Night Shift Work and Risk of Depression: Meta-analysis of Observational Studies

Comparing risk of depression between day and night/shift workers using the PHQ-9: a study utilizing the 2014, 2016, and 2018 Korea National Health and Nutrition Examination Survey data

Background

In today's work scenario, the number of shift workers, including those in night shifts, is increasing. Shift work can adversely affect workers' health in the long run, but studies on the relationship between shift work and depression have shown inconsistent results. This study aimed to determine whether the number of night/shift workers at risk of depression, as predicted by the Patient Health Questionnaire-9 (PHQ-9), is higher than that of day workers.

Methods

This study was conducted based on data from the 6th and 7th Korea National Health and Nutrition Examination Survey, 2014, 2016, and 2018. Work schedules were classified into 2 types: day work and night/shift work. This study used the PHQ-9, a self-reported depression screening test, to identify workers at risk of depression. Statistical analysis was performed using SPSS 26.0, and descriptive statistics, χ² test, and logistic regression analysis were employed.

Results

After adjusting for age, educational level, working hours per week, and income, men engaging in night/shift work were at a higher risk of depression (odds ratio [OR]: 1.407, 95% confidence interval [CI]: 0.937-2.113). The same was confirmed for women (OR: 1.564, 95% CI: 1.176-2.081).

Conclusions

Our results showed that the OR for those engaged in night/shift work with a PHQ-9 score of 10 or more increased. Considering the large volume of psychiatric history and symptoms in Korea, additional research is needed. Additionally, further discussion on ways to provide realistic help to night/shift workers is warranted.

Sox2 Ablation in the Suprachiasmatic Nucleus Perturbs Anxiety- and Depressive-like Behaviors

Mood disorders negatively impact the lives of hundreds of millions of individuals worldwide every year, yet the precise molecular mechanisms by which they manifest remain elusive. Circadian dysregulation is one avenue by which mood disorders are thought to arise. SOX2 is a transcription factor that is highly expressed in the murine suprachiasmatic nucleus (SCN), the circadian master clock, and has been recently found to be an important regulator of Per2, a core component of the molecular clock. Genetic ablation of the Sox2 gene in GABAergic neurons selectively impacts SCN neurons, as they are one of very few, if not the only, GABAergic populations that express Sox2. Here, we show that GABAergic-restricted ablation of Sox2 results in anxio-depressive-like phenotypes in mice as observed in the elevated plus maze, forced swim test, tail suspension test, and sucrose preference test. We further observe a reduction in basal and/or forced swim-induced c-Fos expression, a marker of neuronal activation, in the nucleus incertus, arcuate nucleus, and dentate gyrus of Sox2 conditional knockout (cKO) mice. Given the restricted disruption of SOX2 expression in the SCN of Sox2 cKO mice, we propose that their mood-associated phenotypes are the consequence of a dysregulated central clock that is unable to communicate appropriately timed signals to other brain nuclei that regulate affective behaviors.

Every Night and Every Morn: Effect of Variation in CLOCK Gene on Depression Depends on Exposure to Early and Recent Stress

The role of circadian dysregulation is increasingly acknowledged in the background of depressive symptoms, and is also a promising treatment target. Similarly, stress shows a complex relationship with the circadian system. The CLOCK gene, encoding a key element in circadian regulation has been implicated in previous candidate variant studies in depression with contradictory findings, and only a few such studies considered the interacting effects of stress. We investigated the effect of CLOCK variation with a linkage-disequilibrium-based clumping method, in interaction with childhood adversities and recent negative life events, on two phenotypes of depression, lifetime depression and current depressive symptoms in a general population sample. Methods: Participants in NewMood study completed questionnaires assessing childhood adversities and recent negative life events, the Brief Symptom Inventory to assess current depressive symptoms, provided data on lifetime depression, and were genotyped for 1054 SNPs in the CLOCK gene, 370 of which survived quality control and were entered into linear and logistic regression models with current depressive symptoms and lifetime depression as the outcome variable, and childhood adversities or recent life events as interaction variables followed by a linkage disequilibrium-based clumping process to identify clumps of SNPs with a significant main or interaction effect. Results: No significant clumps with a main effect were found. In interaction with recent life events a significant clump containing 94 SNPs with top SNP rs6825994 for dominant and rs6850524 for additive models on current depression was identified, while in interaction with childhood adversities on current depressive symptoms, two clumps, both containing 9 SNPs were found with top SNPs rs6828454 and rs711533. Conclusion: Our findings suggest that CLOCK contributes to depressive symptoms, but via mediating the effects of early adversities and recent stressors. Given the increasing burden on circadian rhythmicity in the modern lifestyle and our expanding insight into the contribution of circadian disruption in depression especially as a possible mediator of stress, our results may pave the way for identifying those who would be at an increased risk for depressogenic effects of circadian dysregulation in association with stress as well as new molecular targets for intervention in stress-related psychopathologies in mood disorders.

How Is Work Ability Shaped in Groups of Shift and Non-Shift Workers? A Comprehensive Approach to Job Resources and Mediation Role of Emotions at Work

There is much less research on the relationship between shift work and positive states experienced in the workplace, e.g., emotions and work ability. Using the job demands-resources model, conservation of resources theory and the broaden-and-build theory as theoretical frameworks, the direct and indirect (mediated via positive and negative emotions) relations between the complex of job resources and work ability were tested in the group of shift and non-shift workers. Three types of resources related to task, leadership and interpersonal relations were taken into account. Data were collected among 1510 workers. Structural equation modelling (SEM) showed that only leadership was directly related to high work ability in both occupational groups. Indirect effects of positive and negative emotions were strongly supported. Both of them mediate the effects of the three analysed job resources on work ability, but individual job resources impacted were different. Leadership resources led to "good" work ability by the intensification of positive and reduction of negative emotions. Interpersonal resources decrease negative emotions. Task resources, conversely, intensified positive emotions, which in turn increased work ability. These research results shed more light on the ways of shaping work ability among shift and non-shift workers.

Do depression and its associated factors differ in women daytime and shift workers?: an analysis of the Korea National Health and Nutrition Examination Survey 2018

Purpose

This study examined health behaviors, use of health services, and depression among women who perform daytime and shift work in Korea, as well as factors related to depression.

Methods

We conducted a secondary analysis using data from the 2018 data of the 7th Korea National Health and Nutrition Examination Survey. Data on women, 1,493 regular daytime workers and 322 shift workers, were analyzed.

Results

Women shift workers were younger (χ²=43.97, p<.001), had a lower education level (χ²=45.56, p<.001), and lower personal income (χ²=16.85, p=.030) than their daytime counterparts. A higher proportion of shift workers were unmarried (χ²=37.47, p<.001) and they typically worked fewer than 40 hours per week (χ²=69.94, p<.001). The depression score of shift workers was higher than that of daytime workers (t=2.85, p=.005). A higher proportion of shift workers also drank alcohol (χ²=6.49, p=.032) and smoked (χ²=30.79, p<.001). Over 8% of shift workers typically slept fewer than 5 hours per night (χ²=14.17, p=.024). It was confirmed that depression in women shift workers was affected by age, personal income, marital status, health status, and smoking status, in addition to cancer screening participation, unmet medical care needs, and unmet dental care needs.

Conclusion

More attention should be given to the health needs of women working shifts. Health promotion programs specific for women shift workers are needed to improve their physical and mental health, encourage use of medical care services, and improve public health policies and systems.

Effects of Long Working Hours and Night Work on Subjective Well-Being Depending on Work Creativity and Task Variety, and Occupation: The Role of Working-Time Mismatch, Variability, Shift Work, and Autonomy

This study explored the effects of long working hours (LW) and night work (NW) on subjective well-being and the modifying effects of work creativity and task variety (WCTV) and occupation. In addition, we examined the influence of working time-related variables including working-time mismatch, variability, shift work, and autonomy on the effects of LW and NW. This study used data from the 5th Korean Working Conditions Survey on 50,205 workers. LW and NW were defined as 52–60 h (L1) or >60 h (L2) per week, and 1–10 days (N1) or >10 days (N2) of night work per month. Multiple logistic regression was used to examine the effects of LW and NW and the modifying influences of WCTV and occupation. Differences in ORs of LW and NW caused by working time-related variables were investigated, to determine effect sizes and directions. A high level of WCTV alleviated the risks of LW and NW. White-collar workers were more vulnerable to the risk associated with NW. Regarding working-time related variables, working-time mismatch and variability increased the risks of LW and NW, respectively, while shift work alleviated the risks of NW. In countries where flexible work systems are not well utilized, working-time autonomy might not be associated with the risk of LW or NW. This study showed that it is necessary to comprehensively consider the occupation and task characteristics of individual workers performing LW or NW. Further studies of the modifying effects of working time-related variables on LW and NW are needed.

