A prospective cohort study of shift work and risk of ischemic heart disease in Japanese male workers

Exploring factors influencing late evening eating and barriers and enablers to changing to earlier eating patterns in adults with overweight and obesity

Late evening eating is a potential risk factor for overconsumption and weight gain. However, there is limited qualitative research investigating the complex factors that influence late evening eating in adults living with obesity. Identifying the factors that influence late evening eating can inform interventions to reduce late evening eating and associated health risks. Therefore, this study aimed to: i) explore factors that contribute to eating late, and ii) apply the Capability, Opportunity, and Motivation Behaviour (COM-B) model to understand the barriers and enablers to changing to earlier food intake timings in UK adults who report eating late. Semi-structured interviews with seventeen participants [32.47 ± 6.65 years; 34.68 ± 7.10 kg/m2; 71% female (n = 12); 41% White (n = 7)] investigated reasons for late evening eating and the potential barriers and enablers to changing to earlier eating patterns. Thematic analysis identified four main contributors to late evening eating: 1) internal signals (e.g., feeling hungry in the evening); 2) external and situational factors (e.g., work schedules and the food-rich environment); 3) social factors (e.g., interactions with family) and 4) behavioural and emotional factors (e.g., personal preferences and negative feelings in the evening). Time constraints and work schedules were identified as main barriers to changing to earlier eating patterns. Whereas, having high motivation (e.g., contentment with eating earlier in the evening) and interpersonal support were identified as main enablers to eating earlier. This study provides in-depth insights into the psychological, social, and environmental factors contributing to late evening eating. The findings highlight potential targets for future interventions to facilitate earlier eating times in individuals at risk of overweight and obesity.

Molecular subtypes of ischemic heart disease based on circadian rhythm

Coronary atherosclerotic heart disease (CAD) is among the most prevalent chronic diseases globally. Circadian rhythm disruption (CRD) is closely associated with the progression of various diseases. However, the precise role of CRD in the development of CAD remains to be elucidated. The Circadian rhythm disruption score (CRDscore) was employed to quantitatively assess the level of CRD in CAD samples. Our investigation revealed a significant association between high CRDscore and adverse prognosis in CAD patients, along with a substantial correlation with CAD progression. Remarkably distinct CRDscore distributions were also identified among various subtypes. In summary, we have pioneered the revelation of the relationship between CRD and CAD at the single-cell level and established reliable markers for the development, treatment, and prognosis of CAD. A deeper understanding of these mechanisms may offer new possibilities for incorporating "the therapy of coronary heart disease based circadian rhythm" into personalized medical treatment regimens.

Central blockage of sympathetic nerves inhibits the abnormal vital signs and disturbance of the gut microbiota caused by continuous light exposure

Background

Continuous light exposure increases sympathetic excitation in rats, leading to hypertension, left ventricular hypertrophy, and fibrosis. This study was aimed to investigate whether continuous light exposure causes destabilization of vital signs and gut microbiota (GM) in Sprague Dawley (SD) rats and whether clonidine hydrochloride (CH), a central sympathetic depressant drug, could prevent these changes.

Methods

Eight-week-old male SD rats were divided into three groups with different interventions for 14 weeks: control group (CG), 2-mL pure water gavaged daily while on a normal 12-h light/dark cycle; continuous illumination group (CI), 2-mL pure water gavaged daily while receiving continuous exposure to light (300 lx); and drug administration group (DA), CH (10 μg/kg) gavaged daily while receiving continuous exposure to light (300 lx).

Results

The results showed that blood pressure, heart rate, and body weight were significantly higher in the CI group than in the CG and DA groups (P < 0.05). Moreover, the Shannon index was higher in the DA group than in the CI group (P = 0.012). The beta diversity index in the CG group was significantly higher in the CI group (P = 0.039). The pairwise comparison results of the linear discriminant analysis effect size showed that Oscillospirales were enriched in the DA group, whereas the Prevotellaceae lineage (family level) > Prevotella (genus level) > Prevotellaceae_bacterium (species level) were enriched in the CI group. The Muribaculaceae family was more abundant in the CG group than in the CI group.

Conclusion

Sympathetic nerve inhibition restored the abnormal vital signs and GM changes under continuous light exposure.

The Effect of Commencing Rotating Shift Work on Diet and Body Composition Changes in Graduate Paramedics: A Longitudinal Mixed Methods Study

Objectives: Diet quality often changes as shift workers adjust to atypical work schedules, however, limited research exists examining the early effects of starting rotating shift work on diet and body composition. This study explored dietary behavior changes occurring in graduate paramedics during the first year of exposure to rotating shift work, and investigated dietary intake, diet quality and anthropometric changes over two years. Methods: Participants from a graduate paramedic cohort in Melbourne, Australia were approached after two years of shift work for study inclusion. Using a mixed method study approach, the qualitative component comprised individual in-depth interviews to explore perceived dietary behavior changes experienced over the first year of shift work. Interview transcripts were thematically analyzed and guided by the COM-B model (capability, opportunity, motivation, and behavior) and theoretical domains framework (TDF). Diet quality and dietary intake were quantitatively assessed by the Australian Eating SurveyTM at baseline, one year, and two years, along with body weight, waist circumference, and body mass index (BMI) to monitor changes. Results: Eighteen participants were included in the study. From the interviews, participants reported: 1. food choices are driven by wanting to fit in with coworker food habits, 2. food choices and mealtimes are unpredictable and 3. paramedics try to make healthy food choices but give in to less healthy options. While daily energy intake and diet quality scores did not differ in the first two years of shift work, daily energy from takeaway foods significantly increased (mean difference (MD): 2.96% EI; 95% CI: 0.44 - 5.48; p = 0.017) and increases in weight (MD: 2.96 kg; 95% CI: 0.89-5.04; p = 0.003), BMI (MD: 1.07 kg/m2; 95% CI: 0.26 - 1.87; p = 0.006) and waist circumference (MD: 5.07 cm; 95% CI: 1.25-8.89; p = 0.006) were also evident at two years. Conclusions: This study contributes new information on dietary changes and the current early trajectory of unintentional weight gain and takeaway reliance occurring within a graduate paramedic cohort over two years of shift work. To reduce the unintended metabolic consequences commonly observed with rotating shift schedules, workplaces could improve access to healthier food options and enable behavioral support/education to address nutrition-related health risks.

Association of breakfast skipping with habitual dietary intake and BMI in female rotating shift workers

OBJECTIVE

Higher BMI, lower quality of diet and a higher percentage of breakfast-skippers have been reported among rotating shift (RS) workers compared with day shift (DS) workers. As such, this study examined the association between breakfast skipping, habitual food consumption and BMI in RS workers.

DESIGN

Japanese nurses were studied using a self-administered questionnaire that assessed the height, weight, breakfast consumption habits, dietary consumption, physical activity, sleep habits, chronotype and demographic characteristics of the participants.

SETTING

A cross-sectional study was conducted in a population of nurses in Japan. Dietary and health-related questionnaires were mailed to 5536 nurses aged 20-59 years, working at 346 institutions.

PARTICIPANTS

A total of 3646 nurses at 274 institutions responded to the questionnaire. After removing those who met the exclusion criteria, 2450 participants were included in the statistical analysis.

RESULTS

The RS breakfast-skippers had lower total energy intake, diet quality and higher BMI than DS workers, whereas the RS breakfast-consumers had a higher total energy intake and BMI than the DS workers. In the RS workers, breakfast skipping on the days of DS and the end days of evening/night shift was associated with a poorer diet quality. Additionally, breakfast skipping on the days of DS was positively associated with BMI, independent of the total energy intake and diet quality.

CONCLUSIONS

Breakfast skipping on workdays may contribute to a difference in dietary intake and BMI between RS workers and DS workers and may increase BMI in RS workers, independent of dietary intake.

