin (aMT6s) acrophase measured on the diurnal schedule and last consecutive night shift. The model predicted aMT6s acrophase with an absolute mean error of 0.69 h on the diurnal schedule (SD = 0.94 h, 80% within ±1 hour), and 0.95 h on the night schedule (SD = 1.24 h, 68% within ±1 hour). The aMT6s phase shift from diurnal to night schedule was predicted to within ±1 hour in 56% of individuals. Our findings indicate the model can be generalized to a shift work setting, although prediction of inter-individual variability in circadian phase shift during night shifts was limited. This study provides the basis for further adaptation and validation of models for predicting circadian phase in rotating shift workers.
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Stone JE, Phillips AJK, Ftouni S, Magee M, Howard M, Lockley SW, Sletten TL, Anderson C, Rajaratnam SMW, Postnova S. Generalizability of A Neural Network Model for Circadian Phase Prediction in Real-World Conditions. Sci Rep 2019; 9:11001. [PMID: 31358781 PMCID: PMC6662750 DOI: 10.1038/s41598-019-47311-4] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2019] [Accepted: 06/04/2019] [Indexed: 01/24/2023] Open
Abstract
A neural network model was previously developed to predict melatonin rhythms accurately from blue light and skin temperature recordings in individuals on a fixed sleep schedule. This study aimed to test the generalizability of the model to other sleep schedules, including rotating shift work. Ambulatory wrist blue light irradiance and skin temperature data were collected in 16 healthy individuals on fixed and habitual sleep schedules, and 28 rotating shift workers. Artificial neural network models were trained to predict the circadian rhythm of (i) salivary melatonin on a fixed sleep schedule; (ii) urinary aMT6s on both fixed and habitual sleep schedules, including shift workers on a diurnal schedule; and (iii) urinary aMT6s in rotating shift workers on a night shift schedule. To determine predicted circadian phase, center of gravity of the fitted bimodal skewed baseline cosine curve was used for melatonin, and acrophase of the cosine curve for aMT6s. On a fixed sleep schedule, the model predicted melatonin phase to within ± 1 hour in 67% and ± 1.5 hours in 100% of participants, with mean absolute error of 41 ± 32 minutes. On diurnal schedules, including shift workers, the model predicted aMT6s acrophase to within ± 1 hour in 66% and ± 2 hours in 87% of participants, with mean absolute error of 63 ± 67 minutes. On night shift schedules, the model predicted aMT6s acrophase to within ± 1 hour in 42% and ± 2 hours in 53% of participants, with mean absolute error of 143 ± 155 minutes. Prediction accuracy was similar when using either 1 (wrist) or 11 skin temperature sensor inputs. These findings demonstrate that the model can predict circadian timing to within ± 2 hours for the vast majority of individuals on diurnal schedules, using blue light and a single temperature sensor. However, this approach did not generalize to night shift conditions.
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Affiliation(s)
- Julia E Stone
- Cooperative Research Centre for Alertness, Safety and Productivity, Melbourne, Victoria, Australia.
- School of Psychological Sciences and Turner Institute for Brain and Mental Health, Faculty of Medicine, Nursing & Health Sciences, Monash University, Clayton, Victoria, Australia.
| | - Andrew J K Phillips
- Cooperative Research Centre for Alertness, Safety and Productivity, Melbourne, Victoria, Australia
- School of Psychological Sciences and Turner Institute for Brain and Mental Health, Faculty of Medicine, Nursing & Health Sciences, Monash University, Clayton, Victoria, Australia
| | - Suzanne Ftouni
- Cooperative Research Centre for Alertness, Safety and Productivity, Melbourne, Victoria, Australia
- School of Psychological Sciences and Turner Institute for Brain and Mental Health, Faculty of Medicine, Nursing & Health Sciences, Monash University, Clayton, Victoria, Australia
| | - Michelle Magee
- Cooperative Research Centre for Alertness, Safety and Productivity, Melbourne, Victoria, Australia
- School of Psychological Sciences and Turner Institute for Brain and Mental Health, Faculty of Medicine, Nursing & Health Sciences, Monash University, Clayton, Victoria, Australia
| | - Mark Howard
- Cooperative Research Centre for Alertness, Safety and Productivity, Melbourne, Victoria, Australia
- School of Psychological Sciences and Turner Institute for Brain and Mental Health, Faculty of Medicine, Nursing & Health Sciences, Monash University, Clayton, Victoria, Australia
- Institute for Breathing and Sleep, Austin Health, Victoria, Australia
| | - Steven W Lockley
- Cooperative Research Centre for Alertness, Safety and Productivity, Melbourne, Victoria, Australia
- School of Psychological Sciences and Turner Institute for Brain and Mental Health, Faculty of Medicine, Nursing & Health Sciences, Monash University, Clayton, 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
| | - Tracey L Sletten
- Cooperative Research Centre for Alertness, Safety and Productivity, Melbourne, Victoria, Australia
- School of Psychological Sciences and Turner Institute for Brain and Mental Health, Faculty of Medicine, Nursing & Health Sciences, Monash University, Clayton, Victoria, Australia
| | - Clare Anderson
- Cooperative Research Centre for Alertness, Safety and Productivity, Melbourne, Victoria, Australia
- School of Psychological Sciences and Turner Institute for Brain and Mental Health, Faculty of Medicine, Nursing & Health Sciences, Monash University, Clayton, Victoria, Australia
| | - Shantha M W Rajaratnam
- Cooperative Research Centre for Alertness, Safety and Productivity, Melbourne, Victoria, Australia
- School of Psychological Sciences and Turner Institute for Brain and Mental Health, Faculty of Medicine, Nursing & Health Sciences, Monash University, Clayton, Victoria, Australia
| | - Svetlana Postnova
- Cooperative Research Centre for Alertness, Safety and Productivity, Melbourne, Victoria, Australia
- School of Physics, University of Sydney, Sydney, New South Wales, Australia
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Abstract
Last year melatonin was 60 years old, or at least its discovery was 60 years ago. The molecule itself may well be almost as old as life itself. So it is time to take yet another perspective on our understanding of its functions, effects and clinical uses. This is not a formal review-there is already a multitude of systematic reviews, narrative reviews, meta-analyses and even reviews of reviews. In view of the extraordinary variety of effects attributed to melatonin in the last 25 years, it is more of an attempt to sort out some areas where a consensus opinion exists, and where placebo controlled, randomized, clinical trials have confirmed early observations on therapeutic uses. The current upsurge of concern about the multiple health problems associated with disturbed circadian rhythms has generated interest in related therapeutic interventions, of which melatonin is one. The present text will consider the physiological role of endogenous melatonin, and the mostly pharmacological effects of exogenous treatment, on the assumption that normal circulating concentrations represent endogenous pineal production. It will concentrate mainly on the most researched, and accepted area of therapeutic use and potential use of melatonin-its undoubted ability to realign circadian rhythms and sleep-since this is the author's bias. It will touch briefly upon some other systems with prominent rhythmic attributes including certain cancers, the cardiovascular system, the entero-insular axis and metabolism together with the use of melatonin to assess circadian status. Many of the ills of the developed world relate to deranged rhythms-and everything is rhythmic unless proved otherwise.
