How to schedule night shift work in order to reduce health and safety risks

Supporting the management of long-term health risk from night work

Societal demands mean that many companies operate throughout the day to provide services. The impact of night work on long-term health is not clear, but there is sufficient evidence for closer monitoring of this as a concern and industry is not sure what more they need to do about this potential problem. There are many health conditions and potential interventions to reduce risks from night working, but there is no clarity on how to design and implement intervention programmes for long-term health issues. This paper reports on a rapid review of 24 articles to examine how interventions can minimise long-term health risk from night work. The analysis has identified eight types of intervention that have been used in relation to seven types of long-term health conditions but has highlighted weaknesses in evaluation, in relation to the current knowledge of the implementation and effectiveness of the interventions for long-term health. Commentary is provided on how researchers and industry practitioners need to think about risk in different ways, improve implementation of interventions through a systemic approach to work design and organisation, and employ more participatory approaches to embed cultural change in organisations.

Night shift work and breast cancer risk - 2023 update of epidemiologic evidence

Introduction

Night shift work is a complex and frequent occupational exposure, and breast cancer stands as the most prevalent cancer in women. The International Agency for Research on Cancer (IARC) has twice classified night shift work as a probable breast carcinogen, with the latest classification in June 2019. Since that time, new epidemiologic data has emerged.

Methods

We searched PubMed for original articles based on cohort and case-control studies of "breast cancer and night shift work" published after the IARC evaluation in June 2019.

Results

In total six cohorts and four case-control studies were included in our review. Overall, we observed some support for associations between persistent (long duration or high frequency) night shift work and an increase in breast cancer risk, though most studies were relatively small and statistically under-powered. Moreover, the recent studies do not contribute further evidence regarding the interaction with menopausal status, diurnal preference, hormonal subtypes of breast cancer or gene-environment aspects, which were issues that were left from the IARC evaluation.

Conclusions

The available new results somewhat consolidate the epidemiological evidence from IARC's 2019 evaluation, and do not provide further evidence regarding interaction of interest, e.g. menopausal status, etc. Therefore, long term follow-up of prospective cohorts or nested case-control studies, including precise exposure assessment and examinations of relevant interactions such as menopausal status, diurnal preference, hormonal subtypes of breast cancer and gene-environment aspects, are warranted. Meanwhile, protective measures for the night workers should be considered.

Airport security personnel's working hour characteristics and associations with sickness absence-a retrospective cohort study in 2016-2019

We aimed to investigate the associations of working hour characteristics based on the international and local definitions with sickness absence (SA) among airport security personnel. The payroll-based registry data of daily working hours for 2016-2019 at one airport was limited to those with ≥30 work shifts in a year (n=377-687 employees). The conditional Poisson model for incidence rate ratios (IRR) with 95% confidence intervals (CI) was used for analyses. Based on the international definitions, only a few associations were found: each one-unit increase in weekly working hours and the number of consecutive working days were associated with a lower likelihood of SA. The local definitions were more consistently associated with SA: Each one-unit increase in shift length and time between shifts, higher variation in shift length, and the number of consecutive evening and night shifts were associated with a higher likelihood of SA. To conclude, especially the local definitions of working hour characteristics seem to be important limits for short SA. Thus, high variability of shift lengths and prolonged shifts could be avoided to reduce the risk of SA. Overall, keeping the working hours within any of the recommendations among airport security personnel could support well-being and health.

Shift work sleep disorder

Shift work sleep disorder (SWSD) is a circadian rhythm sleep-wake disorders affecting individuals who work in nonstandard hours, particularly night shifts. It manifests as difficulty sleeping during the day and staying awake during work hours, leading to health issues. SWSD is not universally experienced by all shift workers, with about 30% affected. Diagnosing SWSD involves monitoring sleep patterns and differentiating it from other disorders such as sleep apnea. Prevention and treatment include collective measures such as optimizing shift schedules and individual strategies such as sleep/circadian hygiene, light therapy, melatonin use, and, if necessary, prescription medications. Despite these interventions, the primary recommendation is to switch to daytime work, although this may not be feasible for all workers.

Circadian disruption and its impact on the cardiovascular system

Circadian rhythms are highly conserved biorhythms of ~24 h that govern many fundamental biological processes, including cardiovascular (CV) homeostasis. Disrupting the timing of cellular oscillators promotes cellular stress, and induction of pathogenic pathways underpins the pathogenesis of many CV diseases (CVDs). Thus, shift work, late eating, sleep disturbances, and other disruptors can result in an elevated risk of heart disease and increased incidence of adverse CV events. Here, we discuss the importance of circadian rhythms for CV homeostasis, recent developments in understanding the impact of disrupted circadian rhythms on CV health and disease progression, and how understanding the interactions between circadian and CV physiology is crucial for improving interventions to mitigate CVD, especially in populations impacted by disrupted circadian rhythms.

Work Reward Moderates the Association Between Work Effect and Workplace Violence Among Medical Staff in China

Purpose

Workplace violence (WPV) against healthcare workers is a significant public health issue in China and globally. Although the effort-reward imbalance theory claimed that work rewards may moderate the relationship between work effort and WPV, the quantitative evidence is limited. This study aimed to examine if work reward could moderate the associations between work effort and WPV against medical staff based on the effort-reward imbalance theory.

Methods

This is a cross-sectional study, which was conducted in 12 hospitals in Shandong, China. Data collected from 3426 medical staff were analyzed in this study. Work effort was evaluated by working hours and night shift work times per month (NSWM), and work reward was evaluated by monthly income and perceived social status. WPV, occupational characteristics, physical disease, and social-demographic variables were also evaluated in this study.

Results

There were 1788 (52.2%) medical staff, who reported the experience of workplace violence. Working hours, NSWM, and perceived social status were associated with WPV (all p<0.001). Monthly income could moderate the associations between monthly income and WPV or verbal violence (p<0.05), and perceived social status could moderate the associations between NSWM and WPV (p<0.001).

Conclusion

Monthly income could moderate the associations between monthly income and WPV (verbal violence), and perceived social status could moderate the associations between NSWM and WPV, which could be explained by the effort-reward imbalance model. These findings also can be translated into practices to control WPV against medical staff.

Effects of working conditions on the perception of night work safety and health effects on nurses

AIM

To examine night working conditions by shift work type and identify the effects of night working conditions on nurses' perceptions of shift work safety and health effects.

BACKGROUND

Night work is the main factor affecting nurses' health. However, the safety of night working conditions has not been sufficiently examined in previous studies.

METHODS

This study used a cross-sectional research design and an online survey using a tool released by the Australian Manufacturing Workers' Union, and the responses of 348 shift work nurses in Korea were analyzed. Logistic regression analysis was used to examine the effects of shift work conditions on the perceived safety of night work and health effects. The STROBE reporting guidelines were utilized, and data were collected from December 1 to December 31, 2021.

RESULTS

The adjusted logistic regression analysis showed that perceived threat to safety and the health effects of shift work were not significant according to shift type. However, night-shift-work nurses who worked alone (P = 0.003), lacked an emergency recovery system (P = 0.026), and had difficulty commuting perceived a threat to their health (P = 0.007). Additionally, nurses who experienced loss of concentration (P = 0.006) and inadequate rest time (P < 0.001) perceived the health effects of shift work.

DISCUSSION

Urgent monitoring of night work conditions is necessary for the 2-shift work type. Nurses must work night shifts together and an emergency system should be established for their safety.

