The Association Between the Number of Consecutive Night Shifts and Insomnia Among Shift Workers: A Multi-Center Study

Objectives: There is a need to determine the optimal limit of consecutive night shift work to reduce insomnia caused by the accumulation of sleep problems among night shift workers. This study aimed to investigate the prevalence of insomnia caused by consecutive night shifts and evaluate the night shift duration that worsens insomnia the most, using a large amount of medical examination data.Methods: Night shift profiles and baseline demographics data of three hospitals were collected from January 2015 to December 2017. For subjects who had been examined more than once at the same institution, information corresponding to the most recent date was used. Multivariate logistic regression was performed to estimate odds ratios (ORs) and 95% confidence intervals (CIs). Pooled ORs were calculated by using the results of the three institutions.Results: Of the 33,669 participants, 31.3% were female. The average age was 41.1 ± 11.1 years and the prevalence of insomnia was 38.7% (n = 13,025). After adjusting for potential confounders and compared to workers who reported not working in consecutive night shifts, odds of insomnia were greatest among workers reporting working three consecutive nights (OR 2.65, 95% CI 1.97–3.56) followed by those working two nights (OR 1.81, 95% CI 1.45–2.26), five nights (OR 1.78, 95% CI 1.56–2.03), and four nights (OR 1.68, 95% CI 1.55–1.82).Conclusion: Our study demonstrates a significant relationship between consecutive night shift and insomnia with multicenter examination data, using common data model. This study could be a basis for establishing policies and guidelines that improve night shift workers' health.

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Chronotype-specific Sleep in Two Versus Four Consecutive Shifts

Journal of Biological Rhythms ◽

10.1177/07487304211006073 ◽

2021 ◽

pp. 074873042110060

Author(s):

Dorothee Fischer ◽

Till Roenneberg ◽

Céline Vetter

Keyword(s):

Night Shift ◽

Sleep Diary ◽

Sequence Length ◽

Consecutive Night ◽

Shift Workers ◽

Subject Field ◽

Sleep Diaries ◽

Social Jetlag ◽

Sleep Debt ◽

Night Shifts

The study aimed to explore chronotype-specific effects of two versus four consecutive morning or night shifts on sleep-wake behavior. Sleep debt and social jetlag (a behavioral proxy of circadian misalignment) were estimated from sleep diary data collected for 5 weeks in a within-subject field study of 30 rotating night shift workers (29.9 ± 7.3 years, 60% female). Mixed models were used to examine whether effects of shift sequence length on sleep are dependent on chronotype, testing the interaction between sequence length (two vs. four) and chronotype (determined from sleep diaries). Analyses of two versus four morning shifts showed no significant interaction effects with chronotype. In contrast, increasing the number of night shifts from two to four increased sleep debt in early chronotypes, but decreased sleep debt in late types, with no change in intermediate ones. In early types, the higher sleep debt was due to accumulated sleep loss over four night shifts. In late types, sleep duration did not increase over the course of four night shifts, so that adaptation is unlikely to explain the observed lower sleep debt. Late types instead had increased sleep debt after two night shifts, which was carried over from two preceding morning shifts in this schedule. Including naps did not change the findings. Social jetlag was unaffected by the number of consecutive night shifts. Our results suggest that consecutive night shifts should be limited in early types. For other chronotypes, working four night shifts might be a beneficial alternative to working two morning and two night shifts. Studies should record shift sequences in rotating schedules.

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Effects of work organization on the occurrence and resolution of sleep disturbances among night shift workers: a longitudinal observational study

Scientific Reports ◽

10.1038/s41598-021-85017-8 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Seungho Lee ◽

Jae Bum Park ◽

Kyung-Jong Lee ◽

Seunghon Ham ◽

Inchul Jeong

Keyword(s):

Work Experience ◽

Sleep Disturbances ◽

Sleep Problems ◽

Night Shift ◽

Work Organization ◽

Severity Index ◽

Estimating Equation ◽

Health Examination ◽

Related Factors ◽

Shift Workers

AbstractThis study aimed to investigate the association between work organization and the trajectories of insomnia patterns among night shift workers in a hospital. The health examination data of hospital workers, recorded from January 2014 to December 2018, were collected; 6765 records of 2615 night shift workers were included. Insomnia was defined as a score of ≥ 15 on the Insomnia Severity Index (ISI). Participants were categorized into five groups according to insomnia patterns derived from the analysis of their ISI scores. Work organization and socio-demographic characteristics were also investigated. Generalized estimating equation models and linear mixed models were constructed to analyze the longitudinal data. Of the total participants, 53.0% reported insomnia at least once during the follow-up period. The lack of nap opportunities and work-time control was associated with the occurrence of insomnia, whereas more than 5 years of shift work experience was related to the resolution of insomnia. All work-related factors were significantly related to insomnia risk; however, the effects were not significant in the sustained insomnia group. Although sleep problems are inevitable in night shift workers, well-designed work schedules and better work organization can help reduce the occurrence of insomnia among them.