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Riethmeister V, Bültmann U, De Boer MR, Gordijn M, Brouwer S. Examining courses of sleep quality and sleepiness in full 2 weeks on/2 weeks off offshore day shift rotations. Chronobiol Int 2018; 35:759-772. [PMID: 29767546 DOI: 10.1080/07420528.2018.1466794] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
Abstract
To better understand sleep quality and sleepiness problems offshore, we examined courses of sleep quality and sleepiness in full 2-weeks on/2-weeks off offshore day shift rotations by comparing pre-offshore (1 week), offshore (2 weeks) and post-offshore (1 week) work periods. A longitudinal observational study was conducted among N=42 offshore workers. Sleep quality was measured subjectively with two daily questions and objectively with actigraphy, measuring: time in bed (TIB), total sleep time (TST), sleep latency (SL) and sleep efficiency percentage (SE%). Sleepiness was measured twice a day (morning and evening) with the Karolinska Sleepiness Scale. Changes in sleep and sleepiness parameters during the pre/post and offshore work periods were investigated using (generalized) linear mixed models. In the pre-offshore work period, courses of SE% significantly decreased (p=.038). During offshore work periods, the courses of evening sleepiness scores significantly increased (p<.001) and significantly decreased during post-offshore work periods (p=.004). During offshore work periods, TIB (p<.001) and TST (p<.001) were significantly shorter, SE% was significantly higher (p=.002), perceived sleep quality was significantly lower (p<.001) and level of rest after wake was significantly worse (p<.001) than during the pre- and post-offshore work periods. Morning sleepiness was significantly higher during offshore work periods (p=.015) and evening sleepiness was significantly higher in the post-offshore work period (p=.005) compared to the other periods. No significant changes in SL were observed. Courses of sleep quality and sleepiness parameters significantly changed during full 2-weeks on/2-weeks off offshore day shift rotation periods. These changes should be considered in offshore fatigue risk management programmes.
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Affiliation(s)
- V Riethmeister
- a Department of Health Sciences, Community and Occupational Medicine , University Medical Center Groningen, University of Groningen , Groningen , The Netherlands
| | - U Bültmann
- a Department of Health Sciences, Community and Occupational Medicine , University Medical Center Groningen, University of Groningen , Groningen , The Netherlands
| | - M R De Boer
- b Department of Health Sciences and the EMGO+ Institute for Health and Care Research, Faculty of Earth and Life Sciences , VU University Amsterdam , Amsterdam , The Netherlands
| | - M Gordijn
- c Chrono@Work B.V. Groningen, The Netherlands, and Chronobiology Unit , Groningen Institute for Evolutionary Life Sciences, University of Groningen , Groningen , The Netherlands
| | - S Brouwer
- a Department of Health Sciences, Community and Occupational Medicine , University Medical Center Groningen, University of Groningen , Groningen , The Netherlands
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10
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Stone JE, Sletten TL, Magee M, Ganesan S, Mulhall MD, Collins A, Howard M, Lockley SW, Rajaratnam SMW. Temporal dynamics of circadian phase shifting response to consecutive night shifts in healthcare workers: role of light-dark exposure. J Physiol 2018; 596:2381-2395. [PMID: 29589871 DOI: 10.1113/jp275589] [Citation(s) in RCA: 42] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2017] [Accepted: 02/02/2018] [Indexed: 12/14/2022] Open
Abstract
KEY POINTS Shift work is highly prevalent and is associated with significant adverse health impacts. There is substantial inter-individual variability in the way the circadian clock responds to changing shift cycles. The mechanisms underlying this variability are not well understood. We tested the hypothesis that light-dark exposure is a significant contributor to this variability; when combined with diurnal preference, the relative timing of light exposure accounted for 71% of individual variability in circadian phase response to night shift work. These results will drive development of personalised approaches to manage circadian disruption among shift workers and other vulnerable populations to potentially reduce the increased risk of disease in these populations. ABSTRACT Night shift workers show highly variable rates of circadian adaptation. This study examined the relationship between light exposure patterns and the magnitude of circadian phase resetting in response to night shift work. In 21 participants (nursing and medical staff in an intensive care unit) circadian phase was measured using 6-sulphatoxymelatonin at baseline (day/evening shifts or days off) and after 3-4 consecutive night shifts. Daily light exposure was examined relative to individual circadian phase to quantify light intensity in the phase delay and phase advance portions of the light phase response curve (PRC). There was substantial inter-individual variability in the direction and magnitude of phase shift after three or four consecutive night shifts (mean phase delay -1:08 ± 1:31 h; range -3:43 h delay to +3:07 h phase advance). The relative difference in the distribution of light relative to the PRC combined with diurnal preference accounted for 71% of the variability in phase shift. Regression analysis incorporating these factors estimated phase shift to within ±60 min in 85% of participants. No participants met criteria for partial adaptation to night work after three or four consecutive night shifts. Our findings provide evidence that the phase resetting that does occur is based on individual light exposure patterns relative to an individual's baseline circadian phase. Thus, a 'one size fits all' approach to promoting adaptation to shift work using light therapy, implemented without knowledge of circadian phase, may not be efficacious for all individuals.
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Affiliation(s)
- Julia E Stone
- Cooperative Research Centre for Alertness, Safety and Productivity, Melbourne, Victoria, Australia.,School of Psychological Sciences and Monash Institute of Cognitive and Clinical Neurosciences, Faculty of Medicine, Nursing & Health Sciences, Monash University, Clayton, Victoria, Australia
| | - Tracey L Sletten
- Cooperative Research Centre for Alertness, Safety and Productivity, Melbourne, Victoria, Australia.,School of Psychological Sciences and Monash Institute of Cognitive and Clinical Neurosciences, Faculty of Medicine, Nursing & Health Sciences, Monash University, Clayton, Victoria, Australia
| | - Michelle Magee
- Cooperative Research Centre for Alertness, Safety and Productivity, Melbourne, Victoria, Australia.,School of Psychological Sciences and Monash Institute of Cognitive and Clinical Neurosciences, Faculty of Medicine, Nursing & Health Sciences, Monash University, Clayton, Victoria, Australia
| | - Saranea Ganesan
- Cooperative Research Centre for Alertness, Safety and Productivity, Melbourne, Victoria, Australia.,School of Psychological Sciences and Monash Institute of Cognitive and Clinical Neurosciences, Faculty of Medicine, Nursing & Health Sciences, Monash University, Clayton, Victoria, Australia
| | - Megan D Mulhall
- Cooperative Research Centre for Alertness, Safety and Productivity, Melbourne, Victoria, Australia.,School of Psychological Sciences and Monash Institute of Cognitive and Clinical Neurosciences, Faculty of Medicine, Nursing & Health Sciences, Monash University, Clayton, Victoria, Australia
| | - Allison Collins
- Institute for Breathing and Sleep, Austin Health, Victoria, Australia
| | - Mark Howard
- Cooperative Research Centre for Alertness, Safety and Productivity, Melbourne, Victoria, Australia.,School of Psychological Sciences and Monash Institute of Cognitive and Clinical Neurosciences, Faculty of Medicine, Nursing & Health Sciences, Monash University, Clayton, Victoria, Australia.,Institute for Breathing and Sleep, Austin Health, Victoria, Australia
| | - Steven W Lockley
- Cooperative Research Centre for Alertness, Safety and Productivity, Melbourne, Victoria, Australia.,School of Psychological Sciences and Monash Institute of Cognitive and Clinical Neurosciences, Faculty of Medicine, Nursing & Health Sciences, Monash University, Clayton, 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
| | - Shantha M W Rajaratnam
- Cooperative Research Centre for Alertness, Safety and Productivity, Melbourne, Victoria, Australia.,School of Psychological Sciences and Monash Institute of Cognitive and Clinical Neurosciences, Faculty of Medicine, Nursing & Health Sciences, Monash University, Clayton, 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
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11
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Arendt J, Middleton B. Human seasonal and circadian studies in Antarctica (Halley, 75°S). Gen Comp Endocrinol 2018; 258:250-258. [PMID: 28526480 DOI: 10.1016/j.ygcen.2017.05.010] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/30/2017] [Revised: 05/09/2017] [Accepted: 05/12/2017] [Indexed: 02/03/2023]
Abstract