[Impacts of mastication frequency on circadian rhythm of glucose metabolism]

Postprandial glucose concentration is dependent on the time of day and its concentration in the morning is lower than in the evening. The circadian rhythm of glucose metabolism is regulated by the central circadian pacemaker in the suprachiasmatic nucleus (SCN). Both the SCN circadian clock and the pancreatic clock play important role in generating and maintaining the circadian rhythm of glucose metabolism. Also, short sleep duration and circadian misalignment are closely associated with a decrease in insulin sensitivity and an increase in type2 diabetes. Increased frequency of mastication and/or thorough chewing has been reported to alter the secretion of hormones related to appetite and energy metabolism. Furthermore, we have reported that the effect of mastication on postprandial glucose metabolism is dependent on the time of day and frequency of mastication. Morning mastication but not evening decreases postprandial blood glucose concentrations and increases insulin secretion at 30 min and so-called the insulinogenic index as a marker of early-phase β-cell function. This novel finding may aid in reducing the incidence of obesity and type 2 diabetes mellitus. This review covers the basic concept of the mammalian human circadian system, the underlying mechanism causing phase adjustment of the circadian rhythms in the SCN and peripheral organs, and the effect of eating behavior (e.g., chewing frequency) on the circadian rhythm of glucose metabolism.

Shift Work and Early Arterial Stiffness: A Systematic Review

Shift work is a way of organizing rotating schedules throughout the day. This can include 1-3 shifts for the same person on a rotational basis with other workers. Schedules that include night work have been associated with cardiovascular risk, mainly due to circadian misalignment. This systematic review sought to determine whether shift work is a risk factor for increased arterial stiffness. A systematic review of different databases was performed, using the following keywords: work shift, night work, arteriosclerosis, vascular stiffness, arterial stiffness, pulse wave velocity, and their Medical Subject Headings. We selected and analyzed 11 articles regarding pulse wave velocity as an indicator of arterial stiffness. Two studies identified higher levels of arterial stiffness in shift workers compared to day workers, while two studies found the opposite. In addition, four studies found no differences in arterial stiffness between shifts, two studies associated shorter sleep duration with arterial stiffness, and one study observed that physical activity could prevent adverse cardiovascular outcomes in shift workers. The findings are heterogeneous and preclude any robust conclusions. However, the present review points to the need for further studies to investigate arterial stiffness in shift workers, with greater control for confounding factors and longitudinal design.

Work Exposures and Development of Cardiovascular Diseases: A Systematic Review

INTRODUCTION

Cardiovascular diseases (CVDs) are the number one cause of death, and there is evidence that work exposures could be associated with their development. This study aimed to systematically review observational studies of adults exposed to job strain, effort-reward imbalance, long working hours, job insecurity, shift work, and occupational noise, and assess the association of those work exposures with CVDs.

METHODS

The Navigation Guide framework was applied. The population were adults of working age (18-65), and cohort and case-control studies were included. The work exposures were job strain, effort-reward imbalance, long working hours, job insecurity, shift work, and occupational noise. The outcomes were cerebrovascular diseases, ischaemic heart disease, and hypertensive diseases. The selection, data extraction, risk of bias assessment, and quality assessment were carried out by two reviewers independently and disagreements were solved by a third reviewer or by consensus. The synthesis of the results was done by applying the 'vote counting based on direction' method, and the results were summarized in an effect direction plot. The strength of the evidence for every risk factor and CVD was defined by consensus.

RESULTS

A total of 17 643 papers were initially identified in the literature search, but after applying the filters by title and abstract, and full text, 86 studies were finally included. From the included studies, sufficient evidence was found of the harmfulness of job strain for cerebrovascular disease and ischemic heart disease. Furthermore, there was sufficient evidence of the harmfulness of shift work for ischemic heart disease. Evidence of no relationship was found between long working hours and shift work with ischaemic heart disease and hypertensive disease, respectively. The other associations of work exposures and CVDs had limited or inadequate evidence of harmfulness.

CONCLUSIONS

In this comprehensive review, there was sufficient evidence of a harmful relationship between job strain, shift work, and CVDs. For the other work exposures, more high-quality studies are needed. In order to improve current prevention strategies for CVDs, the findings of this review imply that job strain and shift work are work exposures that constitute additional risk factors that could be approached as targets for worksite interventions.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD42020179972.

Metabolic syndrome and its relationship with shift work in petrochemical workers

BACKGROUND: The metabolic syndrome is a complex of interdependent risk factors for cardiovascular disease and diabetes. Shift work might have an impact on metabolic variables, and be a risk factor for type 2 diabetes. To date, only few studies have been done on the prevalence of MetS in industrial work environments in Iran, and most of them have been conducted on a small sample size. OBJECTIVE: The aim of this study was to evaluate the impact of shift work on prevalence of metabolic syndrome in one of the petrochemical companies in Iran. METHODS: This cross-sectional study was conducted among 692 male workers of a petrochemical company in south-west Iran. Metabolic syndrome was diagnosed according to criteria recommended by Adult Treatment Panel III. In order to determine correlation between MetS and its factors with shift work odds ratio (ORs) for the MetS, 95% confidence level (95% CL), chi-square test and logistic regression analysis were performed. RESULTS: Overall 15.1% of workers were diagnosed with metabolic syndrome and 80% of them were shift workers. A significant difference for prevalence of metabolic syndrome and mean values for body mass index, blood pressure, fast blood sugar, waist circumference among shift workers and non-shift workers were identified (p < 0.001). Compared with the day workers, shift workers had a significantly higher risk of MetS (odds ratio = 4.852; 95% CI 2.34–9.974). CONCLUSIONS: There is an association between metabolic syndrome and shift work in petrochemical workers. Promising intervention strategies are needed for prevention of metabolic disorders for shift workers.

The Effect of Change of Working Schedule on Health Behaviors: Evidence from the Korea Labor and Income Panel Study (2005–2019)

This study investigated whether changes in work schedule are associated with health behavior changes. We used data from the Korea Labor and Income Panel Survey from 2005 to 2019. A generalized estimating equation model was used to assess the association between changes of work schedules (day–day, day–shift, shift–day, and shift–shift) and health behaviors. Odds ratios (ORs) with 95% confidence intervals (CIs) were calculated after adjusting for general and socioeconomic characteristics. Fixed daytime work was observed for 25,716 person-years, and fixed shift work was observed for 2370 person-years out of the total 4046 participants during a 14 year period. Workers who changed their work schedule from fixed daytime to shift work and from shift to fixed daytime work contributed to 670 and 739 person-years, respectively. Considering continuous fixed daytime workers as a reference group, continuous exposure to shift work (aOR 1.11, CI 1.01–1.26) and changes from fixed daytime to shift work (aOR 1.18, CI 1.05–1.44) were significantly associated with an increased risk of changing either smoking or drinking behavior to unhealthy patterns. The results of our study suggest that workers who work irregular shift times, in contrast to those with more standard, regular work schedules, are at a higher risk of changing smoking and/or drinking behavior to unhealthy patterns.

Metabolic Homeostasis: It's All in the Timing

Cross-talk between peripheral tissues is essential to ensure the coordination of nutrient intake with disposition during the feeding period, thereby preventing metabolic disease. This mini-review considers the interactions between the key peripheral tissues that constitute the metabolic clock, each of which is considered in a separate mini-review in this collation of articles published in Endocrinology in 2020 and 2021, by Martchenko et al (Circadian rhythms and the gastrointestinal tract: relationship to metabolism and gut hormones); Alvarez et al (The microbiome as a circadian coordinator of metabolism); Seshadri and Doucette (Circadian regulation of the pancreatic beta cell); McCommis et al (The importance of keeping time in the liver); Oosterman et al (The circadian clock, shift work, and tissue-specific insulin resistance); and Heyde et al (Contributions of white and brown adipose tissues to the circadian regulation of energy metabolism). The use of positive- and negative-feedback signals, both hormonal and metabolic, between these tissues ensures that peripheral metabolic pathways are synchronized with the timing of food intake, thus optimizing nutrient disposition and preventing metabolic disease. Collectively, these articles highlight the critical role played by the circadian clock in maintaining metabolic homeostasis.

