Shift work, occupation and coronary heart disease over 6 years of follow-up in the Helsinki Heart Study

Chronic circadian rhythm disorder induces heart failure with preserved ejection fraction-like phenotype through the Clock-sGC-cGMP-PKG1 signaling pathway

Emerging evidence has documented that circadian rhythm disorders could be related to cardiovascular diseases. However, there is limited knowledge on the direct adverse effects of circadian misalignment on the heart. This study aimed to investigate the effect of chronic circadian rhythm disorder on heart homeostasis in a mouse model of consistent jetlag. The jetlag model was induced in mice by a serial 8-h phase advance of the light cycle using a light-controlled isolation box every 4 days for up to 3 months. Herein, we demonstrated for the first time that chronic circadian rhythm disorder established in the mouse jetlag model could lead to HFpEF-like phenotype such as cardiac hypertrophy, cardiac fibrosis, and cardiac diastolic dysfunction, following the attenuation of the Clock-sGC-cGMP-PKG1 signaling. In addition, clock gene knock down in cardiomyocytes induced hypertrophy via decreased sGC-cGMP-PKG signaling pathway. Furthermore, treatment with an sGC-activator riociguat directly attenuated the adverse effects of jetlag model-induced cardiac hypertrophy, cardiac fibrosis, and cardiac diastolic dysfunction. Our data suggest that circadian rhythm disruption could induce HFpEF-like phenotype through downregulation of the clock-sGC-cGMP-PKG1 signaling pathway. sGC could be one of the molecular targets against circadian rhythm disorder-related heart disease.

Assessing cardiovascular stress based on heart rate variability in female shift workers: a multiscale-multifractal analysis approach

Introduction

Sleep-wake cycle disruption caused by shift work may lead to cardiovascular stress, which is observed as an alteration in the behavior of heart rate variability (HRV). In particular, HRV exhibits complex patterns over different time scales that help to understand the regulatory mechanisms of the autonomic nervous system, and changes in the fractality of HRV may be associated with pathological conditions, including cardiovascular disease, diabetes, or even psychological stress. The main purpose of this study is to evaluate the multifractal-multiscale structure of HRV during sleep in healthy shift and non-shift workers to identify conditions of cardiovascular stress that may be associated with shift work.

Methods

The whole-sleep HRV signal was analyzed from female participants: eleven healthy shift workers and seven non-shift workers. The HRV signal was decomposed into intrinsic mode functions (IMFs) using the empirical mode decomposition method, and then the IMFs were analyzed using the multiscale-multifractal detrended fluctuation analysis (MMF-DFA) method. The MMF-DFA was applied to estimate the self-similarity coefficients, α(q, τ), considering moment orders (q) between -5 and +5 and scales (τ) between 8 and 2,048 s. Additionally, to describe the multifractality at each τ in a simple way, a multifractal index, MFI(τ), was computed.

Results

Compared to non-shift workers, shift workers presented an increase in the scaling exponent, α(q, τ), at short scales (τ < 64 s) with q < 0 in the high-frequency component (IMF1, 0.15-0.4 Hz) and low-frequency components (IMF2-IMF3, 0.04-0.15 Hz), and with q> 0 in the very low frequencies (IMF4, < 0.04 Hz). In addition, at large scales (τ> 1,024 s), a decrease in α(q, τ) was observed in IMF3, suggesting an alteration in the multifractal dynamic. MFI(τ) showed an increase at small scales and a decrease at large scales in IMFs of shift workers.

Conclusion

This study helps to recognize the multifractality of HRV during sleep, beyond simply looking at indices based on means and variances. This analysis helps to identify that shift workers show alterations in fractal properties, mainly on short scales. These findings suggest a disturbance in the autonomic nervous system induced by the cardiovascular stress of shift work.

Effectiveness of caffeine and blue-enriched light on cognitive performance and electroencephalography correlates of alertness in a spaceflight robotics simulation

Human cognitive impairment associated with sleep loss, circadian misalignment and work overload is a major concern in any high stress occupation but has potentially catastrophic consequences during spaceflight human robotic interactions. Two safe, wake-promoting countermeasures, caffeine and blue-enriched white light have been studied on Earth and are available on the International Space Station. We therefore conducted a randomized, placebo-controlled, cross-over trial examining the impact of regularly timed low-dose caffeine (0.3 mg per kg per h) and moderate illuminance blue-enriched white light (~90 lux, ~88 melEDI lux, 6300 K) as countermeasures, separately and combined, in a multi-night simulation of sleep-wake shifts experienced during spaceflight among 16 participants (7 F, ages 26-55). We find that chronic administration of low-dose caffeine improves subjective and objective correlates of alertness and performance during an overnight work schedule involving chronic sleep loss and circadian misalignment, although we also find that caffeine disrupts subsequent sleep. We further find that 90 lux of blue-enriched light moderately reduces electroencephalogram (EEG) power in the theta and delta regions, which are associated with sleepiness. These findings support the use of low-dose caffeine and potentially blue-enriched white light to enhance alertness and performance among astronauts and shiftworking populations.

Association between disruption of circadian activity rhythms and obesity

This cross-sectional study aimed to elucidate the association between disruption of circadian activity rhythms and obesity-related indices. This study included 69 older participants (male, n = 36; female, n = 33), and disruption of circadian activity rhythms in daily life was assessed using the cosinor method based on physical activity data. The daily physical activity data were fitted to a cosine curve to estimate the peak phase (acrophase), and the difference in the peak phase (time) for each day was determined. The standard deviation (SD) of the mean peak phase differences over 6 days was obtained. The higher the SD value, the more disturbed the circadian rhythm of activity. Based on the calculated values, the samples were divided into tertiles (small, medium, and large). A significant positive correlation was found between Log SD and body fat percentage on the disruption of circadian activity rhythms and obesity-related indices. In addition, positive associations were observed among body mass, body mass index, and Log SD. However, these associations were not observed in women. These results suggest that disruption of circadian activity rhythms is associated with obesity-related indices and may differ according to sex.

Exploring Australian night shift workers' food experiences within and outside of the workplace: a qualitative photovoice study

OBJECTIVE

Night shift workers are at a 20 to 40 % increased risk of metabolic diseases, which may be associated with their disrupted eating patterns. This qualitative study explores factors that influence night shift workers' eating habits, within and outside of the workplace, to identify target areas for health promotion strategies.

PARTICIPANTS AND SETTING

Eligible participants resided in Australia, working at least three overnight shifts per month.

DESIGN

The photovoice method was used, whereby participants were asked to take photos that represent their typical eating habits. These photos were incorporated as prompts in a semi-structured interview, which explored factors influencing eating habits on night shifts and days-off and perceptions and enablers to healthy eating.