Working Time Characteristics and Mental Health among Corrections and Transportation Workers

OBJECTIVES

Mental health disorders are a leading cause of work disability and while the psychosocial workplace environment plays a critical role, working time characteristics are also implicated. We sought to examine the association between working time characteristics and mental health in a cohort of two unionized, full-time worker populations, correctional supervisors, and transportation maintainers.

METHODS

Using a cross-sectional study design, we surveyed workers on working time characteristics across seven domains including length of the shift, the intensity or proximity of sequential shifts, the time of day, and social aspects of work hours including predictability, variability, control, and free time. Burnout symptoms (Oldenburg Burnout Inventory) and depressive symptoms (eight-item Centers for Epidemiologic Studies Depression Scale) were assessed along with the psychosocial work environment and health behaviors. We used log-binomial regression models to estimate prevalence ratios and 95% confidence intervals after adjusting for age, gender, and company.

RESULTS

A total of 318 workers were surveyed. The majority (72%) of workers reported a fixed shift. The prevalence of burnout symptoms was higher among workers reporting more frequent shift intensity (working 6 or more days in a row) (PR: 1.15, 95% CI: 1.01, 1.31; P = 0.04). Low psychological demands and high worker social support were associated with fewer burnout symptoms, independent of working time characteristics. The prevalence of depressive symptoms was higher in workers reporting more frequent unpredictable work (PR: 1.17, 95% CI: 1.01, 1.35; P = 0.04) and was lower among workers reporting increased schedule control (PR: 0.86, 95% CI: 0.77, 0.96; P = 0.01). Higher worker social support as well as sufficient sleep and adequate exercise were associated with fewer depressive symptoms, independent of working time characteristics.

CONCLUSIONS

Different working time characteristics were associated with work-related mental health (i.e. burnout) as well as general mental health (i.e. depressive symptoms). Work intensity was associated with the prevalence of burnout symptoms and the results suggest that the mechanism may be through the need for recovery from the psychosocial exposures of work. Both schedule control and predictability were associated with depressive symptoms and the results suggest that work-life imbalance and lack of recovery may be implicated. Comprehensive prevention policies that consider work organization along with the psychosocial work environment and work-life balance may help to improve workers' mental health.

Shift Work Disorder, Insomnia, and Depression among Offshore Oil Rig Workers

Objective: Numerous offshore jobs require 24-hour tasks, such as in industrial workplaces (eg, oil rigs). The purpose of this study was to assess shift work disorder (SWD), insomnia, daytime sleepiness, and depression among Iranian offshore oil rig workers in different shift schedules. Method : This cross-sectional study was conducted on Iranian offshore oil workers at the Persian Gulf. A questionnaire package consisted of Epworth Sleepiness Scale (ESS), Insomnia Severity Index (ISI), Beck Depression Inventory (BDI- II), and SWD filled. The scores were calculated among different groups of shift schedules (fixed-day, fixed-night, swing and standby shift workers). ISI, BDI-II, and ESS scores were also compared between individuals with or without SWD. Results: A total of 188 participants were recruited in the study, and all were male. The mean age was 37.06 ± 9.2 years. Among different shift schedules, the highest and lowest ISI and ESS scores were related to fixed-night shifts workers and fixed-day shift workers, respectively. ISI, ESS, and BDI mean scores in different shift schedules were not significantly different (p values = 0.14, 0.57, and 0.93, respectively). SWD was diagnosed in 57 (30.3%) of studied shift workers. The difference between SWD prevalence was not significant between different shift schedules (P value =0.13). Workers with SWD had higher ISI, ESS, and BDI-II score (P values <0.0001, <0.0001, and <0.0001, respectively) and workers without SWD had higher job satisfaction (p value = 0.04). Conclusion: SWD is considered as a serious health-related issue in Persian Gulf oil rig shift workers. Insomnia, daytime sleepiness, and depression are associated with SWD.

An analysis of shiftwork and self-reported depressive symptoms in a police cohort from Buffalo, New York

Shiftwork has been associated with elevated depressive symptoms; police officers frequently work shifts and may experience depressive symptoms. This study assessed the association between depressive symptoms and shiftwork in a police cohort from Buffalo, New York, USA using a repeated cross-sectional design with data collected in 2004-2009 (n = 428) and 2010-2014 (n = 261). Electronic payroll records were used to quantitatively classify officers on the day, evening, or night shift based on the shift they spent most of their working hours. Two self-reported depressive symptomology measures were used as outcomes - the Center for Epidemiological Studies - Depression (CES-D) scale and the Beck Depression Inventory (BDI). Repeated measures linear and logistic regression analyses were used to estimate least squares means or odds, respectively, of depressive symptom questionnaire scores by shiftwork category. Those working the evening/night shift had higher odds for depressive symptoms according to the BDI (based on a cut-point score of 14) than those working the day shift (OR = 4.60, 95% CI = 1.15-18.39). Similar results were observed for the evening shift group. No differences in mean CES-D or BDI scores were observed between groups for short-term shiftwork, long-term shiftwork, or shift changes. After stratifying by stress, as measured by the Perceived Stress Scale (PSS), total Impact of Events (IES), and the Spielberger Police Stress Survey (SPSS), mean values for depressive symptoms were higher in the high-stress categories regardless of shiftwork status. Further research should include biomarkers for depression, a longitudinal study design with a larger cohort, and joint effects of shiftwork and stress on depressive symptoms.

Associations of multiple occupational exposures with major depressive and generalized anxiety disorders: Findings from the French National Working Conditions Survey

BACKGROUND

There have been numerous studies on the associations between psychosocial work factors and mental health, but very few of them explored the cumulative effects of these factors. The objectives were to study the associations between multiple occupational exposures and two common mental disorders, major depressive episode (MDE) and generalized anxiety disorder (GAD), among employees in France.

METHODS

The data came from the 2016 French National Working Conditions Survey based on a representative sample of 20,430 employees (8579 men and 11,851 women) aged 15-65 years. MDE and GAD were assessed using the MINI (Mini International Neuropsychiatric Interview) standardized diagnostic interview. Occupational exposures included 21 psychosocial work factors grouped into five dimensions, four factors related to working time/hours, and four physical work exposures. Logistic regression modeling for weighted data was performed to evaluate the associations of occupational exposures with MDE and GAD in men and women separately.

RESULTS

The prevalence of MDE and GAD was higher among women (8.6% and 8.7%, respectively) than among men (4.3% and 4.6%). Most psychosocial work factors were associated with MDE and/or GAD. A linear increase in the risk of MDE/GAD with the number of psychosocial work factors was found for each dimension, except workplace violence. The risk of MDE also increased linearly with multiple physical work exposures.

CONCLUSIONS

Our results showed that a wide variety of occupational exposures were associated with clinical depression and anxiety, and that the risk of disease increased with multiple exposures to psychosocial and physical factors at work.

A Comparison of Safety, Health, and Well-Being Risk Factors Across Five Occupational Samples

Objective: The aim of this study was to present safety, health and well-being profiles of workers within five occupations: call center work (N = 139), corrections (N = 85), construction (N = 348), homecare (N = 149), and parks and recreation (N = 178). Methods: Baseline data from the Data Repository of Oregon's Healthy Workforce Center were used. Measures were compared with clinical healthcare guidelines and national norms. Results: The prevalence of health and safety risks for adults was as follows: overweight (83.2%), high blood pressure (16.4%), injury causing lost work (9.9%), and reported pain (47.0%). Young workers were least likely to report adequate sleep (46.6%). Construction workers reported the highest rate of smoking (20.7%). All of the adult workers reported significantly lower general health than the general population. Conclusion: The number of workers experiencing poor safety, health and well-being outcomes suggest the need for improved working conditions.

