Shift schedules and circadian preferences: the association with sleep and mood.

Object: We explored the circadian preferences of non-shift workers (non-SWs) and various types of shift workers (SWs), and the associations of these preferences with sleep and mood. Methods: In total, 4,561 SWs (2,419 women and 2,142 men aged 37.00 ± 9.80 years) and 2,093 non-SWs (1,094 women and 999 men aged 37.80 ± 9.73 years) completed an online survey. Of all SWs, 2,415 (1,079 women and 1,336 men aged 37.77 ± 9.96 years) reported regularly rotating or fixed schedules ("regular SWs"), and 2,146 (1,340 women and 806 men aged 36.12 ± 9.64 years) had irregular schedules ("irregular SWs"). Of the regular SWs, 2,040 had regularly rotating schedules, 212 had fixed evening schedules, and 163 had fixed night schedules. All participants completed the Morningness-Eveningness Questionnaire (MEQ) exploring circadian preferences, the short form of the Center for Epidemiological Studies-Depression Scale (CES-D) evaluating depression, the Insomnia Severity Index (ISI), and the Epworth Sleepiness Scale (ESS). Results: Compared to non-SWs, SWs had lower MEQ scores, i.e., more eveningness, after controlling for age, gender, income, occupation, and weekly work hours (F = 87.97, p < 0.001). Irregular SWs had lower MEQ scores than regular SWs (F = 50.89, p < 0.001). Among regular SWs, the MEQ scores of fixed evening and fixed night SWs were lower than those of regularly rotating SWs (F = 22.42, p < 0.001). An association between the MEQ and ESS scores was apparent in non-SWs (r = -0.85, p < 0.001) but not in SWs (r = 0.001, p = 0.92). Conclusion: SWs exhibited more eveningness than non-SWs; eveningness was particularly prominent in SWs with irregular or fixed evening/night shifts. Eveningness was associated with sleepiness only in non-SWs, but not in SWs.

Decoding the impact of night/day shiftwork on well-being among healthcare workers.

This study delved into the complex effects of work schedules on the well-being of healthcare professionals, spotlighting Nigeria's medical landscape. A diverse cohort of 387 participants, spanning doctors, nurses, pharmacists, and laboratory technicians or scientists, formed the research base, with the majority being women (67.7%), with a mean age of 34.67 years. Professionals self-reported their predominant schedules to gauge work patterns, classifying them as day or night shifts. The World Health Organization Quality of Life Brief Version (WHOQOL-BREF) tool assessed the quality of life across the physical, psychological, social relationship, and environmental domains. Psychological distress was measured using the Depression, Anxiety, and Stress Scales (DASS), and perceived social support was evaluated via the Multidimensional Scale of Perceived Social Support (MSPSS). A cross-sectional design was adopted, and the study employed moderated mediation analysis using SmartPLS 4.0. The results underscored the significant ramifications of night shifts on environmental and physical well-being. Psychological health and social relationships were better among day shift than night shift workers. There was a pronounced correlation between night shifts and heightened levels of anxiety, stress, and depression. The mediating role of psychological distress and the moderating influence of social support in these relationships were evident. This study offers invaluable insights into the role of work schedules in shaping the well-being of healthcare professionals, emphasising the protective role of social support and the unique challenges faced by migrant health workers.

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.

Impact of shift work and other work-related factors on anti-SARS-CoV-2 spike-protein serum concentrations in healthcare workers after primary mRNA vaccination - a retrospective cohort study.

BACKGROUND: Knowing whether shift work negatively affects the immune system's response to COVID-19 vaccinations could be valuable for planning future vaccination campaigns for healthcare workers. We aimed to determine the impact of working late or night shifts on serum anti-SARS-CoV-2 spike protein immunoglobulin G (anti-S) antibody levels after primary SARS-CoV-2-mRNA vaccination. METHODS: To obtain detailed information on shift work, we sent a separate online questionnaire to 1475 eligible healthcare workers who participated in a prospective longitudinal study conducted in 15 healthcare institutions in Switzerland. We asked all vaccinated healthcare workers with available anti-S antibody levels after vaccination to complete a brief online survey on their working schedules within one week before and after primary mRNA vaccination. We used multivariate regression to evaluate the association between work shifts around primary vaccination and anti-S antibody levels. We adjusted for confounders already known to influence vaccine efficacy (e.g. age, sex, immunosuppression, and obesity) and for variables significant at the 0.05 alpha level in the univariate analyses. RESULTS: The survey response rate was 43% (n = 638). Ninety-eight responders were excluded due to unknown vaccination dates, different vaccines, or administration of the second dose shortly (within 14 days) after or before serologic follow-up. Of the 540 healthcare workers included in our analysis, 175 (32.4%) had worked at least one late or night shift within seven days before and/or after primary vaccination. In the univariate analyses, working late or night shifts was associated with a nonsignificant -15.1% decrease in serum anti-S antibody levels (p = 0.090). In the multivariate analysis, prior infection (197.2% increase; p <0.001) and immunisation with the mRNA-1273 vaccine (63.7% increase compared to the BNT162b2 vaccine; p <0.001) were the strongest independent factors associated with increased anti-S antibody levels. However, the impact of shift work remained statistically nonsignificant (-13.5%, p = 0.108). CONCLUSION: Working late or night shifts shortly before or after mRNA vaccination against COVID-19 does not appear to significantly impact serum anti-S antibody levels. This result merits consideration since it supports flexible vaccination appointments for healthcare workers, including those working late or night shifts.

