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

Sleep, mental health and physical health in new shift workers transitioning to shift work: Systematic review and meta-analysis

This systematic review and meta-analysis (PROSPERO registration CRD42022309827) aimed to describe how shift work impacts new workers' sleep, mental health, and physical health during the transition to shift work and to consolidate information regarding predictors of shift work tolerance (SWT) during this transition period. Inclusion criteria included: new shift workers; sleep, mental health, or physical health outcomes; prospective study design with the first timepoint assessing workers within three months of starting shift work; and written in English. Searches from six databases returned 12,172 articles as of August 2023. The final sample included 48 papers. Publication quality and risk of bias was assessed using the critical appraisal skills program. Forty-five studies investigated longitudinal changes in sleep, mental health, or physical health outcomes and 29 studies investigated predictors of SWT (i.e., better sleep, mental and physical health). Sleep and mental health outcomes worsened following the onset of shift work, while physical health did not significantly change. Pre-shift work mental health, sleep, and work characteristics predicted SWT later in workers' careers. Shift work adversely impacts new workers' sleep and mental health early in their career, and interventions before beginning shift work are needed to promote better SWT.

Night shift work, genetic risk, and the risk of depression: A prospective cohort study

BACKGROUND

Genetic factors and night shift work both contribute to the risk of depression, but whether the association of night shift work with depression varies by genetic predisposition remains unclear.

OBJECTIVES

To assess whether night shift work is associated with a higher risk of depression regardless of genetic predisposition.

METHODS

We used data from the UK biobank of 247,828 adults aged 38-71 free of depression at baseline from March 13, 2006, to October 1, 2010. Genetic predisposition to depression was assessed using polygenic risk scores (PRS) weighted sums of genetic variant indicator variables and classified as low (lowest tertile), intermediate (tertile 2), and high (highest tertile). Night shift work exposures were collected using a touchscreen questionnaire and were divided into four categories.

RESULTS

After a median follow-up of 12.7 years, 7315 participants developed depression. Compared with day workers, HRs (95 % CIs) of depression were 1.28 (1.19-1.38) for shift work, but never or rarely night shifts, 1.32 (1.20-1.45) for irregular night shifts, and 1.20 (1.07-1.34) for permanent night shifts. Considering lifetime employment and compared with never shift workers, >8 nights/month (HR: 1.40; 95 % CI: 1.19-1.66) and <10 years (HR: 1.30; 95 % CI: 1.09-1.54) of night shift work were associated with a higher risk of depression. In joint effect analyses, compared to participants with low genetic predisposition and day workers, the HRs (95 % CIs) of depression were 1.49 (1.32-1.69) in those with high genetic predisposition and shift work, but never or rarely night shifts, and 1.36 (1.20-1.55) for those with high genetic predisposition and irregular/permanent night shifts. In addition, there was neither multiplicative nor additive interaction between genetic predisposition and night shift work on the risk of depression.

CONCLUSIONS

Night shift work was associated with an increased risk of depression regardless of genetic risk.

Neuropsychiatric disorders, chronotype and sleep: A narrative review of GWAS findings and the application of Mendelian randomization to investigate causal relationships

Genome-wide association studies (GWAS) have been important for characterizing the genetic component and enhancing our understanding of the biological aetiology of both neuropsychiatric disorders and sleep-related phenotypes such as chronotype, which is our preference for morning or evening time. Mendelian randomization (MR) is a post-GWAS analysis that is used to infer causal relationships between potential risk factors and outcomes. MR uses genetic variants as instrumental variants for exposures to study the effect on outcomes. This review details the main results from GWAS of neuropsychiatric disorders and sleep-related phenotypes, and the application of MR to investigate their bidirectional relationship. The main results from MR studies of neuropsychiatric disorders and sleep-related phenotypes are summarized. These MR studies have identified 37 causal relationships between neuropsychiatric disorders and sleep-related phenotypes. MR studies identified evidence of a causal role for five neuropsychiatric disorders and symptoms (attention deficit hyperactivity disorder, bipolar disorder, depressive symptoms, major depressive disorder and schizophrenia) on sleep-related phenotypes and evidence of a causal role for five sleep-related phenotypes (daytime napping, insomnia, morning person, long sleep duration and sleep duration) on risk for neuropsychiatric disorders. These MR results show a bidirectional relationship between neuropsychiatric disorders and sleep-related phenotypes and identify potential risk factors for follow-up studies.

Circadian rhythms and mood disorders: Time to see the light

The importance of time is ever prevalent in our world, and disruptions to the normal light/dark and sleep/wake cycle have now become the norm rather than the exception for a large part of it. All mood disorders, including seasonal affective disorder (SAD), major depressive disorder (MDD), and bipolar disorder (BD), are strongly associated with abnormal sleep and circadian rhythms in a variety of physiological processes. Environmental disruptions to normal sleep/wake patterns, light/dark changes, and seasonal changes can precipitate episodes. Moreover, treatments that target the circadian system have proven to be therapeutic in certain cases. This review will summarize much of our current knowledge of how these disorders associate with specific circadian phenotypes, as well as the neuronal mechanisms that link the circadian clock with mood regulation. We also discuss what has been learned from therapies that target circadian rhythms and how we may use current knowledge to develop more individually designed treatments.

Circadian misalignment impairs oligodendrocyte myelination via Bmal1 overexpression leading to anxiety and depression-like behaviors

Circadian misalignment (CM) caused by shift work can increase the risk of mood impairment. However, the pathological mechanisms underlying these deficits remain unclear. In the present study, we used long-term variable photoperiod (L-VP) in wild-type mice to better simulate real-life shift patterns and study its effects on the prefrontal cortex (PFC) and hippocampus, which are closely related to mood function. The results showed that exposure to L-VP altered the activity/rest rhythms of mice, by eliciting phase delay and decreased amplitude of the rhythms. Mice with CM developed anxiety and depression-like manifestations and the number of mature oligodendrocytes (OL) was reduced in the medial prefrontal cortex and hippocampal CA1 regions. Mood impairment and OL reduction worsened with increased exposure time to L-VP, while normal photoperiod restoration had no effect. Mechanistically, we identified upregulation of Bmal1 in the PFC and hippocampal regions of CM mice at night, when genes related to mature OL and myelination should be highly expressed. CM mice exhibited significant inhibition of the protein kinase B (AKT)/mTOR signaling pathway, which is directly associated to OL differentiation and maturation. Furthermore, we demonstrated in the OL precursor cell line Oli-Neu that overexpression of Bmal1 inhibits AKT/mTOR pathway and reduces the expression of genes OL differentiation. In conclusion, BMAL1 might play a critical role in CM, providing strong research evidence for BMAL1 as a potential target for CM therapy.

Independent and joint trajectories of depression and anxiety symptoms among Chinese male sailors throughout a prolonged non-24-h rotating shift schedule at sea: a parallel-process growth mixture modeling approach

BACKGROUND

The predictive and protective effect of hardiness on mental health remains unclear among shift workers on non-24-h working schedules. The present study aimed to investigate the independent and joint trajectories of depression and anxiety symptoms and the role of hardiness during a prolonged period of non-24-h shift working schedule.

METHODS

Four hundred nine Chinese male sailors (working on 18-h watchstanding schedule) were recruited and completed all 5-wave tests through online questionnaires (at Day 1, 14, 28, 42, 55, respectively) during a 55-day sailing. The questionnaires included sociodemographic variables, hardiness, depression and anxiety symptoms. Independent and joint trajectories of depression and anxiety symptoms were estimated by latent growth mixture models. The effect of hardiness on trajectories was examined by logistic regression models.

RESULTS

2 and 3 latent trajectories were identified for depression and anxiety symptoms, respectively. Based on initial levels and development trends, 3 distinct joint trajectories of depression and anxiety were identifed and named as: "Low-Inverted U" group (73.6%), "Moderate-Deterioration" group (6.9%), and "High-Stable" group (9.5%). Sailors with higher levels of hardiness were more likely to follow the "Low-Inverted U" trajectory of depression and anxiety symptoms (all p < 0.001).

CONCLUSIONS

There existed individual differences in the trajectories of depression and anxiety. Hardiness may have a protective effect that can prevent and alleviate depression and anxiety symptoms. Therefore, hardiness-based intervention programs are encouraged among the shift workers on non-24-h working and rest schedules.

