BACKGROUND: Health problems associated with shift work and night shift work are gaining increasing public attention.
OBJECTIVE: To investigate the association between night shift work and the hazard of mortality.
METHODS: Prospective cohort study.
METHODS: A total of 283,579 individuals with paid employment or self-employment aged 37-73 years were included from the UK Biobank with a median follow-up period of 14.0 years.
METHODS: Participants were divided into day workers and shift workers, including the frequency of night shifts, to evaluate the association between baseline work schedules and all-cause and cause-specific mortality using the Cox proportional hazards model. Additionally, 75,760 participants with work histories were assessed for the association between average frequency and cumulative years of exposure to night shift work and all-cause and cause-specific mortality.
RESULTS: Compared with that of day workers, the adjusted hazard of all-cause mortality was increased by 12.0% (hazard ratio [HR], 1.12; 95% confidence interval [CI], 1.07-1.18) in shift workers, particularly in those with no or rare night shifts (approximately 16.1%; HR, 1.16; 95% CI, 1.08-1.25) and those with irregular night shifts (approximately 9.2%; HR, 1.09; 95% CI, 1.00-1.19). Moreover, a non-linear relationship was identified between cumulative night shift years and all-cause and cause-specific mortality. Only individuals who worked night shifts for 20-30 years exhibited a substantially increased hazard of all-cause (HR, 1.52; 95% CI, 1.15-2.00) and cardiovascular disease (CVD; HR, 2.08; 95% CI, 1.16-3.71) mortality.
CONCLUSIONS: Shift workers, particularly those with rare or irregular night shifts, exhibited an increased hazard of mortality. Additionally, participants who worked night shifts for 20-30 years exhibited a substantially increased hazard of all-cause and CVD mortality.

Introduction: Shift work disrupts sleep-wake cycles and may lead to adverse health outcomes, including cardiovascular disease and metabolic disorders. This study examines the association between shift work and the risks of metabolic syndrome (MetS) and circadian syndrome (CircS) in U.S. workers. Methods: We analyzed data from 4173 participants aged 18 and above from the National Health and Nutrition Examination Survey (NHANES) spanning 2005-2010. Shift work status was determined based on work hours, and MetS and CircS were defined using established criteria. Statistical analyses included weighted multivariate logistic regression models, weighted multivariate linear regression models, and inverse probability weighted propensity score matching to ensure accurate comparison between shift and nonshift workers. Results: The study found no significant association between shift work and the prevalence of MetS. However, shift workers exhibited a higher prevalence of CircS compared with nonshift workers. This association was more pronounced in specific subgroups, including those under 60 years of age and various ethnicities. The study highlights the heightened risk of CircS among shift workers, underscoring the potential impact of shift work on circadian rhythm disruptions. Conclusion: Shift work is associated with an increased risk of CircS but not MetS, according to NHANES 2005-2010 data.

Recent studies suggest that shift working may trigger health issues through disrupted circadian rhythms and altered eating habits. This study aimed to examine the possible associations of shift work with sleep quality, diet quality and obesity-related parameters. This study was conducted with 150 males (75 shift and daytime workers) aged 24-50 years. Dietary intake was determined using the 24-hour recall method, and dietary quality was evaluated using the Healthy Eating Index-2010 (HEI-2010). Anthropometrical measurements and body composition were assessed. The Pittsburgh Sleep Quality Index was used to evaluate sleep quality. Fasting and postprandial glucose and insulin, and fasting lipid levels were analyzed. HOMA-IR was calculated, and blood pressure was measured. The total HEI-2010 score of shift workers (52.6 [45.4-58.8]) was lower than the daytime workers (55.9 [49.1-64.9]) (p = 0.016). Among individuals with good sleep quality, the total HEI-2010 score, seafood and plant proteins, fatty acids, and sodium scores were lower in shift workers compared to others (p < 0.05 for each). Non-obese shift workers had higher body weight, waist circumference, waist/hip ratio, VLDL-cholesterol, triglyceride, postprandial glucose, and insulin levels compared to daytime workers (p < 0.05 for each). This study demonstrates that shift working is associated with lower diet quality independent of sleep quality.