CONCLUSION

Night work conditions should be improved to prevent the hazards of night work and its negative health effects on nurses.

IMPLICATIONS FOR NURSING AND HEALTH POLICY

This study suggests the necessity of a policy to enhance night work safety, including emergency coping systems and sufficient inter-shift rest time.

Towards the year 2049: The next 25 years of occupational health and safety research

OBJECTIVE

In this discussion paper, we close our 2024 series reflecting on the successes, failures, and promises of occupational health and safety research in celebration of the 50th anniversary of the Scandinavian Journal of Work, Environment & Health (SJWEH). This paper aims to elaborate on the future of our research field.

METHODS

We conducted a narrative review of lessons learned in the series, examining insights gained and key takeaways. Additionally, we explored the current and anticipated agendas of major institutions, including the World Health Organization and the European Union, on occupational health and safety, as well as potential developments in the academic publishing industry.

RESULTS

Occupational health and safety research has significantly evolved over the last 50 years, emphasizing longitudinal study designs, enriching observational data with registry-based information, and expanding the scope of hazardous determinants impacting workers` health. Novel statistical approaches have further enabled researchers to address complex associations, such as mediation effects, and to strengthen causal inference in observational studies. At the same time, the publishing business is changing rapidly, with artificial intelligence poised to reshape both research practices and the landscape of academic publishing.

CONCLUSION

In the changing landscape of research and academic publishing, our goal is for SJWEH to continue to be a leading source of high-quality research dedicated to protecting and improving workers' health. We are curious and excited to see where all these current and anticipated changes will lead in the years to come.

Physical and mental fatigue in shift work and mitigation strategies: an integrative review

The new configurations of society have fragmented working hours into shifts, resulting in greater fatigue which affects worker health. Our aim was to identify the relationship between physical and mental fatigue and shift work and the main strategies for mitigating these effects. This review study was conducted between March and May 2023 using the Biblioteca Virtual em Saúde (Virtual Health Library). Twenty seven of the 1,176 identified articles were selected, with health professionals (doctors and nursing professionals), drivers, and aircraft pilots being the most studied populations. The following strategies for mitigating fatigue in shift work stood out: work schedule adjustments, interand intra-workday rest associated with phototherapy, monitoring and evaluating early signs of fatigue, supervised prescription of stimulants (such as caffeine) and sedatives, use of monitoring equipment, and staff education and training.

Cardiovascular adaptations and pathological changes induced by spaceflight: from cellular mechanisms to organ-level impacts

The advancement in extraterrestrial exploration has highlighted the crucial need for studying how the human cardiovascular system adapts to space conditions. Human development occurs under the influence of gravity, shielded from space radiation by Earth's magnetic field, and within an environment characterized by 24-hour day-night cycles resulting from Earth's rotation, thus deviating from these conditions necessitates adaptive responses for survival. With upcoming manned lunar and Martian missions approaching rapidly, it is essential to understand the impact of various stressors induced by outer-space environments on cardiovascular health. This comprehensive review integrates insights from both actual space missions and simulated experiments on Earth, to analyze how microgravity, space radiation, and disrupted circadian affect cardiovascular well-being. Prolonged exposure to microgravity induces myocardial atrophy and endothelial dysfunction, which may be exacerbated by space radiation. Mitochondrial dysfunction and oxidative stress emerge as key underlying mechanisms along with disturbances in ion channel perturbations, cytoskeletal damage, and myofibril changes. Disruptions in circadian rhythms caused by factors such as microgravity, light exposure, and irregular work schedules, could further exacerbate cardiovascular issues. However, current research tends to predominantly focus on disruptions in the core clock gene, overlooking the multifactorial nature of circadian rhythm disturbances in space. Future space missions should prioritize targeted prevention strategies and early detection methods for identifying cardiovascular risks, to preserve astronaut health and ensure mission success.

Sleep duration and quality in permanent night work: an observational field study

PURPOSE

Permanent night workers conceivably show better adaptation of circadian rhythms to night work than shift workers and therefore better possibilities of obtaining sufficient sleep of good quality after night shifts. We investigated the effect of night shifts including number of consecutive shifts on sleep among self-selected permanent night workers, and studied if the effect of night shifts differed between morning and evening types and compared with 3-shift workers.

METHODS

The study population included 90 permanent night workers followed for 14 days (warehouse workers, 1228 observation days, 80% males). For comparison, we included 70 3-shift workers followed for 26 days (police officers, 1774 observation days, 100% men). Total sleep time (TST), primary sleep duration (PSD), and sleep efficiency were assessed by actigraphy. Measures of sleep quality and diurnal type were self-reported.

RESULTS

Among permanent night workers, TST, PSD, difficulties falling asleep, disturbed sleep, and the number of awakenings decreased after night shifts compared with days without night work. Sleep efficiency, difficulties awakening, and non-refreshing sleep increased. More consecutive night shifts were associated with shorter TST and PSD. Sleep outcomes did not differ by diurnal type. Permanent night workers had fewer awakenings after night shifts than 3-shift workers, but no other differences were observed.

CONCLUSION

This study does not provide evidence that supports recommendation of permanent night work to reduce adverse effects of night shifts on sleep. A limited number of consecutive night shifts is recommended to reduce accumulation of sleep debt.

The effects of work on cognitive functions: a systematic review

Introduction

Cognitive functions play a crucial role in individual's life since they represent the mental abilities necessary to perform any activity. During working life, having healthy cognitive functioning is essential for the proper performance of work, but it is especially crucial for preserving cognitive abilities and thus ensuring healthy cognitive aging after retirement. The aim of this paper was to systematically review the scientific literature related to the effects of work on cognitive functions to assess which work-related factors most adversely affect them.

Method

We queried the PubMed and Scopus electronic databases, in February 2023, according to the PRISMA guidelines (PROSPERO ID number = CRD42023439172), and articles were included if they met all the inclusion criteria and survived a quality assessment. From an initial pool of 61,781 papers, we retained a final sample of 64 articles, which were divided into 5 categories based on work-related factors: shift work (n = 39), sedentary work (n = 7), occupational stress (n = 12), prolonged working hours (n = 3), and expertise (n = 3).

Results

The results showed that shift work, occupational stress, and, probably, prolonged working hours have detrimental effects on cognitive functioning; instead, results related to sedentary work and expertise on cognitive functions are inconclusive and extremely miscellaneous.

Discussion

Therefore, workplace health and well-being promotion should consider reducing or rescheduling night shift, the creation of less demanding and more resourceful work environments and the use of micro-breaks to preserve workers' cognitive functioning both before and after retirement.

Systematic review registration

https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42023439172, identifier CRD42023439172.

Working hours and health - key research topics in the past and future

OBJECTIVE

This paper discusses the past and present highlights of working hours and health research and identifies key research needs for the future.

METHOD

We analyzed over 220 original articles and reviews on working hours and health in the Scandinavian Journal of Work, Environment & Health published during the last 50 years. Key publications from other journals were also included.

RESULTS

The majority of identified articles focussed on the effects of shift and night work, with fewer studying long and reduced working hours and work time control. We observed a transition from small-scale experimental and intensive field studies to large-scale epidemiological studies utilizing precise exposure assessment, reflecting the recent emergence of register-based datasets and the development of analytic methods and alternative study designs for randomized controlled designs. The cumulative findings provide convincing evidence that shift work and long working hours, which are often associated with night work and insufficient recovery, increase the risk of poor sleep and fatigue, sickness absence, occupational injuries, and several chronic health conditions such as cardiovascular diseases and cancer. The observed risks are strongly modified by individual and work-related factors.

