More than sleep problems? Testing five key health behaviors as reasons for quality of life issues among shift workers.

BACKGROUND: The shift work schedule is a common work arrangement that can disrupt typical sleep-wake rhythms and lead to negative health consequences. The present study aims to examine the effect of shift work on health-related quality of life (QoL) and explore potential behaviorial mediators (i.e., sleep, eating, exercise, smoking, drinking). METHODS: A cross-sectional survey was conducted among 4,449 petroleum workers in southwest China. Data on shift work status, health behaviors, and physical and mental health QoL were collected. We tested our model using path analysis and the Monte Carlo approach among 2,129 included participants. RESULTS: After adjusting for covariates, shift work did not exhibit a significant direct association with QoL. However, shift work indirectly related to poorer physical health quality of life via less frequent healthy food consumption; shift work also indirectly related to poorer mental health QoL via both less frequent healthy food consumption and physical exercise. No significant indirect effects were found via sleeping, smoking, or drinking. CONCLUSIONS: Results suggest that shift work presents a challenge for QoL among Chinese petroleum workers due to their lesser engagement in two specific health behaviors: healthy eating and physical exercise. Healthy eating and exercise may present an even more prominent threat to shift workers' QoL than sleep and substance use. Strategies targeting shift work schedule as well as eating and exercise behaviors may help protect against poor QoL and adverse physical and mental health outcomes in this vulnerable group.

The association between shift work, shift work sleep disorders and premature ejaculation in male workers.

OBJECTIVE: Shift work and Shift Work Sleep Disorder (SWSD) are known to affect the secretion of several neurotransmitters and hormones associated with premature ejaculation (PE). However, their specific influence on the regulation of male ejaculation remains unclear. This study explores the relationship between shift work, SWSD, and PE. METHODS: From April to October 2023, a cross-sectional survey was conducted across five regions of China to explore the work schedules, sleep quality, and sexual function of male workers. Participants' sleep quality was evaluated using a validated SWSD questionnaire, and their erectile function and ejaculatory control were assessed with the International Inventory of Erectile Function (IIEF-5) scores and Premature Ejaculation Diagnostic Tool (PEDT) scores, respectively. Univariate and multivariate linear regression analyses were employed to identify risk factors associated with PE. Confounders were controlled using multiple regression models, and clinical prediction models were developed to predict PE onset and assess the contribution of risk factors. RESULTS: The study included 1239 eligible participants, comprising 840 non-shift workers and 399 shift workers (148 with SWSD and 251 without SWSD). Compared to non-shift working males, those involved in shift work (ß 1.58, 95% CI 0.75 - 2.42, p < 0.001) and those suffering from SWSD (ß 2.86, 95% CI 1.86 - 3.85, p < 0.001) they had significantly higher PEDT scores. Additionally, we identified daily sleep of less than six hours, depression, anxiety, diabetes, hyperlipidemia, frequent alcohol consumption (more than twice a week), and erectile dysfunction as risk factors for PE. The predictive model for PE demonstrated commendable efficacy. CONCLUSION: Both shift work and SWSD significantly increase the risk of premature ejaculation, with the risk magnifying in tandem with the duration of shift work. This study reveals the potential impact of shift work and SWSD on PE and provides new theoretical foundations for the risk assessment and prevention of this condition.

Multimorbidity and its Associated Factors in Korean Shift Workers: Population-Based Cross-Sectional Study.

BACKGROUND: Multimorbidity is a crucial factor that influences premature death rates, poor health, depression, quality of life, and use of health care. Approximately one-fifth of the global workforce is involved in shift work, which is associated with increased risk for several chronic diseases and multimorbidity. About 12% to 14% of wage workers in Korea are shift workers. However, the prevalence of multimorbidity and its associated factors in Korean shift workers are rarely reported. OBJECTIVE: This study aimed to assess multimorbidity prevalence, examine the factors associated with multimorbidity, and identify multimorbidity patterns among shift workers in Korea. METHODS: This study is a population-based cross-sectional study using Korea National Health and Nutrition Examination Survey data from 2016 to 2020. The study included 1704 (weighted n=2,697,228) Korean shift workers aged 19 years and older. Multimorbidity was defined as participants having 2 or more chronic diseases. Demographic and job-related variables, including regular work status, average working hours per week, and shift work type, as well as health behaviors, including BMI, smoking status, alcohol use, physical activity, and sleep duration, were included in the analysis. A survey-corrected logistic regression analysis was performed to identify factors influencing multimorbidity among the workers, and multimorbidity patterns were identified with a network analysis. RESULTS: The overall prevalence of multimorbidity was 13.7% (302/1704). Logistic regression indicated that age, income, regular work, and obesity were significant factors influencing multimorbidity. Network analysis results revealed that chronic diseases clustered into three groups: (1) cardiometabolic multimorbidity (hypertension, dyslipidemia, diabetes, coronary heart disease, and stroke), (2) musculoskeletal multimorbidity (arthritis and osteoporosis), and (3) unclassified diseases (depression, chronic liver disease, thyroid disease, asthma, cancer, and chronic kidney disease). CONCLUSIONS: The findings revealed that several socioeconomic and behavioral factors were associated with multimorbidity among shift workers, indicating the need for policy development related to work schedule modification. Further organization-level screening and intervention programs are needed to prevent and manage multimorbidity among shift workers. We also recommend longitudinal studies to confirm the effects of job-related factors and health behaviors on multimorbidity among shift workers in the future.