Night-shift work, breast cancer incidence, and all-cause mortality: an updated meta-analysis of prospective cohort studies

OBJECTIVES

Night-shift work exposure is proposed to link to a wide range of health issues, especially cancer incidence, cancer-specific death, and all-cause death. However, the epidemiological associations among night-shift work exposure, breast cancer, breast cancer-specific death, and all-cause mortality remain inconclusive.

METHODS

We performed an updated systematic review and meta-analysis to confirm potential associations among night-shift work exposure, breast cancer, and all-cause mortality.

RESULTS

A total of 31 prospective cohort studies, involving 9.3 million participants, 31,244 incident breast cancer cases, 12,728 cancer-related deaths, 7882 cardiovascular deaths, and 30,807 all-cause mortalities were included. Overall, the summary RR of incident breast cancer in females for an increase of night-shift work was 1.029 (95% CI 1.003-1.055). Compared with standard day workers, night-shift workers had a statistically significantly increased RR (1.086, 95% CI 1.032-1.142) for breast cancer incidence in the subgroup of > 10 years exposure. Furthermore, a positive association was revealed in subgroup studies of rotating night-shift work (RR = 1.053, 95% CI 1.018-1.090). A significant increased risk of cardiovascular mortality was demonstrated in the night-shift work group (RR = 1.031; 95% CI 1.006-1.057).

CONCLUSION

Our systematic review and meta-analysis provided convincing evidence supporting positive associations among night-shift work exposure, breast cancer incidence, and cardiovascular mortality. Taken together, night-shift work exposure significantly increased the risk of breast cancer morbidity by 2.9% for total, 8.6% for the subgroup of more than 10 years night-shift work, and 5.3% for rotating night-shift work. In addition, night-shift work increased the risk of cardiovascular mortality by 3.1%.

Associations of shift work and night work with risk of all-cause, cardiovascular and cancer mortality: a meta-analysis of cohort studies

BACKGROUND

Epidemiological studies on the relationship of shift work or night work with risk of total and cause-specific mortality have given conflicting results. We aimed at conducting a meta-analysis to summarize the evidence from cohort studies.

METHODS

Embase, PubMed, Web of Science and Scopus databases were searched for eligible studies up to Mar 2021. Cohort studies evaluating the associations of shift work or night work with risk of all-cause, cardiovascular or cancer mortality were reviewed. Study-specific risk estimates were pooled by fixed-effect models when the heterogeneity was not detected; otherwise, random-effect models were employed.

RESULTS

We identified seventeen eligible articles (sixteen cohorts). A total of 958,674 cohort participants were included, with 38,413 total deaths, 24,713 cardiovascular deaths and 10,219 cancer deaths during follow-up. According to the Newcastle-Ottawa Scale, fifteen studies were considered as relatively high quality with low risk of bias. Compared with regular daytime workers, the pooled relative risks for all-cause, cardiovascular and cancer mortality were 1.02 (95% CI: 0.99, 1.06), 1.18 (95% CI: 0.94, 1.47) and 1.05 (95% CI: 0.83, 1.34) for those ever exposing to shift work, respectively. Compared with daytime workers or those never exposing to night work, the pooled relative risks for all-cause, cardiovascular and cancer mortality were 1.06 (95% CI: 1.03, 1.08), 1.15 (95% CI: 1.03, 1.29) and 1.04 (95% CI: 1.00, 1.08) for those ever exposing to night work, respectively. Moderate to high level of heterogeneity across the studies was detected. Publication bias was not detected.

CONCLUSION

Night work may be associated with higher risk of all-cause, cardiovascular and cancer mortality, suggesting that night workers compared with daytime workers may be at higher risk of death, especially due to cardiovascular disease.

Social and environmental risks as contributors to the clinical course of heart failure

Heart failure is a major contributor to healthcare expenditures. Many clinical risk factors for the development and exacerbation of heart failure had been reported, including diabetes, renal dysfunction, and respiratory disease. In addition to these clinical parameters, the effects of social factors, such as occupation or lifestyle, and environmental factors may have a great impact on disease development and progression of heart failure. However, the current understanding of social and environmental factors as contributors to the clinical course of heart failure is insufficient. To present the knowledge of these factors to date, this comprehensive review of the literature sought to identify the major contributors to heart failure within this context. Social factors for the risk of heart failure included occupation and lifestyle, specifically in terms of the effects of specific occupations, occupational exposure to toxicities, work style, and sleep deprivation. Socioeconomic factors focused on income and education level, social status, the neighborhood environment, and marital status. Environmental factors included traffic and noise, air pollution, and other climate factors. In addition, psychological stress and behavior traits were investigated. The development of heart failure may be closely related to these factors; therefore, these data should be summarized for the context to improve their effects on patients with heart failure. The present study reviews the literature to summarize these influences.

Association of shift work with cardiovascular disease risk among Chinese workers

To evaluate the association of shift work with 10-year cardiovascular disease (CVD) risk among Chinese workers. We included 23,064 workers in the first follow-up of the Dongfeng-Tongji cohort study. Questionnaires and physical examinations were conducted to collect data for all participants. Framingham Risk Score was calculated according to the multivariable risk algorithms, and used to evaluate 10-year CVD risk. Logistic regression models were used to assess the relationship between shift work and 10-year CVD risk. Among 23,064 individuals, 51.92% of workers suffered shift work, and the proportions of shift work duration of 1-<10, 10-<20, and ≥20 years were 17.29%, 17.35% and 17.30%, respectively. Compared with individuals without a shift work history, the odds ratios (ORs) and 95% confidence intervals (CIs) of 10-year CVD were 1.027 (0.900-1.173), 1.058 (0.927-1.206) and 1.191 (1.036-1.368) for individuals with shift work duration of 1-<10 years, 10-<20 years, and ≥20 years, respectively, after adjusting for potential confounders. And the association was more obvious in males. When shift work and obesity were combined, the OR (95%CI) of high 10-year CVD risk (3.373, 2.390-4.761) was significantly increased for obese individuals with shift work of ≥20 years. Besides, the OR (95%CI) for higher 10-year CVD risk associated with shift work decreased as the leaving shift work duration prolonged. Shift work is associated with a higher 10-year CVD risk, especially among males. Obesity has a synergistic effect on such association while leaving shift work reduces such association.

Non-Pharmacological Interventions to Improve Chronic Disease Risk Factors and Sleep in Shift Workers: A Systematic Review and Meta-Analysis

Shift work is associated with adverse chronic health outcomes. Addressing chronic disease risk factors including biomedical risk factors, behavioural risk factors, as well as sleep and perceived health status, affords an opportunity to improve health outcomes in shift workers. The present study aimed to conduct a systematic review, qualitative synthesis, and meta-analysis of non-pharmacological interventions targeting chronic disease risk factors, including sleep, in shift workers. A total of 8465 records were retrieved; 65 publications were eligible for inclusion in qualitative analysis. Random-effects meta-analysis were conducted for eight eligible health outcomes, including a total of thirty-nine studies. Interventions resulted in increased objective sleep duration (Hedges' g = 0.73; CI: 0.36, 1.10, k = 16), improved objective sleep efficiency (Hedges' g = 0.48; CI: 0.20, 0.76, k = 10) and a small increase in both subjective sleep duration (Hedges' g = 0.11; CI: -0.04, 0.27, k = 19) and sleep quality (Hedges' g = 0.11; CI: -0.11, 0.33, k = 21). Interventions also improved perceived health status (Hedges' g = 0.20; CI: -0.05, 0.46, k = 8), decreased systolic (Hedges' g = 0.26; CI: -0.54, 0.02, k = 7) and diastolic (Hedges' g = 0.06; CI: -0.23, 0.36, k = 7) blood pressure, and reduced body mass index (Hedges' g = -0.04; CI: -0.37, 0.29, k = 9). The current study suggests interventions may improve chronic disease risk factors and sleep in shift workers; however, this could only be objectively assessed for a limited number of risk factor endpoints. Future interventions could explore the impact of non-pharmacological interventions on a broader range of chronic disease risk factors to better characterise targets for improved health outcomes in shift workers.

