Moral decision-making at night and the impact of night work with blue-enriched white light or warm white light: a counterbalanced crossover study

BACKGROUND

Cognitive function, including moral decision-making abilities, can be impaired by sleep loss. Blue-enriched light interventions have been shown to ameliorate cognitive impairment during night work. This study investigated whether the quality of moral decision-making during simulated night work differed for night work in blue-enriched white light, compared to warm white light.

METHODS

Using a counterbalanced crossover design, three consecutive night shifts were performed in blue-enriched white light (7000 K) and warm white light (2500 K) provided by ceiling-mounted LED luminaires (photopic illuminance: ∼200 lx). At 03:30 h on the second shift (i.e. twice) and at daytime (rested), the Defining Issues Test-2, assessing the activation of cognitive schemas depicting different levels of cognitive moral development, was administered. Data from 30 (10 males, average age 23.3 ± 2.9 years) participants were analysed using linear mixed-effects models.

RESULTS

Activation of the post-conventional schema (P-score), that is, the most mature moral level, was significantly lower for night work in warm white light (EMM; estimated marginal mean = 44.3, 95% CI = 38.9-49.6; pholm=.007), but not blue-enriched white light (EMM = 47.5, 95% CI = 42.2-52.8), compared to daytime (EMM = 51.2, 95% CI = 45.9-56.5). Also, the P-score was reduced for night work overall (EMM = 45.9, 95% CI = 41.1-50.8; p=.008), that is, irrespective of light condition, compared to daytime. Neither activation of the maintaining norms schema (MN-score), that is, moderately developed moral level, nor activation of the personal interest schema (i.e. the lowest moral level) differed significantly between light conditions. The MN-score was however increased for night work overall (EMM = 26.8, 95% CI = 23.1-30.5; p=.033) compared to daytime (EMM = 23.1, 95% CI = 18.9-27.2).

CONCLUSION

The results indicate that moral decisions during simulated night work in warm white light, but not blue-enriched white light, become less mature and principle-oriented, and more rule-based compared to daytime, hence blue-enriched white light may function as a moderator. Further studies are needed, and the findings should be tentatively considered.Trial registration: ClinicalTrials.gov (ID: NCT03203538) Registered: 26/06/2017; https://clinicaltrials.gov/study/NCT03203538.

Effects of chronotype on sleep, mood and cardiovascular circadian rhythms in rotating night shift medical workers

PURPOSE

Whether chronotype affects the health outcomes of night shift work populations is unknown. This study aimed to assess the influence of different chronotypes in the rotating night shift population on sleep status, mood, blood pressure (BP), and heart rate variability (HRV), as well as the circadian rhythm of BP and HRV.

METHODS

A total of 208 rotating night shift workers were included. All participants completed structured questionnaires to assess chronotype, mood and sleep status. During their daily lives outside of the night shift, they underwent 24-hour Holter electrocardiogram monitoring and 24-hour ambulatory blood pressure monitoring. Day-time and night-time BP and BP dipping were obtained. Day-time and night-time HRV values (SDNN, RMSSD, LF, HF, LF nu, SD1, SD2 and SD2/SD1) were calculated and fitted to the cosine period curve. Three circandian parameters (mesor, amplitude and acrophase) were extracted to quantify the circadian rhythm of the HRV indices.

RESULTS

Among all three groups, E-type showed more fatigue and sleepiness. In addition, E-type showed blunted diastolic BP dipping. Notably, E-type showed association with higher RMSSD, LF, HF and SD1 in the night time, and higher mesors of RMSSD and LF and amplitude of SD2/SD1 in circadian analysis.

CONCLUSION

Chronotype is a factor affecting fatigue, sleepiness and cardiovascular circadian rhythms of rotating night shift workers. Chronotype should be taken into consideration for managing night-shift rotation to promote occupational health.

The influence of shift work: A bibliometric analysis of research progress and frontiers on health effects

Shift work has been found to disrupt the circadian system, leading to negative health effects. The objective of this study was to assess the progress and frontiers in research on the health-related influence of shift work. The study analyzed 3,696 data points from Web of Science, using the bibliometric software CiteSpace to visualize and analyze the field. The results showed a steady increase in annual publications, particularly in the last 5 years, with a rapid increase in publications from China. The United States contributed the most to the number of publications and worldwide collaborations. The most prolific institution and author were the Brigham and Women's Hospital and Professor Bjorn Bjorvatn, respectively. The Journal of Chronobiology International ranked at the top and focused primarily on shift worker research. In the first decade of study, the primary focus was on the associations between shift work and cardiovascular disease and metabolic disorders. Over time, research on the health effects of shift work has expanded to include cancer and mental health, with subsequent studies investigating molecular mechanisms. This study provides a comprehensive and intuitive analysis of the negative health impacts of shift work. It highlights existing research hotspots and provides a roadmap for future studies. Further research is needed to explore the adverse health consequences and related mechanisms of shift work exposure, as well as interventions to mitigate its health effects.

Association of intra-shift nap duration with heart rate variability in medical night shift workers

Napping during night shifts effectively reduces disease risk and improves work performance, but few studies have investigated the association between napping and physiological changes, particularly in off-duty daily lives. Changes in the autonomic nervous system precede diseases like cardiovascular disease, diabetes, and obesity. Heart rate variability is a good indicator of autonomic nervous system. This study aimed to investigate the link between night shift nap durations and heart rate variability indices in the daily lives of medical workers. As indicators of chronic and long-term alterations, the circadian patterns of heart rate variability indices were evaluated. We recruited 146 medical workers with regular night shifts and divided them into four groups based on their self-reported nap durations. Heart rate variability circadian parameters (midline-estimating statistic of rhythm, amplitude, and acrophase) were obtained by obtaining 24-h electrocardiogram on a day without night shifts, plotting the data of the heart rate variability indices as a function of time, and fitting them into periodic cosine curves. Using clinical scales, depression, anxiety, stress, fatigue, and sleepiness were assessed. Linear regression analysis revealed a positive relationship between 61-120-min naps and 24-h, daytime, and night-time heart rate variability indices, and the parasympathetic activity oscillation amplitude (indexed by high-frequency power, the square root of the mean of the sum of squares of differences between adjacent normal intervals, standard deviation of short-term R-R-interval variability) within one circadian cycle. This study indicated that napping for 61-120 min during night shifts could benefit medical workers' health, providing physiological evidence to promote nap management.

Effects of shift work on sleep quality and cardiovascular function in Taiwanese police officers

This study aimed to investigate the effects of shift work on sleep quality, cardiovascular function, and physical activity (PA) levels in Taiwanese police officers. Twenty-one male police officers aged 26.9 ± 4.1 years old located in Taipei voluntarily participated in this study. The participants completed the resting heart rate (HR) and hemodynamic variables (e.g. blood pressure, BP) before and after day-time (DTW) and night-time (NTW) shift work phases (5 working days and 2 resting days for each phase). Additionally, an actigraphy was administered to measure PA and sleep patterns in the last 3 working days. The average total sleep time and sleep efficiency were 278.5 ± 79. 6 min and 72.9 ± 10%, respectively, in the NTW phases, which were significantly lower than that in the DTW phases. A comparison of the PA characteristics between the two phases revealed that a lower proportion of moderate-vigorous PA (1.2 ± 0.8%) and a greater proportion of sedentary behaviour PA (74.8 ± 6.4%) was found in the NTW phases. The results of hemodynamic measures demonstrated that the police officers have significantly elevated systolic BP by 3.3% and diastolic BP by 3.9% after the NTW phases. Furthermore, the NTW phases exhibited a significantly higher percentage change ratio of systolic BP and diastolic BP compared to the DTW phases. Compared with the DTW phases, the NTW phase was significantly more likely to report higher decreasing parasympathetic-related HR variability with a range of -5.9% to -7.8%. In conclusion, night-time shift work resulted in negative physiological changes leading to adverse effects on the health and well-being of Taiwanese police officers.

Sleep quality and the intention to modify sleep behaviors among night-shift nurses

PURPOSE

To explore the relationship between sleep quality and intent to change sleep behaviors among night-shift nurses.

METHODS

Full-time night-shift nurses in a hospital setting completed a cross-sectional online survey including demographics, Snoring, Tiredness during daytime, Observed apnea, and High Blood Pressure (STOP) Questionnaire, the Pittsburgh Sleep Quality Index (PSQI), and the Intention to Change Behavior Scale (ICBS). The relationship between PSQI and ICBS scores was tested using Spearman's rho correlation coefficient.

RESULTS

Most participants reported poor sleep and did not engage in health behaviors that promote good sleep. There was a weak, positive relationship between PSQI and ICBS scores. Those who reported poor sleep quality indicated a high intent to improve sleep.

CONCLUSION

These findings support the need for night-shift nurses to prioritize enhancing their sleep quality by advocating for policy and practice improvements. The findings also highlight the importance of support from nurse leaders, educators, and researchers to raise awareness and implement holistic strategies for better sleep health.