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Disturbances of Autonomic Regulation of Cardiovascular System at Different Working Regimes with Night Shifts

Kardiologiia ◽

10.18087/cardio.2020.9.n1134 ◽

2020 ◽

Vol 60 (9) ◽

pp. 62-67

Author(s):

Yu. A. Merkulov ◽

A. A. Pyatkov ◽

S. G. Gorokhova ◽

D. M. Merkulova ◽

O. Yu. Atkov

Keyword(s):

Shift Work ◽

Spectral Characteristics ◽

Night Shift ◽

Autonomic Regulation ◽

Total Power ◽

Orthostatic Test ◽

Heart Rhythm Variability ◽

Shift Workers ◽

Rotating Shift Work ◽

Night Shifts

Aim To study temporal and spectral characteristics of heart rhythm variability (HRV) in night shift workers.Materials and methods Along with traditional risk factors, conditions of labor contribute to development of cardiovascular morbidity, including night shift work, which can be associated with disorders of the autonomic regulation detected by analysis of HRV. This study included 100 healthy men. 74 of them were engaged in shift work, including 53 men with rotating shift work, 21 men with fixed night shifts, and 26 men with day-time work. HRV was analyzed by data of 5-min electrocardiogram recording (background recording and orthostatic test).Results Night-shift workers had decreases in total power of regulation (ТР, SDNN) and in the parasympathetic branch (HF, pNN50). Rotating night-shift workers displayed significant decreases in SDNN and pNN50 and pronounced changes in the VLF / LF / HF ratio in the orthostatic test.Conclusion In work with night shifts, the type of autonomic regulation differs from the “standard” functioning of the autonomic nervous system (ANS). This study showed different effects of night work regimens on HRV indexes. With the rotating shift work, the ANS dysregulation was more profound and was evident by a significant decrease in the ANS total tone and parasympathetic activity (SDNN, pNN50) compared to night shifts with fixed working hours. The excessive weakening of the parasympathetic component in the passive orthostatic test can be considered as an early marker for ANS maladaptation.

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61. Can Melatonin Improve Adaptation To Night Shift? A Pilot Study Using an Urban EMS System

Prehospital and Disaster Medicine ◽

10.1017/s1049023x0004574x ◽

1996 ◽

Vol 11 (S2) ◽

pp. S34-S34

Author(s):

Michael Tremea ◽

Mark James ◽

Jeffrey Jones ◽

Jon Krohmer

Keyword(s):

Job Performance ◽

Night Shift ◽

Biological Clock ◽

Consecutive Night ◽

Sleep Diaries ◽

Visual Analog Scales ◽

Significant Difference ◽

Clinical Benefits ◽

Double Blinded ◽

Night Shifts

Purpose: To determine whether melatonin (N-acetyl-5-methoxytryptamine) is effective in helping prehospital personnel working consecutive night shifts reset their biological clock and minimize circadian rhythm disruption.Methods: A double-blinded, randomized, cross-over study was performed using 12 paramedic volunteers. Paramedics were working a span of consecutive night (2300-0700) shifts and received either a melatonin capsule (6 mg) or placebo to be taken prior to each of the consecutive day sleeps. Each participants completed a total of four spans of consecutive night shifts (2-melatonin, 2-placebo). Collected data included daily sleep diaries, quantification of alcohol/caffeine consumed, and possible drug side-effects. Assessment of job performance, mood and alertness were measured every day using 10-cm visual analog scales (VAS).Results: Analysis of sleep diaries demonstrated no significant difference (p >0.05) between the two treatments in respect to mean sleep latency (melatonin = 15.4 min. vs. placebo = 14.6 min), mean sleep duration (melatonin = 6.7 hrs. vs. placebo = 6.9 hrs), or subjectively rated sleep quality (melatonin = 5.8 VAS vs placebo = 5.6 VAS). Similarly, no significant benefits were noted between the mean VAS scores for daily job performance, mood and alertness. Adverse effects were rare, one patient taking melatonin reported a prolonged sedative effect.Conclusion: Despite widespread belief in the benefits of melatonin as a hypnotic agent, no clinical benefits were noted in terms of daytime sleep or job performance in paramedics working consecutive night shifts.