The workload change and depression among emergency medical staff after the open policy during COVID-19: a cross-sectional survey in Shandong, China

Introduction

In the middle of December 2022, the Chinese government adjusted the lockdown policy on coronavirus disease 2019 (COVID-19), a large number of infected patients flooded into the emergency department. The emergency medical staff encountered significant working and mental stress while fighting the COVID-19 pandemic. We aimed to investigate the workload change, and the prevalence and associated factors for depression symptoms among emergency medical staff after the policy adjustment.

Methods

We conducted a cross-sectional online survey of emergency medical staff who fought against COVID-19 in Shandong Province during January 16 to 31, 2023. The respondents' sociodemographic and work information were collected, and they were asked to complete the 9-item Patient Health Questionnaire (PHQ-9) then. Univariate and multivariate logistic regression analyses were applied to identify the potential associated factors for major depression.

Results

Nine hundred and sixteen emergency medical personnel from 108 hospitals responded to this survey. The respondents' weekly working hours (53.65 ± 17.36 vs 49.68 ± 14.84) and monthly night shifts (7.25 ± 3.85 vs 6.80 ± 3.77) increased after the open policy. About 54.3% of the respondents scored more than 10 points on the PHQ-9 standardized test, which is associated with depressive symptoms. In univariate analysis, being doctors, living with family members aged ≤16 or ≥ 65 years old, COVID-19 infection and increased weekly working hours after the open policy were significantly associated with a PHQ-9 score ≥ 10 points. In the multivariate analysis, only increased weekly working hours showed significant association with scoring ≥10 points.

Conclusion

Emergency medical staff' workload had increased after the open policy announcement, which was strongly associated with a higher PHQ-9 scores, indicating a very high risk for major depression. Emergency medical staff working as doctors or with an intermediate title from grade-A tertiary hospitals had higher PHQ-9 scores, while COVID-19 infection and weekly working hours of 60 or more after the open policy were associated with higher PHQ-9 scores for those from grade-B tertiary hospitals. Hospital administrators should reinforce the importance of targeted emergency medical staff support during future outbreaks.

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.

Relationship between Telework Jetlag and Perceived Psychological Distress among Japanese Hybrid Workers

Social jetlag is associated with physical and mental health problems. With the increased popularity of telework, we investigated a specific form of social jetlag that we termed "telework jetlag". This study aimed to clarify the relationship between telework jetlag-the difference in sleep and wake-up times between in-office and telework days-and mental health problems among Japanese hybrid workers. A cross-sectional study was conducted with 1789 participants from October to December 2021 using an online-based questionnaire. Telework jetlag, defined as the difference in the midsleep point between in-office and telework days, was investigated using two groups according to telework jetlag-those lagging <1 h versus ≥1 h. We used the six-item Kessler Scale as a nonspecific psychological distress scale for the outcome. Telework jetlag was significantly associated with psychological distress, and the ≥1 h group had a higher risk (odds ratio: 1.80) of developing high psychological distress (HPD) than the <1 h group in the multivariate analysis. Since most teleworkers are forced to have a hybrid work style that mixes going to work and teleworking, telework jetlag must be addressed to maintain the health of teleworkers.

The unfixed light pattern contributes to depressive-like behaviors in male mice

Light pollution is now associated with an increased incidence of mental disorders in humans, and the unfixed light pattern (ULP) is a common light pollution that occurs in such as rotating shift work. However, how much contribution the ULP has to depression and its potential mechanism are yet unknown. Our study aimed to investigate the effect of the ULP on depressive-like behaviors in mice and to explore the links to the circadian-orexinergic system. Male C57BL/6 J mice were exposed to the ULP by subjecting them to an alternating light pattern every 6 days for 54 days. The tail suspension test (TST) and forced swimming test (FST) were conducted to assess depressive-like behaviors. The rhythm of locomotor activity and the circadian expression of cFOS in the suprachiasmatic nucleus (SCN), clock genes in the liver, and corticosterone (CORT) in serum were detected to observe changes in the circadian system. The circadian expression of orexin-A (OX-A) in the lateral hypothalamus area (LHA) and dorsal raphe nucleus (DRN) and serotonin (5-HT) in the DRN were measured to determine alterations in the orexinergic system. The results showed that mice exposed to the ULP exhibited increased immobility time in the TST and FST. The ULP significantly disrupted the circadian rhythm of locomotor activity, clock genes in the liver, and CORT in the serum. Importantly, when exposed to the ULP, cFOS expression in the SCN showed decreased amplitude. Its projection area, the LHA, had a lower mesor of OX-A expression. OX-A projection to the DRN and 5-HT expression in the DRN were reduced in mesor. Our research suggests that the ULP contributes to depressive-like behaviors in mice, which might be related to the reduced amplitude of circadian oscillation in the SCN and hypoactivity of the orexinergic system. These findings may provide novel insights into rotating shift work-related depression.

Effects of sleep and impulsivity on suicidality in shift and non-shift workers

INTRODUCTION

Shift workers are known to have a higher suicide risk than non-shift workers. Sleep disturbance and impulsivity are also risk factors for suicidality. This study investigated the effects of poor sleep and impulsivity on suicidality in shift and non-shift workers.

METHODS

In total, 4572 shift workers (37.0 ± 9.84 years, 2150 males) and 2093 non-shift workers (37.8 ± 9.73 years, 999 males) participated in an online self-report survey. Suicidality was assessed using the Suicidal Behaviors Questionnaire. The Pittsburgh Sleep Quality Index was employed to explore subjective sleep quality, the Insomnia Severity Index to detect insomnia, the Epworth Sleepiness Scale (ESS) to evaluate excessive daytime sleepiness (EDS), the Center for Epidemiological Studies-Depression (CES-D) Scale to assess depressive symptoms, and the Impulsive Behavior Scale (UPPS-P) to explore impulsivity.

RESULTS

Shift workers showed poorer sleep quality, and greater impulsivity and suicidality, than non-shift workers. Impulsivity, sleep duration, sleep quality, and insomnia were significantly associated with suicidality, independent of depression. For both shift and non-shift workers, sleep quality moderated the association between impulsivity and suicidality. However, the moderating effects of sleep duration and EDS on the association between impulsivity and suicidality were apparent only in non-shift workers, while a moderating effect of insomnia was observed only in shift workers.

CONCLUSION

Shift work, sleep disturbances and impulsivity may exacerbate suicide risk. In addition, the interrelationships among insomnia, EDS, impulsivity, and suicidality may differ between shift and non-shift workers.

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.

Patterns of smartphone usage associated with depressive symptoms in nursing students

Introduction

Rather than focusing on the activities that the smartphone has been used for, the existing literature frequently focuses on the association between problematic use of smartphone independent of the content of use (self-reported) and depressive symptoms in youth. This study aims to explore patterns of smartphone usage and the association with depressive symptoms in nursing students.

Methods

This cross-sectional study of nursing freshmen (n = 1, 716) was conducted between October and November 2018. Participants were recruited from three Chinese public medical universities using stratified cluster sampling. Self-rated frequency of 12 different smartphone activities over the preceding week was evaluated. Depressive symptoms were assessed by using the Patient Health Questionnaire-9 (PHQ-9).

Results

Of the 1,716 students recruited, 1,424 (83.0%) were girls, and the mean [SD] age was 18.90 [1.39] years. Using principal component analysis (PCA), two typical usage patterns were indicated. The "entertainment pattern" factor included a high frequency of streaming images or videos, searching for information, chatting online, online shopping, downloading, reading online, checking social media sites, taking pictures or videos, and playing games. The "communication pattern" had a high frequency of emailing, texting, and calling. Using logistic regression models, the association between smartphone usage patterns and depressive symptoms was tested. The "communication pattern" was significantly associated with a 53% increase in the odds of moderate and above depressive symptoms (AOR = 1.529; 95% CI = 1.286-1.818; p < 0.001), controlling for a set of socio-demographic and smartphone use covariates.

Discussion

This study provides insights into how the patterns of smartphone usage are associated with the severity of depressive symptoms in nursing students. It indicates that it may primarily be how we use our smartphones rather than how much we use them that poses a risk for depression.