Field-based longitudinal evaluation of multimodal worker fatigue assessments in offshore shiftwork

Fatigue in offshore environments is a critical safety hazard, yet the utility of daily fatigue assessments has not been longitudinally examined in these environments. The aim of this exploratory longitudinal field study across two drillships in the Gulf of Mexico was to determine the changes in subjective, performance-based, and physiological fatigue measures over time across different shift types (day, night, and swing) and to identify correlations between these multimodal fatigue assessments. Repeated measures correlation analyses of daily fatigue data from seventy offshore workers revealed that while total sleep time remained unaffected by time on rig, workers' performances on the psychomotor vigilance test (PVT) deteriorated over time across all shift types. Several correlations between the various multimodal measures were consistent with the extant literature on worker fatigue symptoms and perceptual and physiological manifestations. These findings emphasize the utility of PVT and single item self-reports to capture worker fatigue in offshore shiftwork.

Administration of blue light in the morning and no blue-ray light in the evening improves the circadian functions of non-24-hour shift workers

In modern 24-hour society, various round-the-clock services have entailed shift work, resulting in non-24-hour schedules. However, the extent of behavioral and physiological alterations by non-24-hour schedules remains unclear, and particularly, effective interventions to restore the circadian functions of non-24-hour shift workers are rarely explored. In this study, we investigate the effects of a simulated non-24-hour military shift work schedule on daily rhythms and sleep, and establish an intervention measure to restore the circadian functions of non-24-hour shift workers. The three stages of experiments were conducted. The stage-one experiment was to establish a comprehensive evaluation index of the circadian rhythms and sleep for all 60 participants by analyzing wristwatch-recorded physiological parameters and sleep. The stage-two experiment evaluated the effects of an intervention strategy on physiological rhythms and sleep. The stage-three experiment was to examine the participants' physiological and behavioral disturbances under the simulated non-24-hour military shift work schedule and their improvements by the optimal lighting apparatus. We found that wristwatch-recorded physiological parameters display robust rhythmicity, and the phases of systolic blood pressures and heart rates can be used as reliable estimators for the human body time. The simulated non-24-hour military shift work schedule significantly disrupts the daily rhythms of oxygen saturation levels, blood pressures, heart rates, and reduces sleep quality. Administration of blue light in the morning and no blue-ray light in the evening improves the amplitude and synchronization of daily rhythms of the non-24-hour participants. These findings demonstrate the harmful consequences of the non-24-hour shift work schedule and provide a non-invasive strategy to improve the well-being and work efficiency of the non-24-hour shift population.

Home Care Workers' Objective and Subjective Recovery From Work

OBJECTIVE

The aim of this cross-sectional study was to examine the recovery from work in Finnish home care nurses with objective and subjective recovery measures.

METHODS

Heart rate and heart rate variability recordings were performed in home care nurses over a period of one work shift and the following night. Following the measurements, the participants ( N = 91) answered a questionnaire including questions about their self-rated recovery from work and sleep disturbances.

RESULTS

The objectively measured recovery was within the recommended heart rate variability range, yet the self-rated recovery from work was only mediocre. Subjective recovery was not associated with objectively measured recovery.

CONCLUSIONS

There is a discrepancy between objectively and subjectively measured recovery from work. Therefore, an additional objective method in occupational field studies, along with questionnaires, is recommended to measure physiological recovery.

The effect of a night shift nap on post-night shift performance, sleepiness, mood, and first recovery sleep: A randomized crossover trial

OBJECTIVES

This study aimed to test the effect of a 30-minute nap versus a 2-hour nap opportunity taken during a simulated night shift on performance, fatigue, sleepiness, mood, and sleep at the end of shift and during post-night shift recovery.

METHODS

We conducted a randomized crossover trial of three nap conditions (30-minute, 2-hour, and no-nap) during 12-hour simulated night shifts. We tested for differences in performance, fatigue, sleepiness, mood, and sleep during in-lab and at-home recovery. Performance was measured with the Brief Psychomotor Vigilance Test (PVT-B). Subjective ratings were assessed with single-item surveys.

RESULTS

Twenty-eight individuals consented to participate [mean age 24.4 (standard deviation 7.2) years; 53.6% female; 85.7% Emergency Medical Services clinicians]. PVT-B false starts at the end of the 12-hour night shift (at 07:00 hours) and at the start of in-lab recovery (08:00 hours) were lower following the 2-hour nap versus other conditions (P<0.05). PVT-B response time at +0 minutes post-recovery nap was poorer compared to pre-recovery nap for the no-nap condition (P=0.003), yet not detected for other nap conditions (P>0.05). Sleepiness, fatigue, and some mood states were lower at most hourly assessments during the in-lab recovery period following the 2-hour nap condition compared to the other conditions. Sleep during recovery did not differ by duration of night shift nap.

CONCLUSIONS

A 2-hour nap opportunity versus a 30-minute or no-nap opportunity is beneficial for performance, alertness, and mood post-night shift. No differences were detected in sleep during recovery.

Time-of-day effects on speed and accuracy performance during simulated shiftwork

Performance on tasks involving speed and accuracy fluctuate throughout the 24-h day negatively affecting shift workers and organizations. Two simulated work shifts common in occupational settings were used to assess performance on a vigilance and math task. In study 1, 33 sleep-deprived participants completed a nightshift. In study 2, 32 partially sleep-deprived participants completed a dayshift. These studies found that performance differed between the type of task and the type of simulated shift where performance during the nightshift was worse than during the dayshift. In addition, collapsing speed and accuracy on the math task into inverse efficiency scores provided a unique measure that captured the impact of circadian rhythms during shiftwork. The current study also indicated that participants adopted cognitive strategies including speed-accuracy tradeoff and regulatory foci regarding work motivation (prevention focus and promotion focus) when completing the tasks depending on time-of-day, type of shift, circadian rhythms, and amount of sleep deprivation. This suggests that researchers and organizations should consider cognitive strategies in addition to the physiological components of sleep deprivation and circadian rhythms when investigating and documenting the impact of time-of-day due to different types of shiftwork conditions on performance and safety.

Shiftwork, long working hours and markers of inflammation in a national US population-based sample of employed black and white men and women aged ≥45 years

OBJECTIVES

Work schedule demands contribute to circadian disruption and may influence health via an inflammatory response. We examined the impact of shiftwork and long work hours on inflammation in a national US sample.

METHODS

Participants included 12 487 employed black and white men and women aged ≥45 years enrolled in the REasons for Geographic and Racial Differences in Stroke Study who completed an occupational questionnaire (2011-2013) and clinical examination (2013-2016). Cross-sectional associations between shiftwork and work hours with log-transformed high-sensitivity C reactive protein (CRP) and white blood cell (WBC) count were examined by multiple linear regression analysis, overall and by race-sex subgroups.

RESULTS

Overall, rotating shift workers had higher log-CRP concentration compared with day workers (β=0.09, 95% CI:0.02 to 0.16) and findings for WBC were null. Black women had the highest geometric mean CRP (2.82 mg/L), while white men had the highest WBC (6.35×109/L). White men who worked afternoons had higher log-CRP compared with those who worked days (β=0.20, 95% CI: 0.08 to 0.33). Black men engaged in shiftwork <10 years working ≥55 hours/week had higher log-CRP and log-WBC compared with those working days <55 hours/week (β=0.33, 95% CI: 0.02 to 0.64 and β=0.10, 95% CI: 0.003 to 0.19). Among shift workers, non-retired white women working forward and backward shift rotations had higher log-CRP compared with those working forward only (β=0.49, 95% CI: 0.02 to 0.96).

CONCLUSIONS

Shift workers had higher inflammatory markers compared with day workers and race-sex disparities should be examined further. These findings highlight a potential biological pathway linking work schedule demands and chronic disease.

Effects of shift work schedules, compensatory sleep, and work-family conflict on fatigue of shift-working nurses in Chinese intensive care units

BACKGROUND

Shift work is inevitable for nurses in intensive care units. Various studies explored nurses' fatigue in multiple hospital wards. However, few studies focused on fatigue among nurses in intensive care units.

AIMS

To determine the association between shift work schedules, compensatory sleep, work-family conflict, and fatigue of shift-working nurses in critical care units.

STUDY DESIGN

A descriptive cross-sectional multi-center study was conducted in March 2022 among intensive care nurses from five hospitals.

METHODS

Data were collected by online survey, including self-designed demographic questions, the Fatigue Scale-14, the Chinese adult daytime sleepiness scale, and the work-family scale. Pearson correlation was conducted for bivariate analysis. Independent-sample t-test, one-way ANOVA, and multiple linear regression analysis were performed to examine fatigue-related variables.

RESULTS

A total of 326 nurses responded to the survey with an effective response rate of 74.9%. The mean scores of physical fatigue and mental fatigue were 6.80 and 3.72, respectively. The bivariate analyses showed that work-family conflict was positively correlated with physical (r = 0.483, p < .001) and mental fatigue (r = 0.406, p < .001). Multiple linear regression results showed that work-family conflict, daytime sleepiness, and shift system were statistically significant factors influencing physical fatigue (F = 41.793, p < .001). Work-family conflict, sleep duration after the night shift, and daytime sleepiness were the main influencing factors of mental fatigue (F = 25.105, p < .001).