Non-Pharmacological Interventions to Improve Chronic Disease Risk Factors and Sleep in Shift Workers: A Systematic Review and Meta-Analysis

Shift work is associated with adverse chronic health outcomes. Addressing chronic disease risk factors including biomedical risk factors, behavioural risk factors, as well as sleep and perceived health status, affords an opportunity to improve health outcomes in shift workers. The present study aimed to conduct a systematic review, qualitative synthesis, and meta-analysis of non-pharmacological interventions targeting chronic disease risk factors, including sleep, in shift workers. A total of 8465 records were retrieved; 65 publications were eligible for inclusion in qualitative analysis. Random-effects meta-analysis were conducted for eight eligible health outcomes, including a total of thirty-nine studies. Interventions resulted in increased objective sleep duration (Hedges' g = 0.73; CI: 0.36, 1.10, k = 16), improved objective sleep efficiency (Hedges' g = 0.48; CI: 0.20, 0.76, k = 10) and a small increase in both subjective sleep duration (Hedges' g = 0.11; CI: -0.04, 0.27, k = 19) and sleep quality (Hedges' g = 0.11; CI: -0.11, 0.33, k = 21). Interventions also improved perceived health status (Hedges' g = 0.20; CI: -0.05, 0.46, k = 8), decreased systolic (Hedges' g = 0.26; CI: -0.54, 0.02, k = 7) and diastolic (Hedges' g = 0.06; CI: -0.23, 0.36, k = 7) blood pressure, and reduced body mass index (Hedges' g = -0.04; CI: -0.37, 0.29, k = 9). The current study suggests interventions may improve chronic disease risk factors and sleep in shift workers; however, this could only be objectively assessed for a limited number of risk factor endpoints. Future interventions could explore the impact of non-pharmacological interventions on a broader range of chronic disease risk factors to better characterise targets for improved health outcomes in shift workers.

A systematic review and meta-analysis of the association between shift work and metabolic syndrome: The roles of sleep, gender, and type of shift work

This study was conducted to investigate the association between shift work and metabolic syndrome (MetS) and quantify the roles of sleep, gender, and type of shift work. We searched online databases, including PubMed, Scopus, and Web of Science on November 17, 2019. Of the 821 articles identified, 38 observational studies (27 cross-sectional, 10 cohorts, and one nested case-control), conducted on 128,416 participants, met our eligibility criteria. The pooled Odds ratio (OR) and 95% Confidence interval (CI) of MetS in shift-versus day-workers were estimated as 1.14 (1.07, 1.21) and 1.11 (1.06, 1.17) for the unadjusted and adjusted models. This association remained significant only for the studies with a cross-sectional design. There was a significantly higher odds of MetS in the studies conducted only on females (1.13 [1.06, 1.20]) or males (1.12 [1.02, 1.21]). The pooled adjusted OR (95% CI) for the studies without and with sleep adjustment was calculated as 1.14 (1.08, 1.21) and 1.29 (1.06, 1.52). We observed that rotating shift workers had stronger odds of MetS than the other shift workers. In conclusion, our findings revealed the significant odds of an association between shift work and MetS and different effects for sleep, gender, and type of shift work.

Disrupted circadian rhythms and mental health

During the evolution of life, the temporal rhythm of our rotating planet was internalized in the form of circadian rhythms. Circadian rhythms are ~24h internal manifestations that drive daily patterns of physiology and behavior. These rhythms are entrained (synchronized) to the external environment, primarily by the light-dark cycle, and precisely controlled via molecular clocks located within the suprachiasmatic nucleus of the hypothalamus. Misalignment and/or disruption of circadian rhythms can have detrimental consequences for human health. Indeed, studies suggest strong associations between mental health and circadian rhythms. However, direct interactions between mood regulation and the circadian system are just beginning to be uncovered and appreciated. This chapter examines the relationship between disruption of circadian rhythms and mental health. The primary focus will be outlining the association between circadian disruption, in the form of night shift work, exposure to light at night, jet lag, and social jet lag, and psychiatric illness (i.e., anxiety, major depressive disorder, bipolar disorder, and schizophrenia). Additionally, we review animal models of disrupted circadian rhythms, which provide further evidence in support of a strong association between circadian disruption and affective responses. Finally, we discuss future directions for the field and suggest areas of study that require further investigation.

Rhythms, Reward, and Blues: Consequences of Circadian Photoperiod on Affective and Reward Circuit Function

Circadian disruptions, along with altered affective and reward states, are commonly associated with psychiatric disorders. In addition to genetics, the enduring influence of environmental factors in programming neural networks is of increased interest in assessing the underpinnings of mental health. The duration of daylight or photoperiod is known to impact both the serotonin and dopamine systems, which are implicated in mood and reward-based disorders. This review first examines the effects of circadian disruption and photoperiod in the serotonin system in both human and preclinical studies. We next highlight how brain regions crucial for the serotoninergic system (i.e., dorsal raphe nucleus; DRN), and dopaminergic (i.e., nucleus accumbens; NAc and ventral tegmental area; VTA) system are intertwined in overlapping circuitry, and play influential roles in the pathology of mood and reward-based disorders. We then focus on human and animal studies that demonstrate the impact of circadian factors on the dopaminergic system. Lastly, we discuss how environmental factors such as circadian photoperiod can impact the neural circuits that are responsible for regulating affective and reward states, offering novel insights into the biological mechanisms underlying the pathophysiology, systems, and therapeutic treatments necessary for mood and reward-based disorders.

Genomic perspectives on the circadian clock hypothesis of psychiatric disorders

Circadian rhythm disturbances are frequently described in psychiatric disorders such as major depressive disorder, bipolar disorder, and schizophrenia. Growing evidence suggests a biological connection between mental health and circadian rhythmicity, including the circadian influence on brain function and mood and the requirement for circadian entrainment by external factors, which is often impaired in mental illness. Mental (as well as physical) health is also adversely affected by circadian misalignment. The marked interindividual differences in this combined susceptibility, in addition to the phenotypic spectrum in traits related both to circadian rhythms and mental health, suggested the possibility of a shared genetic background and that circadian clock genes may also be candidate genes for psychiatric disorders. This hypothesis was further strengthened by observations in animal models where clock genes had been knocked out or mutated. The introduction of genome-wide association studies (GWAS) enabled hypothesis-free testing. GWAS analysis of chronotype confirmed the prominent role of circadian genes in these phenotypes and their extensive polygenicity. However, in GWAS on psychiatric traits, only one clock gene, ARNTL (BMAL1) was identified as one of the few loci differentiating bipolar disorder from schizophrenia, and macaque monkeys where the ARNTL gene has been knocked out display symptoms similar to schizophrenia. Another lesson from genomic analyses is that chronotype has an important genetic correlation with several psychiatric disorders and that this effect is unidirectional. We conclude that the effect of circadian disturbances on psychiatric disorders probably relates to modulation of rhythm parameters and extend beyond the core clock genes themselves.

Working nights and lower leisure-time physical activity associate with chronic pain in Southern African long-distance truck drivers: A cross-sectional study

Background

In South Africa, the trucking industry employs over 70,000 people and the prevalence of chronic pain in this occupational group was reported at 10%. We investigated factors associated with chronic pain in truck drivers including mental health, physical activity, and sleep, as no study has done so.

Methods

Southern African male, long-distance truck drivers were recruited at truck stops in Gauteng and Free State Provinces, South Africa (n = 614). Chronic pain was defined as pain present for at least the last three months. Depressive symptoms were assessed with the Patient Health Questionnaire-9, post-traumatic stress disorder with the Posttraumatic Stress Disorder Checklist for DSM-5 (PCL-5), exposure to traumatic events with the Life Events Checklist-5 (LEC-5) and daytime sleepiness with the Epworth Sleepiness Scale. Sleep quality was measured on a four-point Likert scale. Leisure-time physical activity was measured using the Godin-Shephard leisure-time physical activity questionnaire. Associations between these factors, demographic factors and chronic pain were investigated.

Results

Multivariate analysis showed that working ≥ 2 nights/week (OR = 2.68, 95% CI = 1.55–4.68) was associated with chronic pain and physical activity was protective (OR = 0.97, 95% CI 0.95–0.98). In an exploratory analysis, greater depressive symptoms (p = 0.004), daytime sleepiness (p = 0.01) and worse sleep quality (p = 0.001) was associated with working ≥ 2 nights/week. Lower leisure-time physical activity was associated with worse sleep quality (p = 0.006), but not daytime sleepiness or depressive symptoms (p>0.05).