Living for extended periods in Antarctica exposes base personnel to extremes of daylength (photoperiod) and temperature. At the British Antarctic Survey base of Halley, 75°S, the sun does not rise for 110 d in the winter and does not set for 100 d in summer. Photoperiod is the major time cue governing the timing of seasonal events such as reproduction in many species. The neuroendocrine signal providing photoperiodic information to body physiology is the duration of melatonin secretion which reflects the length of the night: longer in the short days of winter and shorter in summer. Light of sufficient intensity and spectral composition serves to suppress production of melatonin and to set the circadian timing and the duration of the rhythm. In humans early observations suggested that bright (>2000 lux) white light was needed to suppress melatonin completely. Shortly thereafter winter depression (Seasonal Affective Disorder or SAD) was described, and its successful treatment by an artificial summer photoperiod of bright white light, sufficient to shorten melatonin production. At Halley dim artificial light intensity during winter was measured, until 2003, at a maximum of approximately 500 lux in winter. Thus a strong seasonal and circadian time cue was absent. It seemed likely that winter depression would be common in the extended period of winter darkness and could be treated with an artificial summer photoperiod. These observations, and predictions, inspired a long series of studies regarding human seasonal and circadian status, and the effects of light treatment, in a small overwintering, isolated community, living in the same conditions for many months at Halley. We found little evidence of SAD, or change in duration of melatonin production with season. However the timing of the melatonin rhythm itself, and/or that of its metabolite 6-sulphatoxymelatonin (aMT6s), was used as a primary marker of seasonal, circadian and treatment changes. A substantial phase delay of melatonin in winter was advanced to summer phase by a two pulse 'skeleton' bright white light treatment. Subsequently a single morning pulse of bright white light was effective with regard to circadian phase and improved daytime performance. The circadian delay evidenced by melatonin was accompanied by delayed sleep (logs and actigraphy): poor sleep is a common complaint in Polar regions. Appropriate extra artificial light, both standard white, and blue enriched, present throughout the day, effectively countered delay in sleep timing and the aMT6s rhythm. The most important factor appeared to be the maximum light experienced. Another manifestation of the winter was a decline in self-rated libido (men only on base at this time). Women on the base showed lower aspects of physical and mental health compared to men. Free-running rhythms were seen in some subjects following night shift, but were rarely found at other times, probably because this base has strongly scheduled activity and leisure time. Complete circadian adaptation during a week of night shift, also seen in a similar situation on North Sea oil rigs, led to problems readapting back to day shift in winter, compared to summer. Here again timed light treatment was used to address the problem. Sleep, alertness and waking performance are critically dependent on optimum circadian phase. Circadian desynchrony is associated with increased risk of major disease in shift workers. These studies provide some groundwork for countering/avoiding circadian desynchrony in rather extreme conditions.
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Affiliation(s)
- Josephine Arendt
- Biochemistry and Physiology, Faculty of Health and Medical Sciences, University of Surrey, Guildford GU2 7XH, UK.
| | - Benita Middleton
- Biochemistry and Physiology, Faculty of Health and Medical Sciences, University of Surrey, Guildford GU2 7XH, UK.
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12
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Lee HE, Lee J, Jang TW, Kim IA, Park J, Song J. The relationship between night work and breast cancer. Ann Occup Environ Med 2018; 30:11. [PMID: 29445504 PMCID: PMC5801774 DOI: 10.1186/s40557-018-0221-4] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2016] [Accepted: 01/29/2018] [Indexed: 01/10/2023] Open
Abstract
Background Since the International Agency for Research on Cancer classified shift work that involves circadian disruption as “probably carcinogenic to humans,” there has been growing concern on the relationship between night work and breast cancer. In Korea, about 10–15% of workers are engaged in night-shift work, and breast cancer is one of the most common cancers in women. The purpose of this study was to review epidemiologic evidence on the relationship between night work and breast cancer. Methods We reviewed 21 original articles and 5 meta analyses on relationship between nightwork and breast cancer, and investigated the compensation criteria of Denmark. Results The association between breast cancer and night work has been reported by numerous epidemiologic studies, including cohort studies, case-control studies, and meta-analysis. However, a dose-response relationship has not clearly emerged among workers exposed to less than 20 years of night work. Conclusion Although there are some limitations to the epidemiological studies so far, further consideration of breast cancer cases in patients with high exposure to night work is needed to assess breast cancer as a work-related disease.
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Affiliation(s)
- Hye-Eun Lee
- 1Department of Occupational and Environmental Medicine, Kyung Hee University Hospital, Dongdaemun-gu Kyunghee-daero 23, Seoul, Republic of Korea
| | - Jongin Lee
- 2Department of Occupational and Environmental Medicine, College of Medicine, The Catholic University of Korea, Seoul, Republic of Korea
| | - Tae-Won Jang
- 3Department of Occupational and Environmental Medicine, Hanyang University College of Medicine, Seoul, Republic of Korea
| | - In-Ah Kim
- 3Department of Occupational and Environmental Medicine, Hanyang University College of Medicine, Seoul, Republic of Korea
| | - Jungsun Park
- 4Department of Occupational Health, Catholic University of Daegu, Gyonsan-si, Republic of Korea
| | - Jaechul Song
- 3Department of Occupational and Environmental Medicine, Hanyang University College of Medicine, Seoul, Republic of Korea
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13
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Daugaard S, Garde AH, Bonde JPE, Christoffersen J, Hansen ÄM, Markvart J, Schlünssen V, Skene DJ, Vistisen HT, Kolstad HA. Night work, light exposure and melatonin on work days and days off. Chronobiol Int 2017; 34:942-955. [DOI: 10.1080/07420528.2017.1327867] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Affiliation(s)
- Stine Daugaard
- Aarhus University Hospital, Department of Occupational Medicine, Aarhus, Denmark
| | - Anne Helene Garde
- National Research Centre for the Working Environment, Copenhagen, Denmark
- University of Copenhagen, Institute of Public Health, Copenhagen, Denmark
| | - Jens Peter Ellekilde Bonde
- Bispebjerg Hospital, Department of Occupational Medicine, Copenhagen, Denmark
- University of Copenhagen, Institute of Public Health, Copenhagen, Denmark
| | - Jens Christoffersen
- Velux Danmark A/S, Stakeholder Communications and Sustanability, Horsholm, Denmark
| | - Äse Marie Hansen
- National Research Centre for the Working Environment, Copenhagen, Denmark
- University of Copenhagen, Institute of Public Health, Copenhagen, Denmark
| | - Jakob Markvart
- Aalborg Universitet, Department of Energy Performance, Indoor Environment and Sustainability, Danish Building Research Institute, Copenhagen, Denmark
| | - Vivi Schlünssen
- National Research Centre for the Working Environment, Copenhagen, Denmark
- Aarhus Universitet, Department of Public Health, Aarhus, Denmark
| | - Debra J. Skene
- University of Surrey, Faculty of Health and Medical Sciences, Chronobiology, Guildford GU2 7XH, Surrey, United Kingdom
| | - Helene Tilma Vistisen
- Aarhus University Hospital, Department of Occupational Medicine, Aarhus, Denmark
- Aarhus University Hospital, Aarhus, Denmark
| | - Henrik A. Kolstad
- Aarhus University Hospital, Department of Occupational Medicine, Aarhus, Denmark
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14
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Potter GDM, Skene DJ, Arendt J, Cade JE, Grant PJ, Hardie LJ. Circadian Rhythm and Sleep Disruption: Causes, Metabolic Consequences, and Countermeasures. Endocr Rev 2016; 37:584-608. [PMID: 27763782 PMCID: PMC5142605 DOI: 10.1210/er.2016-1083] [Citation(s) in RCA: 289] [Impact Index Per Article: 36.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Circadian (∼24-hour) timing systems pervade all kingdoms of life and temporally optimize behavior and physiology in humans. Relatively recent changes to our environments, such as the introduction of artificial lighting, can disorganize the circadian system, from the level of the molecular clocks that regulate the timing of cellular activities to the level of synchronization between our daily cycles of behavior and the solar day. Sleep/wake cycles are intertwined with the circadian system, and global trends indicate that these, too, are increasingly subject to disruption. A large proportion of the world's population is at increased risk of environmentally driven circadian rhythm and sleep disruption, and a minority of individuals are also genetically predisposed to circadian misalignment and sleep disorders. The consequences of disruption to the circadian system and sleep are profound and include myriad metabolic ramifications, some of which may be compounded by adverse effects on dietary choices. If not addressed, the deleterious effects of such disruption will continue to cause widespread health problems; therefore, implementation of the numerous behavioral and pharmaceutical interventions that can help restore circadian system alignment and enhance sleep will be important.