CONCLUSIONS

Nurses with higher work-family conflict, daytime sleepiness, and working 12-h shifts have higher levels of physical fatigue. Higher work-family conflict, shorter sleep duration after night shifts, and daytime sleepiness are associated with higher mental fatigue among intensive care nurses.

RELEVANCE TO CLINICAL PRACTICE

Nursing managers and nurses should consider work-family factors and compensatory sleep in their efforts to reduce fatigue. It is necessary to strengthen work-supporting strategies and compensatory sleep guidance for nurses to promote fatigue recovery.

Night work, season and alertness as occupational safety hazards in the Arctic: protocol for the Noralert observational crossover study among Norwegian process operators

INTRODUCTION

The objective of this study is to determine the effects of night work, Arctic seasonal factors and cold working environments on human functions relevant to safety. The study aims to quantify the contribution of (1) several consecutive night shifts, (2) seasonal variation on sleepiness, alertness and circadian rhythm and (3) whether a computational model of sleep, circadian rhythms and cognitive performance can accurately predict the observed sleepiness and alertness.

METHODS AND ANALYSIS

In an observational crossover study of outdoor and indoor workers (n=120) on a three-shift schedule from an industrial plant in Norway (70 °N), measurements will be conducted during the summer and winter. Sleep duration and quality will be measured daily by smartphone questionnaire, aided by actigraphy and heart rate measurements. Sleepiness and alertness will be assessed at regular intervals by the Karolinska Sleepiness Scale and the psychomotor vigilance test, respectively. Saliva samples will assess melatonin levels, and a blood sample will measure circadian time. Thermal exposures and responses will be measured by sensors and by thermography.

ETHICS AND DISSEMINATION

All participants will give written informed consent to participate in the study, which will be conducted in accordance with the Declaration of Helsinki. The Norwegian Regional Committee for Medical Research Ethics South-East D waivered the need for ethics approval (reference 495816). Dissemination plans include academic and lay publications, and partnerships with national and regional policymakers.

Individual, social and environmental factors influencing dietary behaviour in shift workers with type 2 diabetes working in UK healthcare: A cross-sectional survey

BACKGROUND

The present study aimed to understand the individual, social and environmental factors influencing dietary behaviour in shift workers with type 2 diabetes (T2D) working in UK healthcare settings.

METHODS

A cross-sectional study was conducted using data collected from an anonymous online survey. Participant agreement was measured using five-point Likert scale (strongly disagree to strongly agree) against 38 belief statements informed by the Theoretical Domains Framework (TDF) of behaviour change.

RESULTS

From the complete responses (n = 119), 65% worked shifts without nights, 27% worked mixed shift rota including nights and 8% worked only night shifts. The statements ranked with the highest agreements were in the TDF domains: Environment Context/Resources (ECR) - mainly identified as a barrier to healthy eating, Behaviour Regulation (BR) and intention (IN) - identified as enablers to healthy eating. For the belief statement 'the available options for purchasing food are too expensive' (ECR), 80% of night workers and 75% non-night workers agreed/strongly agreed. Taking their own food to work to prevent making unhealthy food choices (BR) had agreement/strong agreement in 73% of non-night and 70% night workers; 74% non-night workers and 80% of night workers agreed/strongly agreed with the statement 'I would like to eat healthily at work' (IN). Mixed shift workers agreed that following dietary advice was easier when working a non-night compared to a night shift (p = 0.002).

CONCLUSIONS

Access and affordability of food were identified as important determinants of dietary behaviour during shifts. The findings support interventions targeting the food environment for shift workers with T2D.

The Associations of Chronotype and Shift Work With Rheumatoid Arthritis

The circadian clock regulates multiple aspects of human physiology including immunity. People have a circadian preference termed chronotype. Those with an evening preference may be better suited to shift work, but also carry higher risk of adverse health. Shift work leads to misalignment of circadian rhythms and is associated with increased risk of inflammatory disease such as asthma and cancer. Here, we investigate the association between chronotype, shift work, and rheumatoid arthritis (RA). The associations between exposures of shift work and chronotype on risk of RA were studied in up to 444,210 U.K. Biobank participants. Multivariable logistic regression models were adjusted for covariates: age, sex, ethnicity, alcohol intake, smoking history, Townsend Deprivation Index (TDI), sleep duration, length of working week, and body mass index (BMI). After adjusting for covariates, individuals with a morning chronotype had lower odds of having rheumatoid arthritis (RA; odds ratio [OR]: 0.93, 95% confidence interval [CI]: 0.88-0.99) when compared to intermediate chronotypes. The association between morning chronotype and RA persisted with a more stringent RA case definition (covariate-adjusted OR: 0.89, 95% CI: 0.81-0.97). When adjusted for age, sex, ethnicity, and TDI, shift workers had higher odds of RA (OR: 1.22, 95% CI: 1.1-1.36) compared to day workers that attenuated to the null after further covariate adjustment (OR: 1.1, 95% CI: 0.98-1.22). Morning chronotypes working permanent night shifts had significantly higher odds of RA compared to day workers (OR: 1.89, 95% CI: 1.19-2.99). These data point to a role for circadian rhythms in RA pathogenesis. Further studies are required to determine the mechanisms underlying this association and understand the potential impact of shift work on chronic inflammatory disease and its mediating factors.

Pros and cons of quick returns-a cross-sectional survey among Swedish nurses and nurse assistants

Short rest (<11h) between evening and day shifts-known as quick returns (QRs)-impede recovery and may impair health. Nevertheless, QRs remain popular among some shift workers. This study explores nurses' and nurse assistants' perceptions of the merits and demerits of QRs from individual and organizational perspectives. Participants were recruited from eleven wards at two Swedish hospitals as part of a larger quasi-experimental intervention study. The majority (79%) had influence over their work schedules. Frequency distributions of responses are presented. Ninety six undertook a baseline survey regarding recovery, tolerance and work performance in relation to QRs. A majority experienced difficulties unwinding before bedtime (76%), insufficient sleep (80%), and daytime fatigue (72%). A third experienced an increased risk of errors and mistakes. However, QRs appeared to facilitate taking reports from patients and planning work, as this task was more often rated as 'very easy' following a QR compared to other shift combinations. Tolerance of QRs varied substantially. In conclusion, QRs seem to benefit continuity in work processes, but may do so at the expense of recovery and safety. Wards planning to reduce QRs-through participatory or fixed schedule models-should consider impacts on work processes.

Circadian misalignment increases 24-hour acylated ghrelin in chronic shift workers: a randomized crossover trial

OBJECTIVE

Shift workers typically experience misalignment between their circadian system and behavioral/environmental cycles and have an increased risk for obesity. Experimental studies in non-shift workers have suggested that circadian misalignment can disrupt energy balance regulation. This study examined the impact of circadian misalignment in the most relevant population, i.e., chronic shift workers.

METHODS

Seven healthy chronic night shift workers underwent a randomized crossover study with two 3-day laboratory protocols: a night work protocol including 12-hour inverted behavioral/environmental cycles (circadian misalignment) and a day work protocol (circadian alignment).

RESULTS

Circadian misalignment led to a ~17% increase in 24-hour acylated ghrelin levels in the chronic shift workers (p = 0.009). Consistently, circadian misalignment resulted in ~14% higher hunger at breakfast in the night shift (p = 0.04). Circadian misalignment did not significantly change fasting and postprandial energy expenditure or respiratory exchange ratio (all p > 0.32). Unexpectedly, 24-hour behavioral activity levels were ~38% higher (p < 0.0001) during circadian misalignment, despite a concurrent increase in sleepiness (p = 0.03).

CONCLUSIONS

These results reveal that circadian misalignment, while carefully controlling for dietary intake, increases acylated ghrelin in chronic shift workers. Further studies should test whether the observed acute effects of circadian misalignment in chronic shift workers contribute to their increased obesity risk in the long term.

Effect of Short versus Long Duration Naps on Blood Pressure during Simulated Night Shift Work: A Randomized Crossover Trial

OBJECTIVE

Blunting of the sleep-related dip in blood pressure (BP) has been linked to numerous cardiovascular outcomes including myocardial infarction. Blunting of BP dipping occurs during night shift work and previous research suggest that a 60-min or longer on-shift nap is needed to restore normal/healthy BP dipping. We sought to determine the effect of different durations of napping on BP during and following simulated night shifts. We hypothesized that the greatest benefit in terms of restoration of normal BP dipping during night shift work would be observed during a longer duration nap versus a shorter nap opportunity.

METHODS

We used a randomized crossover laboratory-based study design. Participants consented to complete three separate 72-hr conditions that included a 12-hr simulated night shift. Nap conditions included a 30-min and 2-hr nap compared to a no-nap condition. Ambulatory BP monitoring was assessed hourly and every 10-30 mins during in-lab naps. Blunted BP dipping during in-lab naps was the primary outcome. Goal enrollment of 25 (35 with attrition) provided 80% power to detect a mean difference of 5 mmHg in BP between nap conditions.