RESULTS

Ten participants completed the study. Thematic analysis generated four main themes, which were mapped onto the Social Ecological Model (SE Model). Aligned with the SE Model, our results show night shift workers' eating habits are influenced by intrapersonal, interpersonal and (work) organisational levels. Participants reported that at work, appropriate food preparation facilities are required to enable healthy food choices. Poor shift work rostering leads to prolonged fatigue on days-off, limiting their ability and motivation to engage in healthy eating. Consequently, night shift workers seem to require additional supports from their social networks and enhanced food literacy skills, in order to adopt/ maintain healthy eating behaviours.

CONCLUSIONS

Night shift work creates individual and environmental barriers to healthy eating, which are present during and outside of work. Health promotion strategies for this population should include multiple approaches to address these barriers.

The Prolonged Effect of Shift Work and the Impact of Reducing the Number of Nightshifts on Arterial Stiffness-A 4-Year Follow-Up Study

AIM

To assess changes in blood pressure (BP) and arterial stiffness among 84 rotating shift and 25 dayworkers (control subjects) at two industrial plants during a 4-year follow-up, and to assess changes in outcome variables among shift workers at the two plants after a reduction in the number of night shifts during the last year of follow-up in one of the plants.

METHODS

We collected demographic data using a questionnaire, examined systolic and diastolic blood pressure (sBP, dBP), central systolic and diastolic aorta pressure (cSP, cDP), augmentation pressure (AP), central pulse pressure (cPP), and pulse wave velocity (PWV). We registered sleep quality. The last 4-14 months of follow-up one plant implemented a 12-week shift plan reducing the total number of night shifts and consecutive night shifts from 16.8 to 14 and from 7.2 to 4. To assess differences in change of outcomes between study groups we applied linear mixed models.

RESULTS

The dayworkers were older, more hypertensive, reported less sleep disturbance, and smoked/snuffed less than the shift workers did. The adjusted annual increase in PWV was 0.34 m/s (95%CI, 0.22, 0.46) among shift workers and 0.09 m/s (95%CI, -0.05, 0.23) in dayworkers, yielding a significant difference of change of 0.25 m/s (95%CI, 0.06, 0.43). No significant differences were found between the two groups of shift workers in any cardiovascular disease (CVD) outcome during the last year of follow-up.

CONCLUSIONS

Shift work in industry is associated with arterial stiffness, reflecting an increased risk of future CVD. No significant changes in arterial stiffness were identified as a consequence of a small reduction in the number of night shifts and consecutive night shifts.

Occupational Disease in New York State: An Update

An assessment of occupational disease in New York State was undertaken that partially replicated and expanded earlier work from 1987. Utilizing an expanded conception of occupational disease, the assessment used a variety of data sources and methods to provide estimates of mortality and morbidity of occupational disease; workers exposed to specific workplace hazards; disparities in occupational disease among racial/ethnic groups and gender; costs and distribution of costs of occupational disease; and accessible occupational medical resources. Examples of the pathways work may impact health in some of the major health issues of current import including stress-related health conditions; substance use; and overweight/obesity were included. The report contains recommendations for addressing the problem of occupational disease in New York State and advocates for the convening of a statewide group to develop an occupational disease prevention agenda.

Shift work and nonalcoholic fatty liver disease incidence among Chinese rail workers: a 4-year longitudinal cohort study

PURPOSE

Occupational harmful factors, such as shift work, are attracting increasing attention as a potential cause of nonalcoholic fatty liver disease (NAFLD). In this study, we aimed to identify the association between shift work and NAFLD incidence in Chinese rail population.

METHODS

A cohort study was conducted among 14,112 rail workers for 4-year follow-up. Shift work frequency and other potential variables were recorded by questionnaires, including demographic, lifestyle, and occupation information. Besides, body mass index, blood pressure, fasting blood glucose, total cholesterol, triglyceride, alanine aminotransferase, and aspartate aminotransferase were measured by anthropometric measurement and blood test. Diagnosis of new NAFLD case was based on abdominal ultrasonography. Cox proportional hazards regression model was used to determine whether shift work has effect on occurrence of NAFLD.

RESULTS

The incidence of NAFLD was 30.43% in total subjects. After adjustment for possible confounders, the RRs of NAFLD were 1.069 (95% CI 0.998-1.146) and 1.179 (95% CI 1.059-1.312) in occasionally shift work group and frequently shift work group respectively, compared to the seldom shift work group. In stratified analyses, the RRs of NAFLD incidence linked to shift work exposure seems increase among female and elder. The results of three sensitivity analyses were similar with main analysis.

CONCLUSIONS

This research provided further evidence of positive harmful effect of shift work on NAFLD incidence in Chinese rail workers, particularly in frequently shift work population. The risk estimate of shift work on NAFLD was higher in female and elder.

Shift Work Disorder Index: initial validation and psychosocial associations in a sample of nurses

STUDY OBJECTIVES

Shift work is common yet does not always result in Diagnostic and Statistical Manual of Mental Disorders, fifth edition (DSM-5)-defined shift work sleep disorder (SWD). This study reports on the reliability and validity of the DSM-5 informed Shift Work Disorder Index (SWDI), the presence of probable SWD in nurses, and demographic, sleep, and psychosocial correlates.

METHODS

Nurses (n = 454) completed the SWDI, psychosocial, and demographic questionnaires. Of the sample, n = 400 completed 14 days of sleep diaries, actigraphy, and additional questionnaires.

RESULTS

The global SWDI demonstrated excellent internal consistency (α = .94), as well as good convergent and divergent validity in the nurse sample. Thirty-one percent of nurses were past-month shift workers, with 14% (ie, 44% of shift workers) having probable SWD based on SWDI. Nurses who worked shift work and/or met SWD criteria were more likely to be younger and unmarried and less likely to have children than day workers and reported greater evening chronotype, insomnia, nightmares, and sleep-related impairment, greater depression, anxiety, posttraumatic stress, and perceived stress symptoms, as well as later and more variable sleep midpoint (actigraphy), shorter sleep duration (actigraphy, diaries), and lower sleep efficiency (diaries).

CONCLUSIONS

The SWDI is an efficient and valid self-report assessment of DSM-5-defined SWD. Shift work and/or SWD were prevalent and associated with worse sleep and psychosocial health, particularly among nurses with probable SWD.

CITATION

Taylor DJ, Dietch JR, Wardle-Pinkston S, et al. Shift Work Disorder Index: initial validation and psychosocial associations in a sample of nurses. J Clin Sleep Med. 2022;18(10):2339-2351.

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.

OUP accepted manuscript

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.

Does rearranging meal times at night improve cardiovascular risk factors? An Australian pilot randomised trial in night shift workers

BACKGROUND AND AIMS

Shift workers face an increased risk of cardiovascular disease (CVD), type-2 diabetes and obesity. Eating during the night is a likely contributing factor, as it coincides with the time at which postprandial metabolism is least efficient. In this pilot randomised crossover trial, we examine the effects of a short overnight fast on CVD risk markers (primarily postprandial triglyceride and glucose response) of night shift workers.

