The Effect of Night Shift on Blood Pressure in Healthcare Workers.

OBJECTIVE: Individuals across all age groups may experience elevated blood pressure due to a combination of internal and environmental factors. Factors influencing arterial pressure include diet, stress, sleep patterns, and lifestyle. This study aims to investigate the susceptibility to high blood pressure among occupational groups working night shifts. METHOD: The study included healthcare worker participants who had at least six night shifts per month. A control group consisted of participants performing the same roles during daytime. Participants with chronic diseases or those taking blood pressure-affecting medication were excluded. Holter recordings were made over a minimum of 48 hours, including both a free day and a work day. RESULTS: The study involved 114 participants-55 in the study group and 59 in the control group. Statistically significant differences were noted between the groups in the daylight-night ratios of systolic and diastolic pressures, with P values of 0.006 and 0.005, respectively. The systolic daylight-night difference was -5.7 ± 5.5% in the study group and -9.0 ± 7.0% in the control group. The diastolic daylight-night difference was -7.9 ± 9.6% in the study group and -12.7 ± 8.2% in the control group. CONCLUSION: Occupations with nighttime work schedules are often associated with non-dipping blood pressure patterns due to sleep disturbances. It is crucial to consider the blunted dipping of blood pressure induced by night shift work when assessing and monitoring hypertension and related medical conditions.

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.

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.

Life satisfaction and job and personal resources among public workers with non-standard work schedules.

BACKGROUND: While the link between non-standard work schedules and poor health outcomes is established, few studies have examined how resources both in and outside of work can support the well-being of workers with non-standard work schedules. METHODS: Using a cross-sectional survey, we assessed the association between one facet of well-being, life satisfaction, and job and personal resources. In 2019, an electronic survey was administered to two unionized, public service populations who work non-standard work schedules: transportation maintainers and correctional supervisors. We assessed life satisfaction with a 10-item scale; a broad set of job resources (reward satisfaction, supervisor support, co-worker support, schedule satisfaction, and working hours fit); and a broad set of personal resources (health status, sleep, physical activity, and finances). We used log-binomial regression models to estimate prevalence ratios and 95% confidence intervals among statistically significant univariate predictors. RESULTS: Of the 316 workers surveyed, the majority were male (86%), White (68%), and reported positive life satisfaction (56%). In multivariate models, the prevalence of positive life satisfaction was higher in workers reporting reward satisfaction (PR:1.35, 95% CI: 1.11, 1.65; p = 0.003), good work schedule fit (PR:1.43, 95% CI: 1.12, 1.83; p = 0.004), good health (PR:2.92, 95% CI: 1.70, 4.99; p < 0.0001), and good finances (PR:1.32, 95% CI: 1.01, 1.72; p = 0.04). CONCLUSION: Employers should consider increasing work recognition, as well as improving schedule fit, financial well-being, and overall good health in support of worker life satisfaction and ultimately well-being.

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.

Moral decision-making at night and the impact of night work with blue-enriched white light or warm white light: a counterbalanced crossover study.

BACKGROUND: Cognitive function, including moral decision-making abilities, can be impaired by sleep loss. Blue-enriched light interventions have been shown to ameliorate cognitive impairment during night work. This study investigated whether the quality of moral decision-making during simulated night work differed for night work in blue-enriched white light, compared to warm white light. METHODS: Using a counterbalanced crossover design, three consecutive night shifts were performed in blue-enriched white light (7000 K) and warm white light (2500 K) provided by ceiling-mounted LED luminaires (photopic illuminance: ∼200 lx). At 03:30 h on the second shift (i.e. twice) and at daytime (rested), the Defining Issues Test-2, assessing the activation of cognitive schemas depicting different levels of cognitive moral development, was administered. Data from 30 (10 males, average age 23.3 ± 2.9 years) participants were analysed using linear mixed-effects models. RESULTS: Activation of the post-conventional schema (P-score), that is, the most mature moral level, was significantly lower for night work in warm white light (EMM; estimated marginal mean = 44.3, 95% CI = 38.9-49.6; pholm=.007), but not blue-enriched white light (EMM = 47.5, 95% CI = 42.2-52.8), compared to daytime (EMM = 51.2, 95% CI = 45.9-56.5). Also, the P-score was reduced for night work overall (EMM = 45.9, 95% CI = 41.1-50.8; p=.008), that is, irrespective of light condition, compared to daytime. Neither activation of the maintaining norms schema (MN-score), that is, moderately developed moral level, nor activation of the personal interest schema (i.e. the lowest moral level) differed significantly between light conditions. The MN-score was however increased for night work overall (EMM = 26.8, 95% CI = 23.1-30.5; p=.033) compared to daytime (EMM = 23.1, 95% CI = 18.9-27.2). CONCLUSION: The results indicate that moral decisions during simulated night work in warm white light, but not blue-enriched white light, become less mature and principle-oriented, and more rule-based compared to daytime, hence blue-enriched white light may function as a moderator. Further studies are needed, and the findings should be tentatively considered.Trial registration: ClinicalTrials.gov (ID: NCT03203538) Registered: 26/06/2017; https://clinicaltrials.gov/study/NCT03203538.