CONCLUSIONS

Although the observed health risks of shift work and long working hours are mostly low or moderate, the widespread prevalence of exposure and the hazardousness of the many associated potential outcomes makes such working time arrangements major occupational health risks. Further research is needed to identify exposure-response associations, especially in relation to the chronic health effects, and to elucidate underlying pathways and effective personalized intervention strategies.

Resilience Building Practices for Women Physicians

Women now make up more than half of the physician workforce, but they are disproportionately plagued by burnout. Medicine is a fast-paced stressful field, the practice of which is associated with significant chronic stress due to systems issues, crowding, electronic medical records, and patient case mix. Hospitals and health care systems are responsible for mitigating system-based burnout-prone conditions, but often their best efforts fail. Physicians, particularly women, must confront their stressors and the daily burden of significant system strain when this occurs. Those who routinely exceed their cumulative stress threshold may experience burnout, career dissatisfaction, and second victim syndrome and, ultimately, may prematurely leave medicine. These conditions affect women in medicine more often than men and may also produce a higher incidence of health issues, including depression, substance use disorder, and suicide. The individual self-care required to maintain health and raise stress thresholds is not widely ingrained in provider practice patterns or behavior. However, the successful long-term practice of high-stress occupations, such as medicine, requires that physicians, especially women physicians, attend to their wellness. In this article, we address one aspect of health, resilience, and review six practices that can create additional stores of personal resilience when proactively integrated into a daily routine.

A comparison between veterinary small animal general practitioners and emergency practitioners in Australia. Part 1: demographic and work-related factors

Occupational stressors are commonly encountered in small animal veterinary practice and have been associated with burnout. The working context of veterinarians differs by specialty, and this can potentially lead to variable exposures to risk factors for burnout. The aim of this study was to explore differences in demographic and working conditions of veterinary general practitioners (GPs) and emergency practitioners (EPs) to compare exposure to different potential stressors. An anonymous, online survey was administered to veterinary GPs and EPs practicing in metropolitan regions of Australia. In total, 320 participant responses were analyzed (n = 237, 74.2% GPs and n = 83, 25.9% EPs). Significant differences (P < 0.05) in the demographics and work-related exposures were found between the two groups. GPs were found to be older than EPs with a greater number of years of experience in their field (P < 0.001). Most veterinary GPs worked only day shifts (207/236, 87.7%); where EPs worked a greater variety of shift patterns, with "only day shifts" being the least common shift pattern (P < 0.001). Most GPs worked a set and predictable roster pattern (195/236, 83.6%), while most EPs did not (51/83, 61.5%). EPs worked more weekends and public holidays (P < 0.001). The EP group performed more hours of work each week but worked less overtime. The main contributing factors for overtime were scheduling factors for GPs and staffing issues for EPs. EPs were commonly not able to take meal-breaks and GPs' meal-breaks were commonly interrupted by work. EPs were more frequently exposed to patient death, euthanasia (including for financial reasons), emotionally distressed clients and delivering negative news (P < 0.001). Both groups indicated that most work environments were collegiate and supportive, and a minority reported toxic colleagues (11.8%) or management teams (26.9%). Just under one-half of respondents reported having witnessed or experienced workplace bullying. Of our respondent group, 52.0% (166/319) were not satisfied with their remuneration. Desire to leave their principal area of practice was prevalent among this survey group (192/319, 60.2%) with approximately one-third considering leaving the veterinary profession. We discuss the implications of these workplace factors, including mitigation strategies.

Move the night way: how can physical activity facilitate adaptation to shift work?

Shift work, involving night work, leads to impaired sleep, cognition, health and wellbeing, and an increased risk of occupational incidents. Current countermeasures include circadian adaptation to phase shift circadian biomarkers. However, evidence of real-world circadian adaptation is found primarily in occupations where light exposure is readily controlled. Despite this, non-photic adaptation to shift work remains under researched. Other markers of shift work adaptation exist (e.g., improvements in cognition and wellbeing outcomes) but are relatively unexplored. Timeframes for shift work adaptation involve changes which occur over a block of shifts, or over a shift working career. We propose an additional shift work adaptation timeframe exists which encompasses acute within shift changes in markers of adaptation. We also propose that physical activity might be an accessible and cost-effective countermeasure that could influence multiple markers of adaptation across three timeframes (Within Shift, Within Block, Within Work-span). Finally, practical considerations for shift workers, shift work industries and future research are identified.

Prevalence of occupational injury and its associated factors among emergency department physicians in China: A large sample, cross-sectional study

BACKGROUND

Medical personnel, particularly emergency department (ED) physicians, face a variety of occupational hazards. However, the current state of occupational injuries among ED physicians remains unknown. This study aimed to assess the occupational injury of Chinese ED physicians and to identify its associated factors.

METHODS

From July to August 2018, a cross-sectional survey was conducted in Chinese emergency departments. A structured questionnaire covering sociodemographic characteristics, individual health behaviours, and work-related characteristics was completed by 10,457 ED physicians. Binary logistic regression was used to analyse the factors associated with occupational injuries.

RESULTS

In this study, 81.13% of ED physicians reported occupational injuries in the previous 12 months. All participants who had experienced occupational injuries had suffered verbal violence. Among physicians who experienced at least one injury, 76.57% and 71.30% reported injuries sustained while moving patients and from falls, slips, and sprains during office visits, respectively. Occupational injuries were significantly associated with gender, education level, drinking behaviour, sleep quality, the frequency of night shifts per month, self-perceived physician shortage, and work-family conflict. Physicians who experienced effort-reward imbalance were at a higher risk of occupational injury.

CONCLUSION

In China, occupational injuries are common among ED physicians. Individual factors as well as work-related factors are independently linked to occupational injuries. To reduce the rate of occupational injuries among ED physicians, health policymakers and healthcare facility managers should consider multi-injury interventions.

Chronic blue light-emitting diode exposure harvests gut dysbiosis related to cholesterol dysregulation

Night shift workers have been associated with circadian dysregulation and metabolic disorders, which are tightly coevolved with gut microbiota. The chronic impacts of light-emitting diode (LED) lighting at night on gut microbiota and serum lipids were investigated. Male C57BL/6 mice were exposed to blue or white LED lighting at Zeitgeber time 13.5-14 (ZT; ZT0 is the onset of "lights on" and ZT12 is the "lights off" onset under 12-hour light, 12-hour dark schedule). After 33 weeks, only the high irradiance (7.2 J/cm2) of blue LED light reduced the alpha diversity of gut microbiota. The high irradiance of white LED light and the low irradiance (3.6 J/cm2) of both lights did not change microbial alpha diversity. However, the low irradiance, but not the high one, of both blue and white LED illuminations significantly increased serum total cholesterol (TCHO), but not triglyceride (TG). There was no significant difference of microbial abundance between two lights. The ratio of beneficial to harmful bacteria decreased at a low irradiance but increased at a high irradiance of blue light. Notably, this ratio was negatively correlated with serum TCHO but positively correlated with bile acid biosynthesis pathway. Therefore, chronic blue LED lighting at a high irradiance may harvest gut dysbiosis in association with decreased alpha diversity and the ratio of beneficial to harmful bacteria to specifically dysregulates TCHO metabolism in mice. Night shift workers are recommended to be avoid of blue LED lighting for a long and lasting time.

