Occupational Risk for Coronary Artery Disease in Shift Workers - A Systematic Review.

BACKGROUND: Coronary artery disease (CAD) prevention in shift workers (SWs) poses a significant challenge worldwide, as CAD remains a major cause of mortality and disability. In the past, SWs were found at higher risk of CAD than non-s SWs. Nevertheless, the pathogenic mechanism between shift work and CAD to date is unclear. This systematic review aims to enhance understanding of the risk of CAD occurrence in SWs. METHODS: A systematic literature review was conducted from January 2013 to December 2023. MEDLINE/Pubmed databases were used initially, and additional relevant studies were searched from references. Shift work was defined as any schedule outside traditional shifts, including the night shift. RESULTS: Fifteen pertinent papers were categorized into risk assessment or risk management. Findings demonstrated an increased risk of CAD among SWs compared to non-SWs, with an increased CAD risk observed for both shift work and night shift work. DISCUSSION: Duration-response associations indicate that greater shift exposure is linked to higher CAD risk. SWs incur an increased risk of CAD through the atherosclerotic process. As shift work duration increases as the risk of atherosclerosis is higher, workers demonstrate a higher prevalence and severity of coronary artery plaques. CONCLUSIONS: The evidence-based results underscore the increased risk of CAD in SWs and are sufficient for proposing guidelines aimed at reducing the risk of CAD in SWs and at managing people with CAD in return to work characterized by disrupted circadian rhythms.

Association of rotating night shift work with tooth loss and severe periodontitis among permanent employees in Japan: a cross-sectional study.

Background: The modern 24/7 society demands night shift work, which is a possible risk factor for chronic diseases. This study aimed to examine the associations of rotating night shift work duration with tooth loss and severe periodontitis. Methods: This cross-sectional study used data from a self-administered questionnaire survey conducted among 3,044 permanent employees aged 20-64 years through a Japanese web research company in 2023. The duration of rotating night shift work was assessed using a question from the Nurses' Health Study. Tooth loss was assessed based on self-reported remaining natural teeth count. Severe periodontitis was assessed using a validated screening questionnaire comprising four questions related to gum disease, loose tooth, bone loss, and bleeding gums. We employed linear regression models for tooth loss and Poisson regression models for severe periodontitis, adjusting for demographic, health and work-related variables and socioeconomic status. Results: Among participants included, 10.9% worked in rotating night shifts for 1-5 years, while 11.0% worked in such shifts for ≥6 years. In fully adjusted models, rotating night shift work duration of 1-5 years was associated with tooth loss (beta -0.74, 95% confidence interval (CI) [-1.55 to 0.08]) and severe periodontitis (prevalence ratio 1.80, 95% CI [1.33-2.43]); however, the association with tooth loss was not statistically significant. Conclusions: This study supports that employees who work short-term rotating night shifts may experience poor oral conditions. Further research is needed to determine whether long-term rotating night shift work is associated with deteriorated oral health.

Behavioral-Social Rhythms and Cardiovascular Disease Risk in Retired Night Shift Workers and Retired Day Workers.