RESULTS

Of the 58 screened, 28 were consented, and 26 completed all three 72-hr conditions. More than half (53.6%) were female. Mean age was 24.4 years (SD7.2). Most (85.7%) were certified as emergency medical technicians or paramedics. The mean percentage dip in systolic BP (SBP) and diastolic BP (DBP) did not differ between the 30-min and 2-hr nap conditions (p > 0.05), yet a greater proportion of participants experienced a 10-20% dip in SBP or DBP during the 2-hr nap versus the 30-min nap (p < 0.05). For every additional minute of total sleep during the 30-min nap, the percentage of SBP dip improved by 0.60%, and the percentage of DBP dip improved by 0.68% (p < 0.05). These improvements approximate to a 6% per minute relative advancement toward normal/healthy BP dipping.

CONCLUSIONS

Restoration of a normal/healthy dip in BP is achievable during short and long duration nap opportunities during simulated night shift work. Our findings support the hypothesis that BP dipping is more common during longer 2-hr versus shorter 30-min naps.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT04469803. Registered on 9 July 2020.

Shift Work and Sleep Disturbance in the Oil Industry

BACKGROUND

Rotating shift work is common in high-hazard industries, despite documented associations with sleep disturbance and impairment. In the oil industry, where rotating and extended shift schedules are used to staff safety-sensitive positions, work intensification and increasing overtime rates have been broadly documented over the last few decades. Research on the impacts of these work schedules on sleep and health has been limited for this workforce.

METHODS

We examined sleep duration and quality among rotating shift workers in the oil industry and explored associations between schedule characteristics, sleep, and health outcomes. We recruited hourly refinery workers from the West and Gulf Coast oil sector members of the United Steelworkers union.

FINDINGS

Impaired sleep quality and short sleep durations were common and associated with health and mental health outcomes common among shift workers. Shortest sleep durations followed shift rotations. Early rise and start times were associated with shorter sleep duration and poorer sleep quality. Drowsiness and fatigue-related incidents were common.

CONCLUSION/APPLICATION TO PRACTICE

We observed lower sleep duration and quality and increased overtime in 12-hour rotating shift schedules. These long workdays with early start times may reduce available hours for quality sleep; here they were associated with reduced exercise and leisure activity which correlated with good sleep. This safety-sensitive population appears severely impacted by poor sleep quality, which has broader implications for process safety management. Later start times, slower rotation, and a reconsideration of two-shift schedules are interventions to consider for improving sleep quality among rotating shift workers.

Immune disruptions and night shift work in hospital healthcare professionals: The intricate effects of social jet-lag and sleep debt

Objectives

We aimed to examine the effects of circadian and sleep rhythm disruptions on immune biomarkers among hospital healthcare professionals working night shifts and rotating day shifts.

Methods

Hospital nurses working either as permanent night shifters (n=95) or as day shifters rotating between morning and afternoon shifts (n=96) kept a daily diary on their sleep and work schedules over a full working week. Blood samples were collected at the beginning and end of the last shift during the week, and participants were categorized into three groups based on work shift: morning shift (39 day shifters sampled at 7:00 and 14:00), afternoon shift (57 day shifters sampled at 14:00 and 21:00), and night shift (95 night shifters sampled at 21:00 and 7:00). Circulating blood counts in immune cells, interleukin-6 and C-reactive protein concentrations as well as total sleep time per 24 hours during work days (TST24w) and free days (TST24f), sleep debt (TST24f - TST24w) and social jet-lag (a behavioral proxy of circadian misalignment) were assessed.

Results

Compared with day shifters, night shifters had shorter sleep duration (TST24w=5.4 ± 1.4h), greater sleep debt (3.2 ± 1.4 h) and social jet-lag (6.7 ± 2.4 h). Variations of immune biomarkers concentrations were consistent with the expected diurnal variations among day shifters (i.e., low level in the morning, increase during the day, peak value in the evening). By contrast, in night shifters, blood concentrations of total lymphocytes, T-helper cells, cytotoxic T-cells, memory B-cells and interleukin-6 were lower at 21:00, increased during the night, and reached higher values at 7:00. Multivariate analyses ruled out significant impact of TST24w, sleep debt, and social jet-lag on immune biomarkers concentrations among day shifters. In contrast, among night shifters, multivariate analyses indicated a combined effect of total sleep time (TST24w), sleep debt and social jet-lag for total lymphocytes and T-helper cells but only a social jet-lag effect for interleukin-6 and a single total sleep time effect for neutrophil and B-Cells.

Conclusions

Altogether, our results point to intricate response patterns of immune rhythms to circadian misalignment and sleep debt in night shifters. Specifically, these altered pattern expressions of immune cells may increase vulnerability to infections and reduce vaccination efficiency in night workers.

Sleep Disturbances and Health Consequences Induced by the Specificity of Nurses' Work

INTRODUCTION

Nursing staff working in a shift or night system are exposed to sleep disorders, which has a direct impact on the emergence of dangerous health consequences for them. Melatonin secretion is abnormal at night and the circadian rhythm is disturbed. The aim of the study was to assess the occurrence of sleep disorders and their consequences for the body in a group of representative nursing staff working in a shift and night system.

PARTICIPANTS

The study was conducted among 126 nurses who are generally healthy, employed in health care facilities in the Małopolskie voivodship.

METHODS

The Athens Insomnia Scale consisting of 8 test items was used to obtain research material: falling asleep, waking up at night, waking up in the morning, total sleep time, sleep quality, well-being the next day, mental and physical fitness the next day, and sleepiness during the next day. As well as an original questionnaire.

RESULTS

The research showed significant negative consequences of shift work on the health of health-care workers. The subjects noticed symptoms related to the nervous system, such as increased nervous tension 53%, lack of patience in 62% of all respondents. As many as 85% pointed to the negative impact of shift work on their family life, 82% of all respondents on social life and 56% of all respondents on sex life. The other variables were not confirmed.

CONCLUSIONS

Symptoms of insomnia are common among night-work nurses.

A feast-and-famine pattern of sleep: Do railway staff get the sleep they need?

The relationship between sleep and health and wellbeing is receiving increasing attention in our society, following decades of research that has demonstrated the impact of insufficient sleep on performance and health. Fatigue has been identified as a factor in 21% of high-risk incidents in the GB rail industry, and insufficient sleep and long periods of being awake are known to be two key contributors to fatigue. This paper presents evidence from a recent survey conducted in the GB rail industry, which enabled the sleep and wakefulness of railway workers to be quantified. There were 7807 responses to the survey, which represents a very large sample. Responses were primarily collected online, though paper copies were made available in some organisations. Respondents reported sleeping less when working nights, more when working days, and the most on days off, which suggests a feast-and-famine pattern of sleep. 41% were getting 6 h of sleep or less when working days, compared to 63% when working nights. Getting 6 h or less of sleep was associated with excessive daytime sleepiness. Although it is accepted that individuals' sleep requirements vary, the patterns that shift workers reported in this survey suggest that many are not achieving the amount of sleep they need. The findings of the survey presented in this paper highlight that there is work to be done to understand and address the causes of insufficient sleep in railway workers.

Moderate-intensity aerobic exercise as an adjunct intervention to improve sleep quality among rotating shift nurses

Nurses working rotating shifts (RS) are at risk of circadian rhythm disruption, which can affect sleep quality and can lead to emotional stress, anxiety, and depression. Aerobic exercise is a type of repetitive and structured physical activity that involves the metabolic system, which utilizes oxygen to produce energy and has been demonstrated to improve shift-workers' health and well-being. The main purpose of engaging in regular moderate-intensity aerobic exercise is to improve cardiopulmonary fitness and functional capacity. When engaging in moderate-intensity aerobic exercise, the increase in arterial pressure is accompanied by a simultaneous increase in heart rate, which signifi-cantly contributes to the rise in blood pressure, which is reversed after exercise due to an increase in parasympathetic activity and a decrease in sympathetic activity. Moderate-intensity aerobic exercise includes walking at a moderate pace, water aerobics, dancing, recreational swimming, gardening, table tennis, and stair climbing at a moderate pace and represents a cost-effective health promotion strategy for im-proving sleep quality and duration. Adherence to a moderate-intensity aerobic exercise program may increase both sleep quality and duration by improving melatonin concentrations, endocrine activities, heart rate and slow wave sleep among nurses working RS. Occupational medicine practitioners should consider creating a workplace health promotion program that incorporates moderate-intensity aerobic exercise for RS-nurses to minimize the impact of shift work on their sleep quality.