Night shift work characteristics and risk of incident coronary heart disease among health care workers: national cohort study

BACKGROUND

Night work has been associated with coronary heart disease. The present study examined exposure-response relations between quantitative night work characteristics and coronary heart disease (angina pectoris or myocardial infarction) with the aim to contribute to evidence-based recommendations for low-risk night work schedules.

METHODS

We followed 100 149 night workers (80% women) and 153 882 day workers (78% women), all health care workers in Denmark with day by day payroll information on night shifts from 2007 to 2015. We analysed data with Poisson regression stratified by sex and adjusted for age, calendar year, diabetes, family history of cardiovascular disease, educational level, occupation, indicators for obesity, hypercholesterolaemia, and hypertension.

RESULTS

Female and male night workers worked on average 1.7 and 1.8 night shifts per month for an average duration of less than 4 years. During follow-up, 1198 night and 2128 day workers were hospitalized with first-time coronary heart disease. When compared with day workers, the overall incidence rate ratios for female and male night workers were 1.06 [95% confidence interval (CI): 0.97, 1.17] and 1.22 (95% CI 1.07, 1.39). Highest risks were observed in top exposure categories for several night work characteristics. However, no consistent exposure-response relations by number of monthly night shifts, cumulative night shifts, years with rotating night shifts, years with any night shift and consecutive night shifts were observed among the night workers of either sex.

CONCLUSIONS

This study of a population with low exposure to night work does not indicate that reducing extent of monthly night shifts, cumulative night shifts, years with rotating night shifts, years with any night shift and consecutive night shifts would reduce the risk of coronary heart disease.

Managing Sustainable Working Hours within Participatory Working Time Scheduling for Nurses and Assistant Nurses: A Qualitative Interview Study with Managers and Staffing Assistants

Aim

To bring insights into how healthcare managers and staffing assistants work to achieve sustainable working hours within a participatory scheduling system.

Background

Hospital nurses and assistant nurses often work on rotating shifts, which affects their opportunities for sleep, recovery, and work-life balance. In Sweden, a participatory scheduling approach is commonly used, where working hours are planned in collaboration between employees, managers, and staffing assistants. Influence over working hours is related to positive outcomes among shift workers. However, it also places responsibility on the employee to schedule working hours that promote health and patient safety, i.e., sustainable working hours. Accordingly, the organisation has responsibilities to support the employee in this regard.

Methods

Semistructured individual interviews were conducted with 11 managers and 9 staffing assistants from four Swedish regions and analysed using thematic analysis.

Results

Several key factors for achieving sustainable working hours within the context of participatory scheduling were described: distribution and clarity of responsibilities, allocating time for scheduling, establishing shared responsibility, considering fairness, fostering an individual relationship with the employee, managing dissatisfaction, providing support, clarifying guidelines for sustainable scheduling, managing inconsistencies between employee requests and sustainable working hours, and considering recovery opportunities and the competence mix on shifts. Additionally, contextual factors, such as staffing levels, working procedures, working time arrangements for night work, and technological support, were highlighted as important.

Conclusion

Achieving sustainable working hours within participatory scheduling involves considering the interactions between factors at the levels of the organisation, the individual, and the technological systems. Implication for Nursing Management. Nurse managers and staffing assistants must work closely with their employees during participatory scheduling to ensure sustainable working hours. Key goals in this regard include establishing a shared responsibility, clarifying responsibilities and guidelines for sustainable scheduling, and allocating time for the scheduling process.

Exploration of genome-wide DNA methylation profiles in night shift workers

The past decades, studies indicated that night shift work is associated with adverse health effects, however, molecular mechanisms underlying these effects are poorly understood. A few previous studies have hypothesized a role for DNA-methylation (DNAm) in this relationship. We performed a cross-sectional epigenome-wide association study, to investigate if night shift work is associated with genome-wide DNAm changes and DNAm-based biological age acceleration, based on previously developed so-called 'epigenetic clocks.' Short term (2-6 years) and intermediate term (10-16 years) night shift workers, along with age and sex matched dayworkers (non-shift workers) were selected from the Lifelines Cohort Study. For genome-wide methylation analysis the Infinium Methylation EPIC array (Ilumina) was used. Linear regression analyses were used to detect differences in methylation at individual CpG-sites associated with night shift work. Pathway analysis was performed based on KEGG pathways and predictions of age acceleration in night shift workers were performed based on four previously developed epigenetic age calculators. Only in women, differences in methylation at individual CpG-sites were observed between night shift workers and non-shift workers. Most of these differentially methylated positions (DMPs) were observed in intermediate term night shift workers. Pathway analysis shows involvement of pathways related to circadian rhythm and cellular senescence. Increased age acceleration was observed only in short-term night shift workers (men and women). This might be indicative of adaptation to night shift work or a so-called healthy worker effect. In conclusion, these results show that DNA methylation changes are associated with night shift work, specifically in women.

Night Shift Work and Sleep Disturbances in Women: A Scoping Review

This scoping review aimed to synthesize evidence on sleep disturbances in female shift workers. The update Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for Scoping Reviews was used. Twelve studies were included, four of which used actigraphy to assess sleep duration, efficiency, and latency. Seven studies evaluated the quality of sleep and three verified the sleepiness of women. This review adds to the body of evidence as the findings are homogeneous and allow a robust conclusion, suggesting that night shift work may be a potential factor for adverse effects on sleep of female shift workers.

Recovery from shift work

One fifth of today's workforce is engaged in shift work and exposed to various mental and physical health risks including shift work disorder. Efficiently recovering from shift work through physical and mental interventions allows us to mitigate negative effects on health, enables a better work-life balance and enhances our overall wellbeing. The aim of this review is to provide a state-of-the-art overview of the available literature. The role of sleep timing and naps, light therapy and psychotherapy, diet and exercise in recovery from shift work is presented here. We further review the impact of shift schedules and social support on post-shift unwinding.

Circadian Disruption in Night Shift Work and Its Association with Chronic Pulmonary Diseases

Globalization and the expansion of essential services over continuous 24 h cycles have necessitated the adaptation of the human workforce to shift-based schedules. Night shift work (NSW) causes a state of desynchrony between the internal circadian machinery and external environmental cues, which can impact inflammatory and metabolic pathways. The discovery of clock genes in the lung has shed light on potential mechanisms of circadian misalignment in chronic pulmonary disease. Here, the current knowledge of circadian clock disruption caused by NSW and its impact on lung inflammation and associated pathophysiology in chronic lung diseases, such as asthma, chronic obstructive pulmonary disease, pulmonary fibrosis, and COVID-19, is reviewed. Furthermore, the limitations of the current understanding of circadian disruption and potential future chronotherapeutic advances are discussed.

Exploring Australian night shift workers' food experiences within and outside of the workplace: a qualitative photovoice study

OBJECTIVE

Night shift workers are at a 20 to 40 % increased risk of metabolic diseases, which may be associated with their disrupted eating patterns. This qualitative study explores factors that influence night shift workers' eating habits, within and outside of the workplace, to identify target areas for health promotion strategies.

PARTICIPANTS AND SETTING

Eligible participants resided in Australia, working at least three overnight shifts per month.

DESIGN

The photovoice method was used, whereby participants were asked to take photos that represent their typical eating habits. These photos were incorporated as prompts in a semi-structured interview, which explored factors influencing eating habits on night shifts and days-off and perceptions and enablers to healthy eating.