OBJECTIVE: Stability in the timing of key daily routine behaviors such as working/doing housework, sleeping, eating, and engaging in social interactions (i.e., behavioral-social rhythms) contributes to health. This study examined whether behavioral-social rhythms were associated with cardiovascular disease (CVD) risk factors in retired night shift workers and retired day workers and explored whether past night shift work exposure moderated this association. METHODS: A total of 154 retired older adults participated in this study. Multiple logistic regression models were used to examine associations between behavioral-social rhythms and CVD risk factors. Independent variables included Social Rhythm Metric (SRM)-5 score and actigraphy rest-activity rhythm intradaily variability (IV) and interdaily stability (IS). Dependent variables were metabolic syndrome prevalence and its five individual components. RESULTS: More regular behavioral-social rhythms were associated with lower odds of prevalent metabolic syndrome (SRM: odds ratio [OR] = 0.57, 95% confidence interval [CI] = 0.35-0.88; IV: OR = 4.00, 95% CI = 1.86-8.58; IS: OR = 0.42, 95% CI = 0.24-0.73) and two of its individual components: body mass index (SRM: OR = 0.56, 95% CI = 0.37-0.85; IV: OR = 2.84, 95% CI = 1.59-5.07; IS: OR = 0.42, 95% CI = 0.26-0.68) and high-density lipoprotein cholesterol (SRM: OR = 0.49, 95% CI = 0.30-0.80; IV: OR = 2.49, 95% CI = 1.25-4.96; IS: OR = 0.35, 95% CI = 0.19-0.66). Past shift work history did not moderate the association between behavioral-social rhythms and metabolic syndrome. CONCLUSIONS: Behavioral-social rhythms were related to CVD risk factors in retired adults regardless of prior night shift work exposure. Older retired workers may benefit from education and interventions aiming to increase behavioral-social rhythm regularity.

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.

Changes in work schedule affect headache frequency among Norwegian nurses: a 3-year-follow-up study.

OBJECTIVES: To explore whether changes in work schedule, number of night shifts and number of quick returns were related to changes in headache frequencies. METHODS: A longitudinal study with questionnaire data from 2014 (baseline) and 2017 (follow-up) on work schedule (day only, shift work without nights and shift work with nights), number of night shifts, number of quick returns (less than 11 hours in-between shifts) and validated headache diagnoses among 1104 Norwegian nurses. Associations were explored by adjusted multivariate regression analyses. RESULTS: The median age at baseline was 37 years (IQR 31-43) and 90.5% were women. In the adjusted logistic regression analysis of changed work schedule between baseline and follow-up, changing from night work was associated with increased odds for reversion from headache >1 days/month to no headache at all last year (OR 2.77 (1.29; 5.95)). Changes towards less night shifts (>10) or quick returns (>10) during the last year were associated with increased odds of reversion of headache to no headache (OR 2.23 (1.20; 4.17) and OR 1.90 (1.04; 3.49)). Only decrease in number of night shifts (>10) during the last year reduced risk of onset of any new headache between baseline and follow-up (OR of 0.39 (0.18; 0.84)). CONCLUSION: Changing from night work and reducing the number of night shifts and quick returns were associated with less headache in this 3-year-follow-up of Norwegian nurses. This adds to the growing body of evidence that night work may have direct negative health consequences.

Relationship between shift work, night work, and headache and migraine risk: A meta-analysis of observational studies.

BACKGROUND: To date, there is insufficient research on whether shift work and night work increase the risk of experiencing headaches and migraines. OBJECTIVES: This study aimed to evaluate the potential association between shift work, night shift work, and headache/migraine. METHODS: We conducted a thorough search of the PubMed, Embase, and Web of Science databases up until October 2023 to identify relevant studies. Our inclusion criteria focused on observational studies that investigated the association between shift work exposure and headache/migraine outcomes. We extracted adjusted risk estimates from each study and calculated pooled odds ratios using either fixed or random-effects models. Our methodology followed the Meta-Analysis Group guidelines for observational studies in epidemiology. To ensure accuracy and consistency, two investigators independently reviewed the retrieved records and extracted data based on the predefined inclusion criteria. RESULTS: This meta-analysis included a total of seven studies involving 422,869 participants. The pooled analysis revealed a significant association between shift work and an increased risk of headaches (HR = 1.32, 95% CI: 1.15-1.52, P < 0.001). Specifically, individuals working night shifts had a 44% higher risk of developing headaches (HR = 1.44, 95% CI: 1.09-1.90, P = 0.011). Furthermore, shift work was also found to be associated with a higher incidence of migraines (HR = 1.63, 95% CI: 1.27-2.08, P < 0.001). Interestingly, night shift work was associated with a decreased incidence of migraines (HR = 0.74, 95% CI: 0.57-0.96, P = 0.024). CONCLUSION: Our study found a noteworthy association between shift work/night work and the occurrence of headaches and migraines. However, it is important to note that our study does not establish a causal relationship. Future research should investigate potential common vulnerability factors, such as genetics or health behaviors. This knowledge can help inform the implementation of preventive measures and interventions to mitigate the health risks associated with shift work.