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Energy, Nutrient and Food Intakes of Male Shift Workers Vary According to the Schedule Type but Not the Number of Nights Worked

Nutrients ◽

10.3390/nu12040919 ◽

2020 ◽

Vol 12 (4) ◽

pp. 919

Author(s):

Sophie Bucher Della Torre ◽

Pascal Wild ◽

Victor Dorribo ◽

Brigitta Danuser ◽

Francesca Amati

Keyword(s):

Eating Habits ◽

Night Shift ◽

Food Group ◽

Pooled Analysis ◽

Dietary Intakes ◽

Food Groups ◽

Shift Workers ◽

Increased Risk ◽

Schedule Type ◽

Night Shifts

Shift work is associated with increased risk of chronic diseases due to circadian rhythm disruptions and behavioral changes such as in eating habits. Impact of type of shifts and number of night shifts on energy, nutrient and food intake is as yet unknown. Our goal was to analyze shift workers’ dietary intake, eating behavior and eating structure, with respect to frequency of nights worked in a given week and seven schedule types. Eating habits and dietary intakes of 65 male shift workers were analyzed in three steps based on 365 24-h food records: (1) according to the number of nights, (2) in a pooled analysis according to schedule type, and (3) in search of an interaction of the schedule and the timing of intake. Mean nutrient and food group intake during the study period did not depend on the number of nights worked. Amount and distribution of energy intake as well as quality of food, in terms of nutrient and food groups, differed depending on the type of schedule, split night shifts and recovery day (day after night shift) being the most impacted. Shift workers’ qualitative and quantitative dietary intakes varied between different schedules, indicating the need for tailored preventive interventions.

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Poor Sleep Quality in Nurses Working or Having Worked Night Shifts: A Cross-Sectional Study

Frontiers in Neuroscience ◽

10.3389/fnins.2021.638973 ◽

2021 ◽

Vol 15 ◽

Author(s):

Qiao Huang ◽

Chong Tian ◽

Xian-Tao Zeng

Keyword(s):

Sleep Quality ◽

Clinical Care ◽

Night Shift ◽

Cross Sectional Study ◽

Poor Sleep ◽

Consecutive Night ◽

Sectional Study ◽

Poor Sleep Quality ◽

Cross Sectional ◽

Night Shifts

Night shifts are part of clinical care. It is unclear whether poor sleep quality of nurses working both consecutive night shifts and day shifts after quitting night shifts is common. In this cross-sectional study, Pittsburgh Sleep Quality Index (PSQI) was used to assess sleep quality as study outcome. Univariable and multivariable linear and logistic regressions were performed to compare PSQI score and prevalence of poor sleep quality between 512 nurses currently working consecutive night shifts and 174 nurses having worked night shifts in the past. The prevalence of poor sleep quality was 62.11% in nurses working consecutive night shifts and 55.75% in nurses having worked night shifts before. In multivariable regressions with adjustment for potential confounders, compared with nurses working consecutive night shifts, nurses having worked past night shifts reported decreased PSQI score [mean difference: −0.82 (95% CI: −1.27 to −0.38, p < 0.001)] and lower poor sleep quality [odds ratio (OR): 0.49 (95% CI: 0.29 to 0.80, p = 0.005)]. In nurses working consecutive night shifts, a rising curve that plateaued at the end was observed between years of consecutive night shifts and PSQI score, p = 0.004. To explore the change in PSQI score after quitting night shift, we constructed a hypothetical prospective cohort from the cross-sectional data. Here, 98 pairs of nurses with consecutive and past night shifts were matched for the number of night shift years, religion, marital status, living condition, hypertension, and hyperlipidemia. In each pair, a hypothetical change in PSQI score was calculated between the two types of nurses and hypothetical years after quitting night shifts was obtained from the matched nurse with past night shifts. A U-shaped curve between change in PSQI and years after quitting night shifts was observed, p = 0.007. The rising curve and U-shaped curve together formed an S-shaped curve, which mapped the change in sleep quality. These results based on the hypothetical cohort constructed from cross-sectional data suggested the presence of persistent poor sleep quality in night shift nurses. Also, we support early and continuous sleep hygiene education and reflection for an optimal strategy for when to cease working night shifts with regard to sleep-related problems.