Unanticipated daytime melatonin secretion on a simulated night shift schedule generates a distinctive 24-h melatonin rhythm with antiphasic daytime and nighttime peaks

The daily rhythm of plasma melatonin concentrations is typically unimodal, with one broad peak during the circadian night and near-undetectable levels during the circadian day. Light at night acutely suppresses melatonin secretion and phase shifts its endogenous circadian rhythm. In contrast, exposure to darkness during the circadian day has not generally been reported to increase circulating melatonin concentrations acutely. Here, in a highly-controlled simulated night shift protocol with 12-h inverted behavioral/environmental cycles, we unexpectedly found that circulating melatonin levels were significantly increased during daytime sleep (p < .0001). This resulted in a secondary melatonin peak during the circadian day in addition to the primary peak during the circadian night, when sleep occurred during the circadian day following an overnight shift. This distinctive diurnal melatonin rhythm with antiphasic peaks could not be readily anticipated from the behavioral/environmental factors in the protocol (e.g., light exposure, posture, diet, activity) or from current mathematical model simulations of circadian pacemaker output. The observation, therefore, challenges our current understanding of underlying physiological mechanisms that regulate melatonin secretion. Interestingly, the increase in melatonin concentration observed during daytime sleep was positively correlated with the change in timing of melatonin nighttime peak (p = .002), but not with the degree of light-induced melatonin suppression during nighttime wakefulness (p = .92). Both the increase in daytime melatonin concentrations and the change in the timing of the nighttime peak became larger after repeated exposure to simulated night shifts (p = .002 and p = .006, respectively). Furthermore, we found that melatonin secretion during daytime sleep was positively associated with an increase in 24-h glucose and insulin levels during the night shift protocol (p = .014 and p = .027, respectively). Future studies are needed to elucidate the key factor(s) driving the unexpected daytime melatonin secretion and the melatonin rhythm with antiphasic peaks during shifted sleep/wake schedules, the underlying mechanisms of their relationship with glucose metabolism, and the relevance for diabetes risk among shift workers.

Biological and practical considerations regarding circadian rhythm and mental health relationships among nurses working night shifts: a narrative review and recommendations

BACKGROUND

Sleep is a vital physiological process regulated by the circadian clock and homeostatic mechanisms. Shift work is necessary to ensure continuity of healthcare provision. Worldwide, nurses work night shifts on a rotational or permanent basis.

OBJECTIVE

To analyse the impact of circadian rhythm disruption due to night shift work on the mental wellbeing of nurses.

METHODS

The literature search was conducted using PubMed and Scopus electronic databases. Selection criteria include studies published in English between 1997 and 2021 that examined the impact of night-shift work on the mental health of nurses.

RESULTS

The searches generated a total of 22 records on the PubMed database, and 9 records on the Scopus database, and a total of 31 studies. 29 papers were identified after removal of duplicates. However, 29 articles were screened based on the review of titles and abstracts. 19 articles were identified for full-test review. Seven papers were included in this review.

CONCLUSIONS

Disrupted circadian rhythms and poor sleep quality and quantity have been identified as two of the most significant elements in the long-term effects of night-shift work on nurses' mental health. Strategies and policies to promote workplace health may reduce the occurrence of mental health disorders among night-shift nurses, whether the shifts are rotational or permanent. Nursing supervisors and hospital administrators should consider developing new guidelines to minimize the negative impact of night shift rotations on mental health and the quality of life among nurses.

The Effects of Shift Work on Cardio-Metabolic Diseases and Eating Patterns

Energy metabolism is tightly linked with circadian rhythms, exposure to ambient light, sleep/wake, fasting/eating, and rest/activity cycles. External factors, such as shift work, lead to a disruption of these rhythms, often called circadian misalignment. Circadian misalignment has an impact on some physiological markers. However, these proxy measurements do not immediately translate into major clinical health outcomes, as shown by later detrimental health effects of shift work and cardio-metabolic disorders. This review focuses on the effects of shift work on circadian rhythms and its implications in cardio-metabolic disorders and eating patterns. Shift work appears to be a risk factor of overweight, obesity, type 2 diabetes, elevated blood pressure, and the metabolic syndrome. However, past studies showed discordant findings regarding the changes of lipid profile and eating patterns. Most studies were either small and short lab studies, or bigger and longer cohort studies, which could not measure health outcomes in a detailed manner. These two designs explain the heterogeneity of shift schedules, occupations, sample size, and methods across studies. Given the burden of non-communicable diseases and the growing concerns about shift workers' health, novel approaches to study shift work in real contexts are needed and would allow a better understanding of the interlocked risk factors and potential mechanisms involved in the onset of metabolic disorders.

Prediction of shiftworker alertness, sleep, and circadian phase using a model of arousal dynamics constrained by shift schedules and light exposure

STUDY OBJECTIVES

The study aimed to, for the first time, (1) compare sleep, circadian phase, and alertness of intensive care unit (ICU) nurses working rotating shifts with those predicted by a model of arousal dynamics; and (2) investigate how different environmental constraints affect predictions and agreement with data.

METHODS

The model was used to simulate individual sleep-wake cycles, urinary 6-sulphatoxymelatonin (aMT6s) profiles, subjective sleepiness on the Karolinska Sleepiness Scale (KSS), and performance on a Psychomotor Vigilance Task (PVT) of 21 ICU nurses working day, evening, and night shifts. Combinations of individual shift schedules, forced wake time before/after work and lighting, were used as inputs to the model. Predictions were compared to empirical data. Simulations with self-reported sleep as an input were performed for comparison.

RESULTS

All input constraints produced similar prediction for KSS, with 56%-60% of KSS scores predicted within ±1 on a day and 48%-52% on a night shift. Accurate prediction of an individual's circadian phase required individualized light input. Combinations including light information predicted aMT6s acrophase within ±1 h of the study data for 65% and 35%-47% of nurses on diurnal and nocturnal schedules. Minute-by-minute sleep-wake state overlap between the model and the data was between 81 ± 6% and 87 ± 5% depending on choice of input constraint.

CONCLUSIONS

The use of individualized environmental constraints in the model of arousal dynamics allowed for accurate prediction of alertness, circadian phase, and sleep for more than half of the nurses. Individual differences in physiological parameters will need to be accounted for in the future to further improve predictions.

Comparison of Sleep and Attention Metrics Among Nurses Working Shifts on a Forward- vs Backward-Rotating Schedule

IMPORTANCE

The association of fast backward-rotating shift work (ie, anticlockwise sequence of afternoon, morning, and night shifts) with subjective and objective measures of sleep-wake quality, daytime attention, and tiredness of health care workers has not yet been established.

OBJECTIVE

To investigate the association of shift rotation direction with tiredness, sleepiness, and sustained attention among nurses working forward- and backward-rotating shifts.

DESIGN, SETTING, AND PARTICIPANTS

Data of this cohort study were collected from nurses working at 5 midsized Italian hospitals. The nurses had either a forward-rotating schedule (ie, morning to afternoon to night) and or a backward-rotating schedule (ie, afternoon to morning to night). The data were collected from July 2017 to February 2020. Data analysis was performed from May to October 2020.

EXPOSURES

Participants were working either forward- or backward-rotating schedules, in which the sequence of 3 shifts (morning, afternoon, and night) changed in a clockwise or anticlockwise direction.

MAIN OUTCOMES AND MEASURES

Sleep data were collected using the Karolinska Sleepiness Scale and Pittsburgh Sleep Quality Index. Sustained attention was measured using the Psychomotor Vigilance Task. Tiredness was evaluated using the Tiredness Symptom Scale.

RESULTS

A total of 144 nurses (mean [SE] age, 41.3 [0.8] years; 92 women [63.9%]) participated in the study; 80 nurses had forward-rotating schedules, and 64 had backward-rotating schedules. Nurses with irregular sleep-wake patterns due to night shift work had poor sleep quality (46 [57.5%] in forward-rotating schedule group; 37 [57.8%] in backward-rotating schedule group). Nurses working backward-rotating shifts exhibited significantly greater sleepiness (F1,139 = 41.23; P < .001) and cognitive slowing (ie, longer median reaction times; F1,139 = 42.12; P < .001) than those working forward rotations. Importantly, these differences were not affected by age, years of employment, and quality of sleep. Of nurses working on a backward-rotating schedule, 60 (93.8%) reported elevated sleepiness (Karolinska Sleepiness Scale score ≥7) after the night shift. The median reaction time (F1,139 = 42.12; P < .001), 10% fastest reaction time (F1,139 = 97.07; P < .001), minor lapses (F1,139 = 46.29; P < .001), and reaction time distribution (F1,139 = 60.13; P < .001) of nurses on backward-rotating schedules indicated a lower level of vigilance, which is negatively associated with neurobehavioral performance.

CONCLUSIONS AND RELEVANCE

In this study, both shift rotation models were negatively associated with health and cognitive performance. These findings suggest that forward shift rotation may be more beneficial than backward rotation for several measured performance attentional outcomes and sleepiness. Optimization of shift rotations should be implemented to decrease the combination of the negative outcomes associated with shift work and reduce the potential risk of medical errors in health care systems.

Human circadian variations

Circadian rhythms, present in most phyla across life, are biological oscillations occurring on a daily cycle. Since the discovery of their molecular foundations in model organisms, many inputs that modify this tightly controlled system in humans have been identified. Polygenic variations and environmental factors influence each person's circadian rhythm, contributing to the trait known as chronotype, which manifests as the degree of morning or evening preference in an individual. Despite normal variation in chronotype, much of society operates on a "one size fits all" schedule that can be difficult to adjust to, especially for certain individuals whose endogenous circadian phase is extremely advanced or delayed. This is a public health concern, as phase misalignment in humans is associated with a number of adverse health outcomes. Additionally, modern technology (such as electric lights and computer, tablet, and phone screens that emit blue light) and lifestyles (such as shift or irregular work schedules) are disrupting circadian consistency in an increasing number of people. Though medical and lifestyle interventions can alleviate some of these issues, growing research on endogenous circadian variability and sensitivity suggests that broader social changes may be necessary to minimize the impact of circadian misalignment on health.