Conclusions

There is a clear relationship between working nights and activity levels, and chronic pain, sleep quality, and depression in truck drivers.

Brain activity and transcriptional profiling in mice under chronic jet lag

Shift work is known to be associated with an increased risk of neurological and psychiatric diseases, but how it contributes to the development of these diseases remains unclear. Chronic jet lag (CJL) induced by shifting light-dark cycles repeatedly is a commonly used protocol to mimic the environmental light/dark changes encountered by shift workers. Here we subjected wildtype mice to CJL and performed positron emission tomography imaging of glucose metabolism to monitor brain activities. We also conducted RNA sequencing using prefrontal cortex and nucleus accumbens tissues from these animals, which are brain regions strongly implicated in the pathology of various neurological and psychiatric conditions. Our results reveal the alterations of brain activities and systematic reprogramming of gene expression in brain tissues under CJL, building hypothesis for how CJL increases the susceptibility to neurological and psychiatric diseases.

Time-restricted feeding prevents depressive-like and anxiety-like behaviors in male rats exposed to an experimental model of shift-work

Individuals who regularly shift their sleep timing, like night and/or shift-workers suffer from circadian desynchrony and are at risk of developing cardiometabolic diseases and cancer. Also, shift-work is are suggested to be a risk factor for the development of mood disorders such as the burn out syndrome, anxiety, and depression. Experimental and clinical studies provide evidence that food intake restricted to the normal activity phase is a potent synchronizer for the circadian system and can prevent the detrimental health effects associated with circadian disruption. Here, we explored whether adult male Wistar rats exposed to an experimental model of shift-work (W-AL) developed depressive and/or anxiety-like behaviors and whether this was associated with neuroinflammation in brain areas involved with mood regulation. We also tested whether time-restricted feeding (TRF) to the active phase could ameliorate circadian disruption and therefore would prevent depressive and anxiety-like behaviors as well as neuroinflammation. In male Wistar rats, W-AL induced depressive-like behavior characterized by hypoactivity and anhedonia and induced increased anxiety-like behavior in the open field test. This was associated with increased number of glial fibrillary acidic protein and IBA-1-positive cells in the prefrontal cortex and basolateral amygdala. Moreover W-AL caused morphological changes in the microglia in the CA3 area of the hippocampus indicating microglial activation. Importantly, TRF prevented behavioral changes and decreased neuroinflammation markers in the brain. Present results add up evidence about the importance that TRF in synchrony with the light-dark cycle can prevent neuroinflammation leading to healthy mood states in spite of circadian disruptive conditions.

Night work for hospital nurses and sickness absence: a retrospective study using electronic rostering systems

There is conflicting evidence on the effect of night work on sickness absence. Most previous studies used self-reporting to identify shift patterns and measure levels of sickness absence. In contrast, this study used objective data from electronic rosters to explore the association of nurses' patterns of night work and sickness absence. This was a retrospective longitudinal study of nurse roster data from 32 general medical and surgical wards in a large acute hospital in England. We used data from 3 years and included both registered nurses and unregistered nursing assistants. We used generalized linear-mixed models to explore the association between night work and the subsequent occurrence of sickness absence. Of 601,282 shifts worked by 1944 nursing staff, 38,051 shifts were lost due to sickness absence. After controlling for potential confounders including proportion of long (≥12 h) shifts worked, proportion of overtime shifts, proportion of shifts worked in the past 7 days, and staff grade, we found that staff working more than 75% of their shifts in the past 7 days as night shifts were more likely to experience sickness absence (aOR = 1.12; 95% CI: 1.03-1.21), compared to staff working on day only schedules. Sub-group analysis found that an association between a high proportion of night shifts worked and long-term sickness (aOR = 1.31; 95% CI: 1.15-1.50), but not short-term sickness. Working high proportions of night shifts, likely representing permanent night work schedules, is associated with a higher risk of long-term sickness absence for nurses working in inpatient adult wards in acute hospitals. The higher sickness absence rates associated with permanent night shifts could result in additional costs or loss of productivity for hospitals. This study challenges the assumption that permanent night schedules maximize circadian adjustment and, therefore, reduce health problems.

Association of shift work with depression and anxiety in middle-aged adults: a large cross-sectional study among Iranian industrial manufacturing employees

Purpose

This study aimed to examine the association of shift work with depression and anxiety in a large sample of formal and contractual employees of a mill steel company, Isfahan, Iran.

Design/methodology/approach

This cross-sectional study was performed in 2014 among 3,060 formal and contractual employees of a mill steel company Isfahan, Iran, randomly selected from 16,000 people. Data gathering was done by some validated Iranian version of self-administered questionnaires including, International Physical Activity – Short Form, Effort–Reward Imbalance, Hospital Anxiety and Depression Scale. Logistic regression was used as the main statistical method.

Findings

The results showed individuals in the rotating shift compared with day shift had a higher risk of depression (OR: 1.43; 95% CI: 1.12–1.84). Whereas after adjustment for various confounders, this relationship was not significant (OR: 1.19; 95% CI: 0.81–1.76). Anxiety was not associated with shift work, both in crude and adjusted models (OR: 1.08; 95% CI: 0.81–1.44) and (OR: 0.90; 95% CI: 0.67–1.19), respectively.

Research limitations/implications

Owing to the cross-sectional design of this study, cause–effect relationships could not be inferred from our findings. All the data used in the present analysis were collected by self-administered questionnaires.

Practical implications

Although our findings did not show significant association between shift work and mental health, further studies are suggested for obtaining informative data worldwide in this regard among workforce particularly among industrial employees.

Originality/value

Few studies have addressed the effects of shift work on mental health among industrial employees worldwide, and there is no study in developing countries.

Symptoms of Posttraumatic Stress, Anxiety, Depression, Levels of Resilience and Burnout in Spanish Health Personnel during the COVID-19 Pandemic

The number of health workers infected with COVID-19 in Spain is one of the highest in the world. The aim of this study is to analyse posttraumatic stress, anxiety and depression during the COVID-19 pandemic. Associations between burnout, resilience, demographic, work and COVID-19 variables are analysed. Cross-sectional data on 1422 health workers were analysed. A total of 56.6% of health workers present symptoms of posttraumatic stress disorder, 58.6% anxiety disorder, 46% depressive disorder and 41.1% feel emotionally drained. The profile of a health worker with greater posttraumatic stress symptoms would be a person who works in the Autonomous Community of Madrid, in a hospital, is a woman, is concerned that a person he/she lives with may be infected, and thinks that he/she is very likely to be infected. The risk variables for anxiety and depression would be a person that is a woman, working 12- or 24-h shifts, and being worried that a family member could be infected. High scores on emotional exhaustion and depersonalization are risk factors for mental health, with resilience and personal fulfilment being protective variables. Data are provided to improve preventive measures for occupational health workers.

Healthy Behaviors through Behavioral Design-Obesity Prevention

Evidence for behavior modification for improved health outcomes was evaluated for nutrition, physical activity (PA), and indoor environmental quality (IEQ). The databases searched included LISTA, PubMed, and Web of Science, with articles rated using an a priori baseline score of 70/100 to establish inclusion. The initial search produced 52,847 articles, 63 of which were included in the qualitative synthesis. Thirteen articles met inclusion for nutrition: cafeteria interventions, single interventions, and vending interventions. Seventeen articles on physical activity were included: stair use, walking, and adjustable desks. For IEQ, 33 articles met inclusion: circadian disruption, view and natural light, and artificial light. A narrative synthesis was used to find meaningful connections across interventions with evidence contributing to health improvements. Commonalities throughout the nutrition studies included choice architecture, increasing the availability of healthy food items, and point-of-purchase food labeling. Interventions that promoted PA included stair use, sit/stand furniture, workplace exercise facilities and walking. Exposure to natural light and views of natural elements were found to increase PA and improve sleep quality. Overexposure to artificial light may cause circadian disruption, suppressing melatonin and increasing risks of cancers. Overall, design that encourages healthy behaviors may lower risks associated with chronic disease.