Assessment of retinal and choroidal microvasculature in night shift medical workers by OCT angiography.

This study evaluated retinal and choroidal microvascular changes in night shift medical workers and its correlation with melatonin level. Night shift medical workers (group A, 25 workers) and non-night shift workers (group B, 25 workers) were recruited. The images of macula and optic nerve head were obtained by swept-source OCT-angiography. Vessel density of retina, choriocapillaris (CC), choriocapillaris flow deficit (CC FD), choroidal thickness (CT) and choroidal vascularity index (CVI) were measured. 6-sulfatoxymelatonin concentration was analyzed from the morning urine. CC FD and CVI were significantly decreased and CT was significantly increased in group A (all P < 0.05). 6-sulfatoxymelatonin concentration was significantly lower in group A (P < 0.05), which was significantly positively correlated with CC FD size (r = 0.318, P = 0.024) and CVI of the most regions (maximum r-value was 0.482, P < 0.001), and was significantly negatively associated with CT of all regions (maximum r-value was - 0.477, P < 0.001). In night shift medical workers, the reduction of melatonin was significantly correlated with CT thickening, CVI reduction and CC FD reduction, which suggested that they might have a higher risk of eye diseases. CC FD could be a sensitive and accurate indicator to reflect CC perfusion.

Assessment and management of sleep disorders in shift workers: Challenges and considerations for general practice.

BACKGROUND: Shift work is characterised by displaced sleep opportunities and associated sleep disturbance. Shift workers often report sleepiness and other wake time symptoms associated with poor sleep. However, clinical sleep disorders are also prevalent in shift workers. Although prevalence rates are similar or higher in shift workers compared with the general population, help seeking in shift workers with sleep disorders is low. OBJECTIVE: This article aims to provide general practitioners with a contemporary overview of the prevalence rates for sleep disorders in shift workers, to clarify the existing evidence relating to mental and physical health consequences of sleep disorders in shift workers and to highlight the need to consider undiagnosed sleep disorders before attributing sleep-related symptoms solely to work schedules. DISCUSSION: Symptoms of sleep loss associated with shift work overlap with symptoms experienced by individuals living with sleep disorders. Although >40% of middle-aged Australians live with a sleep disorder that requires investigation and management, symptoms in shift workers are often attributed to the work schedule and, as a result, might not be investigated for appropriate diagnosis and treatment. We argue that screening for sleep disorders in shift workers with sleep complaints should be a priority.

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.

Disruption of central and peripheral circadian clocks and circadian controlled estrogen receptor rhythms in night shift nurses in working environments.

Chronic disruption of circadian rhythms by night shift work is associated with an increased breast cancer risk. However, little is known about the impact of night shift on peripheral circadian genes (CGs) and circadian-controlled genes (CCGs) associated with breast cancer. Hence, we assessed central clock markers (melatonin and cortisol) in plasma, and peripheral CGs (PER1, PER2, PER3, and BMAL1) and CCGs (ESR1 and ESR2) in peripheral blood mononuclear cells (PBMCs). In day shift nurses (n = 12), 24-h rhythms of cortisol and melatonin were aligned with day shift-oriented light/dark schedules. The mRNA expression of PER2, PER3, BMAL1, and ESR2 showed 24-h rhythms with peak values in the morning. In contrast, night shift nurses (n = 10) lost 24-h rhythmicity of cortisol with a suppressed morning surge but retained normal rhythmic patterns of melatonin, leading to misalignment between cortisol and melatonin. Moreover, night shift nurses showed disruption of rhythmic expressions of PER2, PER3, BMAL1, and ESR2 genes, resulting in an impaired inverse correlation between PER2 and BMAL1 compared to day shift nurses. The observed trends of disrupted circadian markers were recapitulated in additional day (n = 20) and night (n = 19) shift nurses by measurement at early night and midnight time points. Taken together, this study demonstrated the misalignment of cortisol and melatonin, associated disruption of PER2 and ESR2 circadian expressions, and internal misalignment in peripheral circadian network in night shift nurses. Morning plasma cortisol and PER2, BMAL1, and ESR2 expressions in PBMCs may therefore be useful biomarkers of circadian disruption in shift workers.

Relationship between long-term shift work; night work; sleep deficiency and stroke: A systematic review and meta-analysis.

BACKGROUND: The association between shift/night work and the risk of stroke is not supported by strong evidence. OBJECTIVE: This study aimed to obtain evidence of a potential relationship between shift/night shift work and the risk of stroke. METHODS: We searched PubMed, Embase, the Cochrane Library and Web of science databases for eligible studies from inception to January 19, 2024. We followed the statement in the Preferred Reporting Items for Systematic Evaluations and Meta-Analysis (PRISMA). STATA 14.0 software was used for meta-analysis. RESULTS: A total of five studies involving 700,742 subjects were included in this meta-analysis. We found that shift/night workers had a 1.08 times higher risk of stroke than non-shift/night workers (RR: 1.08; 95 % CI: 1.05-1.10; P < 0.001). CONCLUSION: Shift/night work may be a risk factor for stroke. More objective prospective studies are needed to further support this result.