RESULTS

Ten participants completed the study. Thematic analysis generated four main themes, which were mapped onto the Social Ecological Model (SE Model). Aligned with the SE Model, our results show night shift workers' eating habits are influenced by intrapersonal, interpersonal and (work) organisational levels. Participants reported that at work, appropriate food preparation facilities are required to enable healthy food choices. Poor shift work rostering leads to prolonged fatigue on days-off, limiting their ability and motivation to engage in healthy eating. Consequently, night shift workers seem to require additional supports from their social networks and enhanced food literacy skills, in order to adopt/ maintain healthy eating behaviours.

CONCLUSIONS

Night shift work creates individual and environmental barriers to healthy eating, which are present during and outside of work. Health promotion strategies for this population should include multiple approaches to address these barriers.

Wake-up Call: Night Shifts Adversely Affect Nurse Health and Retention, Patient and Public Safety, and Costs

The purpose of this mini review is to (1) summarize the findings on the impact of night shift on nurses' health and wellness, patient and public safety, and implications on organizational costs and (2) provide strategies to promote night shift nurses' health and improve organizational costs. The night shift, compared with day shift, results in poorer physical and mental health through its adverse effects on sleep, circadian rhythms, and dietary and beverage consumption, along with impaired cognitive function that increases nurse errors. Nurse administrators and health care organizations have opportunities to improve nurse and patient safety on night shifts. Low-, moderate-, and higher-cost measures that promote night nurses' health and well-being can help mitigate these negative outcomes. The provided individual and organizational recommendations and innovations support night shift nurses' health, patient and public safety, and organizational success.

Night shift work and risk of aggressive prostate cancer in the Norwegian Offshore Petroleum Workers (NOPW) cohort

BACKGROUND

Night shift work may acutely disrupt the circadian rhythm, with possible carcinogenic effects. Prostate cancer has few established risk factors though night shift work, a probable human carcinogen, may increase the risk. We aimed to study the association between night shift work and chlorinated degreasing agents (CDAs) as possible endocrine disrupters in relation to aggressive prostate cancer as verified malignancies.

METHODS

We conducted a case-cohort study on 299 aggressive prostate cancer cases and 2056 randomly drawn non-cases in the Norwegian Offshore Petroleum Workers cohort (1965-98) with linkage to the Cancer Registry of Norway (1953-2019). Work history was recorded as years with day, night, and rollover (rotating) shift work, and CDA exposure was assessed with expert-made job-exposure matrices. Weighted Cox regression was used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for aggressive prostate cancer, adjusted for education and year of first employment, stratified by 10-year birth cohorts, and with 10, 15, and 20 years of exposure lag periods.

RESULTS

Compared with day work only, an increased hazard of aggressive prostate cancer (HR = 1.86, 95% CI 1.18-2.91; P-trend = 0.046) was found in workers exposed to ≥19.5 years of rollover shift work. This persisted with longer lag periods (HR = 1.90, 95% CI 0.92-3.95; P-trend = 0.007). The exposure-hazard curve for a non-linear model increased linearly (HRs ≥1.00) for 18-26 years of rollover shift work. No association was found with CDA exposure.

CONCLUSIONS

Long-term exposure to rollover shift work may increase the hazard of aggressive prostate cancer in offshore petroleum workers.

A narrative review of occupational scheduling that impacts fatigue and recovery relevant to veterinarian well-being

Background

Sleep insufficiency is a worldwide affliction with serious implications for mental and physical health. Occupational factors play a large role in determining sleep habits. Healthcare workers are particularly susceptible to job-mediated sleep insufficiency and inadequate rest in general. Little is published on sleep practices among veterinarians, and overall recognition of the impacts of inadequate rest within the veterinary profession is poor.

Objectives and procedures

This review describes occupational factors affecting sufficiency of rest and recovery, reviews veterinary-specific and relevant adjacent literature pertaining to sleep patterns, and discusses potential solutions for addressing occupational schedules contributing to sleep insufficiency and inadequate rest. Online databases were searched to extract contemporary literature pertaining to sleep, insufficient rest, and occupational factors, with a focus on veterinary medicine and other healthcare sectors.

Results

Occupational factors leading to inadequate rest among healthcare workers include excessive workloads, extended workdays, cumulative days of heavy work hours, and after-hours on-call duty. These factors are prevalent within the veterinary profession and may contribute to widespread insufficient rest and the resulting negative impacts on health and well-being among veterinarians.

Conclusion and clinical relevance

Sufficient sleep quantity and quality are critical to physical and mental health and are negatively affected by many aspects of the veterinary profession. Critical review of current strategies employed in clinical practice is essential to promote professional fulfillment, health, and well-being among veterinarians.

Consequences of Shift Work and Night Work: A Literature Review

Nonstandard work schedules such as shift work and night work tend to trigger problems for workers in different areas. To illustrate the diversity of areas affected and the relative interest of the scientific community, we conducted a literature review of the effects of shift work and night work on workers. In particular, we intended to identify the main variables addressed in the field of health, the family sphere, and the organizational context. The literature review was carried out using the Web of Science with the following terms: "shift work", "rotating shifts", and "night work". Inclusion criteria incorporated empirical studies and articles written in Portuguese or English published in 2019. We selected 129 of the 619 articles identified. Regarding the impacts of shift work and night work, there existed a high discrepancy of focus between the three defined areas: health, family life, and organizational context. Specifically, health-related variables were the most studied (83.4%), followed by organizational variables (9.2%), and, lastly, family variables (7.4%). Based on these results, it is essential to extend the study of the two underrepresented impacts to other crucial areas, not only for the worker but also for organizations.

The relation between routines for shiftwork scheduling and sickness absence at a Norwegian hospital: A cross-sectional study

BACKGROUND

Shift work is associated with negative health outcomes. Routines for scheduling of shift work can help reduce negative health outcomes of shift work and improve work-life balance and social well-being for nurses working shift work.

OBJECTIVE

To investigate the association between organizational units' routines for shift work scheduling and nurses' sickness absence at the unit level.

DESIGN

Cross-sectional study design combining quantitative questionnaire data on shift work scheduling routines with data of mean percentage of sickness absence at the unit, mean level of exhaustion at the unit, mean age and percentage of women working at the unit.

PARTICIPANTS

A total of 126 leaders at organizational units with nurses working shift work schedule at Oslo University Hospital answered a questionnaire about shift work scheduling.

MEASURES

Three aspects of health-promoting shift work scheduling (fatigue-reducing scheduling, organizational health measures, and individual adaptation) and the extent to which operational considerations were made during shift work scheduling were used as independent variables. Covariates were mean age of nurses at each unit, mean percent female nurses, and mean exhaustion at unit level. Percent sickness absence was used as a dependent variable.

METHODS

Questionnaire data on shift work scheduling routines was merged with information on average age of employees in the unit, ratio female nurses, and units' average score on exhaustion. Multivariable linear regression analyses were used to assess the contribution of routines for shift work scheduling after controlling for mean level of exhaustion, average age, and proportion of women at each unit.

RESULTS

The factors "fatigue reducing scheduling", "organizational health measures" and "operational considerations" had no observed total effect on mean sickness absence. Individual adjustment in shift work scheduling had a direct negative association with sickness absence after controlling for other shift work scheduling routines, exhaustion, age, and gender.

CONCLUSIONS

There is a relationship between the units' routines for shift work scheduling and mean sickness absence at the unit, and the possibility of individual adjustment was the only aspect of shift work scheduling that had an above-zero association with sickness absence.