METHODS AND RESULTS

Night shift workers with abdominal obesity underwent 4-week intervention and control periods, separated by ≥ 2 weeks washout. In the intervention period, an overnight fast (0100 h-0600 h) was implemented, by redistributing 24-h energy intake. Usual dietary habits were followed in the control period. Outcomes between intervention and control were compared using mixed effects linear regression models. Nineteen adults completed the trial [13 females, mean (±SD) age 41 ± 10 years, BMI 30.7 ± 5.7 kg/m²]. Postprandial triglyceride and glucose response post intervention were not different to post control. The overnight fast was well-tolerated by participants with an adherence rate of 95%, assessed by weekly 24-h dietary recalls. Exploratory analysis indicates lower mean body weight post intervention compared to post control (mean difference: -0.9 kg, 95% CI: -1.3 to -0.4).

CONCLUSIONS

Night shift workers who habitually ate during their night shifts were able to rearrange their meal times to maintain a small overnight fast, which may have promoted small weight changes. This warrants further investigation into the role of meal timing in mitigating the metabolic consequences of night shift work.

TRIAL REGISTRATION

Australian New Zealand Clinical Trials Registry (http://anzctr.org.au/) registered on the 30th May 2017 (ACTRN12617000791336).

Metabolomic Profiles of Shift Workers and Day Workers: A Cross-Sectional Study

OBJECTIVE

The purpose of this study was to characterize the metabolomic profiles of shift workers and day workers and to discover the effect of shift work on workers' metabolic health.

METHODS

A total of 824 participants aged 25 to 55 years were recruited, and 485 (275 shift workers and 210 day workers) completed the study. The mean age of the shift workers was 37.32 (5.53) years old, and that of day workers was 36.50 (7.83) years old. Serum and salivary samples were collected for the detection of key biochemical indicators (melatonin, cholesterol, and low-density lipoprotein cholesterol) and for metabolome profile analyses.

RESULTS

Compared with female day workers, female shift workers had a higher BMI, waist circumference, and hip circumference. Correspondingly, we identified 76 significant metabolites (false discovery rate < 0.05) in shift workers, including L-tryptophan, acylcarnitines, and several fatty acids. Three pathways that presented significant differences were biosynthesis of unsaturated fatty acids, linoleic acid metabolism, and ubiquinone and other terpenoid-quinone biosynthesis.

CONCLUSIONS

Compared with day workers, shift workers were more prone to weight gain and central obesity and were at a higher risk for impaired lipid metabolism with disrupted circadian rhythms.

Association of working shifts, inside and outside of healthcare, with severe COVID-19: an observational study

BACKGROUND

Health and key workers have elevated odds of developing severe COVID-19; it is not known, however, if this is exacerbated in those with irregular work patterns. We aimed to investigate the odds of developing severe COVID-19 in health and shift workers.

METHODS

We included UK Biobank participants in employment or self-employed at baseline (2006-2010) and with linked COVID-19 data to 31st August 2020. Participants were grouped as neither a health worker nor shift worker (reference category) at baseline, health worker only, shift worker only, or both, and associations with severe COVID-19 investigated in logistic regressions.

RESULTS

Of 235,685 participants (81·5% neither health nor shift worker, 1·4% health worker only, 16·9% shift worker only, and 0·3% both), there were 580 (0·25%) cases of severe COVID-19. The odds of severe COVID-19 was higher in health workers (adjusted odds ratio: 2·32 [95% CI: 1·33, 4·05]; shift workers (2·06 [1·72, 2·47]); and in health workers who worked shifts (7·56 [3·86, 14·79]). Being both a health worker and a shift worker had a possible greater impact on the odds of severe COVID-19 in South Asian and Black and African Caribbean ethnicities compared to White individuals.

CONCLUSIONS

Both health and shift work (measured at baseline, 2006-2010) were independently associated with over twice the odds of severe COVID-19 in 2020; the odds were over seven times higher in health workers who work shifts. Vaccinations, therapeutic and preventative options should take into consideration not only health and key worker status but also shift worker status.

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.

Socioeconomic and demographic predictors of high blood pressure, diabetes, asthma and heart disease among adults engaged in various occupations: evidence from India

In India, non-communicable diseases (NCDs) accounted for nearly 62% of all deaths in 2016. Four NCDs - high blood pressure, diabetes, asthma and heart disease - together accounted for over 34% of these deaths. Using data from two rounds of the India Human Development Surveys (IHDSs), levels and changes in the prevalence rates of the four NCDs (based on diagnosed cases) among adults aged 15-69 years in India between 2004-05 and 2011-12 were examined by socioeconomic and demographic factors and for five broad occupation categories. The socioeconomic and demographic risk factors for each of these NCDs were determined using multiple linear logistic regression analysis of pooled data from two rounds of the IHDS. The results showed that while urban residence, age, female sex and education were associated with higher odds of high blood pressure, diabetes and heart disease, household economic status was associated with higher odds for all four NCDs. Furthermore, increased higher odds of high blood pressure, diabetes and heart disease were found for the legislator/senior official/professional occupation group compared with non-workers. Skilled agricultural/elementary workers had lower odds of high blood pressure, diabetes, asthma and heart disease. Craft/machine-related trade workers had higher odds of high blood pressure and diabetes, and reduced odds of asthma and heart disease. Compared with non-workers, the odds ratios for asthma were lower for all other occupational categories. During the two study decades, the Government of India implemented several programmes designed to improve the health and well-being of its people. However, more focused attention on the adult population is needed, and special attention should be paid to the issue of the occupational health of the working population through the strict implementation of work place safety protocols and the removal of potential health hazards.

Does Weekend Catch-up Sleep Affect High-Sensitivity C-Reactive Protein Levels Among Korean Workers?: A Cross-Sectional Study Using KNHANES

OBJECTIVE

We sought to determine whether weekend catch-up sleep (CUS) influenced serum high-sensitivity C-reactive protein (hs-CRP) levels in workers.

METHODS

We analyzed the Korean National Health and Nutrition Examination Survey (2016) data from 3304 workers. Univariate and multivariate logistic regression analyses were used to calculate odds ratios and 95% confidence intervals based on serum hs-CRP cut-off values of 1.0 and 3.0 mg/L, respectively.

RESULTS

We found that at least 1-hour and less than 2 hours of weekend CUS reduced the risk of elevated hs-CRP levels (odds ratio 0.80, 95% confidence interval 0.64 to 0.99) in multivariate logistic regression analysis.

CONCLUSION

CUS may reduce serum hs-CRP levels in workers, thereby reducing the risk of cardiovascular disease.