Dose-response relationship between working hours and hypertension: A 22-year follow-up study

Hypertension causes a substantial burden to society. Some studies found that hypertension was associated with the working type and working hours. The purpose of the current study is to assess the dose-response relationship between working hours and hypertension.Data of 12,080 adults aged 18 to 65 years who attended the China Health and Nutrition Survey (CHNS) between 1989 and 2011 were analyzed. Hypertension was determined based on systolic and/or diastolic blood pressure measures, or having doctor-diagnosed hypertension. Multivariable Cox regression and restricted cubic spline to assess the dose-response relationship between working hours and hypertension.A total of 12,080 participants including 5852 females and 6228 males. By the last follow-up (2011), a total of 830 participants were hypertensive, with an incidence of 6.9%. After adjusting socio-demographic, lifestyle factors, as well as occupation type, compared with those who worked 35 to 49 hours per week, participants who worked no more than 34 hours per week (HR: 1.21, 95%CI: 1.03-1.41) and at least 56 hours per week (HR: 1.38, 95%CI: 1.19-1.59) had a higher risk of hypertension. The significant association between long working hours (at least 56 hours per week) and hypertension was observed among females (HR: 1.38, 95%CI: 1.16-1.64) and males (HR: 1.36, 95%CI: 1.04-1.78). Among manual workers, the relationship between long working hours and hypertension was observed (HR: 1.49, 95%CI: 1.10-2.02). The relationship between long working hours (HR: 1.21, 95%CI: 1.01-1.44) and short working hours (HR: 1.37, 95%CI: 1.16-1.61) and hypertension was observed among nonmanual workers. The hazard ratio of hypertension and working time displayed U-shape non-linear relationship (Ptrend < .001, non-linear P < .001). The non-linear response-dose relationship was found in manual worker, nonmanual worker, and male (Ptrend < .001, non-linear P < .001).The association between working time and hypertension showed U-shape relationship. Specifically, overtime work was an important occupational risk factors for adults, and short work time was related to hazard ratio of hypertension in nonmanual workers.

Changes in Fatigue Levels and Sleep Measures of Hospital Nurses During Two 12-Hour Work Shifts

OBJECTIVE

The aims of this study were to explore nurses' fatigue levels and sleep measures during two 12-hour consecutive day shifts and examine the relationships between nurses' fatigue levels within shifts and their previous-night sleep characteristics.

BACKGROUND

Monitoring changes in fatigue and sleep is important to enable effective fatigue management.

METHODS

This was a descriptive, repeated-measures study. Data were collected using surveys and actigraphy 4 times during each consecutive shift (7:00 am-7:30 pm).

RESULTS

General fatigue levels started trending up 4 hours after the start of work; highest levels were reported at 7:30 pm. Fatigue levels accumulated across consecutive shifts. Subjective sleep quality was higher the night before the 2nd shift than the night before the 1st shift. Nurses' poor sleep the night before a shift was related to increased fatigue levels during the next shift.

CONCLUSION

It is important to consider when fatigue management interventions will be most effective and to consider previous-night's sleep when monitoring fatigue.

Meta-analysis of differences in sleep quality based on actigraphs between day and night shift workers and the moderating effect of age

OBJECTIVES

This study was to conduct a meta-analysis of studies that used actigraphs to compare the influence of day and night shifts on the sleep quality of workers as well as examine the moderating effect of age.

METHODS

Databases including PubMed, CINAHL, the Cochrane Library, MEDLINE, and EBSCOhost were searched for relevant studies published in English between January 1st, 2000 and April 30st, 2021. Our main targets were studies that used actigraphs to assess the sleep quality of night shift workers. This meta-analysis included 12 papers and was performed using Comprehensive Meta-Analysis (CMA) Version 3.0. Effect sizes were displayed in a forest plot using standardized mean difference (SMD) and 95% confidence intervals (CI).

RESULTS

Among the sleep quality indices of the day and night shift workers, no significant difference existed in terms of sleep efficiency (SE) (SMD = 0.27, 95% CI: -0.03-0.57), whereas night shift workers presented longer sleep-onset latency (SOL) (SMD = 0.62, 95% CI: 0.15-1.08), greater wake after sleep onset (WASO) (SMD = 0.41, 95% CI: 0.12-0.70), and longer total sleep time (TST) (SMD = 0.85, 95% CI: 0.32-1.39) than did day shift workers. The differences between the day and night shift workers in SOL, WASO, and TST did not vary with age.

CONCLUSIONS

Among the sleep quality indices, night shift workers presented longer SOL and greater WASO than did day shift workers. However, night shift workers could regulate their rest time and had adequate TST; thus, their SE was not different from that of day shift workers.

Sleep quality does not mediate the negative effects of chronodisruption on body composition and metabolic syndrome in healthcare workers in Ecuador

BACKGROUND AND AIMS

The objective of the present work was to determine to what extent sleep quality may mediate the association between chronodisruption (CD) and metabolic syndrome (MS), and between CD and body composition (BC).

METHODOLOGY

Cross-sectional study which included 300 adult health workers, 150 of whom were night shift workers and thereby exposed to CD. Diagnosis of MS was made based on Adult Treatment Panel III criteria. Sleep quality was measured using the Pittsburgh Sleep Quality Index. Body mass index (BMI), fat mass percentage, and visceral fat percentage were measured as indicators of body composition (BC). Data were analyzed using logistic, linear regression and structural equation models.

RESULTS

The odds of health workers exposed to CD to suffer MS was 22.13 (IC₉₅ 8.68-66.07) when the model was adjusted for age, gender, physical activity and energy consumption. CD was also significantly associated with an increase in fat mass and visceral fat percentages, but not to BMI. Surprisingly, there was not enough evidence supporting the hypothesis that sleep quality contributes to the association between CD and MS or between CD and BC.

CONCLUSIONS

Sleep quality does not mediate the negative effects of CD on MS nor on BC.

Home-EEG assessment of possible compensatory mechanisms for sleep disruption in highly irregular shift workers - The ANCHOR study

Study objectives

While poor sleep quality has been related to increased risk of Alzheimer’s disease, long-time shift workers (maritime pilots) did not manifest evidence of early Alzheimer’s disease in a recent study. We explored two hypotheses of possible compensatory mechanisms for sleep disruption: Increased efficiency in generating deep sleep during workweeks (model 1) and rebound sleep during rest weeks (model 2).

Methods

We used data from ten male maritime pilots (mean age: 51.6±2.4 years) with a history of approximately 18 years of irregular shift work. Subjective sleep quality was assessed with the Pittsburgh Sleep Quality Index (PSQI). A single lead EEG-device was used to investigate sleep in the home/work environment, quantifying total sleep time (TST), deep sleep time (DST), and deep sleep time percentage (DST%). Using multilevel models, we studied the sleep architecture of maritime pilots over time, at the transition of a workweek to a rest week.

Results

Maritime pilots reported worse sleep quality in workweeks compared to rest weeks (PSQI = 8.2±2.2 vs. 3.9±2.0; p<0.001). Model 1 showed a trend towards an increase in DST% of 0.6% per day during the workweek (p = 0.08). Model 2 did not display an increase in DST% in the rest week (p = 0.87).

Conclusions

Our findings indicated that increased efficiency in generating deep sleep during workweeks is a more likely compensatory mechanism for sleep disruption in the maritime pilot cohort than rebound sleep during rest weeks. Compensatory mechanisms for poor sleep quality might mitigate sleep disruption-related risk of developing Alzheimer’s disease. These results should be used as a starting point for future studies including larger, more diverse populations of shift workers.

Sleep quality: a critical determinant of perceived quality of life in the administrative-technical workers of an Italian university

OBJECTIVE

This observational study aims to analyze the quality of life of the administrative/technical employees of the University of Ferrara and its relationship with sleep quality, chronotype, and family components.

PATIENTS AND METHODS

We invited all employees (528) to fill a data collection form (age, gender, education level, number of family components, being caregiver and job-related factors) and 3 anonymous questionnaires (VR-12 Health-Related Quality of Life, Pittsburgh Sleep Quality Index, and Morningness-Eveningness Questionnaire).

RESULTS

Out of 323 respondents, 72.5% were female, 76.4% had an age between 41-60 years old, 63.8% had a university degree, and 67.5% an administrative profile. Considering family-related characteristics: 81.1% of respondents lived with ≥2 people, 35.3% had children, and 31.9% declared to be caregiver of a family member, not necessarily co-housing. Most of the employees resulted to be Morning-type (48.6%) and Intermediate-type (46.8%), with a very limited group of Evening-types (4.6%). Quality of sleep resulted to be the main factor affecting the health-related quality of life. Near half of our sample had poor sleep quality (49.2%; 95% CI: 43.6-54.8%). PSQI score resulted significantly higher for people who were caregivers of a familiar (7.0 ± 3.6 vs. 6.1 ± 3.6, p=0.022). Family size and being caregiver of a familiar resulted in significant factors for sleep quality, and indirectly for health-related quality of life.