Circadian Rhythms Disrupted by Light at Night and Mistimed Food Intake Alter Hormonal Rhythms and Metabolism

Availability of artificial light and light-emitting devices have altered human temporal life, allowing 24-hour healthcare, commerce and production, and expanding social life around the clock. However, physiology and behavior that evolved in the context of 24 h solar days are frequently perturbed by exposure to artificial light at night. This is particularly salient in the context of circadian rhythms, the result of endogenous biological clocks with a rhythm of ~24 h. Circadian rhythms govern the temporal features of physiology and behavior, and are set to precisely 24 h primarily by exposure to light during the solar day, though other factors, such as the timing of meals, can also affect circadian rhythms. Circadian rhythms are significantly affected by night shift work because of exposure to nocturnal light, electronic devices, and shifts in the timing of meals. Night shift workers are at increased risk for metabolic disorder, as well as several types of cancer. Others who are exposed to artificial light at night or late mealtimes also show disrupted circadian rhythms and increased metabolic and cardiac disorders. It is imperative to understand how disrupted circadian rhythms alter metabolic function to develop strategies to mitigate their negative effects. In this review, we provide an introduction to circadian rhythms, physiological regulation of homeostasis by the suprachiasmatic nucleus (SCN), and SCN-mediated hormones that display circadian rhythms, including melatonin and glucocorticoids. Next, we discuss circadian-gated physiological processes including sleep and food intake, followed by types of disrupted circadian rhythms and how modern lighting disrupts molecular clock rhythms. Lastly, we identify how disruptions to hormones and metabolism can increase susceptibility to metabolic syndrome and risk for cardiovascular diseases, and discuss various strategies to mitigate the harmful consequences associated with disrupted circadian rhythms on human health.

Sequence analysis of the combinations of work shifts and absences in health care - comparison of two years of administrative data

BACKGROUND

In health care, the shift work is arranged as irregular work shifts to provide operational hours for 24/7 care. We aimed to investigate working hour trends and turnover in health care via identification of time-related sequences of work shifts and absences among health care employees. The transitions between the work shifts (i.e., morning, day, evening, and night shifts), and absences (days off and other leaves) over time were analyzed and the predictors of change in irregular shift work were quantified.

METHODS

A longitudinal cohort study was conducted using employer-owned payroll-based register data of objective and day-to-day working hours and absences of one hospital district in Finland from 2014 to 2019 (n = 4931 employees). The working hour data included start and end of work shifts, any kind of absence from work (days off, sickness absence, parental leave), and employee's age, and sex. Daily work shifts and absences in 2014 and 2019 were used in sequence analysis. Generalized linear model was used to estimate how each identified sequence cluster was associated with sex and age.

RESULTS

We identified four sequence clusters: "Morning" (60% in 2014 and 56% in 2019), "Varying shift types" (22% both in 2014 and 2019), "Employee turnover" (13% in 2014 and 3% in 2019), and "Unstable employment (5% in 2014 and 19% in 2019). The analysis of transitions from one cluster to another between 2014 and 2019 indicated that most employees stayed in the same clusters, and most often in the "Varying shift types" (60%) and "Morning" (72%) clusters. The majority of those who moved, moved to the cluster "Morning" in 2019 from "Employee turnover" (43%), "Unstable employment" (46%) or "Varying shift types" (21%). Women were more often than men in the clusters "Employee turnover" and "Unstable employment", whereas older employees were more often in "Morning" and less often in the other cluster groups.

CONCLUSION

Four clusters with different combinations of work shifts and absences were identified. The transition rates between work shifts and absences with five years in between indicated that most employees stayed in the same clusters. The likelihood of a working hour pattern characterized by "Morning" seems to increase with age.

Are We Ready to Implement Circadian Hygiene Interventions and Programs?

Circadian hygiene, a concept not to be confused with the notion of public or social hygiene, should be discussed among experts and society. Light-dark cycles and other possible synchronizers of the human circadian timing system affect ways of life, including sleeping, eating, working and physical activity. Some of these behaviors have also been investigated individually as synchronizers (e.g., eating times). Therefore, the knowledge held today about circadian rhythms, and their implications for health, allows future perspectives in this field to be mapped. The present article summarizes the latest knowledge on factors influencing circadian rhythms to discuss a perspective for the future of health promotion based on circadian hygiene. However, it is important to highlight that circadian hygiene is the product of an imbrication of individual and societal involvement. First, it is important to adopt practices and devise public health policies in line with circadian hygiene. Second, individual healthy habits require internal rhythms to be examined. Last, the research agenda on circadian hygiene can be developed on a public as well as individual level, raising the question as to how much society is willing to embrace this change.

GlycA, a Biomarker of Low-Grade Inflammation, Is Increased in Male Night Shift Workers

Sustained night shift work is associated with various adverse health risks, including an increased risk of cardiovascular disease, type II diabetes, and susceptibility to infectious respiratory diseases. The extent of these adverse health effects, however, seems to greatly vary between night shift workers, yet the underlying reasons and the mechanisms underlying these interindividual differences remain poorly understood. Metabolomics assays in the blood have recently gained much attention as a minimally invasive biomarker platform capturing information predictive of metabolic and cardiovascular diseases. In this cross-sectional study, we explored and compared the metabolic profiles of 1010 night shift workers and 1010 age- and sex-matched day workers (non-shift workers) from the Lifelines Cohort Study. The metabolic profiles were determined using the ¹H-NMR Nightingale platform for the quantification of 250 parameters of metabolism, including routine lipids, extensive lipoprotein subclasses, fatty acid composition, and various low-molecular metabolites, including amino acids, ketone bodies, and gluconeogenesis-related metabolites. Night shift workers had an increased BMI (26.6 vs. 25.9 kg/m²) compared with day workers (non-shift workers) in both sexes, were slightly more likely to be ever smokers (only in males) (54% vs. 46%), worked on average 5.9 ± 3.7 night shifts per month, and had been working in night shifts for 18.3 ± 10.5 years on average. We observed changes in several metabolic markers in male night shift workers compared with non-shift workers, but no changes were observed in women. In men, we observed higher levels of glycoprotein acetyls (GlycA), triglycerides, and fatty acids compared with non-shift workers. The changes were seen in the ratio of triglycerides and cholesterol(esters) to total lipids in different sizes of VLDL particles. Glycoprotein acetyls (GlycAs) are of particular interest as markers since they are known as biomarkers for low-grade chronic inflammation. When the analyses were adjusted for BMI, no significant associations were observed. Further studies are needed to better understand the relationship between night shift work and metabolic profiles, particularly with respect to the role of sex and BMI in this relationship.

Shift-Work Schedule Intervention for Extending Restart Breaks after Consecutive Night Shifts: A Non-randomized Controlled Cross-Over Study

More knowledge is required to determine the optimal shiftwork schedule to reduce the harmful effects of short restart breaks between shifts. This 5-month intervention study aimed to examine the effectiveness of extended restart breaks from 31 h to 55 h after consecutive night shifts by considering the characteristics of the circadian rhythm to mitigate fatigue and sleep among 30 shift-working nurses. Subjective and objective variables, such as vital exhaustion, distress, hair cortisol, salivary C-reactive protein, and sleep mattress sensor sensation, were repeatedly measured to examine the differences between the intervention and control conditions. Two-way (condition × time) multilevel analyses showed significantly lower levels of vital exhaustion and distress in the intervention condition (p = 0.005 and p = 0.004, respectively). However, the expected benefit of the intervention was not observed in objectively measured variables. These findings suggested that an extended restart break after consecutive night shifts can moderately decrease occupational fatigue and stress.