Working Time Society consensus statements: Psychosocial stressors relevant to the health and wellbeing of night and shift workers

This consensus report summarizes the negative impact of work-related psychosocial factors and job stressors on the health and wellbeing of shift workers. Psychosocial factors may (a) directly affect work schedules or (b) mediate or moderate relationships between work schedules, circadian factors, and health. In this paper, prominent psychosocial models (e.g. Job Strain and Effort-Reward Imbalance) are used to help assess detrimental effects, including pathophysiologic outcomes. Several studies indicate the psychosocial environment can be more problematic for shift workers compared to regular day workers. This is likely due to shift worker's experiencing greater risks of low job control, high physical work demands, lower support from supervisors, and greater levels of over-commitment. Workplace violence is another frequently encountered psychosocial stressor for shift workers more likely to be in regular contact with the general public, such as police officers, security personnel, professional drivers, and other service employees being at elevated risk. A large body of literature confirms night and irregular shift schedules increase risk for injury. Non-diurnal schedules can trigger and worsen such incidents, especially under unsafe conditions. The problem of workplace violence for shift workers, in terms of severity and consequences, is probably underestimated, especially when present among other occupational stressors. Practical considerations and recommendations for action to mitigate the detrimental effects of psychosocial stressors on night and shift workers are presented.

Does modifying the timing of meal intake improve cardiovascular risk factors? Protocol of an Australian pilot intervention in night shift workers with abdominal obesity

INTRODUCTION

Shift work is an independent risk factor for cardiovascular disease (CVD). Shift workers who are awake overnight and sleep during the day are misaligned with their body's endogenous circadian rhythm. Eating at night contributes to this increased risk of CVD by forcing the body to actively break down and process nutrients at night. This pilot study aims to determine whether altering meal timing overnight, in a shift working population, will impact favourably on modifiable risk factors for CVD (postprandial bplasma lipids and glucose concentration).

METHODS AND ANALYSIS

A randomised cross-over study with two 4-week test periods, separated by a minimum of a 2-week washout will be undertaken. The effectiveness of redistributing energy intake overnight versus ad libitum eating patterns on CVD risk factors will be examined in night shift workers (n=20), using a standard acute test meal challenge protocol. Primary outcomes (postprandial lipids and glucose) will be compared between the two conditions: post-intervention and post-control period using analysis of variance. Potential effect size estimates to inform sample size calculations for a main trial will also be generated.

ETHICS AND DISSEMINATION

Ethics approval has been granted by the Monash University Human Research Ethics Committee (2017-8619-10329). Outcomes from this study will determine whether eliminating food intake for a defined period at night (1-6 am) impacts favourably on metabolic risk factors for CVD in night shift workers. Collective results from this novel trial will be disseminated through peer-reviewed journals, and national and international presentations. The results are essential to inform health promotion policies and guidelines for shift workers, especially those who aim to improve their metabolic health.

TRIAL REGISTRATION NUMBER

ACTRN12617000791336; Pre-results.

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.

Alteration in eating habits among shift workers of a poultry processing plant in southern Brazil

The relationship between shift work and the eatinghabits of workers was investigated in a slaughterhouse in southern Brazil. It involved a cross-sectional study with 1,206 workers of both sexes between 18 and 50 years of age. A standardized questionnaire was used to gather demographic, socioeconomic, work shift and eating habit information. The shift of work was categorized into daytime and nighttime, based on the starting and ending times of the shift. The eating habits of workers were evaluated as follows: number and type of meals eaten during the 24 hours of a normal day, the inappropriateness of the hoursof these meals and the dietaryrisk score. This was built on the risk score of the weekly consumption of 13 food items. After adjusting for potential confounders, non-Caucasian and younger male workers were more likely to manifest eating risk habits. Nighttimeshift workers consumed ahigher number of meals/day with greater inappropriateness of meal times than daytimeshift workers. The night shift can negatively influence the eating habits of workers of that shift.

Shift Work: Disrupted Circadian Rhythms and Sleep-Implications for Health and Well-Being

PURPOSE OF REVIEW

Our 24/7 society is dependent on shift work, despite mounting evidence for negative health outcomes from sleep displacement due to shift work. This paper reviews short- and long-term health consequences of sleep displacement and circadian misalignment due to shift work.

RECENT FINDINGS

We focus on four broad health domains: metabolic health; risk of cancer; cardiovascular health; and mental health. Circadian misalignment affects these domains by inducing sleep deficiency, sympathovagal and hormonal imbalance, inflammation, impaired glucose metabolism, and dysregulated cell cycles. This leads to a range of medical conditions, including obesity, metabolic syndrome, type II diabetes, gastrointestinal dysfunction, compromised immune function, cardiovascular disease, excessive sleepiness, mood and social disorders, and increased cancer risk.

SUMMARY

Interactions of biological disturbances with behavioral and societal factors shape the effects of shift work on health and well-being. Research is needed to better understand the underlying mechanisms and drive the development of countermeasures.

Cumulative exposure to shift work and sickness absence: associations in a five-year historic cohort

BACKGROUND

Exposure to shift work has been associated with negative health consequences, although the association between shift work and sickness absence remains unclear. The aim of this study is to investigate associations between cumulative exposure to shift work and sickness absence among ground staff employees of an airline company.

METHODS

This study used data from the MORE (Monitoring Occupational Health Risks in Employees) cohort, which is a 5-year historic cohort. The population of the present study consisted of 7562 ground staff employees. For each employee, work schedules and sickness absence days between 2005 and 2009 were obtained from company records. For the exposure to different shift schedule types and to the cumulative number of night shifts, the association with long-term sickness absence (>7 consecutive sickness absence days) and the number of sickness absence episodes during 2009, was calculated using logistic and Poisson regression analyses. Socio-demographic variables, work-related variables, job classification variables, and previous sickness absence days were regarded as confounders.

RESULTS

After adjusting for previous sickness absence and job classification variables, only the group of employees that switched into working in a three-shift schedule, showed a significantly increased risk for long-term sickness absence (OR = 1.31, 95%CI 1.02-1.69). Night shift exposure was not significantly associated with long-term sickness absence. Exposure to shift work was negatively associated with more sickness absence episodes. Employees who were exposed to more than 46 night shifts also showed a lower risk for more sickness absence episodes. Subgroup analyses showed that single employees and employees without children had an increased risk for long-term sickness absence when exposed to a three-shift schedule, and when they had changed between shift schedule types.

CONCLUSIONS

Cumulative exposure to shift work proved to be negatively associated with more sickness absence episodes, and was not associated with more long-term sickness absence, although selection bias could not be ruled out. Future research should explore the influence of household composition, and take into account both previous sickness absence and psychosocial and physical work factors to obtain a better estimation of the association between shift work and sickness absence.

Study of shift work and risk of coronary events

Background: The effects of shift work on coronary heart diseases (CHD) are well described. Most of the studies on coronary events in shift workers are supportive of the hypothesis that they are at increased risk.

Objective: The objective of this study was to investigate the relation shift work has to risk of CHD in a cohort of men from different Asian races working in a fertilizer plant in the Middle East. Design: This is a case series of cohort study.