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Affiliation(s)
- Gregory D M Potter
- Division of Epidemiology and Biostatistics (G.D.M.P., L.J.H.), LIGHT Laboratories, University of Leeds, Leeds LS2 9JT, United Kingdom; Chronobiology Section (D.J.S., J.A.), Faculty of Health and Medical Sciences, University of Surrey, Guildford GU2 7XH, United Kingdom; Nutritional Epidemiology Group (J.E.C.), School of Food Science and Nutrition, University of Leeds, Leeds LS2 9JT, United Kingdom; and Division of Cardiovascular & Diabetes Research (P.J.G.), LIGHT Laboratories, University of Leeds, Leeds LS2 9JT, United Kingdom
| | - Debra J Skene
- Division of Epidemiology and Biostatistics (G.D.M.P., L.J.H.), LIGHT Laboratories, University of Leeds, Leeds LS2 9JT, United Kingdom; Chronobiology Section (D.J.S., J.A.), Faculty of Health and Medical Sciences, University of Surrey, Guildford GU2 7XH, United Kingdom; Nutritional Epidemiology Group (J.E.C.), School of Food Science and Nutrition, University of Leeds, Leeds LS2 9JT, United Kingdom; and Division of Cardiovascular & Diabetes Research (P.J.G.), LIGHT Laboratories, University of Leeds, Leeds LS2 9JT, United Kingdom
| | - Josephine Arendt
- Division of Epidemiology and Biostatistics (G.D.M.P., L.J.H.), LIGHT Laboratories, University of Leeds, Leeds LS2 9JT, United Kingdom; Chronobiology Section (D.J.S., J.A.), Faculty of Health and Medical Sciences, University of Surrey, Guildford GU2 7XH, United Kingdom; Nutritional Epidemiology Group (J.E.C.), School of Food Science and Nutrition, University of Leeds, Leeds LS2 9JT, United Kingdom; and Division of Cardiovascular & Diabetes Research (P.J.G.), LIGHT Laboratories, University of Leeds, Leeds LS2 9JT, United Kingdom
| | - Janet E Cade
- Division of Epidemiology and Biostatistics (G.D.M.P., L.J.H.), LIGHT Laboratories, University of Leeds, Leeds LS2 9JT, United Kingdom; Chronobiology Section (D.J.S., J.A.), Faculty of Health and Medical Sciences, University of Surrey, Guildford GU2 7XH, United Kingdom; Nutritional Epidemiology Group (J.E.C.), School of Food Science and Nutrition, University of Leeds, Leeds LS2 9JT, United Kingdom; and Division of Cardiovascular & Diabetes Research (P.J.G.), LIGHT Laboratories, University of Leeds, Leeds LS2 9JT, United Kingdom
| | - Peter J Grant
- Division of Epidemiology and Biostatistics (G.D.M.P., L.J.H.), LIGHT Laboratories, University of Leeds, Leeds LS2 9JT, United Kingdom; Chronobiology Section (D.J.S., J.A.), Faculty of Health and Medical Sciences, University of Surrey, Guildford GU2 7XH, United Kingdom; Nutritional Epidemiology Group (J.E.C.), School of Food Science and Nutrition, University of Leeds, Leeds LS2 9JT, United Kingdom; and Division of Cardiovascular & Diabetes Research (P.J.G.), LIGHT Laboratories, University of Leeds, Leeds LS2 9JT, United Kingdom
| | - Laura J Hardie
- Division of Epidemiology and Biostatistics (G.D.M.P., L.J.H.), LIGHT Laboratories, University of Leeds, Leeds LS2 9JT, United Kingdom; Chronobiology Section (D.J.S., J.A.), Faculty of Health and Medical Sciences, University of Surrey, Guildford GU2 7XH, United Kingdom; Nutritional Epidemiology Group (J.E.C.), School of Food Science and Nutrition, University of Leeds, Leeds LS2 9JT, United Kingdom; and Division of Cardiovascular & Diabetes Research (P.J.G.), LIGHT Laboratories, University of Leeds, Leeds LS2 9JT, United Kingdom
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15
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Jensen MA, Hansen ÅM, Kristiansen J, Nabe-Nielsen K, Garde AH. Changes in the diurnal rhythms of cortisol, melatonin, and testosterone after 2, 4, and 7 consecutive night shifts in male police officers. Chronobiol Int 2016; 33:1280-1292. [DOI: 10.1080/07420528.2016.1212869] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Affiliation(s)
| | - Åse Marie Hansen
- National Research Centre for the Working Environment, Copenhagen, Denmark
- Department of Public Health, University of Copenhagen, Copenhagen, Denmark
| | - Jesper Kristiansen
- National Research Centre for the Working Environment, Copenhagen, Denmark
| | | | - Anne Helene Garde
- National Research Centre for the Working Environment, Copenhagen, Denmark
- Department of Public Health, University of Copenhagen, Copenhagen, Denmark
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16
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Ftouni S, Sletten TL, Nicholas CL, Kennaway DJ, Lockley SW, Rajaratnam SMW. Ocular Measures of Sleepiness Are Increased in Night Shift Workers Undergoing a Simulated Night Shift Near the Peak Time of the 6-Sulfatoxymelatonin Rhythm. J Clin Sleep Med 2015; 11:1131-41. [PMID: 26094925 DOI: 10.5664/jcsm.5086] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2014] [Accepted: 05/10/2015] [Indexed: 11/13/2022]
Abstract
STUDY OBJECTIVE The study examined the relationship between the circadian rhythm of 6-sulphatoxymelatonin (aMT6s) and ocular measures of sleepiness and neurobehavioral performance in shift workers undergoing a simulated night shift. METHODS Twenty-two shift workers (mean age 33.4, SD 11.8 years) were tested at approximately the beginning (20:00) and the end (05:55) of a simulated night shift in the laboratory. At the time point corresponding to the end of the simulated shift, 14 participants were classified as being within range of 6-sulphatoxymelatonin (aMT6s) acrophase--defined as 3 hours before or after aMT6s peak--and 8 were classified as outside aMT6s acrophase range. Participants completed the Karolinska Sleepiness Scale (KSS) and the auditory psychomotor vigilance task (aPVT). Waking electroencephalography (EEG) was recorded and infrared reflectance oculography was used to collect ocular measures of sleepiness: positive and negative amplitude/velocity ratio (PosAVR, NegAVR), mean blink total duration (BTD), the percentage of eye closure (%TEC), and a composite score of sleepiness levels (Johns Drowsiness Scale; JDS). RESULTS Participants who were tested within aMT6s acrophase range displayed higher levels of sleepiness on ocular measures (%TEC, BTD, PosAVR, JDS), objective sleepiness (EEG delta power frequency band), subjective ratings of sleepiness, and neurobehavioral performance, compared to those who were outside aMT6s acrophase range. CONCLUSIONS The study demonstrated that objective ocular measures of sleepiness are sensitive to circadian rhythm misalignment in shift workers.