Shift Work Adversely Affects Sleep.

According to this study.

Associations between long-term night shift work and incidence of chronic obstructive pulmonary disease: a prospective cohort study of 277,059 UK Biobank participants.

BACKGROUND: Little is known about the effects of night shifts and their interactions with genetic factors on chronic obstructive pulmonary disease (COPD). In this study, we aim to investigate relationships between long-term night shift work exposure and COPD risk, and assess modification effects of genetic predisposition. METHODS: A total of 277,059 subjects who were in paid employment or self-employed were included in the UK Biobank. Information on current and lifetime employment was obtained, and a weighted COPD-specific genetic risk score (GRS) was constructed. We used Cox proportional hazard models to investigate associations between night shift work and COPD risk, and their interaction with COPD-specific GRS. RESULTS: The cohort study included 277,059 participants (133,063 men [48.03%]; mean [SD] age, 52.71 [7.08] years). During a median follow-up of 12.87 years, we documented 6558 incidents of COPD. From day work, irregular night shifts to regular night shifts, there was an increased trend in COPD incidence (P for trend < 0.001). Compared with day workers, the hazard ratio (HR) and 95% confidence interval (CI) of COPD was 1.28 (1.20, 1.37) for subjects with rarely/sometimes night shifts and 1.49 (1.35, 1.66) for those with permanent night shifts. Besides, the longer durations (especially in subjects with night shifts ≥ 10 years) and increasing monthly frequency of night shifts (in workers with > 8 nights/month) were associated with a higher COPD risk. Additionally, there was an additive interaction between night shifts and genetic susceptibility on the COPD risk. Subjects with permanent night shifts and high genetic risk had the highest risk of COPD (HR: 1.90 [95% CI: 1.63, 2.22]), with day workers with low genetic risk as a reference. CONCLUSIONS: Long-term night shift exposure is associated with a higher risk of COPD. Our findings suggest that decreasing the frequency and duration of night shifts may offer a promising approach to mitigating respiratory disease incidence in night shift workers, particularly in light of individual susceptibility.

Night shift work and cardiovascular diseases among employees in Germany: five-year follow-up of the Gutenberg Health Study.

OBJECTIVE: This study aimed to determine if there is an increased risk of incident cardiovascular diseases (CVD) resulting from cumulative night shift work in the German population-based Gutenberg Health Study (GHS). METHODS: We examined working participants of the GHS at baseline and after five years. Cumulative night shift work in the 10 years before baseline was assessed and categorized as low (1-220 nights ≙ up to 1 year), middle (221-660 nights ≙ 1-3 years), and high (>660 nights ≙ more than 3 years) night shift exposure. Hazard ratios (HR) were estimated for incident "quality-assured CVD events" using Cox proportional hazard models. RESULTS: At baseline, 1092 of 8167 working participants performed night shift work. During the follow-up, 202 incident cardiovascular events occurred. The crude incidence rates for CVD per 1000 person-years were 6.88 [95% confidence interval (CI) 4.80-9.55] for night shift workers and 5.19 (95% CI 4.44-6.04) for day workers. Cumulative incidence curves showed a higher cumulative incidence in workers exposed to night shift work compared to day workers after five years. The adjusted HR for incident CVD events were 1.26 (95% CI 0.68-2.33), 1.37 (95% CI 0.74-2.53) and 1.19 (95% CI 0.67-2.12) for employees in the low, middle and high night shift categories compared to employees without night shift work, respectively. CONCLUSIONS: The observed tendencies indicate that night shift work might be negatively associated with cardiovascular health. We expect the continued follow-up will clarify the long-term impact of night shift work.