Subjects: The medical records for 2562 staff employed at the plant, from the start of the company in 1972 till 2003, were surveyed. Of these, 648 were shift workers and 1914 were daytime workers. A total of 223 employees had cardiovascular event.

Methods: For each case we recorded the date and age at start of employment, and the age at the time of diagnosis. Data from their last medical examination in the company were used to calculate their BMI, and to register whether they were smokers, had diabetes, or were senior or intermediate staff. Univariate and multivariate statistical analyses were performed.

Results: The incidence of CHD is significantly higher in shift workers (13.5%) compared with the daytime workers (7.1%). Also, there was a statistically significant difference between shift workers and daytime workers concerning hypertension and cerebrovascular incidents.

Conclusion: Our results suggest the possibility of an overall relationship between shift work and cardiovascular diseases.

Klokwerk + study protocol: An observational study to the effects of night-shift work on body weight and infection susceptibility and the mechanisms underlying these health effects

BACKGROUND

Night-shift work may cause severe disturbances in the worker's circadian rhythm, which has been associated with the onset of health problems and diseases. As a substantial part of the workforce is exposed to night-shift work, harmful aspects of night-shift work should not be overlooked. The aim of the Klokwerk + study is to study the effects of night-shift work on body weight and infection susceptibility and the mechanisms underlying these health effects. First, we will study the relation between night-shift work exposure and body weight and between night-shift work exposure and infection susceptibility. Second, we will examine the mechanisms linking night-shift work exposure to body weight and infection susceptibility, with a specific focus on sleep, physical activity, diet, light exposure, vitamin D level, and immunological factors. Lastly, we will focus on the identification of biomarkers for chronic circadian disturbance associated with night-shift work.

METHODS/DESIGN

The design of this study is a prospective observational cohort study consisting of 1,960 health care workers aged 18-65 years. The study population will consist of a group of night-shift workers and an equally sized group of non-night-shift workers. During the study, there will be two measurement periods. As one of the main outcomes of this study is infection susceptibility, the measurement periods will take place at approximately the first (September/October) (T0) and the last month (April/May) (T1, after 6 months) of the flu season. The measurements will consist of questionnaires, anthropometric measurements, a smartphone application to determine infection susceptibility, food diaries, actigraphy, light sensors, and blood sample analyses.

DISCUSSION

The Klokwerk + study will contribute to the current need for high-quality data on the health effects of night-shift work and its underlying behavioral and physiological mechanisms. The findings can be the starting point for the development of interventions that prevent negative health effects caused by night-shift work. In addition, the identification of biomarkers indicative of loss of homeostasis due to circadian disturbance may be an important asset in monitoring the effects of such interventions.

Cardiometabolic Health in Submariners Returning from a 3-Month Patrol

Confined space, limited exercise equipment, rotating shift work and reduced sleep may affect cardiometabolic health in submariners. To test this hypothesis, 53 male U.S. Submariners (20–39 years) were studied before and after a 3-month routine submarine patrol. Measures included anthropometrics, dietary and physical activity, biomarkers of cardiometabolic health, energy and appetite regulation, and inflammation. Before deployment, 62% of submariners had a body fat % (BF%) ≥ 25% (obesity), and of this group, 30% met the criteria for metabolic syndrome. In obese volunteers, insulin, the homeostatic model assessment of insulin resistance (HOMA-IR), leptin, the leptin/adiponectin ratio, and pro-inflammatory chemokines growth-related oncogene and macrophage-derived chemokine were significantly higher compared to non-obese submariners. Following the patrol, a significant mean reduction in body mass (5%) and fat-mass (11%) occurred in the obese group as a result of reduced energy intake (~2000 kJ) during the patrol; and, independent of group, modest improvements in serum lipids and a mean reduction in interferon γ-induced protein 10 and monocyte chemotactic protein 1 were observed. Since 43% of the submariners remained obese, and 18% continued to meet the criteria for metabolic syndrome following the patrol, the magnitude of weight loss was insufficient to completely abolish metabolic dysfunction. Submergence up to 3-months, however, does not appear to be the cause of obesity, which is similar to that of the general population.

The relationship between night work and involuntary weight change: data from the fifth Korea National Health and Nutrition Examination Survey (KNHANES 2010-2012)

Background

Previous studies on the association between shift or night work and weight change have been focused on finding the risk of weight gain caused by shift or night work. In this study, we aimed to reveal the risk of weight gain and weight loss associated with night work by using a nationwide representative data.

Methods

This study was performed on 1605 full-time wage workers between the age of 20 and 69 based on the fifth Korea National Health and Nutrition Examination Survey (KNHANES 2010–2012). The association between night work and involuntary weight change in the previous year was divided into the categories of weight gain and weight loss and studied with modifications in socio-demographic variables, health behavior-related variables, and occupational characteristic variables.

Results

The participants working in night work accounted for 10.6 % of total study participants (male; 11.9 %, female 7.4 %). Workers who worked more than 48 hours per week on average accounted for 41.6 % of the total study participants (male; 46.3 %, female 29.1 %).

Odds ratio (OR) of weight loss associated with night work in male workers was 0.34 (95 % confidence interval (CI) 0.16–0.76) after controlling for several related factors. OR of weight loss associated with night work in female workers with long working hours was 1.95 (95 % CI 0.47–80.86) and that of weight gain was 2.83 (95 % CI 0.12–69.83) after adjusting associated factors.

Conclusions

In this cross-sectional study with national representative sample, night work may lower the risk of weight loss in male workers and induce weight change (weight loss or weight gain) in female workers with long working hours. Therefore, future studies with cohort study design for night workers are needed to reveal the mechanisms and health effects of weight change associated with night work and establish proper management solutions with health and labor policies for Korean night workers.

Circadian misalignment affects sleep and medication use before and during spaceflight

Sleep deficiency and the use of sleep-promoting medication are prevalent during spaceflight. Operations frequently dictate work during the biological night and sleep during the biological day, which contribute to circadian misalignment. We investigated whether circadian misalignment was associated with adverse sleep outcomes before (preflight) and during spaceflight missions aboard the International Space Station (ISS). Actigraphy and photometry data for 21 astronauts were collected over 3,248 days of long-duration spaceflight on the ISS and 11 days prior to launch (n=231 days). Sleep logs, collected one out of every 3 weeks in flight and daily on Earth, were used to determine medication use and subjective ratings of sleep quality. Actigraphy and photometry data were processed using Circadian Performance Simulation Software to calculate the estimated endogenous circadian temperature minimum. Sleep episodes were classified as aligned or misaligned relative to the estimated endogenous circadian temperature minimum. Mixed-effects regression models accounting for repeated measures were computed by data collection interval (preflight, flight) and circadian alignment status. The estimated endogenous circadian temperature minimum occurred outside sleep episodes on 13% of sleep episodes during preflight and on 19% of sleep episodes during spaceflight. The mean sleep duration in low-Earth orbit on the ISS was 6.4±1.2 h during aligned and 5.4±1.4 h (P<0.01) during misaligned sleep episodes. During aligned sleep episodes, astronauts rated their sleep quality as significantly better than during misaligned sleep episodes (66.8±17.7 vs. 60.2±21.0, P<0.01). Sleep-promoting medication use was significantly higher during misaligned (24%) compared with aligned (11%) sleep episodes (P<0.01). Use of any medication was significantly higher on days when sleep episodes were misaligned (63%) compared with when sleep episodes were aligned (49%; P<0.01). Circadian misalignment is associated with sleep deficiency and increased medication use during spaceflight. These findings suggest that there is an immediate need to deploy and assess effective countermeasures to minimize circadian misalignment and consequent adverse sleep outcomes both before and during spaceflight.