Lifestyle Factors in the Association of Shift Work and Depression and Anxiety

IMPORTANCE

Shift work may lead to adverse health outcomes. Whether shift work is associated with depression and anxiety, and to what extent lifestyle mediates the associations, remains unknown.

OBJECTIVE

To explore the associations of shift work, its type, frequency, and working years with anxiety and depression and to examine the potential mediating role of lifestyles.

Design, Setting, and Participants

This cohort study included 175 543 employed or self-employed workers who participated in the UK Biobank baseline survey (2006-2010). Data analysis was conducted from November 2022 to January 2023.

EXPOSURES

Employment and shift work status information was obtained from baseline. Lifestyles included smoking, physical activity, alcohol consumption, dietary characteristics, sleep duration, sedentary time, and body mass index (BMI).

MAIN OUTCOMES AND MEASURES

Depression and anxiety were identified based on electronic health records. Cox proportional hazard regression models were used to calculate the association of shift work with anxiety and depression, and cause mediation analyses we used to test the mediating role of lifestyle factors in this association.

RESULTS

Of the 175 543 included participants (mean [SD] age, 52.6 [7.1] years; 88 290 men [50.3%]; 167 495 White participants [95.4%]), 27 637 participants (16.2%) reported shift work. During a median (IQR) follow-up of 9.06 (8.35-9.75) years, 3956 workers (2.3%) developed depression and 2838 (1.7%) developed anxiety. In the fully adjusted model, individuals who reported engaging in shift work, or shift workers, had a higher risk of depression (HR, 1.22; 95% CI, 1.12-1.33; P < .001) and anxiety (HR, 1.16; 95% CI, 1.04-1.28; P < .001), and the risk was positively associated with shift frequency. Among shift workers, there was no significant difference between night shifts and nonnight shifts. In the dose-association analyses, years of shift work were negatively associated with the risk of depression and anxiety. Smoking, sedentary time, BMI, and sleep duration were identified as the main potentially modifiable mediators. These mediators together explained 31.3% of the association between shift work and depression and 21.2% of the association between shift work and anxiety.

CONCLUSIONS AND RELEVANCE

In this cohort study, shift work was significantly associated with a higher risk of depression and anxiety, and lifestyle factors partially mediated the associations. These findings not only support that shift work should be considered an occupational hazard, but also provide evidence for the urgent need for the development of public health interventions that promote healthy lifestyles aimed at improving the mental health of shift workers.

The Correlation Between Night Shift Work Schedules, Sleep Quality, and Depression Symptoms

Purpose

Poor sleep and depressive symptoms are two negative effects of night shift work on physical and mental health. This study evaluated the correlation between sleep quality and depression symptoms among nurses in Saudi Arabia. Specifically, we assessed depressive symptoms and sleep quality observed among nurses who worked night shifts and compared the outcomes with those who worked exclusively day shifts in hospital settings.

Patients and Methods

A total of 191 participants (55.5% men, 44.5% women) participated. The response rate was 63.6%. The hospital anxiety and depression scale (HADS) and Pittsburgh Sleep Quality Index (PSQI) were used to assess depression score and sleep quality, respectively.

Results

Nurses who worked night shifts had substantially higher PSQI ratings (p<0.05) than those who worked day shifts. In addition, there was a clear relationship between the HADS and PSQI scores. According to the binary logistic regression, longer working hours and inadequate sleep were both independently linked to depressive symptoms among nurses.

Conclusion

Poor sleep quality brought on by night shifts may explain why Saudi nurses who work night shifts experience higher rates of depression than those who work day shifts only.

Association between matched chronotype and poor mental health among shift workers: a systematic review and meta-analysis

BACKGROUND

Nearly 0.7 billion workers are involved in the shift work system, leading to concerns about its potential impacts on the large-scale population mental health. This study aimed to synthesise evidence of the associations between matched chronotype and the risk of poor mental health among shift workers.

METHODS

Six computerised databases were searched from inception to September 2022. Observational studies were selected if they reported any association between common mental health parameters and chronotype scores/types of shift workers. The Preferred Reporting Items for Systematic Reviews and Meta-analyses checklist was followed. We extracted adjusted risk estimates to calculate pooled effect sizes and explore sources of heterogeneity. The study was registered in PROSPERO: CRD42022357437.

RESULTS

Fourteen studies including 49 909 workers were identified. Ever shift workers had a higher risk of poor mental health than the day workers (pooled OR 1.15, 95% CI 1.03 to 1.28; I²=14%, p=0.29), with the evening chronotype ever shift workers having a 1.47 times higher risk than those who worked during the day (pooled OR 1.47, 95% CI 1.13 to 1.91; I²=42%, p=0.16). Sensitivity analysis excluding studies with the highest risk of bias of each group demonstrated consistent findings.

CONCLUSIONS

Evening chronotype ever shift workers have poorer mental health than shift workers with other chronotypes. Chronotype remains unrecognised in the contemporary rostering system, making it a hidden contributor to occupational mental health. Work-related physical and mental stresses may be prevented/mitigated with further investigation on optimising shift work schedule combined with individual chronotype preference.

A Novel Screening, Brief Intervention, and Referral to Treatment (SBIRT) Based Model for Mental Health in Occupational Health Implemented on Smartphone and Web-Based Platforms: Development Study With Results From an Epidemiologic Survey

BACKGROUND

While the importance of mental health is well-recognized in the field of occupational health, implementation of effective strategies in the workplace has been limited by gaps in infrastructure, program comprehensiveness, coverage, and adherence. The authors developed a Screening, Brief Intervention, and Referral to Treatment (SBIRT) model based occupational mental health intervention, and implemented in a web-based format with a smartphone application.

METHODS

The SBIRT-based intervention was developed by a multidisciplinary team, including occupational health physicians, nurses, psychiatrists, and software developers. The following mental health areas were included, based on outcomes of an epidemiological survey conducted: insomnia, depression, anxiety, problematic alcohol use, and suicidal risk. The viability of the two-step evaluation process utilizing a combination of the brief version and the full-length version of the questionnaire was examined using responses from the survey. The intervention was adjusted according to the survey results and expert opinions.

RESULTS

The epidemiological survey included 346 employees who completed the long-form version of mental health scales. These data were the used to confirm the diagnostic value of using a combination of short-form and long-form version of the scales for screening in the SBIRT model. The model uses a smartphone application for screening, provision of psychoeducation, and for surveillance. The universal methods of the model ensure it can be implemented by all occupational managers, regardless of their specialization in mental health. In addition to the two-step screening procedure to identify employees at-risk for mental health problems, the model includes a stepped care approach, based on risk stratification, to promote mental health education, management, and follow-up for continuous care.

CONCLUSION

The SBIRT model-based intervention provides an easy-to-implement approach for the management of mental health in the workplace. Further studies are required to examine the effectiveness and feasibility of the model.

An intersectional approach to understanding the correlates of depression in college students: Discrimination, social status, and identity

OBJECTIVE

We assessed the impact of bearing multiple marginalized identities, experiencing discrimination and perceived social status on the prevalence of depression in college students using an intersectional approach.

PARTICIPANTS

Public health students at a diverse urban public university in Northern California (N = 338, response rate = 85%; 77% women, mean age 22).

METHODS

We used a cross-sectional survey to assess demographics, depression, discrimination and social standing using validated scales and estimate the relations between depression and co-factors.

RESULTS

25.4% of students reported depression. Discrimination was associated with a higher level of depression and more severe symptoms. Higher perceived social status was associated with a lower level of depression and less severe symptoms. Hispanic/Latinx first generation women had three times the prevalence of depression as non-Hispanic/Latinx non-first generation men and there was a significant disparity in depression severity.

CONCLUSIONS

Intersectional approaches can shed light on the experiences of marginalized groups.