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Affiliation(s)
- Suzanne Ftouni
- School of Psychological Sciences, Monash University, Clayton, Victoria, Australia
| | - Tracey L Sletten
- School of Psychological Sciences, Monash University, Clayton, Victoria, Australia
| | - Christian L Nicholas
- Sleep Research Laboratory, Melbourne School of Psychological Sciences, University of Melbourne, Melbourne, Victoria, Australia
| | - David J Kennaway
- Robinson Research Institute, School of Paediatrics and Reproductive Health, University of Adelaide, Adelaide, South Australia, Australia
| | - Steven W Lockley
- School of Psychological Sciences, Monash University, Clayton, Victoria, Australia.,Division of Sleep and Circadian Disorders, Departments of Medicine and Neurology, Brigham and Women's Hospital, Boston, Massachusetts.,Division of Sleep Medicine, Department of Medicine, Harvard Medical School, Boston, Massachusetts
| | - Shantha M W Rajaratnam
- School of Psychological Sciences, Monash University, Clayton, Victoria, Australia.,Division of Sleep and Circadian Disorders, Departments of Medicine and Neurology, Brigham and Women's Hospital, Boston, Massachusetts.,Division of Sleep Medicine, Department of Medicine, Harvard Medical School, Boston, Massachusetts
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17
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Jensen MA, Garde AH, Kristiansen J, Nabe-Nielsen K, Hansen ÅM. The effect of the number of consecutive night shifts on diurnal rhythms in cortisol, melatonin and heart rate variability (HRV): a systematic review of field studies. Int Arch Occup Environ Health 2015; 89:531-45. [PMID: 26464315 DOI: 10.1007/s00420-015-1093-3] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2015] [Accepted: 09/28/2015] [Indexed: 04/24/2023]
Abstract
PURPOSE The purpose of this review is to summarize the current knowledge from field studies on how many consecutive night shifts are required for adaptation of diurnal rhythms in cortisol, melatonin and heart rate variability (HRV) to night work. METHODS A systematic search of the databases PubMed and Web of Science resulted in 18 studies selected for review. RESULTS Cortisol was measured in five studies, melatonin in 11 studies and HRV in four studies. Diurnal rhythms were assessed by use of several different measures based on three to eight samples per day for cortisol and melatonin and 24-h recordings for HRV. Most of the studies in the review were small studies with less than 30 participants, and most studies evaluated diurnal rhythms after only two consecutive night shifts whereas only six studies used seven or more consecutive night shifts. The majority of studies found that adaptation to night work had not occurred after two consecutive night shifts, whereas a small number found evidence for full adaptation after seven consecutive night shifts based on diurnal rhythms in cortisol and melatonin. CONCLUSION There are methodological differences in the field studies analyzing diurnal rhythms and large diversity in the occupational fields studied. Nevertheless, we conclude that diurnal rhythms in cortisol, melatonin and HRV are not adapted to night work after 1-3 consecutive night shifts. Studies are needed to establish how many consecutive night shifts are needed for full adaptation of diurnal rhythms to night work.
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Affiliation(s)
- Marie Aarrebo Jensen
- Department of Public Health, University of Copenhagen, Øster Farimagsgade 5, 1014, København K, Denmark.
| | - Anne Helene Garde
- National Research Centre for the Working Environment, Lersø Parkallé 105, 2100, København Ø, Denmark
| | - Jesper Kristiansen
- National Research Centre for the Working Environment, Lersø Parkallé 105, 2100, København Ø, Denmark
| | - Kirsten Nabe-Nielsen
- Department of Public Health, University of Copenhagen, Øster Farimagsgade 5, 1014, København K, Denmark
| | - Åse Marie Hansen
- Department of Public Health, University of Copenhagen, Øster Farimagsgade 5, 1014, København K, Denmark.,National Research Centre for the Working Environment, Lersø Parkallé 105, 2100, København Ø, Denmark
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18
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Dumont M, Paquet J. Progressive decrease of melatonin production over consecutive days of simulated night work. Chronobiol Int 2014; 31:1231-8. [PMID: 25222345 DOI: 10.3109/07420528.2014.957304] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Decreased melatonin production, due to nighttime exposure to light, has been proposed as one of the physiological mechanisms increasing cancer risk in night workers. However, few studies measured melatonin production in night workers, and most of these studies did not measure melatonin over 24 h. One study compared total melatonin production between day and night shifts in rotating night workers and did not find significant differences. However, without baseline measures, it was not possible to exclude that melatonin production was reduced during both day and night work. Here, we used data collected in a simulation study of night work to determine the effect of night work on both nighttime and 24-h melatonin production, during three consecutive days of simulated night work. Thirty-eight healthy subjects (15 men, 23 women; 26.6 ± 4.2 years) participated in a 6-d laboratory study. Circadian phase assessments were made with salivary dim light melatonin onset (DLMO) on the first and last days. Simulated day work (09:00-17:00 h) occurred on the second day, followed by three consecutive days of simulated night work (00:00-08:00 h). Light intensity at eye level was set at 50 lux during both simulated day and night work. The subjects were divided into three matched groups exposed to specific daytime light profiles that produced various degrees of circadian phase delays and phase advances. Melatonin production was estimated with the excretion of urinary 6-sulfatoxymelatonin (aMT6s). For the entire protocol, urine was collected every 2 h, except for the sleep episodes when the interval was 8 h. The aMT6s concentration in each sample was multiplied by the urine volume and then added to obtain total aMT6s excretion during nighttime (00:00-08:00 h) and during each 24-h day (00:00-00:00 h). The results showed that melatonin production progressively decreased over consecutive days of simulated night work, both during nighttime and over the 24 h. This decrease was larger in women using oral contraceptives. There was no difference between the three groups, and the magnitude of the decrease in melatonin production for nighttime and for the 24 h was not associated with the magnitude of the absolute circadian phase shift. As light intensity was relatively low and because the decrease in melatonin production was progressive, direct suppression by nighttime light exposure was probably not a significant factor. However, according to previous experimental observations, the decrease in melatonin production most likely reflects the circadian disruption associated with the process of re-entrainment. It remains to be determined whether reduced melatonin production can be harmful by itself, but long-term and repeated circadian disruption most probably is.
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Affiliation(s)
- Marie Dumont
- Chronobiology Laboratory, Center for Advanced Research in Sleep Medicine, Sacre-Coeur Hospital of Montreal , Montreal, Quebec , Canada and
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19
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Papantoniou K, Pozo OJ, Espinosa A, Marcos J, Castaño-Vinyals G, Basagaña X, Ribas FC, Mirabent J, Martín J, Carenys G, Martín CR, Middleton B, Skene DJ, Kogevinas M. Circadian Variation of Melatonin, Light Exposure, and Diurnal Preference in Day and Night Shift Workers of Both Sexes. Cancer Epidemiol Biomarkers Prev 2014; 23:1176-86. [DOI: 10.1158/1055-9965.epi-13-1271] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
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20
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Deibel SH, Hong NS, Himmler SM, McDonald RJ. The effects of chronic photoperiod shifting on the physiology of female Long-Evans rats. Brain Res Bull 2014; 103:72-81. [DOI: 10.1016/j.brainresbull.2014.03.001] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2013] [Revised: 02/16/2014] [Accepted: 03/03/2014] [Indexed: 12/18/2022]
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21
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FOSSUM IN, BJORVATN B, WAAGE S, PALLESEN S. Effects of shift and night work in the offshore petroleum industry: a systematic review. INDUSTRIAL HEALTH 2013; 51:530-544. [PMID: 23803497 PMCID: PMC4202738 DOI: 10.2486/indhealth.2013-0054] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/14/2013] [Accepted: 05/31/2013] [Indexed: 06/02/2023]
Abstract
Shift and night work are associated with several negative outcomes. The aim of this study was to make a systematic review of all studies which examine effects of shift and night work in the offshore petroleum industry, to synthesize the knowledge of how shift work offshore may affect the workers. Searches for studies concerning effects on health, sleep, adaptation, safety, working conditions, family- and social life and turnover were conducted via the databases Web of Knowledge, PsycINFO and PubMed. Search was also conducted through inspection of reference lists of relevant literature. We identified studies describing effects of shift work in terms of sleep, adaptation and re-adaptation of circadian rhythms, health outcomes, safety and accidents, family and social life, and work perceptions. Twenty-nine studies were included. In conclusion, the longitudinal studies were generally consistent in showing that adaptation to night work was complete within one to two weeks of work, while re-adaptation to a daytime schedule was slower. Shift workers reported more sleep problems than day workers. The data regarding mental and physical health, family and social life, and accidents yielded inconsistent results, and were insufficient as a base for drawing general conclusions. More research in the field is warranted.