CONCLUSIONS

The quality of sleep is the most influencing parameter of the workers' quality of life. Family size and being caregiver of a family member indirectly affect the quality of life by influencing sleep quality. Appropriate consideration and management of these aspects in the working context could improve workers' well-being.

Relationship between white matter microstructure and work hours

Human social activities are realized by a synergy of neuronal activity over various regions of the brain, which is supported by their connectivity. In the present study, we examined associations between social activities, represented by work hours, and brain connectivity as quantified using diffusion tensor imaging (DTI). In 483 healthy participants, DTI analysis was performed using 3 T magnetic resonance imaging, and work hours were calculated, considering hours of paid employment (the "Work for Pay" category), hours of housework (the "Work at Home" category), and hours of school-related study (the "Student" category). The correlations between each class of work time and DTI indices were analyzed. The mean diffusivity (MD) values of the anterior limb of the internal capsule (ALIC) and the superior fronto-occipital fasciculus (SFO) were negatively correlated with total work hours (ALIC: r = -0.192, p =  2.3 × 10^-5; SFO: r = -0.161, p =  3.8 × 10^-4). We also found that the MD values of the ALIC and the SFO were correlated with work hours in the Work for Pay category (ALIC: r = -0.211, p =  3.2 × 10^-6; SFO: r = -0.163, p =  3.4 × 10^-4) but not with those in the Work at Home category or the Student category. These results suggest that social activity is associated with the white matter microstructure of the ALIC and the SFO. The main difference between "Work for Pay" and the other two social activities appears to be the type of motivation-for example, external versus internal. Therefore, the white matter microstructure of the ALIC and SFO may be related to externally motivated social activities.

Poor glycemic control in workers with diabetes mellitus in relation to long working hours: a cross-sectional study

We aimed to investigate the association between working hours and poor glycemic control using a cross-sectional data from the Korea National Health and Nutrition Examination Survey (KNHANES). The participants who were medically diagnosed with diabetes mellitus by a physician were defined as diabetic patients, and patients with hemoglobin A1c (HbA1c) levels >9.0% were considered as "poorly controlled". The association of HbA1c level with working hours was examined by linear regression plot, using local regression line and logistic regression analyses. The local regression plot showed a smooth increasing pattern: the longer were the working hours, the higher were the HbA1c levels, even though it was not statistically significant. Odds ratios of working hours over 52 h per week were higher with the criterion of poor diabetic control (HbA1c >9.0%). The results were significant in elderly female workers (odds ratio 3.30, 95% confidence interval 1.19-9.18). Long working hours were associated with poor glycemic control, specifically among elderly female workers with diabetes.

The Impact of Shift Work on Psychosocial Functioning and Quality of Life Among Hospital-Employed Nurses: A Cross-Sectional Comparative Study

BACKGROUND

Approximately 20% of the European labour force is involved in some type of shift work, with nurses being on the forefront. In Bosnia and Herzegovina, a specific work scheme is pervasive in the health care arena, where all nurses involved in shift work are committed to eight night shifts per month - unlike other European countries that restrict the number of night shifts. Accordingly, we aimed to investigate whether such shift work significantly affects psychosocial functioning and the quality of life of hospital nursing personnel in this country.

SUBJECTS AND METHODS

A comparative cross-sectional study design was applied on a total of 157 hospital nursing professionals at the University Clinical Hospital Mostar during 2019. Subjects were divided into two groups: a total of 51% study subjects worked in specific shifts (12-hour day shift / 24 hours off / 12-hour night shift / 48 hours off), while 49% subjects worked in accordance with the regular 7-hour daily schedule. Standard Shiftwork Index (SSI) questionnaire was used, alongside comprehensive socio-demographic and quality of life appraisal. Descriptive and inferential statistical methods were applied, and statistical significance was set at p<0.05.

RESULTS

This study demonstrated increased amounts of stress, reduced coping abilities and reduced levels of life enjoyment in shift work nurses in comparison to day work nurses. Furthermore, increased anxiety, stress, psychoorganic symptoms and sleep disturbances were significantly more common in shift work hospital nursing staff. In our study, nurses that worked in shifts have experienced negative externalities such as decreased social functioning, as well as reduced family and leisure time. Conversely, significantly higher satisfaction rates with shift work were only shown in regards to compensation.

CONCLUSIONS

Our results reveal many detrimental effects of shift work and contribute to the field of research that is still laden with gaps in understanding its exact impact on the overall health of nursing personnel. Going forward, prospective (and even interventional) studies will be needed to disentangle the exact interplay between work-related factors in various health care systems and subsequent psychosocial disorders in health personnel.

Influence of sleep-wake cycle on body mass index in female shift-working nurses with sleep quality as mediating variable

This study investigated the relationship between the sleep-wake cycle and body mass index (BMI) of female shift-working nurses and examine the mediating effect of sleep quality on this relationship. We recruited a total of 147 female nurses working monthly rotating shifts at a teaching hospital in Taiwan from the day (n=63), evening (n=50), and night (n=34) shifts. Our research instruments utilized a questionnaire to collect demographic and work-related information, the Pittsburgh Sleep Quality Index (PSQI), and actigraphs to record sleep patterns for seven consecutive days. The sleep-wake cycles were then estimated using the dichotomy index (I<O). The I<O values were negatively associated with both BMI (β=-0.28, p=0.001) and PSQI scores (β=-0.29, p<0.001), the bootstrapping results indicated that the estimate of the indirect effect was -0.28, and the 95% confidence interval ranged from -0.68 to -0.05. For female shift-working nurses, sleep quality mediates the influence of the sleep-wake cycle on BMI, indicating that the maintenance of a regular sleep-wake cycle and good sleep quality could be important for female shift-working nurses.

Shift Work and Working at Night in Relation to Breast Cancer Incidence

BACKGROUND

Night shift work has been classified by the International Agency for Research on Cancer as a probable carcinogen in humans. Several studies have assessed night shift work in relation to breast cancer risk, with inconsistent results.

METHODS

In the prospective Sister Study cohort, current and past occupational history was collected for 48,451 participants. We used Cox proportional hazards models to estimate adjusted HRs and 95% confidence intervals (CI) for the association between baseline work schedule characteristics and incident breast cancer.

RESULTS

During follow-up (mean = 9.1 years), 3,191 incident cases were diagnosed. We observed little to no increase in risk associated with work schedule characteristics (ever working rotating shifts: HR = 1.04, 95% CI, 0.91-1.20; ever working rotating night shifts: HR = 1.08, 95% CI, 0.92-1.27; ever working at night: HR = 1.01, 95% CI, 0.94-1.10; and ever working irregular hours: HR = 0.98, 95% CI, 0.91-1.06). Although short-term night work (>0 to 5 years vs. never: HR = 1.12; 95% CI, 1.00-1.26) and rotating shift work at night (>0 to 5 years vs. never: HR = 1.30; 95% CI, 1.05-1.61) were associated with increased breast cancer risk, working nights for more than 5 years was not associated with risk.

CONCLUSIONS

Overall, we observed little evidence that rotating shift work or work at night was associated with a higher risk of breast cancer, except possibly among those who participated in such work for short durations of time.

IMPACT

This study indicates that if night shift work is associated with breast cancer, the increase in risk is small.

Pediatric residents' perceptions of the impact of the 24-hour on-call system on their well-being and education and patient safety. A national survey

Objectives:

To examine pediatric residents’ perceptions of the 24-hour in-hospital shift and its impact on their well-being and education and patient safety.

Methods:

A cross-sectional survey conducted with residents enrolled in pediatric residency programs across Saudi Arabia in February 2017 at the Saudi Commission For Health Specialties, Riyadh Saudi Arabia. We designed a self-administered questionnaire that was distributed using the Saudi Commission for Health Specialties E-mail groups. A 4-point Likert-type scale was used to rank the residents’ responses; and the relative importance index (RII) approach was used to analyze the relative contribution of each indicator to its main theme.

Results:

A total of 314 residents participated in the survey (response rate, 30%). Of these, 168 (53.6%) were females. When asked about their preferences regarding the 24-hour on-call system, 286 residents (91.1%) preferred not to continue with this system. Residents ranked several indicators that they perceived as a negative impact due to the 24-hour on-call system. The first ranked indicator was missing academic activities and elective rotations post-call (mean 3.10 [standard deviation 1.25], RII 90.94%), and the second was decreased performance and decision-making skills during night duty (mean 3.51 [standard deviation 1.0], RII 88.11%).

Conclusion:

We found that the 24-hour on-call system negatively impacts residents’ well-being and education and patient care. Pediatric residency training programs in Saudi Arabia should consider resident duty hour reform and evaluate new on-call models to improve resident well-being and training, as well as patient care.