The quality of moral decision-making, seen as the activation of cognitive schemas depicting different levels of moral development, was reduced during simulated night work in warm white light, but not blue-enriched light, compared to daytime.The quality of moral decision-making sems to be reduced during simulated night work, compared to daytime.More studies assessing the impact of night work and light interventions on the quality of moral decision-making are needed to validate these tentative findings.

A Wake-Up Call to Address Nurse Fatigue.

Research exploring differences in fatigue and sleep quality between day- and night-shift nurses highlights the urgent need for action to mitigate nurse fatigue. Nurses need to prioritize their sleep, and nurse leaders must take proactive measures such as providing education for all doing shiftwork, ensuring completion of job requirements during the shift, and creating a culture where nurses take their scheduled breaks.

[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 on-call shifts on working memory and the role of burnout, sleep, and mental well-being in trainee physicians.

BACKGROUND: Optimal cognitive functions, including working memory (WM), are crucial to enable trainee physicians to perform and excel in their clinical practice. Several risk factors, including on-call shifts, poor mental health, burnout, and sleep problems, can impair clinical practice in trainee physicians, potentially through cognitive impairment; however, these associations have not been fully explored. OBJECTIVE: This study investigated the effect of on-call shifts on WM among trainee physicians and its association with burnout, depression, anxiety, affect, and sleep. MATERIALS AND METHODS: This cross-sectional study involved 83 trainee physicians (45% male). We measured demographic and training-related factors including on-call shifts and working hours. We also assessed depressive symptoms (PHQ-9), both state and trait anxiety (STAI total score), burnout (OLBI total score), positive and negative affect scores (PANAS), and sleep disturbances (PSQI total score). WM was evaluated using spatial working memory (SWM) strategy scores that reflected performance and total error counts. RESULTS: Trainee physicians with more on-calls per month had significantly worse depressive symptoms, burnout scores, and sleep, as well as more negative affect. While controlling for covariates, being on-call more times per month was significantly associated with worse WM. Worse depressive symptoms and burnout scores were also significantly associated with impaired WM. CONCLUSION: Working more on-call shifts is associated with compromised WM. Trainee physicians who experienced more depressive symptoms and burnout had worse WM.

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.

Construct validity and test-retest reliability of a chrononutrition questionnaire for shift work and non-shift work populations.

The irregular eating patterns of both shift workers and evening chronotypes adversely affect cardiometabolic health. A tool that conveniently captures temporal patterns of eating alongside an indicator of circadian rhythm such as chronotype will enable researchers to explore relationships with diverse health outcome measures. We aimed to investigate the test-retest reliability and convergent validity of a Chrononutrition Questionnaire (CNQ) that captures temporal patterns of eating and chronotype in the general population (non-shift workers, university students, retirees, unemployed individuals) and shift work population. Participants attended two face-to-face/virtual sessions and completed the CNQ and food/sleep/work diaries. Outcomes included subjective chronotype, wake/sleep/mid-sleep time, sleep duration, meal/snack regularity, meal/snack/total frequency, times of first/last/largest eating occasions (EO), main meal (MM) 1/2/3, and duration of eating window (DEW). 116 participants enrolled (44.5 ± 16.5 years, BMI: 27.3 ± 5.8 kg/m2, 73% female, 52% general population); 105 completed the study. Reliability was acceptable for chronotype, sleep, and all temporal eating patterns except on night shifts. Convergent validity was good for chronotype and sleep except for certain shift/shift-free days. Generally, meal/snack regularity and frequency, and times of first/last EO showed good validity for the general population but not shift workers. Validity was good for DEW (except work-free days and afternoon shifts) and times of MM 1/2/3 (except afternoon and night shifts), while time of largest EO had poor validity. The CNQ has good test-retest reliability and acceptable convergent validity for the general and shift work population, although it will benefit from further validation, especially regarding regularity, frequency, and times of first and last eating occasions across more days amongst a larger sample size of shift workers. Use of the CNQ by researchers will expand our current understanding of chrononutrition as relationships between timing of food intake and the multitude of health outcomes are examined.

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.