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Affiliation(s)
| | - Bjørn BJORVATN
- Department of Global Public Health and Primary Care,
University of Bergen, Norway
- Norwegian Competence Center for Sleep Disorders, Haukeland
University Hospital, Norway
| | - Siri WAAGE
- Department of Global Public Health and Primary Care,
University of Bergen, Norway
- Norwegian Competence Center for Sleep Disorders, Haukeland
University Hospital, Norway
| | - Ståle PALLESEN
- Department of Psychosocial Science, University of Bergen,
Norway
- Norwegian Competence Center for Sleep Disorders, Haukeland
University Hospital, Norway
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22
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Abstract
Melatonin is an indole hormone secreted by the pineal gland during the hours of darkness in a normally entrained individual. There is a clear circadian rhythm in its production with low levels during the day and a peak in the early hours of the morning. The timing of sample collection is crucial and single time point measurements are of little use. Measurement of melatonin or its major metabolite, 6-sulphatoxymelatonin, is normally carried out to determine the timing of an individual's internal body clock and whether it is synchronized to the 24 h day. Misalignment of the clock or disruption of the rhythm can lead to difficulties in sleeping and health problems such as are associated with jet-lag or shift work. Both melatonin and 6-sulphatoxymelatonin can be measured by RIA or ELISA. Details of sample collection and preparation and the assay procedures are described.
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Affiliation(s)
- Benita Middleton
- Chronobiology Group, Faculty of Health and Medical Sciences, University of Surrey, Guildford, Surrey, UK
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23
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Barger LK, Sullivan JP, Vincent AS, Fiedler ER, McKenna LM, Flynn-Evans EE, Gilliland K, Sipes WE, Smith PH, Brainard GC, Lockley SW. Learning to live on a Mars day: fatigue countermeasures during the Phoenix Mars Lander mission. Sleep 2012; 35:1423-35. [PMID: 23024441 DOI: 10.5665/sleep.2128] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Abstract
STUDY OBJECTIVES To interact with the robotic Phoenix Mars Lander (PML) spacecraft, mission personnel were required to work on a Mars day (24.65 h) for 78 days. This alien schedule presents a challenge to Earth-bound circadian physiology and a potential risk to workplace performance and safety. We evaluated the acceptability, feasibility, and effectiveness of a fatigue management program to facilitate synchronization with the Mars day and alleviate circadian misalignment, sleep loss, and fatigue. DESIGN Operational field study. SETTING PML Science Operations Center. PARTICIPANTS Scientific and technical personnel supporting PML mission. INTERVENTIONS Sleep and fatigue education was offered to all support personnel. A subset (n = 19) were offered a short-wavelength (blue) light panel to aid alertness and mitigate/reduce circadian desynchrony. They were assessed using a daily sleep/work diary, continuous wrist actigraphy, and regular performance tests. Subjects also completed 48-h urine collections biweekly for assessment of the circadian 6-sulphatoxymelatonin rhythm. MEASUREMENTS AND RESULTS Most participants (87%) exhibited a circadian period consistent with adaptation to a Mars day. When synchronized, main sleep duration was 5.98 ± 0.94 h, but fell to 4.91 ± 1.22 h when misaligned (P < 0.001). Self-reported levels of fatigue and sleepiness also significantly increased when work was scheduled at an inappropriate circadian phase (P < 0.001). Prolonged wakefulness (≥ 21 h) was associated with a decline in performance and alertness (P < 0.03 and P < 0.0001, respectively). CONCLUSIONS The ability of the participants to adapt successfully to the Mars day suggests that future missions should utilize a similar circadian rhythm and fatigue management program to reduce the risk of sleepiness-related errors that jeopardize personnel safety and health during critical missions.
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Affiliation(s)
- Laura K Barger
- Division of Sleep Medicine, Department of Medicine, Brigham and Women's Hospital, Boston, MA 02115, USA.
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24
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Dumont M, Lanctôt V, Cadieux-Viau R, Paquet J. Melatonin production and light exposure of rotating night workers. Chronobiol Int 2012; 29:203-10. [PMID: 22324558 DOI: 10.3109/07420528.2011.647177] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Decreased melatonin production, due to acute suppression of pineal melatonin secretion by light exposure during night work, has been suggested to underlie higher cancer risks associated with prolonged experience of night work. However, the association between light exposure and melatonin production has never been measured in the field. In this study, 24-h melatonin production and ambulatory light exposure were assessed during both night-shift and day/evening-shift periods in 13 full-time rotating shiftworkers. Melatonin production was estimated with the excretion of urinary 6-sulfatoxymelatonin (aMT6s), and light exposure was measured with an ambulatory photometer. There was no difference in total 24-h aMT6s excretion between the two work periods. The night-shift period was characterized by a desynchrony between melatonin and sleep-wake rhythms, as shown by higher melatonin production during work and lower melatonin production during sleep when working night shifts than when working day/evening shifts. Light exposure during night work showed no correlation with aMT6s excreted during the night of work (p > .5), or with the difference in 24-h aMT6s excretion between the two work periods (p > .1). However, light exposure during night work was negatively correlated with total 24-h aMT6s excretion over the entire night-shift period (p < .01). In conclusion, there was no evidence of direct melatonin suppression during night work in this population. However, higher levels of light exposure during night work may have decreased total melatonin production, possibly by initiating re-entrainment and causing internal desynchrony. This interpretation is consistent with the proposition that circadian disruption, of which decreased melatonin production is only one of the adverse consequences, could be the mediator between night shiftwork and cancer risks.
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Affiliation(s)
- Marie Dumont
- Chronobiology Laboratory, Center for Advanced Research in Sleep Medicine, Sacre-Coeur Hospital of Montreal, Montreal, Quebec, Canada.
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Boivin DB, Boudreau P, Tremblay GM. Phototherapy and Orange-Tinted Goggles for Night-Shift Adaptation of Police Officers on Patrol. Chronobiol Int 2012; 29:629-40. [DOI: 10.3109/07420528.2012.675252] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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Barclay JL, Husse J, Bode B, Naujokat N, Meyer-Kovac J, Schmid SM, Lehnert H, Oster H. Circadian desynchrony promotes metabolic disruption in a mouse model of shiftwork. PLoS One 2012; 7:e37150. [PMID: 22629359 PMCID: PMC3357388 DOI: 10.1371/journal.pone.0037150] [Citation(s) in RCA: 186] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2012] [Accepted: 04/13/2012] [Indexed: 11/23/2022] Open
Abstract
Shiftwork is associated with adverse metabolic pathophysiology, and the rising incidence of shiftwork in modern societies is thought to contribute to the worldwide increase in obesity and metabolic syndrome. The underlying mechanisms are largely unknown, but may involve direct physiological effects of nocturnal light exposure, or indirect consequences of perturbed endogenous circadian clocks. This study employs a two-week paradigm in mice to model the early molecular and physiological effects of shiftwork. Two weeks of timed sleep restriction has moderate effects on diurnal activity patterns, feeding behavior, and clock gene regulation in the circadian pacemaker of the suprachiasmatic nucleus. In contrast, microarray analyses reveal global disruption of diurnal liver transcriptome rhythms, enriched for pathways involved in glucose and lipid metabolism and correlating with first indications of altered metabolism. Although altered food timing itself is not sufficient to provoke these effects, stabilizing peripheral clocks by timed food access can restore molecular rhythms and metabolic function under sleep restriction conditions. This study suggests that peripheral circadian desynchrony marks an early event in the metabolic disruption associated with chronic shiftwork. Thus, strengthening the peripheral circadian system by minimizing food intake during night shifts may counteract the adverse physiological consequences frequently observed in human shift workers.