Circadian Disruption and Mental Health: The Chronotherapeutic Potential of Microbiome-Based and Dietary Strategies

Mental illness is alarmingly on the rise, and circadian disruptions linked to a modern lifestyle may largely explain this trend. Impaired circadian rhythms are associated with mental disorders. The evening chronotype, which is linked to circadian misalignment, is a risk factor for severe psychiatric symptoms and psychiatric metabolic comorbidities. Resynchronization of circadian rhythms commonly improves psychiatric symptoms. Furthermore, evidence indicates that preventing circadian misalignment may help reduce the risk of psychiatric disorders and the impact of neuro-immuno-metabolic disturbances in psychiatry. The gut microbiota exhibits diurnal rhythmicity, as largely governed by meal timing, which regulates the host's circadian rhythms. Temporal circadian regulation of feeding has emerged as a promising chronotherapeutic strategy to prevent and/or help with the treatment of mental illnesses, largely through the modulation of gut microbiota. Here, we provide an overview of the link between circadian disruption and mental illness. We summarize the connection between gut microbiota and circadian rhythms, supporting the idea that gut microbiota modulation may aid in preventing circadian misalignment and in the resynchronization of disrupted circadian rhythms. We describe diurnal microbiome rhythmicity and its related factors, highlighting the role of meal timing. Lastly, we emphasize the necessity and rationale for further research to develop effective and safe microbiome and dietary strategies based on chrononutrition to combat mental illness.

Effects of outdoor artificial light at night on human health and behavior: A literature review

The quality of life of human beings has improved tremendously through improved productivity, convenience, safety, and livability due to nighttime lights that illuminate outdoor work, leisure, and mobility. Recently, however, concerns have been growing over outdoor artificial light at night (ALAN) and its effects on human beings as well as ecosystems including animals and plants. This literature review aims to deliver a critical overview of the findings and the areas for future research on the effects of outdoor ALAN on human health and behaviors. Through a narrative literature review, we found that scientific research crucially lacks studies on the effects of outdoor ALAN on human behaviors and health, including social interaction, which may be more widespread compared to what is recognized so far. This review also highlights the importance of investigating the causal and complex relationships between outdoor ALAN, health, and behaviors with sleep as a key mediating factor. We elucidate that outdoor ALAN has both positive and negative effects on human life. Therefore, it is important for societies to be able to access facts and evidence about these effects to plan, agree to, and realize the optimal usage of nighttime lighting that balances its merits and demerits. Researchers in related areas of study must investigate and deliver the science of outdoor ALAN to various stakeholders, such as citizens, policymakers, urban and landscape planners, relevant practitioners, and industries. We believe that our review improves the understanding of outdoor ALAN in relation to human life and contributes to sustainable and thriving societies.

The Relationship between Working Night Shifts and Depression among Nurses: A Systematic Review and Meta-Analysis

BACKGROUND

For many years, occupational physicians have debated whether there is a link between working the night shift and depression and other co-occurring mental health issues, with an emphasis on work-related, biological, individual, and environmental factors. We performed this systematic review and meta-analysis to estimate the overall association between sleep deprivation and depression among nurses working night shifts.

METHODS

A systematic search was carried out across the electronic databases PubMed, Scopus, and Web of Science from inception to 30 September 2022, for studies that reported a relationship between estimated night shift work and depression in nurses. The outcomes were measured using the odds ratio (OR) and matching 95% confidence interval (CI). The I² statistic was used to assess heterogeneity. The Grading of Recommendations Assessment, Development and Evaluation technique was used to evaluate the quality of the evidence, and the Newcastle-Ottawa Scale was utilized to assess the methodological quality of each of the included studies. We determined the overall relationship between working nights and the onset of depression.

RESULTS

A total of 20 studies were included in the systematic review. Furthermore, 8 studies were included in the meta-analysis due to their common use of the OR as an effect measure. The 8 studies gave an overall estimate indicating a statistically significant association between night shift work and depression among nurses (OR = 1.49 95% CI: 1.26, 1.76). The prediction interval for the overall estimate was (0.995, 2.231). This implies that the true OR in a future study would most likely fall within this range, with a 95% certainty.

CONCLUSIONS

The outcome of this systematic review and meta-analysis showed a significant association between night shift work, the circadian and sleep disruption it causes, and the risk of depression in nurses. This demonstrates that nurses who work night shifts are at risk of developing depression.

Shift work schedule and sleep patterns in relation to incident depression: Evidence from a prospective cohort study

This study aims to explore the joint associations of shift work and sleep patterns with incident depression. The present prospective cohort using data from UK biobank, included 220,651 participants aged 38 to 71 years recruited between 2006 and 2010. Every participant finished a self-completed touch-screen questionnaire. Hazards ratios (HRs) with corresponding 95% confidence intervals (CIs) of incident depression were reported for shift work and sleep patterns by Cox-proportional hazard models. The average follow-up time was 12.13±1.94 years and the incidence rate of depression was 2.95 (2.89-3.02) per 1000 person-years. After fully adjustment, the participants with irregular and permanent night shifts companied by any sleep pattern were significantly associated with increased risk of incident depression compared with no shift work companied by favorable sleep patterns. The females seemed to be more vulnerable when having night shifts and unfavorable sleep patterns compared with the males. The increased risk of incident depression associated with shift work regardless of night shifts and evening/weekend shifts was not able to offset by favorable sleep patterns. The workers with unhealthy sleep patterns, especially inappropriate sleep duration and insomnia companied by shift work schedule should be paid more attention considering higher risk of depression.

The association between shift work and the incidence of reflux esophagitis in Korea: a cohort study

Shift work has adverse health effects such as diabetes, cardiovascular disease, sleep disturbance, depression, and breast cancer. Gastro-esophageal reflux disease (GERD) results in lesions such as reflux esophagitis (RE) and Barrett's esophagus. This study investigated the association between shift work and RE. A cohort study was conducted with 140,553 participants who were followed up at least once from 2012 to 2018. Type of working and shift types were collected using standardized questionnaires. Esophagogastroduodenoscopy (EGD) was performed by experienced endoscopists who were blinded to the aims of this study. According to the Los Angeles classification, RE was categorized based on the extent of esophageal mucosal breaks. During the 469,217.2 person-years of follow-up, 35,185 participants developed incident cases of RE. The multivariable adjusted hazard ratio (95% confidence intervals) for incident cases comparing shift work to fixed day work was 1.09 (1.04-1.13). This association was more strongly observed in the younger age group (18-39 years old) and the female group. In conclusion, shift work was significantly associated with the incidence of RE. Particularly, the results were more significant in the younger and female groups.

Distribution of working hour characteristics by race, age, gender, and shift schedule among U.S. manufacturing workers

Shift work is a common occupational exposure, however, few studies have examined aspects of shift work beyond night work and long hours, such as rotational patterns or weekend work, which may contribute to poor health through disruption of the body's circadian rhythms. In this manuscript, we calculated the prevalence of working hour characteristics using algorithms for type (e.g., day), duration, intensity, rotational direction, and social aspects (e.g., weekend work) in a nationwide cohort of American manufacturing workers (N = 23,044) between 2003 and 2014. Distributions of working hour characteristics were examined by schedules (e.g., permanent day, day/night) and demographics, and were cross-classified in a matrix to examine co-occurrence. Approximately 55% of shifts may cause circadian rhythm disruption as they were non-day shifts or day shifts with a quick return or rotation, or were 13 h or longer. Older workers, female workers, and White workers worked permanent day shifts most often, while workers of color worked more day/night schedules. Night and evening shifts had more frequent shift rotations, quick returns, and longer hours than day shifts. Yet, day shifts, which are presumed to have little negative circadian impact, may cause circadian rhythm disruption as long hours, quick returns and rotations also occurred within day shifts.

High prevalence of insomnia among physiatrists in the Czech Republic: A web-based questionnaire survey

BACKGROUND

Physicians who suffer from poor sleep quality are at an increased risk of mistakes and poor decision-making. We deemed it noteworthy to assess sleep quality in practicing physiatrists, previously reported to be at higher risk of physician burnout, which was documented associated with sleep deprivation.

OBJECTIVE

The aim was to estimate the prevalence of sleep disturbance among practicing physiatrists and evaluate the association of sleep quality with their sleep hygiene habits and depression.

METHODS

Of the 101 study participants (77 females) who met the inclusion criteria, the majority was between the age of 25 and 40 years (70.3% ); 62 (61.4% ) were specialists and 39 (38.6% ) were in training. In this cross-sectional study, practicing physiatrists were invited to complete an anonymous and voluntary web-based survey. The survey consisted of questions covering demographic information, nicotine and caffeine consumption, exercise habits, and three questionnaires: the Pittsburgh Sleep Quality Index (PSQI), the Beck Depression Inventory-II (BDI-II), and the Sleep Hygiene Index (SHI).