Work-related factors among people with diabetes and the risk of cardiovascular diseases: A systematic review

BACKGROUND

Diabetes is a major risk factor for cardiovascular diseases (CVD). This systematic review aims to explore the work-related factors among people with diabetes in developing CVD.

METHODS

Four electronic databases were searched on 1 February 2021 using a comprehensive search strategy without any time restriction. Two independent researchers screened the articles and extracted data. The risk of bias was assessed independently using the risk of bias assessment tool for non-randomized studies (RoBANS). A narrative synthesis was conducted considering the heterogeneity of the included articles.

RESULTS

A total of five articles incorporating 4 409 810 participants from three geographic regions were included that highlights the research gap. As per the included studies, Occupational drivers with diabetes were at a higher risk of CVD in comparison to the nondrivers, workers with diabetes having a long working hour were at a higher risk of CVD mortality, workers with a lower occupational status were at a higher risk of 10-years stroke risk, and occupational physical activity and occupational commuting lowered the risk of CVD deaths.

CONCLUSIONS

This systematic review summarized the available evidence on work-related factors influencing the risk of CVD in people with diabetes. The findings should be interpreted cautiously pondering the limited evidence and imprecision. We identified only five articles related to the topic, and there were no studies from Japan. The scarcity of studies on work-related factors on the prognosis of diabetic patients implies the need for more research in this field. We recommend further exploration of the topic designing primary studies.

Traumatic stress and the circadian system: neurobiology, timing and treatment of posttraumatic chronodisruption

Background: Humans have an evolutionary need for a well-preserved internal 'clock', adjusted to the 24-hour rotation period of our planet. This intrinsic circadian timing system enables the temporal organization of numerous physiologic processes, from gene expression to behaviour. The human circadian system is tightly and bidirectionally interconnected to the human stress system, as both systems regulate each other's activity along the anticipated diurnal challenges. The understanding of the temporal relationship between stressors and stress responses is critical in the molecular pathophysiology of stress-and trauma-related diseases, such as posttraumatic stress disorder (PTSD). Objectives/Methods: In this narrative review, we present the functional components of the stress and circadian system and their multilevel interactions and discuss how traumatic stress can affect the harmonious interplay between the two systems. Results: Circadian dysregulation after trauma exposure (posttraumatic chronodisruption) may represent a core feature of trauma-related disorders mediating enduring neurobiological correlates of traumatic stress through a loss of the temporal order at different organizational levels. Posttraumatic chronodisruption may, thus, affect fundamental properties of neuroendocrine, immune and autonomic systems, leading to a breakdown of biobehavioral adaptive mechanisms with increased stress sensitivity and vulnerability. Given that many traumatic events occur in the late evening or night hours, we also describe how the time of day of trauma exposure can differentially affect the stress system and, finally, discuss potential chronotherapeutic interventions. Conclusion: Understanding the stress-related mechanisms susceptible to chronodisruption and their role in PTSD could deliver new insights into stress pathophysiology, provide better psychochronobiological treatment alternatives and enhance preventive strategies in stress-exposed populations.

Association between circadian disruption and diseases: A narrative review

Circadian rhythms play an important role in a wide range of human physiology and pathology. Individuals increasingly experience situations such as night-shift work schedules, likely leading to circadian disruption. Recent studies have also demonstrated that patients with other diseases often show symptoms of circadian disruption as manifested by the sleep-wake cycle and other biological rhythms. Circadian disruption often results in changes to the phase, period, and amplitude of the sleep-wake cycle, melatonin rhythm, and core body temperature. Several cardiometabolic, psychiatric, and neurodegenerative diseases are closely related to circadian disruption. Several interventions are also available, including phototherapy, exogenous melatonin, and exercise. The cumulative findings suggest that circadian disruption can increase risk for some cardiometabolic diseases. Circadian disruption also acts as a concomitant symptom of several psychiatric and neurodegenerative diseases. More attention should be paid to evaluating the impact of circadian disruption on these related diseases, as well as the benefits of the mitigation interventions for both circadian disruption and related diseases.

Shift work, and particularly permanent night shifts, promote dyslipidaemia: A systematic review and meta-analysis

BACKGROUND AND AIMS

Shift work is common worldwide and linked to deleterious cardiovascular effects that might be underlined by dyslipidemia. The aim of this systematic review and meta-analysis is to determine the impact of shiftwork on dyslipidemia.

METHODS

Searching in PubMed, Cochrane Library, Science Direct and Embase databases without language restriction on 15 February 2020, included studies that describe blood lipids levels or a risk measure in shift workers compared with fixed-day workers (controls). Differences by study-level characteristics were estimated using stratified meta-analysis by type of shift work, and meta-regression to examine relations between dyslipidemia and demographic, lifestyle and work characteristics. Estimates were pooled using random-effect meta-analysis.

RESULTS

We included a total of 66 articles, representing 197,063 workers. Shift work globally increased the levels of triglycerides (overall SMD = 0.09; 95CI 0.05 to 0.13; p < 0.001), and globally decreased the levels of c-HDL (-0.08; 95CI -0.12 to -0.03; p = 0.001). Permanent night shift workers were an at-risk type of shift for dyslipidemia with significantly higher blood levels of total cholesterol (0.22; 95CI 0.01 to 0.42; p = 0.043) and triglycerides (0.18; 0.03 to 0.33; p = 0.017), and significantly lower blood levels of c-HDL (-0.16; 95CI -0.32 to 0.00; p = 0.05). Permanent night shift workers were more at-risk for total cholesterol than rotating 3 × 8 shift workers (Coefficient 0.22; 95CI 0.01 to 0.42; p = 0.038) and rotating 2 × 12 shift workers (0.24; 0.02 to 0.46; p = 0.037), and more at-risk for triglycerides than rotating day shift workers (0.21; 95CI 0.03 to 0.38; p = 0.023). Results were non-significant for c-LDL, nor depending on type of shifts.

CONCLUSIONS

Shift work, and particularly permanent night shift, is associated with dyslipidaemia via elevated total cholesterol and triglycerides, and reduced HDL-cholesterol. Our current study provides a practical and valuable strengthening of the evidence-base required for preventive health initiatives and workplace reform.

Subjective and objective assessments after a change from a 4-crew, 12-h shift to a 3-crew, 12-h shift schedule: an observational study

PURPOSE

To clarify the subjective and objective impacts of a change in a 12-h shift schedule, involving a reduction in the number of crews, on workers at an electronic parts production company.

METHODS

Forty-two workers participated in this study. Subjective indicators (e.g. questionnaires) and objective indicators [e.g., psychomotor vigilance task (PVT)], as well as an activity monitor-based sleep assessment, were measured during a > 1-year period that encompassed the shift schedule change. The study outcome was a comparison of work-related injury rates measured 1 year before and after the change in shift schedule.

RESULTS

After the shift schedule change, questionnaire scores regarding work-related burdens and PVT performance parameters, including mean response time and number of lapses, increased significantly. However, we also observed divergences in the trends of the subjective and objective measures 1 year after the change. Despite these variations in both types of measures, we observed no significant differences in work-related injury rates measured before and after the shift schedule change.