The long-term effect of work schedule, shift work disorder, insomnia and restless legs syndrome on headache among nurses: A prospective longitudinal cohort study.

BACKGROUND: The preset study aimed to explore whether work schedules and sleep disorders predict the onset of headache. METHODS: A longitudinal study was conducted with questionnaire data from 2014 (baseline) and 2017 (follow-up) on work schedule, number of night shifts, number of quick returns, insomnia, shift work disorder (SWD), restless legs syndrome (RLS) and validated headache diagnoses among 1560 Norwegian nurses. Associations were explored by multivariate regression analyses. RESULTS: Work related factors at baseline did not predict onset of headache three years later. In the adjusted logistic regressions, insomnia at baseline predicted increased risk of new onset of migraine (odds ratio (OR) = 1.58; 95% confidence interval (CI) = 1.08-2.33), chronic headache (OR = 2.02; 95% CI = 1.04-4.66) and medication-overuse headache (OR = 3.79; 95% CI = 1.26-11.42) at follow-up. SWD at baseline predicted new onset of migraine (OR = 1.64; 95% CI = 1.07-2.50) and RLS at baseline predicted new onset of headache ≥1 day per month (OR = 1.55; 95% CI = 1.01-2.36) and migraine (OR = 1.55; 95% CI = 1.03-2.32) at follow-up. No factors predicted tension-type headache. CONCLUSIONS: Overall, work related factors did not predict the onset of headache three years later, whereas insomnia, SWD and RLS at baseline all increased the risk of future headaches.

[Sleep Strategies for Shift Work Nurses].

To meet the demands of a 24/7 society, shift work is necessary. Shift work is outside the traditional regular 9-to-5 work schedule, is characterized by irregular working hours, and exists in various industries. However, this abnormal working time can disrupt the natural day and night rhythm, and if poorly adjusted, it can lead to shift work sleep disorder (SWSD). SWSD is associated with multiple health risks, including impaired cognitive function, increased risk of accidents, and various metabolic and cardiovascular diseases. The frontline nurses typically work shifts to provide comprehensive patient care. This article aims to discuss sleep physiology, apply existing literature to discuss the impact on nurses resulting from shift work, and further offer strategies to regulate sleep to promote physical and mental health. These strategies range from organizational interventions (e.g., optimizing shift schedules) to individual interventions (e.g., lifestyle changes) and the use of chronobiological techniques (e.g., light therapy) to promote the adjustment of circadian rhythms, etc.

Exploration of the individual, social and environmental factors influencing dietary behaviour in shift workers with type 2 diabetes working in UK healthcare-The Shift-Diabetes Study: A qualitative study using the theoretical domains framework.

AIM: To identify factors influencing dietary behaviour in shift workers with type 2 diabetes (T2D) working in UK healthcare settings. METHODS: Semi-structured qualitative interviews based on the theoretical domains framework (TDF) were conducted with a convenience sample (n = 15) of shift workers (32-59 years) diagnosed with T2D who worked night shifts as part of a mixed shift schedule. The TDF was applied to analyse transcripts using a combined deductive framework and inductive thematic analysis approach. Identified influences were mapped to the behaviour change technique taxonomy to identify potential strategies to change dietary behaviour in this context. RESULTS: Key barriers to healthy dietary behaviours were access and cost of food available during night work (TDF domain: Environment Context and Resources). Factors identified as both enablers and barriers included: availability of staff facilities and time to take a break, (Environment Context and Resources), the physical impact of night work (Beliefs About Consequences), eating in response to stress or tiredness (Emotion), advance planning of meals/food and taking own food to work (Behavioural Regulation). Potential techniques to address these influences and improve dietary behaviour in this context include: meal planning templates, self-monitoring and biofeedback, and increasing accessibility and availability of healthier food choices during night shifts. CONCLUSIONS: The dietary behaviour of shift workers with T2D is influenced by interacting individual, socio-cultural and environmental factors. Intervention should focus on environmental restructuring and strategies that enable monitoring and meal planning.