RESULTS

Sixty-five (64.4% ) respondents showed poor sleep quality (PSQI >  5), and 23 (22.8% ) showed at least mild symptoms of depression (BDI-II>13). The mean PSQI, SHI, BDI-II scores were 6.85±3.09, 18.18±5.35, and 8.36±7.52, respectively. Poor sleep quality was significantly positively correlated with symptoms of depression and sleep hygiene misbehavior.

CONCLUSION

We found that 64.4% of practicing physiatrists suffered from poor sleep quality, and 22.8% showed at least mild symptoms of depression. Considerable efforts should be directed toward sleep hygiene behavior and mental health improvement.

The Association between Replacement Drivers and Depressive Symptoms

A replacement driver is a type of gig worker who provides driving services to the target point with the drunk driver's own car. This study aimed to examine the association of replacement drivers (ref: paid workers) with depressive symptoms. Information on replacement drivers was collected through online/offline surveys. Data from the 8th Korea National Health and Nutrition Examination Survey were applied to construct the control group. The Patient Health Questionnaire-9; ≥5 points was defined as depressive symptoms. Adjusted odds ratios (aOR) and 95% confidence intervals (CI) were calculated by performing multivariable logistic regression analysis. The mean age of replacement drivers was 56.11. The prevalence of depressive symptoms in replacement drivers and controls were 49.63% and 12.64%, respectively. Replacement drivers showed a higher association with depressive symptoms than paid workers (aOR 7.89, 95% CI [5.53-11.26]). This relationship was prominent in the older, low-education, and low-income groups. Linear discriminant analysis was the most effective in predicting depressive symptoms among the machine learning models. Using the replacement driver feature increased the AUC values of the models. Given the strong association between depressive symptoms and replacement drivers, in-depth studies to establish guidelines to prevent mental diseases among replacement drivers are required.

Scheduling practices for pregnant emergency medicine residents

Background

Night shift work is associated with adverse pathophysiologic effects on maternal and fetal well-being. Although emergency medicine (EM) residents work frequent night shifts, there is no existing guidance for residency program directors (PDs) regarding scheduling pregnant residents. Our study assessed scheduling practices for pregnant EM residents, differences based on program and PD characteristics, barriers and attitudes toward implementing a formal scheduling policy, and PDs' awareness of literature describing adverse effects of night shifts on maternal-fetal outcomes.

Methods

We conducted an anonymous, web-based survey of U.S. EM residencies (N = 276). Quantitative data were summarized; chi-square analysis and logistic regression were used to assess relationships between program and PD characteristics and schedule accommodations. Qualitative description was used to analyze an open-ended question, organizing findings into major and minor themes.

Results

Of the 167 completed surveys (response rate 61%), 67% of programs reported no formal policy for scheduling pregnant residents but made adjustments on an individual basis including block changes (85%), decreased (46%) or no night shifts (34%), and working shifts earlier in pregnancy to cover later shifts (20%). Barriers to adjustments included staffing constraints (60%), equity concerns (45%), or impact on wellness (41%) among all residents and privacy (28%). PDs endorsed scheduling adjustments as important (mean 8.1, 0-10 scale) and reported guidance from graduate medical education governance would be useful (60%). Larger program size, but not PD gender or proportion of female residents, was associated with an increased likelihood of scheduling modifications. Twenty-five percent of PDs reported little knowledge of literature regarding night shift work and pregnancy. Qualitative themes supported quantitative findings.

Conclusions

Most EM residency programs do not have formal scheduling policies for pregnant residents, but most PDs support making adjustments and do so informally. More education and guidance for PDs are needed to promote the development of formal policies.

Association between sleep quality and type of shift work in Korean firefighters

Background

Shift work that interferes with normal sleep patterns, is known to be a cause of sleep disturbance and has been studied through various occupational groups. However, it is not known which shift type is better for sleep health.

Methods

This study included 568 firefighters. Sleep quality was evaluated using Pittsburgh Sleep Quality Index. Sleep quality was categorized into 2 groups; good quality (≤ 5 points) and poor quality (≥ 6 points). Demographic variables, depression, anxiety, type of shift, and job were collected by self-reported questionnaires. The χ² test, t-test, and multiple logistic regression analysis were used to evaluate the effect of shift type on the sleep quality of firefighters.

Results

Three hundred thirty-seven firefighters (59.3%) have poor sleep quality. Compared to day workers, the odds ratios (ORs) of poor sleep quality were 2.169 (95% confidence interval: 1.137-4.134) in 6-day cycle, 2.161 (1.150-4.062) in 9-day cycle, 1.805 (1.087-2.997) in 21-day cycle, and 1.485 (0.718-3.069) in 3-day cycle. The ORs of poor sleep quality were 1.697(1.021-2.823) in fire suppression and 2.325 (1.213-4.455) in emergency medical service compared to administration.

Conclusions

All shift work type except for the 3-day cycle was associated with poor sleep quality compared to day work.

Circadian rhythms and disorders of the timing of sleep

The daily alternation between sleep and wakefulness is one of the most dominant features of our lives and is a manifestation of the intrinsic 24 h rhythmicity underlying almost every aspect of our physiology. Circadian rhythms are generated by networks of molecular oscillators in the brain and peripheral tissues that interact with environmental and behavioural cycles to promote the occurrence of sleep during the environmental night. This alignment is often disturbed, however, by contemporary changes to our living environments, work or social schedules, patterns of light exposure, and biological factors, with consequences not only for sleep timing but also for our physical and mental health. Characterised by undesirable or irregular timing of sleep and wakefulness, in this Series paper we critically examine the existing categories of circadian rhythm sleep-wake disorders and the role of the circadian system in their development. We emphasise how not all disruption to daily rhythms is driven solely by an underlying circadian disturbance, and take a broader, dimensional approach to explore how circadian rhythms and sleep homoeostasis interact with behavioural and environmental factors. Very few high-quality epidemiological and intervention studies exist, and wider recognition and treatment of sleep timing disorders are currently hindered by a scarcity of accessible and objective tools for quantifying sleep and circadian physiology and environmental variables. We therefore assess emerging wearable technology, transcriptomics, and mathematical modelling approaches that promise to accelerate the integration of our knowledge in sleep and circadian science into improved human health.

Artificial light at night and risk of mental disorders: A systematic review

BACKGROUND

Emerging evidence suggests a possible association between artificial light at night (LAN) exposure and physiological and behavioral changes, with implications on mood and mental health. Due to the increased amount of individuals' LAN exposure, concerns have been raised regarding harmful impact of light pollution on mental health at the population level.

AIM

To perform a systematic review of observational studies to investigate if light at night, assessed both indoor and outdoor, may be associated with an increased risk of mental diseases in humans.

METHODS

We reviewed the epidemiological evidence on the association between LAN exposure, assessed either via satellite photometry or via measurements of bedroom brightness, and mental disorders. We systematically searched the PubMed, Embase and Web of Science databases up to April 1, 2022. Studies were included if they assessed the link between indoor or outdoor artificial light at night and one or more mental disorders in human populations.

RESULTS

Nine eligible studies were included in this review: six studies had a cross-sectional design, two had a longitudinal design with a median follow-up of 24 months, and one was a case-cohort study. Overall, we found moderate evidence of a positive association between LAN exposure and depressive symptoms and to a lesser extent other mental disorders, though the number of studies was limited and potential residual confounding such as socioeconomic factors, noise, or air pollution may have influenced the results.

CONCLUSIONS

Although more robust evidence is needed, the epidemiological evidence produced so far seems to support an association between LAN and risk of depressive disorders.