CONCLUSION

This study revealed that a reduction in the number of crews in a 12-h shift schedule has a negative impact on the subjective and objective indicator after the change in shift schedule; only indicators of alertness did not recover at 1 year after the change. Assessments of the workers' performances and the regular implementation of health and safety programs for more than 1 year are needed to maintain workers' health after the change in shift schedule.

The impact of shift work on glycemic characteristics assessed by CGM and its association with metabolic indices in non-diabetic subjects

AIM

To explore the glycemic characteristics of non-diabetic shift workers and associations with metabolic indices.

METHODS

In this cross-sectional study, 450 non-diabetic males, including 238 shift workers, aged 23-58 years, were recruited after a screening oral glucose tolerance test. Blood samples and anthropometric data were collected. Hundred and fifty of them finished a continuous glucose monitoring for 3-7 days.

RESULTS

Compared to daytime workers, shift workers presented with larger WHR (p < 0.001), higher HOMA-IR (p < 0.001), higher hs-CRP level (p < 0.001) and worse lipid profiles. In glycemic characteristics, shift workers with normal glucose regulation had a similar mean blood glucose (MBG), daytime MBG, percentage of time of hyperglycemia, hypoglycemia, euglycemia, and fluctuation parameters, including standard deviation of blood glucose (SDBG), mean amplitude of glycemic excursions (MAGE) and mean of daily differences (p > 0.05, respectively), while they had a higher nighttime MBG (p = 0.026) and blood glucose (BG) at 3 a.m. (p = 0.015). For subjects with impaired glucose regulation, both groups had no difference in any clinical characteristics or glycemic parameters (p > 0.05, respectively). Further regression analysis revealed the association between MBG/SDBG/MAGE/nighttime MBG/BG at 3 a.m. and age/WHR/hs-CRP/TC.

CONCLUSION

For non-diabetic shift workers, the glycemic characteristic was the elevated nighttime glycemia, presented as higher nighttime MBG and BG at 3 a.m. And both metrics were closely associated with central obesity. Elevated nighttime glycemia was an early signal of glucose metabolism disorder in shift workers.

Trajectories of mobility limitations over 24 years and their characterization by shift work and leisure-time physical activity in midlife

BACKGROUND

We aimed to investigate trajectories of mobility limitations (MLs) over a period of 24 years. In addition, we aimed to study how shift work and leisure-time physical activity (LTPA) in midlife predict assignment to MLs trajectories separately for those retired on statutory pensions (SPs) and on disability pensions (DPs).

METHODS

Subjects who responded MLs questionnaires (1985-2009, N = 3048) in Finnish Longitudinal Study on Aging Municipal Employees were included in this prospective cohort study. LTPA and shift work were measured during baseline. International Classification of Functioning was used to code MLs. Growth mixture modeling was used to identify the trajectories of MLs. Odds ratio (OR) and their 95% Confidence interval (CI) were assessed by using multinomial logistic regression.

RESULTS

We identified four trajectories of MLs, namely low persistent, low increasing, high decreasing and high persistent. Among the SP recipients, shift work with night shifts was associated with an increased risk (adjusted OR 1.49; 95% CI 1.03-2.14) of belonging to the high persistent MLs trajectory. The inactive LTPA (SP: OR 5.99, 95% CI 3.39-10.58, DP: OR 6.81, 95% CI 2.52-18.43) was similarly associated with high persistent MLs trajectory.

CONCLUSION

Nearly two-thirds of the people retired due to disability belonged to high MLs trajectory. High persistent MLs trajectory was associated with physical inactivity in midlife among those retired on SP and on DP. Shift work with night shift predicted high persistent MLs in SP strata. Active involvement in LTPA during midlife could be beneficial to spend MLs free later life.

Impact of Circadian Disruption on Cardiovascular Function and Disease

The circadian system, that is ubiquitous across species, generates ∼24 h rhythms in virtually all biological processes, and allows them to anticipate and adapt to the 24 h day/night cycle, thus ensuring optimal physiological function. Epidemiological studies show time-of-day variations in adverse cardiovascular (CV) events, and controlled laboratory studies demonstrate a circadian influence on key markers of CV function and risk. Furthermore, circadian misalignment, that is typically experienced by shift workers as well as by individuals who experience late eating, (social) jet lag, or circadian rhythm sleep-wake disturbances, increases CV risk factors. Therefore, understanding the mechanisms by which the circadian system regulates CV function, and which of these are affected by circadian disruption, may help to develop intervention strategies to mitigate CV risk.

Sleep, Sleep Disorders, and Sexual Dysfunction

Good sleep is necessary for good health. Sleep health is increasingly recognized as important for physical and mental health by both the medical profession and the general public, and there is great interest in how to avoid and treat sleep disorders and problems. Recent research indicates that insufficient sleep, disrupted sleep, and sleep disorders affect many aspects of human health including sexual function. In fact, patients with urological disorders or erectile dysfunction (ED) may have a sleep disorder that contributes to their urological or sexual dysfunction. Obstructive sleep apnea, insomnia, shift work disorder, and restless legs syndrome are all common sleep disorders and are associated with ED and/or other urological disorders. Therefore, careful attention should be paid to the diagnosis and treatment of concomitant sleep disorders in patients with sexual dysfunction. In this review, we provide an overview of what sleep is and how it is assessed in the clinic or laboratory; our current understanding of the functions of sleep and sleep health; a description of common sleep disorders, as well as how they are diagnosed and treated; and how sleep and its disorders are associated with male sexual dysfunction. Sleep is considered to be a 'third pillar of health', along with diet and exercise. With an understanding of common sleep disorders and how they can impact male sexual function, the urologist can ensure that sleep disorders are considered as a contributor to sexual dysfunction in their patients in order to provide them with the optimal treatment for overall health.

Shift Work and Leukocyte Count Changes among Workers in Bangkok

OBJECTIVES

Previous epidemiological evidence for the association of shift work exposure and increased leukocyte count is cross-sectional in nature, thus limiting cause-effect inference. We therefore used a longitudinal design to: (i) compare leukocyte counts at baseline between shift and day workers and (ii) examine the time trend of leukocyte counts over the follow-up period for these workers.

METHODS

A retrospective cohort study was conducted among 6737 workers aged <60 years at two large organizations (a humanitarian organization and a university) in Bangkok, Thailand who had participated in at least two annual health check-ups during the period 2005-2016. Shift work exposure history was assessed by a self-administered questionnaire and categorized into day, former, and current shift workers. Data on leukocyte count were collected annually as part of worksite health screening during the observation period. Association of shift work exposure and increased leukocyte count was then examined cross-sectionally and longitudinally by using multiple linear regression and multilevel analysis of repeated measures data, respectively. In addition, trends for leukocyte count over the follow-up period and work years were examined using LOWESS smooth curves.

RESULTS

Compared to day work, the current shift work was associated with increased leukocyte counts. The magnitude of percentage increase was the highest for basophil counts, followed by eosinophil and lymphocyte counts. Both cross-sectional and longitudinal evidence revealed this association, although it was less pronounced longitudinally. For total leukocyte count, the magnitude of difference was constant across the 11-year follow-up period. However, for lymphocyte and basophil counts, these discrepancies tapered over the work years until they no longer differed (for lymphocyte count) or even differed in the opposite direction (for basophil count) in later work years.

CONCLUSION

This study confirmed previous cross-sectional evidence that shift work exposure-increased leukocyte counts and that this was reversible. Whether this increase in immune cell count also results in an increased immune cell activity and serves as the intermediary in the association between shift work exposure and subsequent chronic disease development needs further investigation.