A pre-drive ocular assessment predicts alertness and driving impairment: A naturalistic driving study in shift workers

Sleepiness is a major contributor to motor vehicle crashes and shift workers are particularly vulnerable. There is currently no validated objective field-based measure of sleep-related impairment prior to driving. Ocular parameters are promising markers of continuous driver alertness in laboratory and track studies, however their ability to determine fitness-to-drive in naturalistic driving is unknown. This study assessed the efficacy of a pre-drive ocular assessment for predicting sleep-related impairment in naturalistic driving, in rotating shift workers. Fifteen healthcare workers drove an instrumented vehicle for 2 weeks, while working a combination of day, evening and night shifts. The vehicle monitored lane departures and behavioural microsleeps (blinks >500 ms) during the drive. Immediately prior to driving, ocular parameters were assessed with a 4-min test. Lane departures and behavioural microsleeps occurred on 17.5 % and 10 % of drives that had pre-drive assessments, respectively. Pre-drive blink duration significantly predicted behavioural microsleeps and showed promise for predicting lane departures (AUC = 0.79 and 0.74). Pre-drive percentage of time with eyes closed had high accuracy for predicting lane departures and behavioural microsleeps (AUC = 0.73 and 0.96), although was not statistically significant. Pre-drive psychomotor vigilance task variables were not statistically significant predictors of lane departures. Self-reported sleep-related and hazardous driving events were significantly predicted by mean blink duration (AUC = 0.65 and 0.69). Measurement of ocular parameters pre-drive predict drowsy driving during naturalistic driving, demonstrating potential for fitness-to-drive assessment in operational environments.

Night-Time Shift Work and Related Stress Responses: A Study on Security Guards

Work-related stress can induce a break in homeostasis by placing demands on the body that are met by the activation of two different systems, the hypothalamic–pituitary–adrenal axis and the sympathetic nervous system. Night-shift work alters the body’s exposure to the natural light–dark schedule and disrupts circadian (daily) rhythms. The greatest effect of night-shift work is the disruption of circadian rhythms. The impact that these disruptions may have on the pathogenesis of many diseases, including cancer, is unknown. This study aims to discover the relationship among three different job activities of security guards and their stress-related responses by evaluating salivary cortisol levels and blood pressure. Methods: Ninety security guards, including night-time workers and night-time and daily-shift workers, were recruited for this study. Each security guard provided two saliva samples before and after three scheduled time points: (i) at 22:00, (ii) at 06:30, and (iii) at 14:00. Results: The results of the study showed a significant alteration in cortisol levels. Night-time shift cortisol levels significantly increased before and after the work shifts. A physiological prevalence of the vagal tone on the cardiocirculatory activity was found during night-shift work. Conclusions: This study indicates that cortisol levels and blood pressure are sensitive markers of biological responses to severe work stress. Shift-change consequences may occur at the end of the night shift when there is a significant increase in the cortisol level and a significant variation in cardiovascular parameters.

Frequency of night shift and menstrual cycle characteristics in Japanese nurses working under two or three rotating shifts

OBJECTIVES

In Japan, the prevalence of irregular menstrual cycles and its association with the frequency of night shifts have scarcely assessed. The present study aimed to evaluate the relationship between irregular menstrual cycles and the frequency of night shifts in Japanese female nurses.

METHODS

We conducted a cross-sectional web-based self-administered questionnaire survey in 2019. An irregular menstrual cycle was defined as a cycle length of ≤21 days or ≥39 days at least a few times over the past year or amenorrhea for at least 3 months. We used Poison regression analysis with a robust error variance to calculate the prevalence ratios adjusted for age, body mass index, hospital size, and the department in which they worked.

RESULTS

A total of 1249 women were included, and 679 (54.4%) and 195 (15.6%) of them worked under two and three rotating shifts. The prevalence of irregular menstrual cycles was 24.8%, 37.4%, and 35.9% in the no night, two rotating, and three rotating shifts groups, respectively. While the frequency of night shifts had a dose-responsive relationship with irregular menstrual cycles in the two rotating shifts group, it was not observed in the three rotating shifts group. However, the risk of work getting affected by dysmenorrhea or premenstrual symptoms increased in the three rotating shifts group.

CONCLUSIONS

Over 30% of Japanese female nurses working under night shifts had irregular menstrual cycles. The high frequency of night shifts increased the risk of irregular menstrual cycles and secondary amenorrhea in the two rotating shifts group.

Effect of implementing an overwork-prevention act on working hours and overwork-related disease: A mediation analysis

OBJECTIVES

Overwork has been recognized as a risk factor for cerebrovascular and cardiovascular disease (CCVD). To our best knowledge, Japan is the first country in the world to implement an independent act (the 2014 Act) for the prevention of overwork-related disease, which was promoted through application of preventive measures, such as reductions in working hours. We assessed changes in working hours and overwork-related CCVD before and after introduction of the 2014 Act.

METHODS

We calculated the overwork-related CCVD incidence rate and average monthly working hours for 10 industry groups in Japan with data from 2012 to 2018. We applied a causal mediation analysis to estimate the total effect of implementing the 2014 Act on the overwork-related CCVD and the effect mediated by working hours.

RESULTS

An average of 271 for every 48 million employees developed overwork-related CCVD per year. After introducing the 2014 Act, the incidence rate ratio of overwork-related CCVD was 0.881-fold lower (95% CI 0.780-0.995) compared with before the policy change. The 2014 Act contributed to a decrease of 26% (78 cases per year; 95% CI 29-173) of the overwork-related CCVD incidence per year. Approximately 41% (32 cases per year) of this effect could be explained by reduced working hours.

CONCLUSIONS

Our study highlights the impact of the 2014 Act in Japan on the reduction in working hours, which further contributes to the reduction in overwork-related CCVD. Policymakers should consider adopting our innovative approach to assess the mediation effect underlying the implementation of new policies.

Association between procrastination, white-collar work and obesity in Japanese male workers: a cross-sectional study

OBJECTIVE

To investigate the associations among procrastination (time inconsistency), work environment and obesity-related factors in Japanese male workers.

DESIGN

Cross-sectional study.

SETTING

Data were collected at two work sites of Japanese electronics manufacturing company in 2015.

PARTICIPANTS

795 full-time male workers in a Japanese electric company, aged 35-64 years, who underwent health checkups in 2015.

MAIN OUTCOME MEASURES

Body mass index (BMI), adult weight change, obesity (BMI ≥25 kg/m²), adult weight gain over 10 kg (AWG10) and metabolic syndrome (MetS). Multivariable linear and logistic regression analyses were performed to assess the associations of procrastination assessed by using a one-item questionnaire and white-collar and blue-collar work with obesity-related factors.

RESULTS

White-collar workers with high procrastination levels showed positive associations with BMI (B: 0.75, 95% CI 0.06 to 1.44) and adult weight change (B: 1.77, 95% CI 0.26 to 3.29), and had increased odds of AWG10 (OR: 1.85, 95% CI 1.04 to 3.29) and MetS (OR: 2.29 95% CI 1.18 to 4.44) after adjustment for age, education, work-related factors and lifestyle factors. However, such positive associations were not observed among blue-collar workers.

CONCLUSIONS

Procrastination and white-collar work might have a joint effect on weight gain during adulthood and consequential obesity.

Cardiac Autonomic Activity in Commercial Aircrew During an Actual Flight Duty Period

BACKGROUND: The work schedules of airline crewmembers include extended workdays, compressed work periods, and limited time for recovery, which may lead to cardiovascular strain and fatigue. The aim of this study was to evaluate changes in heart rate variability (HRV) during work and sleep, and with respect to work characteristics and breaks.METHODS: We followed 49 airline crewmembers during four consecutive workdays of ≥39 h. Data included HRV measurements, a questionnaire, and sleep/work diaries. HRV parameters include root mean square of successive differences (RMSSD), standard deviation of the normal beat-to-beat differences (SDNN), and the low and high frequency ratio (LF/HF).RESULTS: The results indicate higher levels of cardiovascular strain on the 4th compared to the 1st workday, most prominent among cabin crewmembers. In this group, we observed indications of decreased cardiovascular strain by increasing duration of sleep, demonstrated by increased RMSSD (B = 2.7, 95% CI 1.6, 3.8) and SDNN (B = 4.4, 95% CI 3.0, 5.7), and decreased LF/HF (B = -0.2, 95% CI, -0.4,-0.01). Similarly, longer duration of breaks was associated with lower cardiovascular strain, indicated by increased RMSSD (B = 0.1, 95% CI 0.03, 0.1) and SDNN (B = 0.1, 95% CI 0.1, 0.1). Among pilots, increased LF/HF indicated higher cardiovascular strain in those who often or always reported of high workload (B = 4.3, 95% CI 2.3, 6.3; and B = 7.3, 95% CI 3.2, 11.4, respectively).DISCUSSION: The results support the contention that the studied work period increases cardiac strain among airline crew. Work characteristics, breaks, and sleep are associated with changes in HRV.Goffeng EM, Nordby K-C, Tarvainen M, Järvelin-Pasanen S, Wagstaff A, Skare Ø, Lie J-A. Cardiac autonomic activity in commercial aircrew during an actual flight duty period. Aerosp Med Hum Perform. 2019; 90(11):945-952.