The relationship between quality of sleep and night shift rotation interval

BACKGROUND

Shift work is closely related with workers' health. In particular, sleep is thought to be affected by shift work. In addition, shift work has been reported to be associated with the type or direction of shift rotation, number of consecutive night shifts, and number of off-duty days. We aimed to analyze the association between the night shift rotation interval and the quality of sleep reported by Korean female shift workers.

METHODS

In total, 2,818 female shift workers from the manufacturing industry who received an employee physical examination at a single university hospital from January to August in 2014 were included. Subjects were classified into three groups (A, B, and C) by their night shift rotation interval. The quality of sleep was measured using the Korean version of the Pittsburgh Sleep Quality Index (PSQI). Descriptive analysis, univariate logistic regression, and multivariate logistic regression were performed.

RESULTS

With group A as the reference, the odds ratio (OR) for having a seriously low quality of sleep was 1.456 (95% CI 1.171-1.811) and 2.348 (95% CI 1.852-2.977) for groups B and C, respectively. Thus, group C with the shortest night shift rotation interval was most likely to have a low quality of sleep. After adjustment for age, obesity, smoking status, alcohol consumption, exercise, being allowed to sleep during night shifts, work experience, and shift work experience, groups B and C had ORs of 1.419 (95% CI 1.134-1.777) and 2.238 (95% CI 1.737-2.882), respectively, compared to group A.

CONCLUSION

Our data suggest that a shorter night shift rotation interval does not provide enough recovery time to adjust the circadian rhythm, resulting in a low quality of sleep. Because shift work is influenced by many different factors, future studies should aim to determine the most optimal shift work model and collect accurate, prospective data.

Evaluation of the effect of shift work on serum cholesterol and triglyceride levels

Background:

Working outside daylight hours (7 am to 7 pm) is called shift work. Shift work is a common practice in many industries and factories such as steel industries, petroleum industries, power plants, and in some services such as medicine and nursing and police forces, in which professionals provide services during day and night.

Objectives:

Considering the contradictory reports of different studies, we decided to evaluate the effect of shift work on cholesterol and triglyceride (TG) levels through a historical cohort on steel industry workers.

Patients and Methods:

This retrospective cohort study was performed on all the staff of Isfahan’s Mobarakeh Steel Company between years 2002 and 2011. There were 5773 participants in this study. Data were collected from the medical records of the staff using the census method. For analysis of data, generalized estimating equation (GEE) regression was used.

Results:

The results showed a significant difference in cholesterol levels between shift workers and day workers on the first observation (P < 0.001), yet no such difference was observed for TG (P = 0.853). Moreover, the results showed that the variables of age, work experience and BMI were not similar between shift workers and day workers. Therefore, to remove the effect of such variables, we used GEE regression. Despite the borderline difference of cholesterol between regular shift workers and day workers, this correlation was not statistically significant (P = 0.051). The results for TG also showed no correlation with shift work.

Conclusions:

According to the findings of this study, there is no relationship between shift work and changes in serum TG and cholesterol. The lack of relationship can be due to shift plans for shift workers, nutrition, or the “Healthy Heart project” at Isfahan Mobarakeh Steel Company.

Duration of Time on Shift Before Accidental Blood or Body Fluid Exposure for Housestaff, Nurses, and Technicians

Background.

Shift work has been found to be associated with an increased rate of errors and accidents among healthcare workers (HCWs), but the effect of shift work on accidental blood and body fluid exposure sustained by HCWs has not been well characterized.

Objectives.

To determine the duration of time on shift before accidental blood and body fluid exposure in housestaff, nurses, and technicians and the proportion of housestaff who sustain a blood and body fluid exposure after 12 hours on duty.

Methods.

This retrospective, descriptive study was conducted during a 24-month period at a large urban teaching hospital. Participants were HCWs who sustained an accidental blood and body fluid exposure.

Results.

Housestaff were on duty significantly longer than both nursing staff (P = .02) and technicians (P < .0001) before accidental blood and body fluid exposure. Half of the blood and body fluid exposures sustained by housestaff occurred after being on duty 8 hours or more, and 24% were sustained after being on duty 12 hours or more. Of all HCWs, 3% reported an accidental blood and body fluid exposure, with specific rates of 7.9% among nurses, 9.4% among housestaff, and 3% among phlebotomists.

Conclusions.

Housestaff were significantly more likely to have longer duration of time on shift before blood and body fluid exposure than were the other groups. Almost one-quarter of accidental blood and body fluid exposures to housestaff were incurred after they had been on duty for 12 hours or more. Housestaff sustained a higher rate of accidental blood and body fluid exposures than did nursing staff and technicians.

Shift work and occupational stress in police officers

Background

Shift work has been associated with occupational stress in health providers and in those working in some industrial companies. The association is not well established in the law enforcement workforce. Our objective was to examine the association between shift work and police work-related stress.

Methods

The number of stressful events that occurred in the previous month and year was obtained using the Spielberger Police Stress Survey among 365 police officers aged 27–66 years. Work hours were derived from daily payroll records. A dominant shift (day, afternoon, or night) was defined for each participant as the shift with the largest percentage of total time a participant worked (starting time from 4:00 AM to 11:59 AM, from 12 PM to 7:59 PM, and from 8:00 PM to 3:59 AM for day, afternoon, and night shift, respectively) in the previous month or year. Analysis of variance and covariance were used to examine the number of total and subscale (administrative/professional pressure, physical/psychological danger, or organizational support) stressful events across the shift.

Results

During the previous month and year, officers working the afternoon and night shifts reported more stressful events than day shift officers for total stress, administrative/professional pressure, and physical/psychological danger (p < 0.05). These differences were independent of age, sex, race/ethnicity, and police rank. The frequency of these stressful events did not differ significantly between officers working the afternoon and night shifts.

Conclusion

Non–day shift workers may be exposed to more stressful events in this cohort. Interventions to reduce or manage police stress that are tailored by shift may be considered.