Chronotype, circadian rhythm, and psychiatric disorders: Recent evidence and potential mechanisms

The circadian rhythm is crucial for physiological and behavioral functions. Chronotype, which represents individual preferences for activity and performance, is associated with human health issues, particularly psychiatric disorders. This narrative review, which focuses on the relationship between chronotype and mental disorders, provides an insight into the potential mechanism. Recent evidence indicates that (1) the evening chronotype is a risk factor for depressive disorders and substance use disorders, whereas the morning chronotype is a protective factor. (2) Evening chronotype individuals with bipolar disorder tend to have more severe symptoms and comorbidities. (3) The evening chronotype is only related to anxiety symptoms. (4) The relationship between chronotype and schizophrenia remains unclear, despite increasing evidence on their link. (5) The evening chronotype is significantly associated with eating disorders, with the majority of studies have focused on binge eating disorders. Furthermore, the underlying mechanisms or influence factors are described in detail, including clock genes, brain characteristics, neuroendocrinology, the light/dark cycle, social factors, psychological factors, and sleep disorders. These findings provide the latest evidence on chronotypes and psychiatric disorders and serve as a valuable reference for researchers.

Exploring the Associated Factors of Depression, Anxiety, and Stress among Healthcare Shift Workers during the COVID-19 Pandemic

Background: The recent pandemic of COVID-19 has had a tremendous impact on healthcare frontliners. This study sought to assess healthcare shift workers’ depression, anxiety, and stress and its associated factors. Methods: The sampling frame includes healthcare shift workers directly managing COVID-19 cases around Klang Valley, Malaysia. The participants’ mental health status was assessed using the Depression, Anxiety, Stress Scale-21 (DASS-21). The associated factors specified in this study include sleep quality, physical activities, and eating habits. Pearson’s χ2 and simple and multivariable binary logistic regression models were constructed following the Hosmer–Lemeshow approach to determine the potential associated factors. Results: A total of 413 participants were recruited. Overall, 40.7% of participants had one or more symptoms of depression, anxiety, or stress. Poor sleep quality was significantly associated with all mental health outcomes of depression, anxiety, and stress. Inactivity was found to be strongly associated with symptoms of depression and anxiety. At the same time, eating habits were strongly associated with anxiety and stress. Conclusions: Sleep quality, inactivity, and eating habits that were found to be associated with the mental health status of healthcare shift workers are modifiable factors that must be addressed to curb mental health issues among this group of workers.

Effects of Factors Related to Shift Work on Depression and Anxiety in Nurses

Background

Although shift work is the foundation of the provision of 24-h continuous care in hospitals, it can negatively impact mental health in hospital workers such as nurses. Despite the connection between mental health and overall health, little is known about the effect of shift work-related factors on mental health in this population.

Objectives

We investigated the effect of scheduling practices, physical and psychological characteristics related to shift work, and personal habits during shift work on depression and anxiety among nurses.

Methods

In this multi-center cross-sectional study, 11,061 nurses from 20 hospitals in the Shandong Province of China completed an online survey between December 2020 and February 2022. Multivariate ordered logistic regression analysis was performed to examine shift-related factors associated with depression and anxiety in the study population.

Results

The completion rate of all nurses' questionnaires was 83.00% (n = 9,181). Among the 9,181 respondents, 66.20% (n = 6,078) were shift nurses. Depression and anxiety were found in 58.82 and 62.08% of shift nurses, respectively, and these rates were influenced by fatigue during shift work, psychological stress before/during/after night shifts, feeling of being refreshed after resting before/after night shifts, using sleep medication before/after night shifts, physical discomfort during night shifts, busyness during night shifts, food intake during shift work, working > 40 h/week during shift work, and sleep quality before/after night shifts.

Conclusions

Depression and anxiety in shift nurses may be addressed by reducing their workload, sources of stress during night shifts, and facilitating rest and relaxation.

Rotating Night Shift Work and Healthy Aging After 24 Years of Follow-up in the Nurses' Health Study

IMPORTANCE

Rotating night shift work is associated with higher mortality. Whether it is also associated with overall health among those who survive to older ages remains unclear.

OBJECTIVE

To examine whether rotating night shift work is associated with healthy aging after 24 years of follow-up in the Nurses' Health Study, a cohort study among registered female nurses.

DESIGN, SETTING, AND PARTICIPANTS

For this cohort study, a composite healthy aging phenotype was ascertained among 46 318 participants who were aged 46 to 68 years and free of major chronic diseases in 1988 when the history of night shift work was assessed. In a secondary analysis in which cognitive function decline was considered in the healthy aging definition, 14 273 nurses were involved. Data were analyzed from March 1 to September 30, 2021.

EXPOSURES

Duration of rotating night shift work.

MAIN OUTCOMES AND MEASURES

Healthy aging was defined as reaching at least 70 years of age and being free of 11 major chronic diseases, memory impairment, physical limitation, or deteriorated mental health.

RESULTS

Of 46 318 female nurses (mean [SD] age at baseline, 55.4 [6.1] years), 3695 (8.0%) achieved healthy aging after 24 years of follow-up. After adjusting for established and potential confounders, compared with women who never worked rotating night shifts, the odds of achieving healthy aging decreased significantly with increasing duration of night shift work. The odds ratios were 0.96 (95% CI, 0.89-1.03) for 1 to 5 years, 0.92 (95% CI, 0.79-1.07) for 6 to 9 years, and 0.79 (95% CI, 0.69-0.91) for 10 or more years of night shift work (P = .001 for trend). This association did not differ substantially by age and lifestyles and was consistent for 4 individual dimensions of healthy aging. Results were similar in a secondary analysis, with an odds ratio of 0.73 (95% CI, 0.60-0.89; P < .001 for trend) comparing 10 or more years of night shift work vs no night shift work.

CONCLUSIONS AND RELEVANCE

In this cohort study, rotating night shift work was associated with decreased probability of healthy aging among US female nurses. These data support the notion that excess night shift work is a significant health concern that may also lead to deteriorated overall health among older individuals.

Psychosocial Work Stress and Health Risks – A Cross-Sectional Study of Shift Workers From the Hotel and Catering Industry and the Food Industry

Purpose

Psychosocial work stress, and shift and night work are considered risk indicators for impaired health. Using the effort-reward (ER) model, it was possible to examine which relationships exist for shift workers between clusters (CL) of different levels of psychosocial work stress and overcommitment (OC) and cardiovascular or psychological health indicators, and which predictive value is evident in individual health indicators to explain the clusters.

Methods

The data were collected as part of an occupational health prevention program. The analysis sample consisted of 199 shift workers from alternating shift systems with and without night work (43%) (average age: 40 ± 12 years, men: 47%). Psychosocial work stress was recorded using the ER imbalance (ERI) questionnaire. To determine the clusters, ERI and OC were entered into a cluster analysis. Blood pressure, body mass index, waist-hip ratio, PROCAM score (risk of a heart attack within the next 10 years), sporting activity, and smoking were included as cardiovascular indicators, psychological wellbeing (GHQ-12) and inability to recovery (IR) (FABA) as psychological health indicators. Shift system, sex, and age were entered into the statistical analyses as control variables. Multinomial logistic regression models were used to identify health-related predictors to explain the ER-OC clusters.

Results

Three different ER-OC clusters emerged: low-stress: 36%, normal: 44%, risk: 20%. While normal psychosocial work stress is present in the low-stress and the normal CL, in the risk CL 28% of the shift workers show a health-endangering ERI and 48% show an excessive OC. No significant cluster-specific differences were determined for the cardiovascular health indicators. Rather, the known sex and age effects were confirmed and the shift system had no significant effect. Significantly more shift workers in the risk CL had impaired psychological health (18 vs. 1/6%) and an IR (52 vs. 0/12%) than in the low-stress and normal CL. IR turned out to be the strongest predictor of the explanation for the ER-OC clusters (49%).

Conclusion

IR could be assigned an independent diagnostic value for the assessment of psychosocial work stresses and discussed as a new component of occupational health screening concepts for shift workers. Independently of this, the health indicators signal an urgent need for occupational health prevention and care.

The Difference of Suicidal Ideation Between Shift Workers and Day Workers by Gender

Shift work does not synchronize with the 24-hour human circadian rhythm, so shift workers experience various problems related to this disruption. This study investigated the relationship between suicidal risk and emotional difficulties such as depression and anxiety in shift workers according to gender. We analyzed data collected from 79,009 health checkup recipients. We checked psychosocial factors for different genders using the Chi-square test and t-tests. To examine the relationship between shift work and suicidal ideation, we estimated an odds ratio after adjustment for age, depression, and insomnia. There was no difference in terms of the risk of suicidal ideation between shift workers and day workers among women (adjusted odds ratio [AOR], 0.957; 95% confidence interval [CI], 0.826-1.109), whereas the risk of suicidal ideation was significantly higher for shift workers than for day workers among men (AOR, 1.157; 95% CI, 1.021-1.310). This study confirmed that associated factors of shift work-related suicidal ideation could act differently by gender. Shift work for women is generally associated with emotional difficulties such as depression and anxiety, whereas maladaptation to shift work may be related to suicidal ideation among men. A gender-specific suicide prevention approaches will be needed for shift workers.