Feasibility of application-based psychomotor vigilance testing to assess fatigue in doctors working night shifts and correlation with smartwatch assessed shift intensity.

OBJECTIVES: To assess: (1) the feasibility of novel data collection methods (wearable technology and an application-based psychomotor vigilance test (PVT)), (2) the impact of night shift working on fatigue, both objective and perceived, for doctors working night shifts in acute hospital specialties and (3) the effects of shift intensity and naps obtained on participant fatigue. METHODS: We adopted an innovative, multimodal approach to data collection allowing assessment of objective and perceived measures of fatigue, in addition to markers of shift intensity. This comprised 5 min PVT for objective quantification of fatigue (via the validated, smartphone-based NASA PVT+ application), wearable electronic devices (Fitbit Versa2) for assessment of shift intensity (step counts and active minutes) and questionnaires to elicit perceptions of fatigue and shift intensity. RESULTS: Data was collected from 25 participants for a total of 145 night shifts. Objective fatigue (assessed by PVT performance) was significantly increased post night shift, with a PVT mean reaction time 257 ms pre shift versus 283 ms post shift (p<0.0001). However, differences in PVT pre and post shift were not affected by night shift intensity, nor breaks or naps taken on shift. Differences in psychomotor performance between doctors working in different specialties were also observed. CONCLUSIONS: The data collection methods used were found to be feasible with good participant engagement. Findings support existing evidence that night shift working in healthcare workers is associated with fatigue, with psychomotor impairment observed post shift. Lower shift intensity and napping did not appear to mitigate this effect.

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.

Impact of 24 h shifts on urinary catecholamine in emergency physicians: a cross-over randomized trial.

24-h shift (24 hS) exposed emergency physicians to a higher stress level than 14-h night shift (14 hS), with an impact spreading on several days. Catecholamines are supposed to be chronic stress biomarker. However, no study has used catecholamines to assess short-term residual stress or measured them over multiple shifts. A shift-randomized trial was conducted to study urinary catecholamines levels of 17 emergency physicians during a control day (clerical work on return from leave) and two working day (14 hS and 24 hS). The Wilcoxon matched-pairs test was utilized to compare the mean catecholamine levels. Additionally, a multivariable generalized estimating equations model was employed to further analyze the independent relationships between key factors such as shifts (compared to control day), perceived stress, and age with catecholamine levels. Dopamine levels were lower during 24 hS than 14 hS and the control day. Norepinephrine levels increased two-fold during both night shifts. Epinephrine levels were higher during the day period of both shifts than on the control day. Despite having a rest day, the dopamine levels did not return to their normal values by the end of the third day after the 24 hS. The generalized estimating equations model confirmed relationships of catecholamines with workload and fatigue. To conclude, urinary catecholamine biomarkers are a convenient and non-invasive strong measure of stress during night shifts, both acutely and over time. Dopamine levels are the strongest biomarker with a prolonged alteration of its circadian rhythm. Due to the relation between increased catecholamine levels and both adverse psychological effects and cardiovascular disease, we suggest that emergency physicians restrict their exposure to 24 hS to mitigate these risks.

[Relationship between thyroid function changes with work-/night-shifts and history of thyroid pathology among health personnel].

BACKGROUND: The study aim was to analyze the relationship between functional thyroid pathology and the exposure to work shifts / night shifts, and describe the most prevalent thyroid disorders based on the type of shift. METHODOLOGY: Cross-sectional study performed in the emergency department of a hospital in Almeria (Spain). Relationships between thyroxine and thyrotropin levels (TSH) and work shifts, professional category and history of thyroid pathology were analyzed. RESULTS: The study included 133 workers; 80.5% female, average age was 46.11 years (38 - 65), and 52% were part of the nursing staff; thyroid disorders were more frequent in female participants. Most participants (81.2%) had rotating shifts schedules and 11.3% night shifts (12.1% female and 7.7% male). Thyroid alterations were found in 27% of the participants (usually elevated TSH levels and normal thyroxine levels), particularly in those doing night shifts (61.1%). TSH alterations were more frequent in individuals doing night shifts than in rotating shifts (53.3 vs 13.0%; p<0.001). Individuals working night shifts had mean TSH values in the normal range, although significantly higher than the individuals in the rest of the shifts; thyroxine levels were found to be similar. No thyroid disorders were found in day shift participants. Night shift and a history of thyroid pathology were independent predictors of thyroid disorders. CONCLUSIONS: Night shift schedules and history of thyroid disorders are more frequent in female, both related to the presence of thyroid disorders, indicating the need to include the evaluation of these disorders in health surveillance programs and analyze gender differences.

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.