UNASSIGNED: This study examines working hours, shift work, and remote work patterns by occupation and industry among U.S. full-time workers, along with the association between working and sleeping hours.
UNASSIGNED: Utilizing data from 2011 to 2020 American Time Use Survey, this national household survey examines how individuals aged 15 years or older in the United States spend their time within a 24-hour period.
UNASSIGNED: In 2011 to 2019, U.S. full-time workers averaged 8.1 hours of work and 7.8 hours spent sleep on workdays, increasing to 9.6 hours on non-workdays. Among all occupations, Emergency medical technicians and paramedics had the longest average working hours (10.4 hours). Protective services occupations had the highest percentage (41.7%) of workers reporting often working shifts other than daytime. Among all industries, truck transportation industry had the longest average working hours (9.2). Food services and drinking places industries had the highest percentage (28.6%) of workers reporting often working shifts other than daytime. Working hours showed a negative association with sleeping hours. In 2020, 34.0% of full-time workers reported remote work due to COVID-19, with the largest percentage (72.3%) occurring in business and financial operations.
UNASSIGNED: The study findings offer essential benchmarks for comparing working hours and schedules across diverse occupations and industries. These insights empower occupational health practitioners to advocate for prevention measures, addressing health concerns arising from prolonged working hours and shift work.

Circadian fluctuations in physiological setpoints are determined by the suprachiasmatic nucleus (SCN) which exerts control over many target structures within and beyond the hypothalamus via projections. The SCN, or central pacemaker, orchestrates synchrony between the external environment and the internal circadian mechanism. The resulting cycles in hormone levels and autonomic nervous system (ANS) activity provide precise messages to specific organs, adjusting, for example, their sensitivity to approaching hormones or metabolites. The SCN responds to both photic (light) and non-photic input. Circadian patterns are found in both heart rate and blood pressure, which are linked to daily variations in activity and autonomic nervous system activity. Variations in blood pressure are of great interest as several cardiovascular diseases such as stroke, arrhythmias, and hypertension are linked to circadian rhythm dysregulation. The disruption of normal day-night cycles, such as in shift work, social jetlag, or eating outside of normal hours leads to desynchronization of the central and peripheral clocks. This desynchronization leads to disorganization of the cellular processes that are normally driven by the interactions of the SCN and photic input. Here, we review autonomic system function and dysfunction due to regulation and interaction between different cardiorespiratory brain centers and the SCN, as well as social, lifestyle, and external factors that may impact the circadian control of blood pressure.

Resident physicians on long-term night shifts often face sleep deprivation, affecting the immune response, notably neutrophils, vital to innate defense mechanisms. Sleep-deprived residents exhibit altered neutrophil counts and reduced phagocytosis and NADPH oxidase activity, critical to combating infections. Our study focused on neutrophil extracellular traps (NETs), a defense process against pathogens not previously linked to sleep loss. Results revealed that sleep-deprived residents exhibited a 19.8 % reduction in NET formation compared to hospital workers with regular sleep patterns (P < 0.01). Additionally, key NETs proteins, Neutrophil Elastase and Myeloperoxidase, were less active in sleep-deprived individuals (1.53mU; P < 0.01 and 0.95U; P < 0.001 decrease, accordingly). Interestingly, the ability to form NETs resumed to normal levels three months post-residency among pediatric residents. The causal relationship between reduced NETs due to sleep deprivation and the increased susceptibility to infections, as well as its implications for infection severity, is a critical area for further investigation.

Non-alcoholic fatty liver disease (NAFLD) is a relatively common disease, and preventing its occurrence is important for both individual health and reducing social costs. Shift work is reported to have several negative effects on health. An association has been observed between NAFLD and both sleep time and quality; however, this association remains unclear in night shift workers. We aimed to evaluate the relationship between shift work and the incidence of NAFLD. Overall, 45,149 Korean workers without NAFLD were included at baseline. NAFLD was defined as the presence of a fatty liver observed on ultrasonography without excessive alcohol use. incidence rate ratios for incident NAFLD were estimated using negative binomial regression according to age groups (20s, 30s, 40s, and 50s). In the 20s age group, shift work showed a significant incidence rate ratio (IRR) for NAFLD in all models. After adjusting for all variables, the IRR (95% confidence interval) was 1.24 (1.08-1.43) in the 20s age group. In their 20s, a significant association between shift work and incident NAFLD was consistently observed among women and workers with poor sleep quality. In this large-scale cohort study, shift work was significantly associated with the development of NAFLD among young workers in their 20s.