Social jetlag is associated with an increased likelihood of having depressive symptoms among the Japanese working population: the Furukawa Nutrition and Health Study

STUDY OBJECTIVES

Social jetlag, a mismatch between biological and social timing, has been reported to be associated with depressive symptoms among general population. However, evidence on this association is lacking among non-shift workers, who are under pressure to adapt themselves to a work schedule. We investigated the cross-sectional association of social jetlag with depressive symptoms among Japanese non-shift workers.

METHODS

This study included 1,404 employees, aged 18-78 years, who completed a study questionnaire at a periodic health checkup. Social jetlag was calculated as the absolute value of the difference in the midpoint of sleep times between weekdays and weekends. Depressive symptoms were assessed using the Center for Epidemiologic Studies Depression Scale. Multivariable logistic regression was used to estimate the odds ratio (OR) with adjustments for potential confounders including diet and chronotype.

RESULTS

Of the study participants, 63.5%, 28.4%, and 8.1% had less than 1 hour, 1 to less than 2 hours, and at least 2 hours of social jetlag, respectively. Greater social jetlag was significantly associated with an increased likelihood of having depressive symptoms. The multivariable-adjusted OR (95% confidence interval) were 1.30 (0.95 to 1.78) and 2.14 (1.26-3.62) for 1 to less than 2 hour and at least 2 hours compared to less than 1 hour of social jetlag. The association between social jetlag and depressive symptoms appeared to be linear, according to restricted cubic spline regression.

CONCLUSION

Results suggest that greater social jetlag is associated with an increased likelihood of having depressive symptoms among non-shift workers.

Prospective Associations Between Working Time Arrangements and Psychiatric Treatment in Denmark: Protocol for a Cohort Study

BACKGROUND

The burden of mental ill health in working-age populations has prompted research on possible links between work-related factors and mental ill health. Long working hours and night shift work are some of the factors that have been studied in relation to the risk of developing mental ill health. Yet, previous studies have not generated conclusive evidence, and further studies of high quality are needed.

OBJECTIVE

This study aims to investigate the prospective association between working time arrangements and mental health in terms of psychotropic drug usage or psychiatric hospital treatment in the general working population of Denmark.

METHODS

Data on total weekly working hours in any job and night shift work from the Danish Labor Force Survey 2000-2013 will be linked to data from the Psychiatric Central Research Register (expected 2400 cases during 700,000 person years at risk) and National Prescription Registry (expected 17,400 cases during 600,000 person years at risk). Participants will be followed for up to 5 years. We will use Poisson regression to separately analyze incidence rates of redeemed prescriptions for psychotropic medicine and incidence rates of psychiatric hospital treatment due to mood disorders, anxiety disorders, or stress-related disorders as a function of weekly working hours and night shift work. The analyses will be controlled for sex, age, calendar time of the interview, and socioeconomic status.

RESULTS

This is a study protocol. Power calculations indicate that the study has sufficient statistical power to detect relatively small differences in risks and minor interactions (eg, ~90% power to detect a rate ratio of 1.1 for psychoactive medication use). We expect the analyses to be completed by the end of 2020 and the results to be published in 2021.

CONCLUSIONS

In this study protocol, all hypotheses and statistical models of the project have been completely defined before we link the exposure data to the outcome data. The results of the project will indicate to what extent and in what direction the national burden of mental ill health in Denmark has been influenced by long working hours and night shift work.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

DERR1-10.2196/18236.

Interactive effects of personal resources and job characteristics on mental health: a population-based panel study

Purpose

We examined 10 job characteristics in a large population-based sample and tested for positive and negative effects on mental health. In addition, we tested for possible effects on mental health from interactions with locus of control and self-esteem.

Methods

The sample comprised longitudinal data on 2353 male and 1960 female employees from the German socio-economic panel collected between 2010 and 2012. Mental health was assessed with the mental component summary score derived from the short-form 12 health survey. We computed hierarchical regression analyses while controlling for potential confounds and baseline mental health. Interaction effects were specified with post hoc simple slope analyses.

Results

Time pressure, interruptions, job insecurity, and conflicts were negative predictors of mental health in all models. The personal resource of self-esteem was a positive predictor. Moreover, there were interactions: opportunities for promotion were beneficial only for employees with medium or high levels of self-esteem, whereas the contrary was true for employees with very low self-esteem. Working on weekends was negatively related to mental health for people with moderate to low internal control but not for people with high internal control.

Conclusions

The findings suggest that there are job demands that are related to poor mental health regardless of personal resources. These aspects are important to consider in workplace risk assessment. By contrast, with other job characteristics (e.g., opportunities for promotion, weekend work), the effects vary between individuals.

Electronic supplementary material

The online version of this article (10.1007/s00420-020-01555-0) contains supplementary material, which is available to authorized users.

Association of Work Patterns and Periodontitis Prevalence in Korean Adults Aged 50 Years or Older: A Nationwide Representative Study

This study analyzed the relationship between the work pattern and the prevalence of periodontitis. We analyzed the data of 3320 adults (1779 men, 1543 women) aged 51–80 years from the Korean National Health and Nutrition Examination Survey (2013–2015). The work pattern was divided into two groups (regular and irregular). The periodontal status was assessed using the community periodontal index. We observed a statistically significant difference in the association between work patterns and prevalence of periodontitis in Korean women aged over 50 years. For female workers with irregular work patterns, the prevalence of periodontitis was lower than that in workers with regular work patterns by 10.3% (40.3% vs. 30.0%, p = 0.011). The annual health examination rate was significantly higher in the irregular group than in the regular group (for men 77.9% vs. 73.5%; p < 0.001, for women 76.4% vs. 75.9%; p < 0.001). In female workers with irregular work patterns, the annual dental examination rate was significantly higher than that in workers with a regular work pattern by 7.7% (34.3% vs. 26.6%, p = 0.043). In conclusion we found a statistically significant difference between the work patterns and prevalence of periodontitis in Korean women aged over 50 years.

Napping and cognitive performance during night shifts: a systematic review and meta-analysis

Study Objectives

To examine the benefits of napping during night shifts on cognitive performance.

Methods

Medline, Cochrane Library, Science direct, and Embase databases were searched up to July 1, 2019. Cognitive performance during night shifts, both before and following napping or under control conditions (no nap), in working-aged adults, were analyzed by time and by type of cognitive function (executive function, attention, instrumental function, and memory). Estimates were pooled using random-effects meta-analysis.

Results

A total of 18 articles (6 in real-work and 12 in laboratory) with a total of 494 participants were included. The mean nap duration was 41.6 ± 28.3 min, occurring between 12.00 am and 4.10 am, with a mean time set at 2.12 am. Cognitive performance did not differ at baseline between the groups (effect size 0.02, 95% CI −0.09 to 0.13). There was an overall improvement in performance following a nap compared to the control condition without a nap (0.25, 0.10 to 0.41). Positioning naps early in the night and activity (simulated work tasks) tended to improve cognitive performance (−0.57, −1.16 to 0.002, and 0.082, −0.04 to 0.33, respectively). The improvements were primarily seen 30 min after awakening. Only memory deteriorated immediately after awakening without an overall change in global cognitive performance.

Conclusion

Napping during night shifts seems to improve cognitive performance. Napping early in the night and activity may benefit cognitive performance over time. Considering lack of data in real work environments, further studies are warranted before preconizing napping during night shifts as a preventive strategy (safety, health, and economic outcomes).

Shift work and long work hours and their association with chronic health conditions: A systematic review of systematic reviews with meta-analyses

Background

Previous reviews have demonstrated that shift work and long work hours are associated with increased risk for chronic conditions. However, these reviews did not comprehensively assessed the body of evidence, and some were not conducted in a systematic manner. A better understanding of the health consequences of shift work and long work hours will aid in creating policy and practice recommendations. This review revisits the epidemiologic evidence on the association of shift work and long work hours with chronic conditions with particular emphasis on assessing the quality of the evidence.