The Time-Varying Effect of Participatory Shift Scheduling on Working Hour Characteristics and Sickness Absence: Evidence from a Quasi-Experiment in Hospitals

Participatory shift scheduling for irregular working hours can influence shift schedules and sickness absence. We investigated the effects of using participatory shift scheduling and shift schedule evaluation tools on working hour characteristics and sickness absence. We utilized a panel data for 2015-2019 with 16,557 hospital employees (6143 in the intervention and 10,345 in the control group). Difference-in-differences regression with ward-level clustered standard errors was used to estimate the average treatment effect on the treated coefficients relative to timing of the intervention with 95% confidence intervals (CI). Using participatory scheduling tool increased long working hours and weekend work and had delayed effects on the short (1-3 days) sickness absences. Increased effects were observed: 0.2 [95% CI 0.0-0.4] days for the second, and 0.8 [95% CI 0.5-1.0] for the third year after the onset of intervention. An average increase of 0.5 [95% CI 0.1-0.9] episodes on all sickness absence episodes was observed for the third year. Using the shift schedule evaluation tool with the participatory shift scheduling tool attenuated the adverse effects. To conclude, participatory shift scheduling increased some potentially harmful working hour characteristics but its effects on sickness absence were negligible, and further attenuated by using the shift schedule evaluation tool.

Research priorities to reduce risks from work hours and fatigue in the healthcare and social assistance sector

BACKGROUND

The services of Healthcare and Social Assistance (HCSA) workers are needed by society around the clock. As a result, these workers are exposed to shift work and long work hours. The combination of demanding work schedules and other hazards in the HCSA work environment increases the health and safety risks to these workers, as well as to their patients/clients and the public.

METHODS

This paper has three aims: (1) provide an overview of the burden of shift work, long hours, and related sleep and fatigue problems in this sector; (2) suggest research priorities that would improve these; and (3) discuss potential positive impacts of addressing these research priorities for the health and safety of workers and the public. The authors used a modified Delphi approach to anonymously rank-order priorities for improving HCSA worker health and safety and public safety. Input was also obtained from attendees at the 2019 National Institute for Occupational Safety and Health (NIOSH) Work Hours, Sleep, and Fatigue Forum.

RESULTS

The highest rated research priorities were developing better designs for work schedules, and improving the HCSA culture and leadership approaches to shift work and long work hours. Additional priorities are identified.

CONCLUSION

Research in these priority areas has the potential to benefit HCSA workers as well as their patients/clients, employers, and society.

Development and validation of the Nurse's Workplace Mental Health Questionnaire

OBJECTIVES

This study aimed to develop and validate the Nurse's Workplace Mental Health Questionnaire (NWMHQ).

METHODS

The questionnaire was developed based on the two continua model of mental illness and health proposed by Keyes. The initial questionnaire was generated through literature review, two rounds of Delphi expert consultation, followed by a pilot survey. Finally, the reliability and validity of the questionnaire were validated through an online survey of 2,815 registered nurses selected from the public hospitals in 11 provinces from June to July 2020.

RESULTS

The item-content validity index (I-CVI) of the questionnaire ranged from 0.750 to 1.000 and the average scale-level content validity index (S-CVI/Ave) was 0.906. Cronbach's α coefficient was 0.948 and test-retest reliability was 0.850. The self-rating depression scale score was negatively related to the NWMHQ score (r = -0.664, P < 0.01). The exploratory factor analysis (EFA) yielded six factors (emotional status, psychological security, positive relationship, resilience, self-efficacy, and subjective well-being), consisting of 32 items. The cumulative variance contribution rate was 65.58%. Confirmatory factor analysis (CFA) showed an acceptable fit.

CONCLUSION

The NWMHQ developed in this study showed good reliability and validity. This questionnaire may help assess the mental health status of nurses and help nursing managers to develop appropriate targeted psychological interventions.

Night Work and Sustainable Working Life-A Prospective Trajectory Analysis of Swedish Twins

The aim was to investigate the changes in sustainable working life over 10-13 years of follow-up and the effect of baseline night work. Data from the Swedish national registers were used to define sustainable working life. Survey data in the 1998-2003 "SALT" with 34,680 twins or in the 2004-2006 "STAGE" with 19,637 twins were utilized to assess night work at baseline. Group-based trajectory and multinomial regression models were applied. The results of the SALT cohort yielded five trajectory solutions: stable sustainable working life (40%), stable lack of sustainable working life (25%), later decreasingly sustainable working life (15%), increasingly sustainable working life (14%), and early decreasingly sustainable working life (7%). In the STAGE cohort, four trajectories were detected: stable sustainable working life (83%), decreasingly sustainable working life (7%), stable lack of sustainable working life (5%), and increasing sustainable working life (5%). Night work was associated with the decreasing or increasing sustainable working life in the trajectory groups. To conclude, the largest parts of both cohorts followed trajectories of stable sustainable working lives. Night work was associated with both the trajectories of decreasing and increasing sustainable working lives.

Cancer Hazard Evaluations for Contemporary Needs: Highlights From New National Toxicology Program Evaluations and Methodological Advancements

The National Toxicology Program strives to raise awareness of cancer hazards in our environment. Identifying cancer hazards is key to primary prevention, informing public health decision making, and decreasing the global cancer burden. In December 2021, the US congressionally mandated 15th Report on Carcinogens was released, adding 8 new substances to the cumulative report. Chronic infection with Helicobacter pylori is listed as "known to be a human carcinogen." Antimony trioxide and 6 haloacetic acids found as water disinfection by-products-dichloroacetic acid, dibromoacetic acid, bromochloroacetic acid, tribromoacetic acid, bromodichloroacetic acid, chlorodibromoacetic acid-are listed as "reasonably anticipated to be a human carcinogen." A new dashboard provides interactive visualization and interrogation of the 256 listed substances, their uses, and associated cancers. Also, the National Toxicology Program recently published a Cancer Hazard Assessment Report on exposure scenarios associated with circadian disruption, concluding that persistent night shift work can cause breast cancer and certain lighting conditions may cause cancer. As highlighted in these reports and evaluations, we are evolving our approaches to meet contemporary challenges. These approaches include focusing on real-world exposures and advancing our methods to address challenges in cancer hazard assessments (eg, developing more structured approaches to evaluate mechanistic data and incorporating read-across approaches to assess chemicals lacking adequate human or animal cancer data). To promote public health, we provide information on environmental health disparities and disease prevention. Building on these efforts, we aim to continue our contributions to the war on cancer, declared 50 years ago.

Self-Reported Sleepiness after 2, 4, and 7 Consecutive Night Shifts and Recovery Days in Danish Police Officers

BACKGROUND

Night shift work often implies shorter sleep duration and this can lead to sleepiness, which has been associated with an increased risk of accidents and injuries. The aim is to study how the number of consecutive night shifts affects self-reported sleepiness.

PARTICIPANTS AND METHODS

The study was a quasi-experimental, within-subject crossover study with 73 police officers. Three work schedules of two, four, and seven consecutive night shifts followed by the same number of recovery days, i.e., days worked or days off, was performed by all participants. Sleepiness was self-reported using the Karolinska sleepiness scale (KSS) every fourth hour on the last night shift and the last recovery day in each sequence.