We investigated the role of sleep and work hours on wellbeing among day- and shift workers. We tested a mediation-moderation hypothesis proposing that; 1) sleep would mediate the association between the work schedule and the impact of sleep/sleepiness on wellbeing; 2) work hours would moderate the link between work schedule and sleep. We made random phone calls to 1,162 participants and identified 172-day and 130 shift workers that worked ≥ 35-hours/week. The work schedule had a positive indirect effect on the impact of sleep/sleepiness via sleep duration (β=0.0511, SE=0.0309, [0.0008, 0.3219]. The relationship between shift work and sleep duration was negative (β=-0.35, SE=0.14, p<0.01), and sleep duration was negatively associated with a greater impact of sleep/sleepiness on wellbeing (β=-0.15, SE=0.06, p<0.02). The path between the work schedule and sleep duration was moderated by work hours; fewer work hours resulted in shift workers reporting a greater impact of sleep/sleepiness on wellbeing. The results support the mediation-moderation hypothesis. Work hours and sleep duration are key characteristics in work schedule design.

UNASSIGNED: Disturbance of circadian rhythms caused by shift work has adverse effects on insulin resistance. Many previous studies have confirmed that shift work and insulin resistance are related using homeostasis model assessment-insulin resistance, one of the insulin resistance indicators. However, the triglycerides and glucose index (TyG index) has recently been studied as an insulin resistance indicator. The aim of this study is to investigate the association of shift work and TyG index, one of the indirect indicators of insulin resistance, using results of health checkups in one workplace.
UNASSIGNED: Based on medical examination data collected in February 2019, a total of 3,794 subjects from one chemical plant in Korea were selected for this study. Cut-off value of TyG index for predicting development of diabetes mellitus (DM) was 4.69. A multiple logistic regression analysis was performed after adjusting for age, employment period, obesity, abdominal obesity, smoking, drinking, physical activity, hypertension, stroke, heart disease.
UNASSIGNED: As a result of logistic regression analysis, compared to day workers, odds ratio (OR) with a TyG index above cut-off value for predicting development of DM in shift workers was 1.220 after adjusting for age, employment period, obesity, abdominal obesity, smoking, drinking, physical activity, hypertension, stroke, heart disease (Model 1, OR: 1.276; 95% confidence interval [CI]: 1.099-1.482; Model 2, OR: 1.232; 95% CI: 1.055-1.438; Model 3, OR: 1.220, 95% CI: 1.030-1.444).
UNASSIGNED: There was a significant association between shift work and TyG index among male workers in a chemical plant. More research studies on the association between shift work and TyG index are needed in the future.

Maritime industries utilize many different watch keeping schedules to maintain vigilance and crew safety around the clock. These schedules can be fatiguing, negatively impacting vigilant attention. This has led to the consideration of schedules that might allow for more sleep time, but how these schedules impact higher order cognitive function remains unclear. These schedules require assessment with tasks that are relevant to real-world operations on maritime vessels. This study investigated the effect of four schedules on higher order cognitive function. N = 27 (16 female) participants were recruited to a 10-day laboratory study, comparing four schedules. The schedules investigated were eight-on/eight-off/four-on/four-off (8/8/4/4) with sleep from 09:30 to 16:00 (condition A); six-on/six-off (6/6) with sleep from 08:30 to 12:30 and 21:30 to 00:00 (condition B); four-on/four-off (4/4/4/4/4/4) with sleep from 18:00 to 00:30 (condition C); and four-on/four-off (4/4/4/4/4/4) with sleep from 01:30 to 08:00 (condition D). Higher order cognitive function was assessed 2-3× daily whilst \"on watch\" using tests of visual scanning, learning, working memory, mental flexibility, and visuomotor control. Conditions were ranked and stability of performance on watch was compared between conditions using Kruskal-Wallis tests. Cognitive function within condition B was ranked the worst for most of the tasks. However, the stability of higher order cognitive function was poorest across the waking day within condition A. These findings highlight the variability in cognitive capacities during different watch keeping schedules.