Methods and findings

We conducted a systematic review of systematic reviews with meta-analyses (SR-MA) that assessed the link between shift work or long work hours and chronic conditions (PROSPERO CRD42019122084). We evaluated the risk of bias of each SR-MA using AMSTAR v2 and assessed the overall evidence for each condition using the GRADE approach. We included 48 reviews covering cancers, cardiovascular diseases, metabolic syndrome and related conditions, pregnancy complications, depression, hypertension, and injuries. On average, only 7 of 16 AMSTAR items were fulfilled. Few SR-MAs had a registered protocol and nearly all failed to conduct a comprehensive search. We found moderate grade evidence linking shift work to breast cancer and long work hours to stroke. We found low grade evidence linking both shift work and long work hours with low to moderate increase in risk for some pregnancy complications and cardiovascular diseases. Low grade evidence also link long work hours and depression.

Conclusions

Moderate grade evidence suggest that shift work and long work hours increase the risk of breast cancer and stroke, but the evidence is unclear on other chronic conditions. There is a need for high-quality studies to address this gap. Stakeholders should be made aware of these increased risks, and additional screening and prevention should be considered, particularly for workers susceptible to breast cancer and stroke.

Circadian rhythm disruption and mental health

Circadian rhythms are internal manifestations of the solar day that permit adaptations to predictable environmental temporal changes. These ~24-h rhythms are controlled by molecular clockworks within the brain that are reset daily to precisely 24 h by exposure to the light-dark cycle. Information from the master clock in the mammalian hypothalamus conveys temporal information to the entire body via humoral and neural communication. A bidirectional relationship exists between mood disorders and circadian rhythms. Mood disorders are often associated with disrupted circadian clock-controlled responses, such as sleep and cortisol secretion, whereas disruption of circadian rhythms via jet lag, night-shift work, or exposure to artificial light at night, can precipitate or exacerbate affective symptoms in susceptible individuals. Evidence suggests strong associations between circadian rhythms and mental health, but only recently have studies begun to discover the direct interactions between the circadian system and mood regulation. This review provides an overview of disrupted circadian rhythms and the relationship to behavioral health and psychiatry. The focus of this review is delineating the role of disruption of circadian rhythms on mood disorders using human night shift studies, as well as jet lag studies to identify links. We also review animal models of disrupted circadian rhythms on affective responses. Lastly, we propose low-cost behavioral and lifestyle changes to improve circadian rhythms and presumably behavioral health.

The Comorbidity of Musculoskeletal Disorders and Depression: Associations with Working Conditions Among Hospital Nurses

Background: Musculoskeletal disorders (MSDs) are the leading cause of pain and disability among nurses and are frequently accompanied by depression. However, the association between the comorbidity of MSDs and depression and working conditions has not been studied, which was the aim of this study. Methods: In 2015, all nurses (n = 1,102) employed at a community hospital in the Northeast United States were invited to participate in this cross-sectional study. A survey was distributed in which participants were asked to report on MSDs, depressive symptoms, as well as subjective working conditions assessed including physical demands, psychological demands, decision authority, social support, and work-family conflict. Findings: 397 nurses responded (36%), and the prevalence of the comorbidity of MSDs and depression was 14.5%. Poisson regression (PR) models suggested that work-family conflict was associated with increased risk of the comorbidity (PR = 2.18; 95% confidence interval [CI] = 1.33-3.58), as was 8-hour night shift (PR = 2.77; 95% CI = [1.22, 6.31]) or 12-hour day shift (PR = 2.20; 95% CI = [1.07, 4.50]). Other working conditions were not directly associated with the comorbidity. Conclusions/Application to Practice: The comorbidity of MSDs and depression is prevalent among hospital nurses, and work-family conflict and working night shift or longer shifts were significantly associated with this. Effective workplace programs are needed to address nurses' working conditions to reduce their work-family conflict, thereby improving their musculoskeletal and mental health.

Investigating the effects of exposure to extremely low frequency electromagnetic fields on job burnout syndrome and the severity of depression; the role of oxidative stress

OBJECTIVES

This study was designed to investigate the possible effect of exposure to extremely low frequency electromagnetic fields (ELF-EMFs) on occupational burnout syndrome and the severity of depression experienced among thermal power plant workers and the role of oxidative stress.

METHODS

In this cross-sectional study, 115 power plant workers and 124 administrative personnel of a hospital were enrolled as exposed and unexposed groups, respectively, based on inclusion and exclusion criteria. Levels of oxidative stress biomarkers, including malondialdehyde (MDA), superoxide dismutase (SOD), catalase (Cat), and total antioxidant capacity were measured in serum samples. Exposure to electric and magnetic fields was measured using the IEEE Std C95.3.1 standard at each workstation. The burnout syndrome and the severity of depression were assessed using the Maslach Burnout and Beck Depression Inventory.

RESULTS

The levels of MDA and SOD were significantly lower in the exposed group than the unexposed group. The exposed group reported a higher prevalence of burnout syndrome and higher depression severity. Multiple linear regression showed that work experience, MDA level, and levels of exposure to magnetic fields are the most important predictor variables for burnout syndrome and severity of depression. In addition, a decrease in the level of Cat was significantly associated with increased burnout syndrome.

CONCLUSION

The thermal power plant workers exposed to ELF-EMFs are at risk of burnout syndrome and depression. These effects may be caused directly by exposure to magnetic fields or indirectly due to increased oxidative stress indices.

Psychological depletion in physicians and nurses exposed to workplace violence: A cross-sectional study using propensity score analysis

BACKGROUND

Workplace safety is a key issue in health care. However, workplace violence represents a serious threat to workplace safety and has become a global public health problem. Workplace violence may also lead to the psychological depletion of healthcare workers. Previous studies, although cross-sectional, did not use methods such as propensity score matching to assess the potential causality of workplace violence on mental health.

OBJECTIVES

To investigate the effects of workplace violence on depression and anxiety symptoms by propensity score matching, and to explore the prevalence of depression and anxiety symptoms in physicians and nurses.

DESIGN

A cross-sectional study.

SETTINGS AND PARTICIPANTS

A cross-sectional survey was conducted among 3000 physicians and nurses in 15 public hospitals in Heilongjiang and Beijing provinces using a purposive sampling method.

METHODS

Individual baseline characteristics and outcomes were compared across workplace violence and non-workplace violence groups using Pearson's Chi-squared tests for categorical variables and Mann-Whitney U tests for all non-parametric continuous variables. Propensity score matching was used to compare depression and anxiety symptoms in physicians and nurses who had experienced workplace violence with the symptoms of those who had not. Binary logistic regression analysis was used to analyse the associated factors of depression and anxiety symptoms.

RESULTS

A total of 2637 participants were involved in this study: 1264 (47.9%) were assigned to the exposed group, and 1373 (52.1%) to the non-exposed group. The prevalence of workplace violence among physicians and nurses in the past year was 47.9% (1264/2637). Before matching, the prevalence of depression and anxiety symptoms in physicians and nurses was 58.8% and 39.7%, respectively. Participants who experienced physical and non-physical violence were more likely to suffer from depression symptoms (odds ratios 1.999, 95% confidence interval: 1.497-2.670), and anxiety symptoms (odds ratios 1.999, 95% confidence interval: 1.497-2.670) than those who had not. Participants' age, education levels, and occupation types were common influencing factors of depression and anxiety symptoms. The results also showed that nurses are more likely to suffer from anxiety and depression symptoms than physicians.

CONCLUSIONS

It is necessary to develop effective control strategies at the individual, hospital and national levels to protect health care workers from workplace violence. When healthcare workers experience workplace violence, it is important to pay attention to their emotional reactions and to provide them with support in order to avoid adverse impacts on mental health. Further practices and research initiatives to examine the longitudinal relation among workplace violence, anxiety, and depression are recommended.