Cohort Studies Versus Case-Control Studies on Night-Shift Work and Cancer Risk: The Importance of Exposure Assessment.

It is a general assumption that the prospective cohort study design is the gold standard approach and is superior to the case-control study design in epidemiology. However, there may be exceptions if the exposure is complex and requires collection of detailed information on many different aspects. Night-shift work, which impairs circadian rhythms, is an example of such a complex occupational exposure and may increase the risks of breast, prostate, and colorectal cancer. So far, for logistical reasons, investigators in cohort studies have assessed shift work rather crudely, lacking information on full occupational history and relevant shift-work metrics, and have presented mostly null findings. On the other hand, most cancer case-control studies have assessed the lifetime occupational histories of participants, including collection of detailed night-shift work metrics (e.g., type, duration, intensity), and tend to show positive associations. In this commentary, we debate why cohort studies with weak exposure assessment and other limitations might not necessarily be the preferred or less biased approach in assessing the carcinogenicity of night-shift work. Furthermore, we propose that risk-of-bias assessment and comparison of associations between studies with low versus high risks of bias be considered in future synthesis of the evidence.

Association between shift work in early pregnancy, snacking, and inappropriate weight gain during pregnancy: The Japan Environment and Children's Study.

OBJECTIVES: This study aimed to investigate the relationship between night shifts and snacking behaviors during pregnancy using Japanese maternal-infant longitudinal data from a large-scale study. METHODS: This study used the Japan Environment and Children's Study dataset jecs-ta-20190930, released in October 2019. After simple analysis using analysis of variance and multiple comparisons, crude odds ratios (cOR) and adjusted odds ratios (aORs) were calculated. To evaluate eating habits, we examined habitual fast food and snacks (e.g., potato chips, corn puffs and tortilla chips) consumption, midnight snacks, and regular missing breakfast. RESULTS: There was no significant association between inappropriate weight gain during pregnancy and night shift work in early pregnancy. The aOR for consuming snacks more than once a week after noticing pregnancy for shift workers was 1.34 (95% confidence interval 1.27-1.41; p < 0.001) compared with worker without night shiftwork. The aOR for shift workers consuming fast food more than three times a week during pregnancy was 1.40 (95% confidence interval 0.79-2.33; p > 0.05). CONCLUSIONS: Pregnant night shift workers did not show excessive weight gain but had an increased frequency of consumption of snack foods compared with pregnant dayshift workers.

Trabajo a turnos y Vitamina D / Could serum Vitamin D levels be altered when working shifts?

Este trabajo es un comentario del artículo: Martelli M, Salvio G, Santarelli L, Bracci M. Shift Work and Serum Vitamin D Levels: A Systematic Review and Meta-Analysis. Int J Environ Res Public Health. 2022 Jul 22;19(15):8919. doi: 10.3390/ijerph19158919 (AU)

This text is a commentary on the article: Martelli M, Salvio G, Santarelli L, Bracci M. Shift Work and Serum Vitamin D Levels: A Systematic Review and Meta-Analysis. Int J Environ Res Public Health. 2022 Jul 22;19(15):8919. doi: 10.3390/ijerph19158919 (AU)