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Affiliation(s)
| | - Jana Husse
- Max Planck Institute of Biophysical Chemistry, Göttingen, Germany
| | - Brid Bode
- Max Planck Institute of Biophysical Chemistry, Göttingen, Germany
| | - Nadine Naujokat
- Max Planck Institute of Biophysical Chemistry, Göttingen, Germany
| | | | | | - Hendrik Lehnert
- Department of Internal Medicine I, University of Lübeck, Lübeck, Germany
| | - Henrik Oster
- Max Planck Institute of Biophysical Chemistry, Göttingen, Germany
- Department of Internal Medicine I, University of Lübeck, Lübeck, Germany
- * E-mail:
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Arendt J. Biological rhythms during residence in polar regions. Chronobiol Int 2012; 29:379-94. [PMID: 22497433 PMCID: PMC3793275 DOI: 10.3109/07420528.2012.668997] [Citation(s) in RCA: 80] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2011] [Revised: 12/28/2011] [Accepted: 01/22/2012] [Indexed: 11/25/2022]
Abstract
At Arctic and Antarctic latitudes, personnel are deprived of natural sunlight in winter and have continuous daylight in summer: light of sufficient intensity and suitable spectral composition is the main factor that maintains the 24-h period of human circadian rhythms. Thus, the status of the circadian system is of interest. Moreover, the relatively controlled artificial light conditions in winter are conducive to experimentation with different types of light treatment. The hormone melatonin and/or its metabolite 6-sulfatoxymelatonin (aMT6s) provide probably the best index of circadian (and seasonal) timing. A frequent observation has been a delay of the circadian system in winter. A skeleton photoperiod (2 × 1-h, bright white light, morning and evening) can restore summer timing. A single 1-h pulse of light in the morning may be sufficient. A few people desynchronize from the 24-h day (free-run) and show their intrinsic circadian period, usually >24 h. With regard to general health in polar regions, intermittent reports describe abnormalities in various physiological processes from the point of view of daily and seasonal rhythms, but positive health outcomes are also published. True winter depression (SAD) appears to be rare, although subsyndromal SAD is reported. Probably of most concern are the numerous reports of sleep problems. These have prompted investigations of the underlying mechanisms and treatment interventions. A delay of the circadian system with "normal" working hours implies sleep is attempted at a suboptimal phase. Decrements in sleep efficiency, latency, duration, and quality are also seen in winter. Increasing the intensity of ambient light exposure throughout the day advanced circadian phase and was associated with benefits for sleep: blue-enriched light was slightly more effective than standard white light. Effects on performance remain to be fully investigated. At 75°S, base personnel adapt the circadian system to night work within a week, in contrast to temperate zones where complete adaptation rarely occurs. A similar situation occurs on high-latitude North Sea oil installations, especially when working 18:00-06:00 h. Lack of conflicting light exposure (and "social obligations") is the probable explanation. Many have problems returning to day work, showing circadian desynchrony. Timed light treatment again has helped to restore normal phase/sleep in a small number of people. Postprandial response to meals is compromised during periods of desynchrony with evidence of insulin resistance and elevated triglycerides, risk factors for heart disease. Only small numbers of subjects have been studied intensively in polar regions; however, these observations suggest that suboptimal light conditions are deleterious to health. They apply equally to people living in temperate zones with insufficient light exposure.
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Affiliation(s)
- Josephine Arendt
- Centre for Chronobiology, Faculty of Health and Medical Sciences, University of Surrey, Guildford, Surrey, UK.
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Abstract
The internal circadian clock adapts slowly, if at all, to rapid transitions between different shift schedules. This leads to misalignment (desynchrony) of rhythmic physiological systems, such as sleep, alertness, performance, metabolism and the hormones melatonin and cortisol, with the imposed work-rest schedule. Consequences include sleep deprivation and poor performance. Clock gene variants may influence tolerance of sleep deprivation. Shift work is associated with an increased risk of major disease (heart disease and cancer) and this may also, at least in part, be attributed to frequent circadian desynchrony. Abnormal metabolism has been invoked as a contributory factor to the increased risk of heart disease. There is recent evidence for an increased risk of certain cancers, with hypothesized causal roles of light at night, melatonin suppression and circadian desynchrony. Various strategies exist for coping with circadian desynchrony and for hastening circadian realignment (if desired). The most important factor in manipulating the circadian system is exposure to and/or avoidance of bright light at specific times of the 'biological night'.
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Affiliation(s)
- Josephine Arendt
- Centre for Chronobiology, Faculty of Health and Medical Sciences, University of Surrey, Guildford, Surrey GU2 7XH, UK.
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Paul MA, Gray GW, Lieberman HR, Love RJ, Miller JC, Trouborst M, Arendt J. Phase advance with separate and combined melatonin and light treatment. Psychopharmacology (Berl) 2011; 214:515-23. [PMID: 21069516 DOI: 10.1007/s00213-010-2059-5] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/23/2010] [Accepted: 10/13/2010] [Indexed: 10/18/2022]
Abstract
INTRODUCTION Melatonin and light treatment are recommended for hastening adaptation to time zone change. We evaluated an afternoon regimen of 3 mg sustained release (SR) melatonin with and without next morning green light treatment for circadian phase advance. Effects of melatonin and light were tested separately and then combined to determine if the total phase change is additive or synergistic. MATERIAL AND METHODS For each condition (melatonin, placebo, light, melatonin plus light), 11 subjects spent from Tuesday evening until Friday afternoon in the laboratory. For all four conditions, the following sleep schedule was maintained: night 1, 2345 to 0630 hours, night 2, 1600 to 0530 hours, and night 3, 2345 to 0700 hours. For the light-only condition, light treatment was administered between 0700 and 0800 hours on Thursday. For melatonin-only or placebo conditions, capsules were administered at 1600 hours on Wednesday. For the combined condition, melatonin was administered at 1600 hours on Wednesday with light treatment between 0600 and 0700 hours on Thursday. Circadian phase was assessed by calculating dim light melatonin onset (DLMO) from salivary melatonin, using a mean baseline +2 standard deviations (BL+2 SD) threshold. For all four conditions, pre-treatment and post-treatment DLMO assessments were on Tuesday and Thursday evenings, respectively. RESULTS Phase advances were: melatonin at 1600 hours, 0.72 h p<0.005, light treatment from 0700 to 0800 hours, 0.31 h, non-significant, and the combined treatment, 1.04 h p<0.0002. CONCLUSION The phase advance from the combination of afternoon melatonin with next morning light is additive.
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Affiliation(s)
- Michel A Paul
- Defence Research & Development Canada, 1133 Sheppard Ave. West, P.O. Box 2000, Toronto, ON, Canada.