Case fatality of myocardial infarction among shift workers

PURPOSE

Shift work has been associated with an excess risk of cardiovascular disease (CVD) and more specifically myocardial infarction (MI). The majority of the studies that found a positive association between shift work and CVD have been based on incidence data. The results from studies on cardiovascular-related mortality among shift workers have shown little or no elevated mortality associated with shift work. None of the previous studies have analysed short-term mortality (case fatality) after MI. Therefore, we investigated whether shift work is associated with increased case fatality after MI compared with day workers.

METHODS

Data on incident cases with first MI were obtained from case-control study conducted in two geographical sites in Sweden (Stockholm Heart Epidemiology Program and Västernorrland Heart Epidemiology Program), including 1,542 cases (1,147 men and 395 women) of MI with complete working time information and 65 years or younger. Case fatality was defined as death within 28 days of onset of MI. Risk estimates were calculated using logistic regression.

RESULTS

The crude odds ratios for case fatality among male shift workers were 1.63 [95 % confidence interval (CI) 1.12, 2.38] and 0.56 (95 % CI 0.26, 1.18) for female shift workers compared with day workers. Adjustments for established cardiovascular risk factors such as diabetes type II and socio-economic status did not alter the results.

CONCLUSION

Shift work was associated with increased risk of case fatality among male shift workers after the first MI.

Metabolic effects of sleep disruption, links to obesity and diabetes

PURPOSE OF REVIEW

To highlight the adverse metabolic effects of sleep disruption and to open ground for research aimed at preventive measures. This area of research is especially relevant given the increasing prevalence of voluntary sleep curtailment, sleep disorders, diabetes, and obesity.

RECENT FINDINGS

Epidemiological studies have established an association between decreased self-reported sleep duration and an increased incidence of type 2 diabetes (T2D), obesity, and cardiovascular disease. Experimental laboratory studies have demonstrated that decreasing either the amount or quality of sleep decreases insulin sensitivity and decreases glucose tolerance. Experimental sleep restriction also causes physiological and behavioral changes that promote a positive energy balance. Although sleep restriction increases energy expenditure because of increased wakefulness, it can lead to a disproportionate increase in food intake, decrease in physical activity, and weight gain.

SUMMARY

Sleep disruption has detrimental effects on metabolic health. These insights may help in the development of new preventive and therapeutic approaches against obesity and T2D based on increasing the quality and/or quantity of sleep.

Circadian system, sleep and endocrinology

Levels of numerous hormones vary across the day and night. Such fluctuations are not only attributable to changes in sleep/wakefulness and other behaviors but also to a circadian timing system governed by the suprachiasmatic nucleus of the hypothalamus. Sleep has a strong effect on levels of some hormones such as growth hormone but little effect on others which are more strongly regulated by the circadian timing system (e.g., melatonin). Whereas the exact mechanisms through which sleep affects circulating hormonal levels are poorly understood, more is known about how the circadian timing system influences the secretion of hormones. The suprachiasmatic nucleus exerts its influence on hormones via neuronal and humoral signals but it is now also apparent that peripheral tissues contain circadian clock proteins, similar to those in the suprachiasmatic nucleus, that are also involved in hormone regulation. Under normal circumstances, behaviors and the circadian timing system are synchronized with an optimal phase relationship and consequently hormonal systems are exquisitely regulated. However, many individuals (e.g., shift-workers) frequently and/or chronically undergo circadian misalignment by desynchronizing their sleep/wake and fasting/feeding cycle from the circadian timing system. Recent experiments indicate that circadian misalignment has an adverse effect on metabolic and hormonal factors such as circulating glucose and insulin. Further research is needed to determine the underlying mechanisms that cause the negative effects induced by circadian misalignment. Such research could aid the development of novel countermeasures for circadian misalignment.

Nutrient intake and adherence to dietary recommendations among US workers

OBJECTIVE

To assess nutrient intake according to dietary guidelines among US worker groups.

METHODS

Participants of 1999 to 2004 National Health and Nutrition Examination Survey completed two 24-hour recall dietary interviews to assess daily intake of protein, carbohydrate, fat, cholesterol, calcium, sodium, and fiber. Employed participants (n = 8987) were classified as (1) white collar, (2) service worker, (3) farmer, and (4) blue collar.

RESULTS

Nutrient intake varied by occupational group, particularly for fiber, sodium, calories, and percentage of calories from protein, saturated fat, and carbohydrate. Adherence to recommendations was noted for saturated fat and cholesterol, but workers were poorly adherent to recommendations for all other nutrients, particularly fiber.

CONCLUSIONS

Workers display differences in nutrient intake across occupational groups with poor eating behaviors evident across all groups. Fiber is particularly poorly consumed, with less than 5% of all US workers meeting the recommendations.

Deficient of a clock gene, brain and muscle Arnt-like protein-1 (BMAL1), induces dyslipidemia and ectopic fat formation

A link between circadian rhythm and metabolism has long been discussed. Circadian rhythm is controlled by positive and negative transcriptional and translational feedback loops composed of several clock genes. Among clock genes, the brain and muscle Arnt-like protein-1 (BMAL1) and circadian locomotor output cycles kaput (CLOCK) play important roles in the regulation of the positive rhythmic transcription. In addition to control of circadian rhythm, we have previously shown that BMAL1 regulates adipogenesis. In metabolic syndrome patients, the function of BMAL1 is dysregulated in visceral adipose tissue. In addition, analysis of SNPs has revealed that BMAL1 is associated with susceptibility to hypertension and type II diabetes. Furthermore, the significant roles of BMAL1 in pancreatic β cells proliferation and maturation were recently reported. These results suggest that BMAL1 regulates energy homeostasis. Therefore, in this study, we examined whether loss of BMAL1 function is capable of inducing metabolic syndrome. Deficient of the Bmal1 gene in mice resulted in elevation of the respiratory quotient value, indicating that BMAL1 is involved in the utilization of fat as an energy source. Indeed, lack of Bmal1 reduced the capacity of fat storage in adipose tissue, resulting in an increase in the levels of circulating fatty acids, including triglycerides, free fatty acids, and cholesterol. Elevation of the circulating fatty acids level induced the formation of ectopic fat in the liver and skeletal muscle in Bmal1 -/- mice. Interestingly, ectopic fat formation was not observed in tissue-specific (liver or skeletal muscle) Bmal1 -/- mice even under high fat diet feeding condition. Therefore, we were led to conclude that BMAL1 is a crucial factor in the regulation of energy homeostasis, and disorders of the functions of BMAL1 lead to the development of metabolic syndrome.

The influence of being overweight on the relationship between shift work and increased total cholesterol level

PURPOSE

The aim of this study was to clarify the influence of shift work on serum total cholesterol (T-Cho) levels according to body mass index (BMI) at entry in Japanese male workers.