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

BACKGROUND: Night work has been associated with coronary heart disease. The present study examined exposure-response relations between quantitative night work characteristics and coronary heart disease (angina pectoris or myocardial infarction) with the aim to contribute to evidence-based recommendations for low-risk night work schedules. METHODS: We followed 100 149 night workers (80% women) and 153 882 day workers (78% women), all health care workers in Denmark with day by day payroll information on night shifts from 2007 to 2015. We analysed data with Poisson regression stratified by sex and adjusted for age, calendar year, diabetes, family history of cardiovascular disease, educational level, occupation, indicators for obesity, hypercholesterolaemia, and hypertension. RESULTS: Female and male night workers worked on average 1.7 and 1.8 night shifts per month for an average duration of less than 4 years. During follow-up, 1198 night and 2128 day workers were hospitalized with first-time coronary heart disease. When compared with day workers, the overall incidence rate ratios for female and male night workers were 1.06 [95% confidence interval (CI): 0.97, 1.17] and 1.22 (95% CI 1.07, 1.39). Highest risks were observed in top exposure categories for several night work characteristics. However, no consistent exposure-response relations by number of monthly night shifts, cumulative night shifts, years with rotating night shifts, years with any night shift and consecutive night shifts were observed among the night workers of either sex. CONCLUSIONS: This study of a population with low exposure to night work does not indicate that reducing extent of monthly night shifts, cumulative night shifts, years with rotating night shifts, years with any night shift and consecutive night shifts would reduce the risk of coronary heart disease.

Shift work and risk of incident gastroesophageal reflux disease: the association and mediation.

Introduction: Shift work has become an increasingly common work mode globally. This study aimed to investigate the association between shift work and the risk of incident gastroesophageal reflux disease (GORD), an upward gastrointestinal disorder disease worldwide, and to explore the mediating factors. Method: A total of 262,722 participants from the UK Biobank free of GORD and related gastrointestinal diseases were included to investigate the association and potential mediators between shift work and incident GORD. Multivariate-adjusted Cox models were used to evaluate the association between shift work status and GORD incidence. Results: Compared to non-shift workers, shift workers had a 1.10-fold greater risk of incident GORD [95% confidence intervals (CIs): 1.03, 1.18], after adjusting for a range of potential confounders. However, the excess risk of GORD attenuated to the null after further adjusting for selected mediators. Specifically, the association was mediated by sleep patterns (25.7%), healthy behaviors (16.8%), depressive symptoms (20.2%), chronic conditions (13.3%), and biological factors (17.6%). After adjustment for all the mediators together, the association was attenuated by 71.5%. Discussion: Our findings indicated that long-term shift workers may have a higher risk of incident GORD, yet the excess risk may be explained by poor sleep quality, unhealthy behaviors, depressive symptoms, etc. This has positive implications for protecting the health of shift workers.

Night shift work, sleep duration and endometrial cancer risk: A pooled analysis from the Epidemiology of Endometrial Cancer Consortium (E2C2).

Data on the role of circadian related factors in the etiology of endometrial cancer are scarce. We collected individual data on night shift work or daily sleep duration from 7,207 cases and 22,027 controls participating in 11 studies from the Epidemiology of Endometrial Cancer Consortium (E2C2). Main analyses were performed among postmenopausal women: 6,335 endometrial cancer cases and 18,453 controls. Using individual data, study-specific odd ratios (ORs) and their corresponding 95% confidence intervals (CIs) were estimated with logistic regression and pooled analyses were conducted using random-effects meta-analyses. A non-significant inverse association was observed between endometrial cancer and night shift work (OR=0.89, 95%CI=0.72-1.09; I2=0.0%, Pheterogeneity=0.676). Associations did not vary by shift type (permanent or rotating), or duration of night work. Categorizations of short (<7h) or long (≥9h) sleep duration were not associated with endometrial cancer risk (ORshort=1.02, 95%CI=0.95-1.10; I2=55.3%, Pheterogeneity=0.022; ORlong=0.93, 95%CI=0.81-1.06; I2=11.5%, Pheterogeneity=0.339). No associations were observed per 1-h increment of sleep (OR=0.98, 95%CI=0.95-1.01; I2=46.1%, Pheterogeneity=0.063), but an inverse association was identified among obese women (OR=0.93, 95%CI=0.89-0.98 per 1-h increment; I2=12.7%, Pheterogeneity=0.329). Overall, these pooled analyses provide evidence that night shift work and sleep duration are not strong risk factors for endometrial cancer in postmenopausal women.