RESULTS

We observed differences in the level of sleepiness between recovery days and night shift days but no differences in the pattern of sleepiness levels on night shift days in the different work schedules. The highest levels of KSS were observed before bedtime (at 07:00 after a night shift and 23:00 on a recovery day).

CONCLUSION

The number of consecutive night shifts did not affect the self-reported levels of self-reported sleepiness among Danish police officers.

A Longitudinal Study on Trajectories of Night Work and Sickness Absence among Hospital Employees

This study aimed to investigate trajectories of night shift work in irregular shift work across a 12-year follow-up among hospital employees with and without sickness absence (SA). The payroll-based register data of one hospital district in Finland included objective working hours and SA from 2008 to 2019. The number of night shifts per year was used in group-based trajectory modeling (GBTM). The results indicate that, among those who had any sickness absence episodes, the amount of night work decreased prior to the first SA. In general, trajectories of night shift work varied from stably high to low-but-increasing trajectories in terms of the number of shifts. However, a group with decreasing pattern of night work was identified only among those with sickness absence episodes but not among those without such episodes. To conclude, the identified trajectories of night work with or without sickness absences may indicate that, among those with sickness absence episodes, night work was reduced due to increasing health problems. Hence, the hospital employees working night shifts are likely a selected population because the employees who work at night are supposed to be healthier than those not opting for night work.

Working hour characteristics in the Finnish retail sector - a registry study on objective working hour data

Earlier research is lacking on the prevalence and nature of objective working hour characteristics in the retail sector. We developed a codification in the retail sector and investigated differences in objective working hour characteristics by part-time work, sex and age. The payroll-based registry data of objective working hours consisted >12,000 employees of the retail sector in Finland for 2018-2020. Descriptive statistics for means, standard deviations (SD) and range of annual working hour characteristics were calculated, the differences in means were tested, partially based on the protocol established for health care sector. The final sample had 60-63% part-time employees and 23% men. Morning shifts were more frequent (48-51%) among full-time employees compared to 27-30% of the part-time employees. Evening shifts, 43-46%, were frequent among part-time employees vs. 26% in full-time. No sex differences were detected, and age group differences only among part-time employees. To conclude, the codification for registry-based working hour data enables us to identify individual differences in working hour characteristics. The working hour characteristics differed between part-time and full-time employees, not between sexes, whereas age differences were minor and among part-time employees. The codification could be used in studies of the retail sector in association with health and wellbeing.

Night-shift work is associated with increased susceptibility to SARS-CoV-2 infection

Night-shift workers experience disturbances of their circadian rhythm and sleep, which may make them more susceptible to infectious diseases. Therefore, we studied whether night-shift workers are at higher risk of testing positive for SARS-CoV-2 infection than day workers. In this prospective study, data were used from 20 questionnaire rounds of the Dutch Lifelines COVID-19 cohort that was initiated in March 2020. In the different questionnaire rounds, 2285 night-shift workers and 23,766 day workers reported whether they had tested positive for SARS-CoV-2. Cox proportional hazards regression models adjusted for demographic, work, and health covariates were used to compare SARS-CoV-2 incidence between night-shift and day workers. From March 2020-January 2021, 3.4% of night-shift workers and 2.2% of day workers reported to have tested positive for SARS-CoV-2 (p < .001). After adjustment for covariates, night-shift workers had a 37% higher risk of testing positive for SARS-CoV-2 (hazard ratio: 1.37, 95% confidence interval: 1.05-1.77). In this study, we show that night-shift workers were more likely to test positive for SARS-CoV-2 than day workers, which adds to the growing evidence that night-shift work may influence the complex processes involved in infection susceptibility. Further mechanistic insight is needed to understand the relation between night-shift work and (SARS-CoV-2) infection susceptibility.

Night work, chronotype and cortisol at awakening in female hospital employees

To examine the effect of night shift on salivary cortisol at awakening (C1), 30 min later (C2), and on the cortisol awakening response (CAR, the difference between C2 and C1). We compared shift and non-shift workers with a focus on the impact of worker chronotype. Our study included 66 shift-working females (mean age = 37.3 years, SD = 10.2) and 21 non-shift working females (mean age = 47.0 years, SD = 8.9). The shift workers collected their saliva samples at C1 and C2 on each two consecutive day shifts and night shifts. Non-shift workers collected their samples on two consecutive day shifts. We applied linear mixed-effects models (LMM) to determine the effect of night shift on CAR and log-transformed C1 and C2 levels. LMMs were stratified by chronotype group. Compared to non-shift workers, shift workers before day shifts (i.e. after night sleep) showed lower cortisol at C1 (exp [Formula: see text]=0.58, 95% CI 0.42, 0.81) but not at C2. In shift workers, the CARs after night shifts (i.e. after day sleep) were lower compared to CARs before day shifts ([Formula: see text]= - 11.07, 95% CI - 15.64, - 6.50). This effect was most pronounced in early chronotypes (early: [Formula: see text]= - 16.61, 95% CI - 27.87, - 5.35; intermediate: [Formula: see text]= - 11.82, 95% CI - 18.35, - 5.29; late: [Formula: see text]= - 6.27, 95% CI - 14.28, 1.74). Chronotype did not modify the association between night shift and CAR. In our population of shift workers, there was a mismatch between time of waking up and their natural cortisol peak at waking up (CAR) both during day and night shift duties.

Sleep, sleepiness and need for recovery of industrial employees after a change from an 8- to a 12-hour shift system

Employees often prefer 12-hour work shifts but they can increase sleepiness and injury risk. We assessed whether sleep, sleepiness, satisfaction and need for recovery changed after changing from an 8-hour to a 12-hour shift system. The participants were 178 employees of the paper, pulp and chemical industries. Using a quasi-experimental controlled intervention design, 83 employees, who changed from an 8-hour shift schedule to a 12-hour shift schedule were compared to those who remained in the 8-hour shift schedule (n=95). Participants filled in a survey on sleep, sleepiness, satisfaction and need for recovery at baseline and 9-12 months after the shift schedule change. We used generalized estimation equation models adjusted for age, sex, shift work experience in years and baseline shift system. Sleep length was longer in the 12-hour shift schedule before the first morning shift and between morning shifts. Sleepiness during morning shifts was less frequent and satisfaction with the shift system was more prevalent in the 12-hour shift schedule. Also, perceived negative associations of the current shift system with work-life balance were less common in the 12-hour shift schedule. The differences found between the shift systems were minor and the results did not indicate significant disadvantages of the 12-hour fast forward-rotating shift system.

The potential anti-cancer effects of melatonin on breast cancer

Melatonin is the primary hormone of the pineal gland that is secreted at night. It regulates many physiological functions, including the sleep-wake cycle, gonadal activity, free radical scavenging, immunomodulation, neuro-protection, and cancer progression. The precise functions of melatonin are mediated by guanosine triphosphate (GTP)-binding protein (G-protein) coupled melatonin receptor 1 (MT1) and MT2 receptors. However, nuclear receptors are also associated with melatonin activity. Circadian rhythm disruption, shift work, and light exposure at night hamper melatonin production. Impaired melatonin level promotes various pathophysiological changes, including cancer. In our modern society, breast cancer is a serious problem throughout the world. Several studies have been indicated the link between low levels of melatonin and breast cancer development. Melatonin has oncostatic properties in breast cancer cells. This indolamine advances apoptosis, which arrests the cell cycle and regulates metabolic activity. Moreover, melatonin increases the treatment efficacy of cancer and can be used as an adjuvant with chemotherapeutic agents.