Shift Work and Poor Mental Health: A Meta-Analysis of Longitudinal Studies

Background. Shift work is characterized by employees working outside the standard hours of 7:00 am to 6:00 pm. Because shift work includes night work, the normal sleep-wake cycle (circadian rhythm) is disrupted, with potential consequences for shift workers' physical and mental health.Objectives. To assess the pooled effects of shift work on mental health and to evaluate whether these differ in men and women.Search Methods. We searched PubMed, Scopus, and Web of Science databases for peer-reviewed or government reports published up to August 2018Selection Criteria. To be included, studies had to be longitudinal or case-control studies of shift work exposure associated with adverse mental health outcomes. For subanalyses, we grouped these outcomes as anxiety symptoms, depressive symptoms, or general poor mental health symptoms.Data Collection and Analysis. We followed the Meta-Analysis of Observational Studies in Epidemiology Group guidelines. We extracted adjusted risk estimates for each study to calculate pooled effect sizes (ESs) using random effect models and metaregression analysis to explore sources of heterogeneity.Main Results. We included 7 longitudinal studies, with 28 431 unique participants. Shift work was associated with increased overall risk of adverse mental health outcomes combined (ES = 1.28; 95% confidence interval [CI] = 1.02, 1.62; I² = 70.6%) and specifically for depressive symptoms (ES = 1.33; 95% CI = 1.02, 1.74; I² = 31.5%). Gender differences explained more than 90% of heterogeneity, with female shift workers more likely to experience depressive symptoms than female non-shift workers (odds ratio = 1.73; 95% CI = 1.39, 2.14).Authors' Conclusions. To our knowledge, this is the first meta-analysis to investigate the pooled effects of shift work on the risk of poor mental health, including subanalyses by type of poor mental health and gender. Shift workers, particularly women, are at increased risk for poor mental health, particularly depressive symptoms.Public Health Implications. Depression accounts for 4.3% of the global burden of disease and incidence, with mental disorders worldwide predicted to cost US $16.3 million by 2030. With 1 in 5 people in the United States and Europe doing shift work, and the increased risk of poor mental health among shift workers, shift work industries are a priority context for reducing this burden. Workplace health promotion programs and policies are needed to minimize shift workers' risk of poor mental health.

Reduced melatonin synthesis in pregnant night workers: Metabolic implications for offspring

Several novel animal studies have shown that intrauterine metabolic programming can be modified in the event of reduced melatonin synthesis during pregnancy, leading to glucose intolerance and insulin resistance in the offspring. It is therefore postulated that female night workers when pregnant may expose the offspring to unwanted health threats. This may be explained by the fact that melatonin is essential for regulating energy metabolism and can influence reproductive activity. Moreover, the circadian misalignment caused by shift work affects fertility and the fetus, increasing the risk of miscarriage, premature birth and low birth weight, phenomena observed in night workers. Thus, we hypothesize that light-induced melatonin suppression as a result of night work may alter intrauterine metabolic programming in pregnant women, potentially leading to metabolic disorders in their offspring.

Circadian regulation of depression: A role for serotonin

Synchronizing circadian (24 h) rhythms in physiology and behavior with the environmental light-dark cycle is critical for maintaining optimal health. Dysregulation of the circadian system increases susceptibility to numerous pathological conditions including major depressive disorder. Stress is a common etiological factor in the development of depression and the circadian system is highly interconnected to stress-sensitive neurotransmitter systems such as the serotonin (5-hydroxytryptamine, 5-HT) system. Thus, here we propose that stress-induced perturbation of the 5-HT system disrupts circadian processes and increases susceptibility to depression. In this review, we first provide an overview of the basic components of the circadian system. Next, we discuss evidence that circadian dysfunction is associated with changes in mood in humans and rodent models. Finally, we provide evidence that 5-HT is a critical factor linking dysregulation of the circadian system and mood. Determining how these two systems interact may provide novel therapeutic targets for depression.

Night shift work before and during pregnancy in relation to depression and anxiety in adolescent and young adult offspring

We investigated the relationship between maternal history of nightshift work before and shift work during pregnancy and offspring risk of depression and anxiety, among mothers participating in the Nurses Health Study II and in their offspring enrolled in the Growing Up Today Study 2 between 2004 and 2013. Case definitions were based on offspring self-reports of physician/clinician-diagnosed depression and/or anxiety, regular antidepressant use and depressive symptoms assessed using the Center for Epidemiologic Studies Depression Scale. Multivariable-adjusted odds ratios (ORs) and 95% confidence intervals (CIs) were estimated using generalized estimating equation models. We found no associations between maternal nightshift work before pregnancy or during pregnancy and offspring mental health disorders (e.g., nightshift work before pregnancy: depression (based on physician/clinician diagnosis): OR_{ever nightwork}= 1.14; 95% CI, 0.88-1.47; either depression or anxiety: OR_{ever nightwork}= 0.93; 95% CI, 0.81-1.08; nightshift work during pregnancy: depression: OR_{ever nightwork}= 1.14; 95% CI, 0.68-1.94; depression or anxiety: OR_{ever nightwork}=1.17; 95% CI, 0.70-1.98) and no dose-response relationship with longer history of nightshift work (all P_Trend>0.10). Stratifying by maternal chronotype revealed a higher risk of depression for offspring whose mothers worked nightshifts before pregnancy and reported being definite morning chronotypes (a proxy for circadian strain) (OR_{ever nightwork}= 1.95; 95% CI, 1.17, 3.24 vs. OR_{ever nightwork}= 0.93; 95% CI, 0.68, 1.28 for any other chronotype; P_Interaction= 0.03). Further studies replicating our findings and refined understanding regarding the interplay of nightshift work and chronotype and its potential influences on offspring mental health are needed.

Shiftwork and Biomarkers of Subclinical Cardiovascular Disease: The BCOPS Study

OBJECTIVE

To assess the association of shiftwork with biomarkers of subclinical cardiovascular disease and examine the moderating role of body mass index (BMI) in a police cohort.

METHODS

A cross-sectional analysis was conducted among officers who were categorized as working the day, evening, or night shift. Comparisons with inflammatory biomarkers were performed among shifts using analysis of variance/covariance and further stratified by BMI to assess potential effect modification.

RESULTS

Associations were observed between day and night shiftworkers for leukocytes, tumor necrosis factor alpha, and homocysteine. After BMI stratification, higher c-reactive protein (CRP) levels were observed among evening shiftworkers with a BMI more than or equal to 30 kg/m versus the day shift.

CONCLUSIONS

Future studies examining prospective changes in these markers will allow for more comprehensive evaluation of their association with shiftwork.

Working Time Society consensus statements: Evidence-based effects of shift work on physical and mental health

Potential effects of shift work on health are probably related to the misalignment between the light-dark cycle and the human activity-rest cycle. Light exposure at night mediates these effects, including social misalignment and leads to an inversion of activity and rest, which, in turn, is linked to changes in behaviours. This article reviews the epidemiological evidence on the association between shift work and health, and possible mechanisms underlying this association. First, evidence from findings of the meta-analyses and systematic reviews published in the last 10 yr is presented. In addition, it reports the larger single-occupation studies and recent large population-based studies of the general workforce. Koch's postulates were used to evaluate the evidence related to the development of disease as a result of exposure to shift work. Finally, we discussed limitations of the multiple pathways that link shift work with specific disorders and the methodological challenges facing shift work research. We concluded that the clearest indications of shift work being the cause of a disease are given when there is a substantial body of evidence from high quality field studies showing an association and there is good evidence from laboratory studies supporting a causal explanation of the link.

Healthy working time arrangements for healthcare personnel and patients: a systematic literature review

BACKGROUND

A number of working time arrangements have been linked to negative consequences for both health personnel and their patients. A common hypothesis put forth to explain these findings suggests that certain working time arrangements lead to negative patient consequences due to the adverse impact they have on employee health. The purpose of this study is to use systematic reviews to investigate whether employee health explains the relationship between working time arrangements and patient safety.

METHODS

A systematic literature review was performed including published reviews and original studies from MEDLINE, PsycINFO, Cinahl and Web of Science investigating working time arrangements for healthcare personnel, employee health and patient safety. In addition, we screened reference lists of identified reviews. Two reviewers independently identified relevant publications according to inclusion criteria, extracted findings and assessed quality.

RESULTS

Six thousand nine hundred thirty papers were identified, of which 52 studies met our criteria. Articles were categorized into five groups according to how they approached the research question: 1) independent analyses of relationship between working time arrangements and employee health, and of working time arrangements and patient safety (5 studies); 2) relationship between working time arrangements on both employee health and patient safety (21 studies); 3) working time arrangements and employee health as two explanatory variables for patient safety (8 studies); 4) combinations of the above analyses (7 studies); 5) other relevant studies (5 studies). Studies that find that working time is detrimental to employee health, generally also find detrimental results for patient safety. This is particularly shown through increases in errors by health personnel. When controlling for employee health, the relationship between working time arrangements and patient safety is reduced, but still significant.

CONCLUSIONS

Results suggest that employee health partially (but not completely) mediates the relationship between working time arrangements and patient safety. However, there is a lack of studies directly investigating employee health as a mediator between working time arrangements and patient safety. Future studies should address this research gap.