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.

[Advance in occupational health risks and management of shift work].

The occupational health issues of shift workers has received increasing attention in the field of occupational health, and discussed in this article through literature review on the health risks and management of shift work both domestically and internationally. Based on this, a series of impacts of shift work on the physiological and psychological health of workers, as well as their family and social life, are revealed. Combined with relatively mature regulations and policies in foreign countries, it is proposed that China should fully learn from the relevant experience of health management in shift work abroad, Strengthen research and explore effective management intervention measures to provide ideas for accelerating the development of scientifically feasible regulations and policies related to occupational health in shift work in China.

Impact of Shiftwork on Retinal Vasculature Diameters over a 5-Year Period: A Preliminary Investigation Using the BCOPS Study Data.

Our aim was to investigate the impact of shiftwork on changes in central retinal arteriolar equivalent (CRAE), a measure of arteriolar width, and central retinal venular equivalent (CRVE), a measure of venular width, over five years. The participants were 117 officers (72.7% men) examined at the first (2011-2014) and second (2015-2019) follow-up examinations in the Buffalo Cardio-Metabolic Occupational Police Stress study. Shiftwork data were obtained from the City of Buffalo, NY payroll records. Retinal diameters were measured using a standardized protocol. ANCOVA was used to compare mean change in CRAE and CRVE between the two examinations across shiftwork categories. Among men only, those who worked ≥70% hours on day shifts had a larger decrease in mean CRAE (-7.13 µm ± 2.51) compared to those who worked <70% day (-0.08 ± 0.96; p = 0.011). Among patrol officers, those who worked ≥70% day had a larger decrease in CRAE compared to those who worked <70% day (p = 0.015). Also, officers who worked ≥70% day had an increase in mean CRVE (µm) (4.56 ± 2.56) compared to those who worked <70% (-2.32 ± 1.32; p = 0.027). Over the five-year period, we observed adverse changes in arteriolar and venular diameters among officers who worked ≥70% on day shifts. The results should be interpreted with caution due to the small sample sizes.

The Effect of Shift Working on Dietary Patterns of Healthcare Practitioners during the COVID-19 Pandemic: A Cross-Sectional Study.

Background and Objectives: Health professionals' working schedules often do not allow them to follow a balanced way of life, and the nature of their work can affect their weight and eating habits. The aim of the present study is to shed some light on the impact of night shift working on the dietary practices of healthcare practitioners in Greece. Materials and Methods: This was a cross-sectional study. With the use of an administered questionnaire several parameters were assessed, including anthropometric characteristics, weight history, as well as nutritional habits of the same group of participants during night shifts and when at regular working hours. Moreover, nutritional beliefs of the subjects were recorded, as well as the level of adherence to the Mediterranean diet. Results: It was observed that in all food groups, including water, used to compare the nutritional patterns of the participants during night shifts and when working regular hours, statistical differences were noted (p = 0.001). Furthermore, the participants who reported a higher adherence to the Mediterranean diet and self-reported healthier nutritional habits, had a statistically lower weight compared to the participants that rarely followed the specific model or reported unhealthier eating routine (p = 0.010 and p = 0.015, respectively). Conclusions: We conclude that shift-working healthcare professionals are associated with disturbed eating behaviours leading to the high consumption of unhealthy food. The implementation of interventions that will concentrate on educating health workers on balanced nutrition and improving physical environment (i.e., food availability, healthier food choices) seems to be of great importance.

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.

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

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

Molecular-Level Dysregulation of Insulin Pathways and Inflammatory Processes in Peripheral Blood Mononuclear Cells by Circadian Misalignment.

Circadian misalignment due to night work has been associated with an elevated risk for chronic diseases. We investigated the effects of circadian misalignment using shotgun protein profiling of peripheral blood mononuclear cells taken from healthy humans during a constant routine protocol, which was conducted immediately after participants had been subjected to a 3-day simulated night shift schedule or a 3-day simulated day shift schedule. By comparing proteomic profiles between the simulated shift conditions, we identified proteins and pathways that are associated with the effects of circadian misalignment and observed that insulin regulation pathways and inflammation-related proteins displayed markedly different temporal patterns after simulated night shift. Further, by integrating the proteomic profiles with previously assessed metabolomic profiles in a network-based approach, we found key associations between circadian dysregulation of protein-level pathways and metabolites of interest in the context of chronic metabolic diseases. Endogenous circadian rhythms in circulating glucose and insulin differed between the simulated shift conditions. Overall, our results suggest that circadian misalignment is associated with a tug of war between central clock mechanisms controlling insulin secretion and peripheral clock mechanisms regulating insulin sensitivity, which may lead to adverse long-term outcomes such as diabetes and obesity. Our study provides a molecular-level mechanism linking circadian misalignment and adverse long-term health consequences of night work.