Normal Light-Dark and Short-Light Cycles Regulate Intestinal Inflammation, Circulating Short-chain Fatty Acids and Gut Microbiota in Period2 Gene Knockout Mice

Regular environmental light–dark (LD) cycle-regulated period circadian clock 2 (Per2) gene expression is essential for circadian oscillation, nutrient metabolism, and intestinal microbiota balance. Herein, we combined environmental LD cycles with Per2 gene knockout to investigate how LD cycles mediate Per2 expression to regulate colonic and cecal inflammatory and barrier functions, microbiome, and short-chain fatty acids (SCFAs) in the circulation. Mice were divided into knockout (KO) and wild type (CON) under normal light–dark cycle (NLD) and short-light (SL) cycle for 2 weeks after 4 weeks of adaptation. The concentrations of SCFAs in the serum and large intestine, the colonic and cecal epithelial circadian rhythm, SCFAs transporter, inflammatory and barrier-related genes, and Illumina 16S rRNA sequencing were measured after euthanasia during 10:00–12:00. KO decreased the feeding frequency at 0:00–2:00 but increased at 12:00–14:00 both under NLD and SL. KO upregulated the expression of Per1 and Rev-erbα in the colon and cecum, while it downregulated Clock and Bmal1. In terms of inflammatory and barrier functions, KO increased the expression of Tnf-α, Tlr2, and Nf-κb p65 in the colon and cecum, while it decreased Claudin and Occludin-1. KO decreased the concentrations of total SCFAs and acetate in the colon and cecum, but it increased butyrate, while it had no impact on SCFAs in the serum. KO increased the SCFAs transporter because of the upregulation of Nhe1, Nhe3, and Mct4. Sequencing data revealed that KO improved bacteria α-diversity and increased Lachnospiraceae and Ruminococcaceae abundance, while it downregulated Erysipelatoclostridium, Prevotellaceae UCG_001, Olsenella, and Christensenellaceae R-7 under NLD in KO mice. Most of the differential bacterial genus were enriched in amino acid and carbohydrate metabolism pathways. Overall, Per2 knockout altered circadian oscillation in the large intestine, KO improved intestinal microbiota diversity, the increase in Clostridiales abundance led to the reduction in SCFAs in the circulation, concentrations of total SCFAs and acetate decreased, while butyrate increased and SCFAs transport was enhanced. These alterations may potentially lead to inflammation of the large intestine. Short-light treatment had minor impact on intestinal microbiome and metabolism.

Induction of internal circadian desynchrony by misaligning zeitgebers

24-h rhythms in physiology and behaviour are orchestrated by an endogenous circadian clock system. In mammals, these clocks are hierarchically organized with a master pacemaker residing in the hypothalamic suprachiasmatic nucleus (SCN). External time signals—so-called zeitgebers—align internal with geophysical time. During shift work, zeitgeber input conflicting with internal time induces circadian desynchrony which, in turn, promotes metabolic and psychiatric disorders. However, little is known about how internal desynchrony is expressed at the molecular level under chronodisruptive environmental conditions. We here investigated the effects of zeitgeber misalignment on circadian molecular organisation by combining 28-h light–dark (LD-28) cycles with either 24-h (FF-24) or 28-h feeding-fasting (FF-28) regimes in mice. We found that FF cycles showed strong effects on peripheral clocks, while having little effect on centrally coordinated activity rhythms. Systemic, i.e., across-tissue internal circadian desynchrony was profoundly induced within four days in LD-28/FF-24, while phase coherence between tissue clocks was maintained to a higher degree under LD-28/FF-28 conditions. In contrast, temporal coordination of clock gene activity across tissues was reduced under LD-28/FF-28 conditions compared to LD-28/FF-24. These results indicate that timed food intake may improve internal synchrony under disruptive zeitgeber conditions but may, at the same time, weaken clock function at the tissue level.

The Suprachiasmatic Nucleus Regulates Anxiety-Like Behavior in Mice

Individuals suffering from mood and anxiety disorders often show significant disturbances in sleep and circadian rhythms. Animal studies indicate that circadian rhythm disruption can cause increased depressive- and anxiety-like behavior, but the underlying mechanisms are unclear. One potential mechanism to explain how circadian rhythms are contributing to mood and anxiety disorders is through dysregulation of the suprachiasmatic nucleus (SCN) of the hypothalamus, known as the “central pacemaker.” To investigate the role of the SCN in regulating depressive- and anxiety-like behavior in mice, we chronically manipulated the neural activity of the SCN using two optogenetic stimulation paradigms. As expected, chronic stimulation of the SCN late in the active phase (circadian time 21, CT21) resulted in a shortened period and dampened amplitude of homecage activity rhythms. We also repeatedly stimulated the SCN at unpredictable times during the active phase of mice when SCN firing rates are normally low. This resulted in dampened, fragmented, and unstable homecage activity rhythms. In both chronic SCN optogenetic stimulation paradigms, dampened homecage activity rhythms (decreased amplitude) were directly correlated with increased measures of anxiety-like behavior. In contrast, we only observed a correlation between behavioral despair and homecage activity amplitude in mice stimulated at CT21. Surprisingly, the change in period of homecage activity rhythms was not directly associated with anxiety- or depressive-like behavior. Finally, to determine if anxiety-like behavior is affected during a single SCN stimulation session, we acutely stimulated the SCN in the active phase (zeitgeber time 14-16, ZT14-16) during behavioral testing. Unexpectedly this also resulted in increased anxiety-like behavior. Taken together, these results indicate that SCN-mediated dampening of rhythms is directly correlated with increased anxiety-like behavior. This work is an important step in understanding how specific SCN neural activity disruptions affect depressive- and anxiety-related behavior.

Associations between genetic loci, environment factors and mental disorders: a genome-wide survival analysis using the UK Biobank data

It is well-accepted that both environment and genetic factors contribute to the development of mental disorders (MD). However, few genetic studies used time-to-event data analysis to identify the susceptibility genetic variants associated with MD and explore the role of environment factors in these associations. In order to detect novel genetic loci associated with MD based on the time-to-event data and identify the role of environmental factors in them, this study recruited 376,806 participants from the UK Biobank cohort. The MD outcomes (including overall MD status, anxiety, depression and substance use disorders (SUD)) were defined based on in-patient hospital, self-reported and death registry data collected in the UK Biobank. SPACOX approach was used to identify the susceptibility loci for MD using the time-to-event data of the UK Biobank cohort. And then we estimated the associations between identified candidate loci, fourteen environment factors and MD through a phenome-wide association study and mediation analysis. SPACOX identified multiple candidate loci for overall MD status, depression and SUD, such as rs139813674 (P value = 8.39 × 10^-9, ZNF684) for overall MD status, rs7231178 (DCC, P value = 2.11 × 10^-9) for depression, and rs10228494 (FOXP2, P value = 6.58 × 10^-10) for SUD. Multiple environment factors could influence the associations between identified loci and MD, such as confide in others and felt hated. Our study identified novel candidate loci for MD, highlighting the strength of time-to-event data based genetic association studies. We also observed that multiple environment factors could influence the association between susceptibility loci and MD.

Disruption of Circadian Rhythm Genes in Obstructive Sleep Apnea Patients-Possible Mechanisms Involved and Clinical Implication

Obstructive sleep apnea (OSA) is a chronic condition characterized by recurrent pauses in breathing caused by the collapse of the upper airways, which results in intermittent hypoxia and arousals during the night. The disorder is associated with a vast number of comorbidities affecting different systems, including cardiovascular, metabolic, psychiatric, and neurological complications. Due to abnormal sleep architecture, OSA patients are at high risk of circadian clock disruption, as has been reported in several recent studies. The circadian clock affects almost all daily behavioral patterns, as well as a plethora of physiological processes, and might be one of the key factors contributing to OSA complications. An intricate interaction between the circadian clock and hypoxia may further affect these processes, which has a strong foundation on the molecular level. Recent studies revealed an interaction between hypoxia-inducible factor 1 (HIF-1), a key regulator of oxygen metabolism, and elements of circadian clocks. This relationship has a strong base in the structure of involved elements, as HIF-1 as well as PER, CLOCK, and BMAL, belong to the same Per-Arnt-Sim domain family. Therefore, this review summarizes the available knowledge on the molecular mechanism of circadian clock disruption and its influence on the development and progression of OSA comorbidities.