Breakfast consumption and the risk of depressive symptoms: The Furukawa Nutrition and Health Study

Breakfast consumption has been suggested to influence mood, but prospective evidence on this issue is limited. We prospectively investigated the association between the frequency of breakfast consumption and the risk of depressive symptoms in Japanese employees. Participants were 716 employees aged 19-68 years who were free from depressive symptoms and mental disorders at baseline and who attended the 3-year follow-up survey. Depressive symptoms were assessed using the Center for Epidemiologic Studies Depression Scale. The frequency of breakfast consumption was categorized into "daily", "5-6 times/week", "3-4 times/week", "1-2 times/week", or "≤1 times/week". Logistic regression was used to estimate odds ratios of depressive symptoms according to breakfast consumption adjusted for dietary and lifestyle factors. Participants who consumed breakfast ≤1 times/week had an increased risk of depressive symptoms compared to those who ate breakfast every day, even after adjusting for other dietary factors (multivariable-adjusted odds ratio 2.92; 95% confidence interval, 1.37-6.22) The risk of depressive symptoms tended to increase with decreasing frequency of breakfast consumption (P for trend = 0.02). The omission of breakfast is related to increased risk of depressive symptoms among Japanese employees, independently of other dietary and non-dietary factors.

Effect of work schedule on prospective antidepressant prescriptions in Sweden: a 2-year sex-stratified analysis using national drug registry data

INTRODUCTION

Depression-related mood disorders affect millions of people worldwide and contribute to substantial morbidity and disability, yet little is known about the effects of work scheduling on depression. This study used a large Swedish survey to prospectively examine the effects of work schedule on registry-based antidepressant prescriptions in females and males over a 2-year period.

METHODS

The study was based on an approximately representative sample (n=3980 males, 4663 females) of gainfully employed participants in the Swedish Longitudinal Occupational Survey of Health. Sex-stratified analyses were conducted using logistic regression. For exposure, eight categories described work schedule in 2008: 'regular days' (three categories of night work history: none, ≤3 years, 4+ years), 'night shift work', 'regular shift work (no nights)', 'rostered work (no nights)', 'flexible/non-regulated hours' and 'other'. For the primary outcome measure, all prescriptions coded N06A according to the Anatomical Therapeutic Chemical System were obtained from the Swedish National Prescribed Drug Register and dichotomised into 'any' or 'no' prescriptions between 2008 and 2010. Estimates were adjusted for potential sociodemographic, health and work confounders, and for prior depressive symptoms.

RESULTS

In 2008, 22% of females versus 19% of males worked outside of regular daytime schedule. Registered antidepressant prescription rates in the postsurvey period were 11.4% for females versus 5.8% for males. In fully adjusted models, females in 'flexible/non-regulated' schedules showed an increased OR for prospective antidepressant prescriptions (OR=2.01, 95% CI=1.08 to 3.76). In males, odds ratios were most increased in those working 'other' schedules (OR=1.72, 95% CI=0.75 to 3.94) and 'Regular days with four or more years' history of night work' (OR=1.54, 95% CI=0.93 to 2.56).

CONCLUSIONS

This study's findings support a relationship between work schedule and prospective antidepressant prescriptions in the Swedish workforce. Future research should continue to assess sex-stratified relationships, using detailed shift work exposure categories and objective registry data where possible.

Sleep- and Wake-Promoting Drugs: Where Are They Being Sourced, and What Is Their Impact?

Background: Recent decades have seen both an increased number of shift workers in order to deliver services 24/7, and increased potential for social interactions at all hours of the day. People have sought to engage in strategies, which either promote vigilance or facilitate sleep, with the use of sleep- and wake-promoting drugs representing one strategy. Methods: We investigated use of sleep- and wake-promoting drugs in participants (n = 377) who completed a survey investigating the type and source of sleep- and wake-promoting drugs, and their impact on sleep and performance outcomes. Results: The most commonly reported wake-promoting drugs were amphetamine and dextroamphetamin salts, modafinil, and illicit substances including methamphetamine and cocaine, while the most commonly reported sleep-promoting drugs were benzodiazepines and antihistamines. Use of a sleep-promoting drug in the past month was associated with higher odds of having poorer sleep quality (OR = 3.15) and moderate-high insomnia (OR = 3.30), while use of a wake-promoting drug was associated with poor sleep quality (OR = 3.76), or making a fatigue-related error (OR = 2.65). Conclusions: These findings represent novel data on the use and source of sleep- and wake-promoting- drugs, and suggest that despite their use, poor sleep and performance outcomes persist, likely representing individuals struggling to keep up with the 24/7 world.

Occupational factors associated with major depressive disorder: A Brazilian population-based study

BACKGROUND

There have been very few studies exploring the occupational risk factors for major depressive disorder (MDD) in the working populations in Latin America. The aim of this study was to explore the associations between a large set of occupational factors and MDD in the Brazilian working population.

METHODS

The study was based on the cross-sectional data from the Brazilian National Health Survey, 2013. 60,202 people were interviewed (response rate: 91.9%). Among them, 36,442 were working, 19,450 men and 16,992 women. MDD was measured using the diagnostic algorithm (DSM-IV criteria) of the PHQ-9. Occupational factors included job characteristics, working time factors, psychosocial work stressors and physico-chemical exposures. Logistic regression models were performed and adjusted for sociodemographic factors. All analyses were conducted using weighted and stratified data by gender.

RESULTS

The following occupational factors were associated with a higher risk of MDD: working part time (≤20 h a week) and stress at work for both genders, workplace violence, intense physical activity, exposure to noise and chemicals among women, and prolonged exposure to sun among men. Associations of stress and violence at work with MDD were particularly strong.

LIMITATIONS

Cross-sectional study design, healthy worker effect and reporting bias may have impacted the results.

CONCLUSIONS

This study, one of the first studies among the Brazilian working population, showed that psychosocial work stressors were the strongest risk factors for MDD. Physico-chemical exposures deserve more attention in association with MDD. Prevention policies oriented toward the work environment may help to prevent depression at the workplace.

A call for Applied Knowledge and Lived Interdisciplinarity in the medical care of depressed employees: a cross-sectional survey with German occupational physicians and psychotherapists

OBJECTIVES

To identify approaches for an effective patient-centred care of depressed employees, we investigated occupational physicians' (OPs) and psychotherapists' (PTs) knowledge about job stressors on the development of depression, application of this knowledge, interdisciplinary cooperation and perceived barriers.

STUDY DESIGN

A cross-sectional online survey.

PARTICIPANTS

OPs (163; 48.5% male) and PTs (69; 43.5% male) providing complete data on the survey out of 257 OPs and 112 PTs who started the survey. There have been 458 (OPs) and 821 (PTs) initial clicks.

METHODS

Main outcome measures were the importance ratings of specific job stressors, the frequency of asking patients about those stressors, the need for interdisciplinary cooperation, as well as perceived barriers for cooperation. We performed multivariate analysis of variance, intraclass correlation coefficients (ICCs) and Spearman's rank-order correlations.

RESULTS

The achieved response rate for OPs was 56.1% and for PTs 13.6%. Both disciplines agreed on the importance of job stressors regarding depression (ICC=0.90; 95% CI: 0.54 to 0.98), but both ranked these factors differently from the current state of research. As to knowledge application, OPs showed positive associations between the importance of job stressors and the frequency of asking employees about them (eg, job insecurity (r_s=0.20, p=0.005)) and PTs for social stressors (eg, interpersonal conflicts (r_s=0.38, p=0.001)). OPs (mean=3.41) reported a higher necessity of interdisciplinary cooperation than PTs (mean=3.17; F(1,230)=7.02, p=0.009). Furthermore, cooperation was reported as difficult to implement. PTs perceived barriers (eg, time restriction) as more hindering (mean=3.2) than OPs (mean=2.8; F(1,171)=8.16, p=0.005).

CONCLUSIONS

Both disciplines are aware of the relevance of job stressors as risk factors for depression, but should be encouraged to ask employees more frequently about them. The need for interdisciplinary cooperation and possible barriers are discussed. It is crucial to emphasise the meaning of sufficient cooperation, since closing this gap for improving patient-centred care especially for employees suffering from depression is necessary.