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Alvarez D, Figueiredo M, Rotenberg L. Aspectos do regime de embarque, turnos e gestão do trabalho em plataformas offshore da Bacia de Campos (RJ) e sua relação com a saúde e a segurança dos trabalhadores. REVISTA BRASILEIRA DE SAÚDE OCUPACIONAL 2010. [DOI: 10.1590/s0303-76572010000200004] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
O artigo aborda pesquisa desenvolvida na indústria petrolífera offshore da Bacia de Campos (Rio de Janeiro, Brasil), campo empírico que acompanhamos de forma sistemática desde 2003 e que se situa no rol dos sistemas sociotécnicos complexos. Nosso objetivo é destacar os riscos potenciais associados à organização do trabalho, em especial o regime de embarque e o sistema de turnos adotados nas plataformas de petróleo por algumas das empresas atuantes na região. Isto porque entendemos que, no contexto investigado, os problemas relacionados à saúde - aí inclusos os que se situam na esfera mental - e à segurança dos trabalhadores possuem relação importante com aspectos da organização do trabalho, como aqueles que aqui se encontram em foco. Indicam-se proposições de mudança com o intuito de reduzir os impactos deletérios de tais fatores sobre a saúde e a segurança dos trabalhadores. A base teórico-metodológica utilizada na pesquisa se fundamenta, principalmente, no instrumental da Ergonomia da Atividade e da Psicodinâmica do Trabalho, numa perspectiva ergológica.
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THORNE HC, HAMPTON SM, MORGAN LM, SKENE DJ, ARENDT J. Returning from night shift to day life: Beneficial effects of light on sleep. Sleep Biol Rhythms 2010. [DOI: 10.1111/j.1479-8425.2010.00451.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Dumont M, Blais H, Roy J, Paquet J. Controlled Patterns of Daytime Light Exposure Improve Circadian Adjustment in Simulated Night Work. J Biol Rhythms 2009; 24:427-37. [DOI: 10.1177/0748730409343795] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Circadian misalignment between the endogenous circadian signal and the imposed rest-activity cycle is one of the main sources of sleep and health troubles in night shift workers. Timed bright light exposure during night work can reduce circadian misalignment in night workers, but this approach is limited by difficulties in incorporating bright light treatment into most workplaces. Controlled light and dark exposure during the daytime also has a significant impact on circadian phase and could be easier to implement in real-life situations. The authors previously described distinctive light exposure patterns in night nurses with and without circadian adaptation. In the present study, the main features of these patterns were used to design daytime light exposure profiles. Profiles were then tested in a laboratory simulation of night work to evaluate their efficacy in reducing circadian misalignment in night workers. The simulation included 2 day shifts followed by 4 consecutive night shifts (2400-0800 h). Healthy subjects (15 men and 23 women; 20-35 years old) were divided into 3 groups to test 3 daytime light exposure profiles designed to produce respectively a phase delay (delay group, n = 12), a phase advance (advance group, n = 13), or an unchanged circadian phase (stable group, n = 13). In all 3 groups, light intensity was set at 50 lux during the nights of simulated night work. Salivary dim light melatonin onset (DLMO) showed a significant phase advance of 2.3 h (± 1.3 h) in the advance group and a significant phase delay of 4.1 h (± 1.3 h) in the delay group. The stable group showed a smaller but significant phase delay of 1.7 h (± 1.6 h). Urinary 6-sulfatoxymelatonin (aMT6s) acrophases were highly correlated to salivary DLMOs. Urinary aMT6s acrophases were used to track daily phase shifts. They showed that phase shifts occurred rapidly and differed between the 3 groups by the 3rd night of simulated night work. These results show that significant phase shifts can be achieved in night workers by controlling daytime light exposure, with no nighttime intervention.
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Affiliation(s)
- Marie Dumont
- Chronobiology Laboratory, Sacré-Cœur Hospital of Montreal, Montreal, Québec Canada, Department of Psychiatry, Université de Montréal, Montreal, Québec, Canada,
| | - Hélène Blais
- Chronobiology Laboratory, Sacré-Cœur Hospital of Montreal, Montreal, Québec Canada
| | - Joanie Roy
- Chronobiology Laboratory, Sacré-Cœur Hospital of Montreal, Montreal, Québec Canada
| | - Jean Paquet
- Chronobiology Laboratory, Sacré-Cœur Hospital of Montreal, Montreal, Québec Canada
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Abstract
Jet lag is due to the misalignment of the internal circadian clock(s) with external time cues. For short stopovers (1-2 days) adapting the circadian system is not advised, and at present immediate circadian adaptation is virtually impossible. The use of short-term measures such as judicious naps, caffeine and short acting hypnotics to maintain alertness and sleep is preferred. For intermediate length stays (3-5 days) a phase position with the circadian nadir situated within the sleep period is desirable but difficult to achieve. For longer stays (more than 4-5 days) strategies to hasten adaptation include timed exposure to and avoidance of light. The use of artificial light enriched with short wavelengths may be beneficial. The American Academy of Sleep Medicine recommends the timed use of the chronobiotic melatonin to hasten adaptation. Large individual differences in rate and direction of adaptation make timing treatment according to individual circadian phase difficult. Individual differences in tolerance to the sleep deprivation of jet lag may relate to a length polymorphism in the human clock gene PER3. The maximum efficacy for jet lag avoidance is by pre-flight adaptation, however, this requires time and commitment.
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Affiliation(s)
- Josephine Arendt
- Centre for Chronobiology, Faculty of Health and Medical Sciences, University of Surrey, Guildford, Surrey, UK.
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Thorne H, Hampton S, Morgan L, Skene DJ, Arendt J. Differences in sleep, light, and circadian phase in offshore 18:00-06:00 h and 19:00-07:00 h shift workers. Chronobiol Int 2008; 25:225-35. [PMID: 18484362 DOI: 10.1080/07420520802106850] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
Complaints concerning sleep are high among those who work night shifts; this is in part due to the disturbed relationship between circadian phase and the timing of the sleep-wake cycle. Shift schedule, light exposure, and age are all known to affect adaptation to the night shift. This study investigated circadian phase, sleep, and light exposure in subjects working 18:00-06:00 h and 19:00-07:00 h schedules during summer (May-August). Ten men, aged 46+/-10 yrs (mean+/-SD), worked the 19:00-07:00 h shift schedule for two or three weeks offshore (58 degrees N). Seven men, mean age 41+/-12 yrs, worked the 18:00-06:00 h shift schedule for two weeks offshore (61 degrees N). Circadian phase was assessed by calculating the peak (acrophase) of the 6-sulphatoxymelatonin rhythm measured by radioimmunoassay of sequential urine samples collected for 72 h at the end of the night shift. Objective sleep and light exposure were assessed by actigraphy and subjective sleep diaries. Subjects working 18:00-06:00 h had a 6-sulphatoxymelatonin acrophase of 11.7+/-0.77 h (mean+/-SEM, decimal hours), whereas it was significantly later, 14.6+/-0.55 h (p=0.01), for adapted subjects working 19:00-07:00 h. Two subjects did not adapt to the 19:00-07:00 h night shift (6-sulphatoxymelatonin acrophases being 4.3+/-0.22 and 5.3+/-0.29 h). Actigraphy analysis of sleep duration showed significant differences (p=0.03), with a mean sleep duration for those working 19:00-07:00 h of 5.71+/-0.31 h compared to those working 18:00-06:00 h whose mean sleep duration was 6.64+/-0.33 h. There was a trend to higher morning light exposure (p=0.07) in the 19:00-07:00 h group. Circadian phase was later (delayed on average by 3 h) and objective sleep was shorter with the 19:00-07:00 h than the 18:00-06:00 h shift schedule. In these offshore conditions in summer, the earlier shift start and end time appears to favor daytime sleep.
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Affiliation(s)
- Helen Thorne
- Faculty of Health and Medical Sciences, Neuroendocrinology Group, Centre for Chronobiology, University of Surrey, Guildford, Surrey, UK
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