Significant Impacts of Work-Related Cerebrovascular and Cardiovascular Diseases among Young Workers: A Nationwide Analysis

Background: While occupational factors linked to the onset of cerebrovascular and cardiovascular diseases (CVDs) have been reported among workers, much remains unknown about the impacts that occupation has on the onset of CVDs in various age groups. We attempted to describe temporal trends in total and work-related CVDs (WRCVDs) rates stratified by age and year and explore the relative contributions of work to the CVD risk. Methods: This study was conducted using two populations from the Labor Insurance Database as the working population and the National Health Insurance Research Database as the general population. We included all people aged 15⁻75 years from 2006 to 2013. All CVD events and WRCVD events were identified. A Poisson regression was used to estimate the morbidity rate ratio (RR) stratified by age and period, and an RR adjusted for residual confounding was also used. Results: Incident CVD rates increased with aging in the general population (from 1113.55 to 1853.32 per 100,000 persons), and WRCVD rates increased in the working population over time (from 2.10 in 2006 to 8.60 in 2013 per 100,000 persons). In the age and period analysis, CVD attacks showed disparities in different populations. The RR of the WRCVD risk was mainly in the working population aged >45 years, and the RR of the CVD risk occurred in the oldest group (aged 55⁻64 years) of the general population. The population-attributable risk of working exposure was 13.5%. After eliminating residual confounding factors, higher population attributed risk (PAR) work-related excessive CVD risk mainly occurred in workers aged 25⁻34 and 35⁻44 years. A decreasing PAR trend was found in the age groups as follows: 15⁻24, 25⁻34, 35⁻44, 45⁻54, and 55⁻64 years, with percentages of 17.64%, 16.89%, 16.46%, 10.6%, and 0.65%, respectively. Conclusions: There is evidence that period and age trends of CVD rates differed between the working population and general population. Relative effects attributed to work were more severe in younger workers, particularly in workers aged <55 years.

Multilevel Interactions of Stress and Circadian System: Implications for Traumatic Stress

The dramatic fluctuations in energy demands by the rhythmic succession of night and day on our planet has prompted a geophysical evolutionary need for biological temporal organization across phylogeny. The intrinsic circadian timing system (CS) represents a highly conserved and sophisticated internal "clock," adjusted to the 24-h rotation period of the earth, enabling a nyctohemeral coordination of numerous physiologic processes, from gene expression to behavior. The human CS is tightly and bidirectionally interconnected to the stress system (SS). Both systems are fundamental for survival and regulate each other's activity in order to prepare the organism for the anticipated cyclic challenges. Thereby, the understanding of the temporal relationship between stressors and stress responses is critical for the comprehension of the molecular basis of physiology and pathogenesis of disease. A critical loss of the harmonious timed order at different organizational levels may affect the fundamental properties of neuroendocrine, immune, and autonomic systems, leading to a breakdown of biobehavioral adaptative mechanisms with increased stress sensitivity and vulnerability. In this review, following an overview of the functional components of the SS and CS, we present their multilevel interactions and discuss how traumatic stress can alter the interplay between the two systems. Circadian dysregulation after traumatic stress exposure may represent a core feature of trauma-related disorders mediating enduring neurobiological correlates of trauma through maladaptive stress regulation. Understanding the mechanisms susceptible to circadian dysregulation and their role in stress-related disorders could provide new insights into disease mechanisms, advancing psychochronobiological treatment possibilities and preventive strategies in stress-exposed populations.

Night-time work and all-cause mortality in the general working population of Denmark

PURPOSE

A recent study among female nurses in Denmark found an increased mortality among night-time workers, which has raised concerns about the sufficiency of the EU Working Time Directive. The aim of the present study was to examine the relationship between night-time work and all-cause mortality among full-time employees in the general workforce of Denmark.

METHODS

Interview data from the Danish Labour Force Surveys, 1999-2013, were linked to national registers with individual-level data on occupation, industry, socioeconomic status (SES), emigrations and deaths. The participants (N = 159,933) were followed from the end of the calendar year of the interview until the end of 2014. Poisson regression was used to estimate rate ratios for all-cause mortality, with and without stratification by sex and socioeconomic status. A likelihood ratio test was used to test the overall null-hypothesis, which stated that the mortality rates were independent of night-time work, SES × night-time work and sex × night-time work.

RESULTS

The likelihood ratio test did not reject the null hypothesis (p = 0.14). The rate ratio for all-cause mortality among employees with vs. without night-time work was estimated at 1.07 (95% CI 0.97-1.19) after adjustment for age, sex, SES, calendar time, weekly working hours and time passed since the start of follow-up.

CONCLUSIONS

The present study did not find any statistically significant associations between night-time work and all-cause mortality among employees in the general workforce of Denmark.

A Review of Data of Findings on Night Shift Work and the Development of DM and CVD Events: a Synthesis of the Proposed Molecular Mechanisms

PURPOSE OF REVIEW

Night shift work has become highly prevalent in our 24/7 societies, with up to 18% of the US work force working alternate shift schedules. However, studies indicate that there may be adverse health effects of chronic night work across diverse populations. These effects are likely due to misalignment of the circadian system with work schedules, mediated by the system's primary marker melatonin as well as other downstream molecules.

RECENT FINDINGS

Melatonin has multiple biologic actions that are relevant to cardiometabolic disease, including modulation of oxidative stress, inflammation, and (via the melatonin receptor) vasoconstriction. Behavioral traits, such as chronotype and meal timing, have recently been shown to interact with the effects of night work on cardiometabolic health. Together with recent findings suggesting a role for circadian genes in cardiometabolic risk, the interactions of night shift work and behavioral traits are likely to facilitate novel treatment and prevention approaches for cardiovascular disease and type 2 diabetes, incorporating aspects of clock and timing.

Needs survey on the priority given to periodical medical examination items among occupational physicians in Japan

Objectives:

To clarify the priority given to periodical medical examination items among occupational physicians in Japan.

Methods:

Sixty-two occupational physicians who participated in this study selected statutory and non-statutory items within two types of budget plans: one lower (8,500 yen) than the total fee of statutory medical examinations (9,250 and 11,290 yen), and the other higher (12,000 yen) than the total fee. Medical fee points were used to set the cost of each medical examination item. A three round Delphi method was used from May to July 2016 to clarify the consensus opinion of occupational physicians.

Results:

The statutory items (selection rate: between 66 and 100%), except for waist circumference (15%) and sputum examination (0%), and serum creatinine (58%, non-statutory item) were included in the smaller budget plan (8,500 yen). In the larger budget plan (12,000 yen), the statutory items (selection rate: between 92 and 100%), except for waist circumference (39%) and sputum examination (0%), and some non-statutory items, namely serum creatinine (95%), leukocytes (92%), uric acid (89%), and fecal occult blood reaction (81%), had a selection rate over 80%. In addition, statutory items with higher accuracy were preferred, which included the following: air conduction pure-tone audiometry (92%), imaging diagnosis of thoracic X-ray examinations by a specialist (97%), glycated hemoglobin levels (98%), and electrocardiogram assessment by a specialist (100%).

Conclusion:

The statutory items, except for waist circumference and sputum examination, and some of the non-statutory items (e.g., serum creatinine) were given higher priority among occupational physicians in Japan.