Developing an intervention to support dietary change for shift workers living with type 2 diabetes: A stakeholder consultation.

BACKGROUND: Shift workers, compared to day workers, are more likely to be diagnosed with type 2 diabetes (T2D). Currently, there is no tailored programme of dietary support available to either shift workers living with T2D or employers. METHODS: An intervention development consultation workshop was convened in June 2023 with the aim of evaluating potential interventions to identify those with a potential to take forward for further development. Findings from prior formative research into factors influencing dietary behaviour in shift workers with T2D were mapped to potential interventions addressing the barriers and enablers to healthy eating reported by shift workers with T2D. The findings of the Shift-Diabetes Study were presented in the context of the COM-B (Capability, Opportunity, Motivation, Behaviour) theoretical framework of behaviour change. Three interventions in turn were presented to attendees: (1) Educational resources and structured education, (2) Increasing availability and accessibility of food on a night shift and (3) Biofeedback and tailored advice. Seven workshop attendees were invited to express their thoughts, using the APEASE criteria (Affordability, Practicability, Effectiveness, Acceptability, Side-effects/Safety, Equity) to guide the discussion. The workshop was conducted online and recorded, and transcripts were thematically coded to the APEASE framework. RESULTS/CONCLUSIONS: The workshop highlighted the importance of multilevel interventions to support dietary behaviour change in this occupational group. Priority actions identified include (i) understanding barriers to 24/7 food availability, (ii) including shift workers in clinical diabetes studies and (iii) research to understand the effectiveness of continuous glucose monitoring in shift workers with T2D.

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.

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

OBJECTIVE: This paper discusses the past and present highlights of working hours and health research and identifies key research needs for the future. METHOD: We analyzed over 220 original articles and reviews on working hours and health in the Scandinavian Journal of Work, Environment & Health published during the last 50 years. Key publications from other journals were also included. RESULTS: The majority of identified articles focussed on the effects of shift and night work, with fewer studying long and reduced working hours and work time control. We observed a transition from small-scale experimental and intensive field studies to large-scale epidemiological studies utilizing precise exposure assessment, reflecting the recent emergence of register-based datasets and the development of analytic methods and alternative study designs for randomized controlled designs. The cumulative findings provide convincing evidence that shift work and long working hours, which are often associated with night work and insufficient recovery, increase the risk of poor sleep and fatigue, sickness absence, occupational injuries, and several chronic health conditions such as cardiovascular diseases and cancer. The observed risks are strongly modified by individual and work-related factors. CONCLUSIONS: Although the observed health risks of shift work and long working hours are mostly low or moderate, the widespread prevalence of exposure and the hazardousness of the many associated potential outcomes makes such working time arrangements major occupational health risks. Further research is needed to identify exposure-response associations, especially in relation to the chronic health effects, and to elucidate underlying pathways and effective personalized intervention strategies.

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

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

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.

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

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

Validity of self-reported night shift work among women with and without breast cancer.

OBJECTIVES: This study aimed to estimate the validity of self-reported information on ever-night shift work among women with and without breast cancer and illustrate the consequences for breast cancer risk estimates. METHODS: During 2015-2016, 225 women diagnosed with breast cancer and 1800 matched controls without breast cancer employed within the Danish hospital regions during 2007-2016 participated in a questionnaire-based survey. Their reported night shift work status was linked with objective payroll register day-by-day working hour data from the Danish Working Hour Database and the Danish Cancer Registry. For the breast cancer patients and their matched controls, we estimated sensitivity and specificity for ever-working night shifts using the payroll data as the gold standard. We also used quantitative bias analysis to estimate the impact on relative risk estimates for a hypothetical population. RESULTS: For breast cancer patients, we observed a sensitivity of ever-night shifts of 86.2% and a specificity of never-night shifts of 82.6%. For controls, the sensitivity was 80.6% and the specificity 83.7%. Odds ratio for breast cancer in a hypothetical population decreased from 1.12 [95% confidence interval (CI) 1.03-1.21] to 1.05 (95% CI 0.95-1.16) when corrected by the sensitivity and specificity estimates. CONCLUSION: This study shows that female breast cancer patients had slightly better recall of previous night shift work than controls. Additionally, both breast cancer patients and controls recalled previous never-night shift work with low specificity. The net effect of this misclassification is a small over-estimation of the relative breast cancer risk due to night shift work.

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.