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Designing Light for Night Shift Workers: Application of Nonvisual Lighting Design Principles in an Industrial Production Line

Applied Sciences ◽

10.3390/app112210896 ◽

2021 ◽

Vol 11 (22) ◽

pp. 10896

Author(s):

Johannes Zauner ◽

Herbert Plischke

Keyword(s):

Shift Work ◽

Industrial Production ◽

Night Shift ◽

Stimulus Range ◽

Automation System ◽

Shift Workers ◽

Health And Wellbeing ◽

Rotating Shift Work ◽

Lighting Simulation ◽

Night Shifts

Chronodisruption deteriorates the health and wellbeing of shift workers. Artificial light at night and the lack of light during the day are major contributors to chronodisruption and need to be optimized in shift work scenarios. Here, we present one solution for a lighting and automation system in an industrial production workplace. The setting is a rapidly rotating shift work environment with morning, evening, and night shifts. We describe a procedure to specify the new lighting through a software-agnostic nonvisual lighting simulation for artificial and daylighting scenarios. Through this process, a new luminaire is created, called Drosa, that allows for a large melanopic stimulus range between 412 and 73 lx melanopic equivalent daylight (D65) illuminance vertically at eye level, while maintaining a neutral white illuminance at task level between 1250 and 900 lx, respectively. This is possible through a combination of glare-free spotlights with adjustable areal wing lights. An individually programmed automation system controls the light dosage and timing during the day and night. The work is relevant for other shift work scenarios, where the presented example and the discussed rationale behind the automation might provide insights. The work is further relevant for other lighting scenarios beyond industrial shift work, as the nonvisual lighting simulation process can be adapted to any context.

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Diurnal rhythms of cortisol and melatonin in night eating and non-night eating male police officers

European Journal of Public Health ◽

10.1093/eurpub/ckz186.330 ◽

2019 ◽

Vol 29 (Supplement_4) ◽

Author(s):

J K Sørensen ◽

M A Jensen ◽

ÅM Hansen ◽

R Rugulies ◽

A H Garde

Keyword(s):

Diurnal Rhythm ◽

Police Officers ◽

Night Shift ◽

Eating Behaviour ◽

Cortisol Concentration ◽

Diurnal Rhythms ◽

Consecutive Night ◽

Night Eating ◽

Main Meal ◽

Night Shifts

Abstract Background Working during the night has in previous studies been associated with behavioural changes and diseases. Disturbance between behavioural and biological circadian rhythms have been suggested as a possible mechanism linking night work with cardiovascular diseases and pre-diabetic changes. The aim of this study was to investigate if night eating during two, four and seven consecutive night shifts is associated with differences in the diurnal rhythms of cortisol and melatonin in male police officers in Denmark. Methods We conducted an experimental study among 37 male police officers in Denmark who all collected data on the last night shift in three different work schedules with two, four and seven consecutive night shifts, respectively. Night eating was self-reported and defined as eating at least one main meal between midnight and early morning. Differences in the diurnal rhythms of concentrations of cortisol and melatonin in saliva were tested by phase changes and amplitude differences. Results Sixteen (43.2%) police officers ate a main meal during the last night shift in all three work schedules. The timing of the lowest cortisol concentration was on average delayed with 2:10 hours (95% CI 0:24-3:56 hours) and the level of the lowest cortisol concentration was on average supressed with 66% (95% CI 47-94%) for night eaters compared to non-night eaters. There was no association with number of consecutive night shifts. The phase and amplitude of melatonin were not statistically significantly different between night eaters and non-night eaters. Conclusions Night eating behaviour is associated with differences in the diurnal rhythm of cortisol in Danish male police officers working during the night. The difference in cortisol rhythm between night eaters and non-night eaters on night shifts is not affected by the number of consecutive night shifts. Key messages Night eating behaviour is associated with differences in the diurnal rhythm of cortisol. Future studies should focus on potential health outcomes of night eating behaviour among night workers.

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Differential effects of light at night and shift rotation pattern on the circadian system in night workers.

Journal of Clinical Oncology ◽

10.1200/jco.2012.30.15_suppl.1556 ◽

2012 ◽

Vol 30 (15_suppl) ◽

pp. 1556-1556

Author(s):

Pedram Razavi ◽

Eva S Schernhammer ◽

Keyword(s):