Circadian locomotor output cycles kaput accelerates atherosclerotic plaque formation by upregulating plasminogen activator inhibitor-1 expression

To explore the association between clock circadian regulator circadian locomotor output cycles kaput gene (CLOCK) and the forming of atherosclerotic plaques and its underlying mechanisms, mouse aortic endothelial cells (MAECs) and atherosclerosis (AS) mouse model were recruited for our study. The apoE gene knockout mouse was used as the model of AS and we accelerated the formation of unstable plaques through the combination of carotid artery ligation and high-fat (HF) diet administration (0.2% cholesterol, 20% fat). The mRNA and protein expressions of CLOCK in peripheral blood monouclear cells of acute coronary syndrome (ACS) patients or mouse AS model were detected by qPCR, western blot analysis and immunohistochemical staining. The number of adherent cells and atherosclerotic plaques was counted to assess the effects of CLOCK on the progression of ACS, and adherence-associated genes, such as vascular cell adhesion molecule (VCAM)-1, C-C motif chemokine ligand 2 (CCL-2), and CCL-5. The results showed that CLOCK expression was significantly increased in both ACS patients and AS mouse model. The levels of CLOCK, leukemia inhibitory factor (LIF), intercellular adhesion molecule 1 (ICAM-1), perilipin 2 (ADFP), nuclear factor kappa B (NF-κB), and plasminogen activator inhibitor-1 (PAI-1), as well as the number of atherosclerotic plaques were elevated in the AS mouse model, as compared with the control group. Chromatin immunoprecipitation assay showed that CLOCK bound directly to the promoter of PAI-1 gene and CLOCK could positively regulate the expressions of LIF, ICAM-1, ADFP, NF-κB, and PAI-1. Reduction of CLOCK expression would decrease the expressions of VCAM-1, CCL-2, and CCL-5, and the number of adherent cells and atherosclerotic plaques, but these effects were neutralized when PAI-1 was simultaneously overexpressed in either mouse model or MAECs. Our results demonstrate that CLOCK overexpression triggers the formation of atherosclerotic plaques by directly upregulating PAI-1 expression.

The impact of night-shift work on platelet function in healthy medical staff

Objectives:

Rotating shift work has been reported to increase the risk of cardiovascular diseases. Vascular endothelial dysfunction and platelet activation are among the leading causes of thrombus formation in patients with myocardial infarction or stroke. Endothelial function has been shown to be impaired immediately after night-shift work; however, it is not known whether platelets are also activated. The aim of this study was to investigate the acute impact of night-shift work on platelet function.

Methods:

This observational study included 11 healthy medical staff members (seven women, median age 32 years). We examined each subject's platelet aggregation rates and the serum concentrations of eicosanoid mediators after night-shift work and on day-shift work without preceding night-shift work (baseline).

Results:

Platelet aggregation did not differ from baseline levels after night-shift work. However, serum cyclooxygenase (COX)-metabolized eicosanoid mediators, particularly thromboxane (Tx) B₂ (a stable metabolite of TxA₂ and the most important marker of platelet activation), were significantly higher after the night-shift than at baseline (median 65.3 vs 180.4 ng/ml).

Conclusions:

Although platelet aggregation did not increase, there was an increase in serum COX-metabolized eicosanoid mediators such as TxB₂ in healthy medical staff after night-shift work. This platelet hypersensitivity may be one of the mechanisms underlying the significant association between night-shift work and adverse cardiovascular outcomes.

Association Between Sleep Timing, Obesity, Diabetes: The Hispanic Community Health Study/Study of Latinos (HCHS/SOL) Cohort Study

Study Objectives

Recent studies implicate inadequate sleep duration and quality in metabolic disease. Fewer studies have examined the timing of sleep, which may be important because of its potential impact on circadian rhythms of metabolic function. We examined the association between sleep timing and metabolic risk among Hispanic/Latino adults.

Methods

Cross-sectional data from community-based study of 13429 participants aged 18-74 years. People taking diabetic medications were excluded. Sleep timing was determined from self-reported bedtimes and wake times. Chronotype was defined as the midpoint of sleep on weekends adjusted for sleep duration on weekdays. Other measurements included body mass index (BMI), fasting glucose levels, estimated insulin resistance (HOMA-IR), glucose levels 2 hours post oral glucose ingestion, and hemoglobin A1c. Survey linear regression models tested associations between sleep timing and metabolic measures. Analyses were stratified by diabetes status and age-group when significant interactions were observed.

Results

Among participants with diabetes, fasting glucose levels were positively associated with bedtime (approximately +3%/hour later, p < .01) and midpoint of sleep (approximately +2%/hour later, p < .05). In participants with and without diabetes combined, HOMA-IR was positively associated with midpoint of sleep (+1.5%/hr later, p < .05), and chronotype (+1.2%/hour later, p < .05). Associations differed by age-group. Among those < 36 years, later sleep timing was associated with lower BMI, lower fasting glucose, and lower HbA1c, but the opposite association was observed among older participants.

Conclusions

Later sleep timing was associated with higher estimated insulin resistance across all groups. Some associations between sleep timing and metabolic measures may be age-dependent.

Effect of night-time temperatures on cause and age-specific mortality in London

Supplemental Digital Content is available in the text.

Background:

High ambient temperatures are associated with an acute increase in mortality risk. Although heat exposure during the night is anecdotally cited as being important, this has not been rigorously demonstrated in the epidemiological literature.

Methods:

We quantified the contribution of nighttime temperatures using time-series quasi-Poisson regression on cause and age-specific daily mortality in London between 1993 and 2015. Daytime and nighttime exposures were characterized by average temperatures between 9 am and 9 pm and between 4 am and 8 am, respectively, lagged by 7 days. We also examined the differential impacts of hot and cool nights preceded by very hot days. All models were adjusted for air quality, season, and day of the week. Nighttime models were additionally adjusted for daytime exposure.

Results:

Effects from nighttime exposure persisted after adjusting for daytime exposure. This was highest for stroke, RR (relative risk) = 1.65 (95% confidence interval (CI) = 1.27 to 2.14) estimated by comparing mortality risk at the 80th and 99th temperature percentiles. Compared to daytime exposure, nighttime exposure had a higher mortality risk on chronic ischemic and stroke and in the younger age groups. Respiratory mortality was most sensitive to daytime temperatures. Hot days followed by hot nights had a greater mortality risk than hot days followed by cool nights.

Conclusions:

Nighttime exposures make an additional important contribution to heat-related mortality. This impact was highest on warm nights that were preceded by a hot day, which justifies the alert criteria in heat–health warning system that is based on hot days followed by hot nights. The highest mortality risk was from stroke; targeted interventions would benefit patients most susceptible to stroke.

Association between shift work and microalbuminuria: data from KNHANES(2012-2014)

Background

Shift work disturbs workers’ biological clocks and this condition can cause various health problems including cardiovascular disease. The elevated albuminuria level has been significantly associated with the risk of the cardiovascular disease even within a normal reference range. Therefore, this study aimed to investigate the association between shift work and microalbuminuria.

Methods

Workers aged over 20 years from the fifth and sixth Korea National Health and Nutrition Examination Survey(KNHANES 2012–2014; n = 3000) were included in this analysis. The multiple logistic regression analysis was performed to determine the association between shift work and microalbuminuria stratified by gender.

Results

The prevalence of microalbuminuria in male subjects was higher among day workers, but the difference was not significant. However, the prevalence of microalbuminuria among females was higher in shift workers with statistical significance. For female, the Odds ratio of microalbuminuria in shift workers was significantly higher with 1.86 (95% CI 1.02–3.39) compared with day workers. After dividing into 5 subgroups of the shift work pattern, the odds ratio of microalbuminuria for fixed night shift was significantly higher at 4.68 (95% CI 1.29–17.00) compared with day workers.

Conclusions

This study showed that shift work was associated with microalbuminuria in female workers. Especially we found out the association between fixed night shift and microalbuminuria in female workers.

Job stress and behavioral characteristics in relation to coronary heart disease risk among Japanese police officers

This study examined the association between job-related behavioral characteristics and the risk of coronary heart diseases (CHD) in Japanese male police officers. Compared to office clerks, police officers exhibited greater age-related increases of the prevalence of CHD risk factors, and a clustering number of CHD risk factors was significantly higher in the group of those over 45 yr of age. Among the police officers, coronary-prone behavior was more frequent than that seen in office clerks. The police officers with coronary-prone behavior tended to engage in shift work and to work overtime more; yet they were less likely to perceive job stress and to express the relevant physical and psychological symptoms than those without coronary-prone behavior. The subjects with such behavioral characteristics had a significantly greater number of CHD risk factors. In a multiple regression analysis, coronary-prone behavior together with age, social support, walking hours per day, and amount of alcohol consumption were selected as significant determinants of a cluster of CHD risk factors. These results suggest that coronary-prone behavior may contribute to the higher prevalence of CHD risk factors in police officers via leading the long working hours and the work-related unfavorable lifestyles, such as alcohol drinking and physical inactivity.