Precarious Work Schedules and Sleep: A Study of Unionized Full-Time Workers

Unlike precarious employment which is temporary and insecure, with inadequate pay, benefits, and legal protections, precarious work schedules can affect workers with permanent full-time jobs in sectors where employment has historically been secure, well-compensated, and even unionized. Precarious work schedules - characterized by long shifts, non-daytime hours, intensity and unsocial work hours - are increasingly prevalent. Relations between precarious work schedules and poor health are not well understood, and less is known about how to attenuate this relation. We examined the indirect effects of precarious work schedules on fatigue and depressive symptoms through sleep quantity. Two moderators - schedule flexibility and sleep quality - were examined as buffers of these associations. Workers from the Departments of Correction and Transportation in a northeast state (N = 222) took surveys and reported on demographics, work schedule characteristics, schedule flexibility, sleep quality and quantity, fatigue, and depressive symptoms. Results revealed that precarious work schedules had indirect effects on fatigue and depressive symptoms through sleep quantity. Schedule flexibility moderated the relation between precarious work schedules and sleep quantity, such that workers with greater schedule flexibility had more hours of sleep. Sleep quality moderated the association between sleep quantity and fatigue and depressive symptoms, such that workers reported greater fatigue and depressive symptoms when they had poorer sleep quality. Findings have direct applicability for developing initiatives that enhance Total Worker Health® through individual and organizational changes.

Supplementary Information

The online version contains supplementary material available at 10.1007/s41542-022-00114-y.

Association of Delayed Sleep/Wake Rhythm with Depression During the First COVID-19 Lockdown in France

PURPOSE

The containment of the population during the COVID-19 pandemic led to the emergence or recurrence of psychiatric conditions and sleep disorders. The influence of sleep/wake rhythm on mental health is well known. The objective of our study was to evaluate the link between the shift in sleep/wake rhythm and the presence of depressive symptoms during the March to May 2020 lockdown in the French population.

PARTICIPANTS AND METHODS

Participants (n = 2513) were recruited via newspapers and social networks in March 2020. We evaluated i) the chronotype before and during the lockdown, assessed by the change in mid-sleep time on work-free days corrected for sleep debt on workdays (delta MSFsc); ii) morningness-eveningness circadian preference (Horne & Ostberg questionnaire); iii) depressive symptoms (Patient Health Questionnaire-9, PHQ-9). The delta MSFsc and the PHQ-9 score were compared between circadian preference types. A multivariate model adjusted for age, sex, circadian preference, housing type, and marital status was used to assess the influence of delta MSFsc on the PHQ-9 score in the whole population.

RESULTS

The population consisted of 77% women, of median (IQR) age 39 (30-48) years. Compared with the pre-lockdown period, the median (IQR) MSFsc was shifted by 30 (0-66) min during the lockdown, with a significant difference between evening [60 (15-120) min], morning [15 (0-46) min] and neutral [30 (0-70) min] circadian type individuals, p < 0.001. One-third of all participants had moderate to severe depressive symptoms (PHQ-9 ≥ 10). A 1-hour shift in MSFsc was associated with a 0.50-point increase [95% CI (0.28; 0.72), p < 0.001] in the PHQ-9.

CONCLUSION

A phase delay in the chronotype was observed in the general population during lockdown. Such disruption was associated with depressive symptoms but the direction of the relationship remains hypothetical. The impact on mental health of preventive measures targeting the sleep/wake rhythm in this context needs further evaluation.

Sleep deprivation and burnout syndrome among pre-hospital emergency medical service employees in Slovenia

Introduction: Sleep deprivation and burnout are common in employees who work in shifts, night shifts, overtime as well as those who work under stressful and unpredictable circumstances. The purpose of the study was to explore the quality of sleep, determine burnout level components and investigate the level of these components and their impact on the quality of sleep among employees in pre-hospital emergency medical services.Methods: A quantitative non-experimental research method was used. Data were collected using a standardized Pittsburgh sleep quality index questionnaire and a standardized Maslach burnout inventory questionnaire. The survey was completed by 204 healthcare professionals. Data were analyzed with univariate and bivariate statistics.Results: The average Pittsburgh Sleep Quality Index score was 4.97, s = 3.23. Poorer quality of sleep is exhibited by female respondents (57.4 %), respondents who are employed in more overloaded pre-hospital emergency service units (52.3 %) and those who work 24 hours or more (67.7 %). Overall, 17.6 % respondents exhibited high emotional exhaustion, 32.8 % exhibited high depersonalization and 9.3 % exhibited low personal accomplishment. A weak correlation was present between sleep quality and emotional exhaustion (r = 0.381, p < 0.01), depersonalization (r = 0.293, p < 0.01) and personal accomplishment (r = 0.368, p < 0.01).Discussion and conclusion: Healthcare professionals represent a vulnerable group that is subject to poor sleep quality and burnout syndrome, therefore, the need for empowering them in terms of proper sleep hygiene and burnout prevention is indicated.

Association of Night Shift Work With Chronic Spontaneous Urticaria and Effect Modification by Circadian Dysfunction Among Workers

Purpose: Night shift work is common in the current working environment and is a risk factor for many diseases. The study aimed to explore the relationship between night shift work with chronic spontaneous urticaria (CSU), and the modification effect of circadian dysfunction on it. Methods: A cross-sectional survey was conducted among Chinese workers. Exposure was measured by night work history and duration. Circadian dysfunction was characterized by excessive daytime sleepiness (EDS). The diagnosis of CSU was made by dermatologists who were investigating on the spot. The effect size was expressed as odds ratios (ORs). Results: A total of 8,057 participants were recruited, and 7,411 (92%) with complete information were included in the final analyses. The prevalence rates of CSU for workers without night shift and those with night shift history were 0.73 and 1.28%, respectively. Compared with workers who never worked night shifts, the risk of CSU increased with the length of night shift work: OR = 1.55 (95% confidence interval [CI]: 0.78-3.06) for duration <5 years and OR = 1.91 (95% CI: 1.12-3.26) for duration ≥5 years. EDS s EDS has been shown to modify this combination. Among workers without EDS, there was no association between night shift and CSU (OR = 0.94; 95% CI: 0.49-1.79). Whereas, in participants with EDS, the correlation was significant (OR = 3.58; 95% CI: 1.14-11.20). However, the effect modification by sleep disturbance was not observed. Conclusions: Night shift work is a risk factor for CSU, and there is a dose-response relationship between night shift work hours and the risk of CSU. This connection may be modified by circadian dysfunction.

Sleep and circadian rhythm actigraphy measures, mood instability and impulsivity: A systematic review

The normal spectrum trait measures of mood instability and impulsivity are implicated in and comprise core symptoms of several psychiatric disorders. A bidirectional relationship between these traits and sleep disturbance and circadian rhythm dysfunction has been hypothesised, although has not been systematically assessed using objective measures in naturalistic settings. We systematically reviewed the literature following PRISMA guidelines, according to a pre-registered protocol (PROSPERO: CRD 42018108213). Peer-reviewed quantitative studies assessing an association between actigraphic variables and any measure of mood instability or impulsivity in participants aged 12-65 years old were included. Studies were critically appraised using the AXIS tool. Twenty-three articles were retained for inclusion. There was significant heterogeneity in the selection and reporting of actigraphic variables and metrics of mood instability and impulsivity. We identified emerging evidence of a positive association between circadian rest-activity pattern disturbance and delayed sleep timing with both mood instability and impulsivity. Evidence for an association with sleep duration, sleep efficiency or sleep quality was inconsistent. Future research should focus on longitudinal intra-individual associations to establish the directionality between these measures and may lead to the development of chronotherapeutic interventions for a number of psychiatric disorders.