Shift Work ◽

Night Shift ◽

Circadian System ◽

Activity Level ◽

Melatonin Level ◽

Consecutive Night ◽

Light At Night ◽

Night Shift Work ◽

Single Night ◽

Night Shifts

1556 Background: Light at night as in shift work suppresses nocturnal secretion of melatonin, a pineal hormone with oncostatic properties. Several studies have associated night shift work with higher risk of cancer, leading WHO in 2007 to classify rotating night shift work as “probably carcinogenic”. We conducted one of the most comprehensive studies, to date, to evaluate the effects of light and night shift work on melatonin measurements in the field. Methods: Study participants were 130 active nurses (84 current rotating night shift workers and 46 day shift workers) participating in NHS2. Each nurse wore a head-mounted light- and accelerometer for a 3-day study period, during which each spontaneous urine was collected for repeated urinary 6-sulfatoxymelatonin (melatonin) measurements. In addition, nurses were asked to fill out paper questionnaires and diaries. We used mixed models to evaluate the influence of light, activity and night shift work on urinary melatonin level adjusting, for age, lifestyle, and occupational history. We log-transformed main variables and report geometric means (GM [standard deviation]). Results: Greater levels of light were associated with lower melatonin (P < 0.0001), independent of activity level. An increase in light intensity from 10 to 100 lux was associated with a 12% decrease in geometric mean of melatonin level; however, this inverse association was only significant at night (Ptrend = 0.01). At night, each hour increase in exposure to ≥ 20 lux light lowered melatonin level by 5.7% (Ptrend < 0.0001). A single night shift affected the circadian system by lowering melatonin peak by 22% (day shift: GM = 17.57 [2.73]; night shift: GM = 13.64 [2.54]) and induced a phase shift (PS) of 0.9 hours, -changes that reset to normal by the next day. Two consecutive night shifts had a similar effect as a single shift. However, the effect was worse after three consecutive night shifts (GM = 10.11 [2.77]; PS = 2.2 hours). Conclusions: We found significant inverse associations of intensity and duration of exposure to light at night with urinary melatonin, independent of activity level. Three consecutive night shifts affected the circadian system more strongly than two consecutive, or a single night shift.

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Abstract 14384: Light Therapy Improves Circadian Blood Pressure Control and Glucose Homeostasis in Rotating Night Shift Workers via Mechanisms Independent of Melatonin

Circulation ◽

10.1161/circ.142.suppl_3.14384 ◽

2020 ◽

Vol 142 (Suppl_3) ◽

Author(s):

Juliane Hannemann ◽

Anika Laing ◽

Benita Middleton ◽

Jonathan Cridland ◽

Bart Staels ◽

...

Keyword(s):

Blood Pressure ◽

Circadian Rhythms ◽

Glucose Tolerance ◽

Shift Work ◽

Therapy Group ◽

Night Shift ◽

Light Therapy ◽

Pressure Control ◽

Shift Workers ◽

Night Shifts

Introduction: Night shift work is associated with high rates of hypertension, heart disease, and metabolic syndrome. These cardiometabolic diseases have been linked to the disruption of circadian rhythms in night shift workers. Rotating night shift work is increasingly common in the working population worldwide. Hypothesis: We hypothesized that light therapy might help to normalize disrupted circadian rhythms and stabilize diurnal control of blood pressure and glucose tolerance in rotating night shift workers. Methods: We randomized 24 rotating night shift workers (mean age, 36±13 years, 7 males) who had spent a median of 6 years on rotating night shifts with a median of 6 night shifts/month to 12 weeks of light therapy (light during first half of each night shift and in the morning of off-work days) or no intervention and compared them with 12 daytime workers (37±11 years, 6 males). We measured oral glucose tolerance (OGTT), 24h blood pressure and arterial stiffness, and the circadian profiles of melatonin, cortisol, metanephrine and normetanephrine at baseline, after 12 weeks of intervention, and 12 weeks after the end of intervention. Results: At baseline, fewer night shift workers showed dipper status of blood pressure as compared to daytime workers (21% vs. 55%; p<0.001). After 12 weeks of light therapy, there was a highly significant increase in the proportion of dippers (to 42%; p<0.0001). We also observed a significant decrease in serum glucose during OGTT in the light therapy group (-22%; p<0.05), with no change in serum insulin. Whilst circadian profiles of melatonin and cortisol were unchanged, there was a significant reduction in nighttime plasma metanephrine and normetanephrine levels in the light therapy group (p<0.01). Conclusions: Chronotherapeutic light therapy significantly improves diurnal blood pressure control and glucose tolerance in rotating night shift workers. This effect is unrelated to mechanisms traditionally linked to the circadian clock like melatonin and cortisol, but it is paralleled by reduced catecholamine levels. Our data suggest that chronotherapeutic light therapy may improve the adjustment to atypical working hours in rotating night shift workers, thereby reducing stress and improving cardiometabolic function.

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