Akt1 Controls the Timing and Amplitude of Vascular Circadian Gene Expression

The AKT signaling pathway is important for circadian rhythms in mammals and flies ( Drosophila). However, AKT signaling in mammals is more complicated since there are 3 isoforms of AKT, each performing slightly different functions. Here we study the most ubiquitous AKT isoform, Akt1, and its role at the organismal level in the central and vascular peripheral clocks. Akt1^-/- mice exhibit relatively normal behavioral rhythms with only minor differences in circadian gene expression in the liver and heart. However, circadian gene expression in the Akt1^-/- aorta, compared with control aorta, follows a distinct pattern. In the Akt1^-/- aorta, positive regulators of circadian transcription have lower amplitude rhythms and peak earlier in the day, and negative circadian regulators are expressed at higher amplitudes and peak later in the day. In endothelial cells, negative circadian regulators exhibit an increased amplitude of expression, while the positive circadian regulators are arrhythmic with a decreased amplitude of expression. This indicates that Akt1 conditions the normal circadian rhythm in the vasculature more so than in other peripheral tissues where other AKT isoforms or kinases might be important for daily rhythms.

Circadian clocks, diets and aging

Diets and feeding regimens affect many physiological systems in the organism and may contribute to the development or prevention of various pathologies including cardiovascular diseases or metabolic syndromes. Some of the dietary paradigms, such as calorie restriction, have many well-documented positive metabolic effects as well as the potential to extend longevity in different organisms. Recently, the circadian clocks were put forward as integral components of the calorie restriction mechanisms. The circadian clocks generate the circadian rhythms in behavior, physiology, and metabolism; circadian disruption is associated with reduced fitness and decreased longevity. Here we focus on recent advances in the interplay between the circadian clocks and dietary paradigms. We discuss how the regulation of the circadian clocks by feeding/nutrients and regulation of nutrient signaling pathways by the clocks may contribute to the beneficial effects of calorie restriction on metabolism and longevity, and whether the circadian system can be engaged for future medical applications.

The Association Between Shift Work and Health Behavior: Findings from the Korean National Health and Nutrition Examination Survey

Background

Shift workers are increasing worldwide, and various negative health effects of shift work have been reported. This study aimed to evaluate the relationship between shift work and health behavior.

Methods

This cross-sectional study included a total of 11,680 Korean adults (6,061 men and 5,619 women) aged ≥20 years old who participated in the Fifth Korean National Health and Nutrition Examination Survey, 2010–2012. Multiple logistic regression analysis was performed to evaluate the association between shift work and health behavior after adjusting for covariates.

Results

In men, shift work was associated with an increased risk of inadequate sleep (odds ratio [OR], 1.18; 95% confidence interval [CI], 1.00 to 1.40) compared to day work. In women, shift work was associated with an increased risk of smoking (OR, 1.73; 95% CI, 1.34 to 2.22) and inadequate sleep (OR, 1.24; 95% CI, 1.05 to 1.47) compared to day work. In an age-stratified subgroup analysis, female shift workers aged ≥50 years old demonstrated an increased risk of smoking (OR, 5.55; 95% CI, 3.60 to 8.55), alcohol consumption (OR, 2.22; 95% CI, 1.53 to 3.23), and inadequate sleep (OR, 1.50; 95% CI, 1.10 to 2.05) compared to female day workers.

Conclusion

Shift work is associated with worse health behavior, and this is most evident in women aged ≥50 years. Targeted strategies to reduce the negative health effects of shift work should be implemented, with consideration of shift workers' demographic characteristics.

Association between depressive symptoms and morningness-eveningness, sleep duration and rotating shift work in Japanese nurses

Higher depressive symptoms have been reported in rotating shift workers compared with day workers. Depressive symptoms in adults who do not engage in night work have also been shown to be associated with chronotype and sleep duration. This study examines associations between depressive symptoms, morningness-eveningness (i.e. the degree to which people prefer to be active in the morning or the evening), sleep duration and rotating shift work. Japanese nurses (1252 day workers and 1780 rotating shift workers, aged 20-59) were studied using a self-administered questionnaire. The questionnaire covered depressive symptoms, morningness-eveningness, sleep habits and demographic characteristics of the participants. The Center for Epidemiologic Studies Depression Scale (CES-D) was used to determine the levels of depressive symptoms. A Japanese version of the Morningness-Eveningness Questionnaire (MEQ) was used to measure morningness-eveningness. The CES-D score of shift workers was significantly (p < 0.05) higher than that of day workers. The MEQ score was significantly (p < 0.05) lower (i.e. greater eveningness) in shift workers than in day workers. Sleep duration on the day shift was significantly (p < 0.05) shorter in shift workers than in day workers. Simple linear regression revealed that the MEQ score, sleep duration on the day shift and current work shift (i.e. rotating shift work) were significantly (p < 0.05) associated with the CES-D score. Multivariate linear regression indicated that greater eveningness and shorter sleep duration were independently associated with higher CES-D scores, while rotating shift work was not. These associations between the MEQ score, the sleep duration and the CES-D score were also confirmed in both day workers and shift workers when the groups were analyzed separately. These results suggest that greater eveningness and shorter sleep duration on the day shift were independently associated with higher levels of depressive symptoms, which may explain associations between rotating shift workers and depressive symptoms. These findings have important implications for the development of novel strategies for preventing poor mental health in day workers and rotating shift workers.

Shift work is associated with metabolic syndrome in male steel workers-the role of resistin and WBC count-related metabolic derangements

AIMS

There is increasing evidence linking a shift work schedule with various adverse health effects. The present study aimed to examine the relationship between shift work and the metabolic syndrome (MetS) in male steel workers, and also the possible mechanism of shift work-related metabolic derangements.

METHODS

A total of 1732 men aged 42 ± 8 years were enrolled in this cross-sectional study, including 862 day workers and 870 shift workers. Circulating levels of resistin were measured by ELISA using monoclonal specific antibodies.

RESULTS

The shift workers had higher rates of MetS and its components (central obesity, hypertension, and hypertriglyceridemia) than the day workers. In multiple logistic regression analysis, shift work was independently associated with MetS. In further analysis, the shift workers had elevated circulating levels of resistin (13 ± 10 vs. 10 ± 7 ng/mL) and total white blood cell (WBC) count (6.865 ± 1.819 vs. 6.304 ± 1.547 10⁹/L) than the day workers. In addition, both resistin level and total WBC count were significantly associated with shift work, MetS, and its components (body mass index, fasting glucose, triglyceride, and high-density lipoprotein-cholesterol levels), and plasma resistin levels were significantly associated with total WBC count (β = 0.34, p < 0.0001).

CONCLUSION

Shift work was independently associated with MetS in male steel workers. Resistin and WBC count were associated with shift work-related metabolic derangements.

Daily Eating Patterns and Their Impact on Health and Disease

Cyclical expression of cell-autonomous circadian clock components and key metabolic regulators coordinate often discordant and distant cellular processes for efficient metabolism. Perturbation of these cycles, either by genetic manipulation, disruption of light/dark cycles, or, most relevant to the human population, via eating patterns, contributes to obesity and dysmetabolism. Time-restricted feeding (TRF), during which time of access to food is restricted to a few hours, without caloric restriction, supports robust metabolic cycles and protects against nutritional challenges that predispose to obesity and dysmetabolism. The mechanism by which TRF imparts its benefits is not fully understood but likely involves entrainment of metabolically active organs through gut signaling. Understanding the relationship of feeding pattern and metabolism could yield novel therapies for the obesity pandemic.