Sleep quality according to chronotype in nurses working 8-hour shifts.

BACKGROUND: To date, studies have been focused on sleep disturbances of nurses working during night shifts. There is a lack of understanding regarding the sleep quality of nurses working in the rapid rotation system for each type of shift work. AIMS: To determine the relationship between chronotype and sleep quality according to shift type (i.e. day, evening and night shifts) in nurses working 8-hour rotating shifts. METHODS: A cross-sectional, descriptive study was conducted from two tertiary hospitals in South Korea from December 2021 to September 2022, including nurses working 8-hour rotating shifts (N = 74). They completed questionnaires to measure general, occupational and sleep-related characteristics, chronotype, insomnia severity and daytime sleepiness. Additionally, sleep parameters were collected from actigraphy and sleep diaries for 7 days. RESULTS: A total of 64% of nurses had an evening chronotype and 37% of nurses had an intermediate chronotype. Nurses had significantly less total sleep time and worsened sleep latency and efficiency during the day shift compared to other shift types. Compared to nurses with an intermediate chronotype, those with an evening chronotype had poorer sleep quality during day shift work. CONCLUSIONS: Strategies to enhance nurses' sleep quality during day shifts should consider a two-level approach: individual approaches, such as improving sleep hygiene, and administrative approaches, such as establishing a chronotype-based shift system for scheduling.

Moderating effect of shift work on sleep and depression in individuals at high risk of bipolar disorder.

BACKGROUND: Social Zeitgeber Theory posits that disruptions in social rhythms can increase susceptibility to bipolar disorder (BD). Shift work (SW) is one of the external factors that cause instability in social rhythms and the sleep-wake cycle. This study evaluated the moderating influences of SW on the risks of BD and sleep-related parameters and depressive symptoms. Furthermore, we evaluated the specific work schedules including daytime, nighttime, and regular and irregular rotating SW. METHODS: An online survey was administered to 6665 participants, with 3379 (50.7 %) classified as individuals with high scores of Mood Disorder Questionnaire (MDQ). The survey included the Pittsburgh Sleep Quality Index (PSQI), Insomnia Severity Scale (ISI), Epworth Sleepiness Scale (ESS), and Center for Epidemiologic Studies Depression Scale (CES-D). RESULTS: A multivariate regression model revealed significant interactive effects of MDQ positivity and SW on PSQI, ISI, and CES-D scores, but not ESS scores. In a secondary analysis of the high MDQ screen group, daytime workers had lower scores in sleep disturbances and depressive symptoms compared to those engaged in other forms of SW. LIMITATIONS: Online surveys were accessible voluntarily, leading to potential selection bias. Cross-sectional data identified associations, not causal relationships. Only a self-reported questionnaire was used. CONCLUSIONS: Our findings emphasize the advantages of a daytime work schedule for individuals at high risk of BD. In accordance with the principles of social rhythm interpersonal therapy, sleep interventions for individuals at high risk of BD should include the maintenance of a consistent daytime schedule.

Mediation Mendelian randomisation study on the effects of shift work on coronary heart disease and traditional risk factors via gut microbiota.

Background: Epidemiological evidence suggests that there is an increased risk of coronary heart disease (CHD) related to jobs involving shift work (JSW), but the causality of and mechanism underlying such a relationship remain unclear. Therefore, we aimed to explore the relationship between JSW and CHD, investigating both causality and potential mediating factors. Methods: We performed univariate, multivariate, and mediation Mendelian randomisation (MR) analyses using data from large genome-wide association studies focussed on JSW and CHD, as well as data on some CHD risk factors (type 2 diabetes, hypertension, obesity, and lipids measurement) and 196 gut microbiota taxa. Single-nucleotide polymorphisms significantly associated with JSW acted as instrument variables. We used inverse-variance weighting as the primary method of analysis. Results: Bidirectional MR analysis indicated a robust effect of JSW on increased CHD risk; however, the existence of CHD did not affect the choice of JSW. We identified a mediating effects of type 2 diabetes and hypertension in this relationship, accounting for 11.89% and 14.80% of the total effect of JSW on CHD, respectively. JSW were also causally associated with the risk of type 2 diabetes and hypertension and had an effect on nine microbial taxa. The mediating influence of the Eubacterium brachy group at the genus level explained 16.64% of the total effect of JSW on hypertension. We found limited evidence for the causal effect of JSW on obesity and lipids measurements. Conclusions: Our findings suggest a causal effect of JSW on CHD, diabetes, and hypertension. We also found evidence for a significant connection between JSW and alterations in the gut microbiota. Considering that certain microbial taxa mediated the effect of JSW on hypertension risk, targeting gut microbiota through therapeutics could potentially mitigate high risks of hypertension and CHD associated with JSW.

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.

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.

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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.