METHODS

A 14-year prospective cohort study was conducted in day workers (n = 4079) and alternating shift workers (n = 2807) who received annual health check-ups between 1991 and 2005 in a Japanese steel company. The association between job schedule and increases in T-Cho was investigated using multivariate pooled logistic regression analyses with age, BMI, lifestyle (smoking habit, drinking habit, habitual exercise), and the results of blood chemistries (creatinine, glycosylated hemoglobin A1c, aspartic aminotransferase, γ-glutamyl transpeptidase, uric acid) serving as covariates in those who were not overweight (BMI < 25 kg/m(2), n = 5082) and overweight (BMI ≥ 25 kg/m(2), n = 1804) at entry, respectively. The endpoints in the study were either a 20%, 25%, 30%, 35%, 40%, or 45% increase in T-Cho during the period of observation compared to T-Cho at entry.

RESULTS

In subjects who were not overweight at entry, alternating shift work was associated significantly with five serum T-Cho endpoints (≥20%: odds ratio [OR] = 1.15, 95% confidence interval [CI)] = 1.05, 1.26; ≥25%: OR = 1.17, 95% CI = 1.05, 1.31; ≥35%: OR = 1.24, 95% CI = 1.05, 1.46; ≥40%: OR = 1.30, 95% CI = 1.06, 1.61; ≥45%: OR = 1.31, 95% CI = 1.01, 1.71). However, alternating shift work was not associated with any of the six T-Cho endpoints in subjects who were overweight at entry.

CONCLUSIONS

In the present study, shift work was shown to be a potential risk factor for increased T-Cho in non-overweight Japanese male workers. However, we did not obtain a consistent association between shift work and an increase in T-Cho levels in overweight subjects. The results suggest that the effect of shift work on lipid regulation may be influenced by BMI.

Health behaviors of Operating Engineers

Operating Engineers (heavy equipment operators in construction) may be at particular risk for heart disease and cancer related to their exposure to environmental dust and smoking, the sedentary nature of their job, and long hours of exposure to the sun. The aim of this study was to characterize the health behaviors of Operating Engineers. This cross-sectional survey from a convenience sample of Operating Engineers (N = 498) used validated instruments to measure smoking, drinking, diet, exercise, sleep, and sun exposure. Univariate and bivariate analyses to detect differences by age were conducted. The sample scored significantly worse on all five health behaviors compared to population norms. Those who were older were less likely to smoke and chew tobacco and more likely to eat fruits and vegetables. Many were interested in services to improve their health behaviors. Health behavior interventions are needed and wanted by Operating Engineers.

The Magnitude of Mortality from Ischemic Heart Disease Attributed to Occupational Factors in Korea - Attributable Fraction Estimation Using Meta-analysis

Objectives

Ischemic heart disease (IHD) is a major cause of death in Korea and known to result from several occupational factors. This study attempted to estimate the current magnitude of IHD mortality due to occupational factors in Korea.

Methods

After selecting occupational risk factors by literature investigation, we calculated attributable fractions (AFs) from relative risks and exposure data for each factor. Relative risks were estimated using meta-analysis based on published research. Exposure data were collected from the 2006 Survey of Korean Working Conditions. Finally, we estimated 2006 occupation-related IHD mortality.

Results

For the factors considered, we estimated the following relative risks: noise 1.06, environmental tobacco smoke 1.19 (men) and 1.22 (women), shift work 1.12, and low job control 1.15 (men) and 1.08 (women). Combined AFs of those factors in the IHD were estimated at 9.29% (0.3-18.51%) in men and 5.78% (-7.05-19.15%) in women. Based on these fractions, Korea's 2006 death toll from occupational IHD between the age of 15 and 69 was calculated at 353 in men (total 3,804) and 72 in women (total 1,246).

Conclusion

We estimated occupational IHD mortality of Korea with updated data and more relevant evidence. Despite the efforts to obtain reliable estimates, there were many assumptions and limitations that must be overcome. Future research based on more precise design and reliable evidence is required for more accurate estimates.

Comparison of peripheral endothelial function in shift versus nonshift workers

Shift working is related to increased cardiovascular morbidity. Peripheral endothelial dysfunction, an inherent feature of early atherosclerosis, has been suggested as a surrogate marker of cardiovascular risk. Whether shift working is associated with peripheral endothelial dysfunction has not been investigated to date. A total of 48 male shift workers (SWs) and 47 male nonshift workers (NSWs) (mean age 43 ± 5 years) were recruited from a glass manufactory. The SWs and NSWs were matched according to age, body mass index, smoking habits, family history of premature coronary artery disease, prevalence of hypercholesterolemia and hypertension, and work place. Their sport habits were also documented. Peripheral endothelial function was assessed using the EndoPAT technique to determine the peripheral arterial tone (PAT) index. According to the study design, no difference was found in the risk factor profiles between the SWs and NSWs. Despite a greater percentage of regular physical activity among the SWs (16.7 vs 4.3%, p = 0.05), shift working was associated with a reduced PAT index compared to working only on the day shift (PAT index 1.73 ± 0.4 vs 1.94 ± 0.5, p = 0.03). In the NSW group, the participants with regular physical training (n = 16) had a greater PAT index than those without regular physical activity (n = 12; PAT index 2.28 ± 0.45 vs 1.86 ± 0.51, p = 0.03). No such difference was found in the SWs. In conclusion, SWs had a reduced PAT index compared with NSWs, suggesting endothelial dysfunction. Therefore, the known increased cardiovascular risk in those shift working might be related to endothelial dysfunction.

Working the night shift causes increased vascular stress and delayed recovery in young women

Shiftwork has been associated with elevated blood pressure (BP) and decreased heart-rate variability (HRV), factors that may increase the long-term risk of cardiovascular-related mortality and morbidity. This study explored the effect of shiftwork on dynamic changes in autonomic control of HRV (cardiac stress), systolic BP and diastolic BP, i.e., SBP and DBP (vascular stress), and recovery in the same subjects working different shifts. By studying the same subjects, the authors could reduce the effect of possible contribution of between-subject variation from genetic predisposition and environmental factors. The authors recruited 16 young female nurses working rotating shifts—day (08:00–16:00 h), evening (16:00–00:00 h), and night (00:00–08:00 h)—and 6 others working the regular day shift. Each nurse received simultaneous and repeated 48-h ambulatory electrocardiography and BP monitoring during their work day and the following off-duty day. Using a linear mixed-effect model to adjust for day shift, the results of the repeated-measurements and self-comparisons found significant shift differences in vascular stress. While working the night shift, the nurses showed significant increases in vascular stress, with increased SBP of 9.7 mm Hg. The changes of SBP and DBP seemed to peak during waking time at the same time on the day off as they did on the working day. Whereas HRV profiles usually returned to baseline level after each shift, the SBP and DBP of night-shift workers did not completely return to baseline levels the following off-duty day (p < .001). The authors concluded that although the nurses may recover from cardiac stress the first day off following a night shift, they do not completely recover from increases in vascular stress on that day. (Author correspondence: jdwang@ntu.edu.tw)

Shiftwork Problems

U radu se raspravlja o negativnim utjecajima smjenskog rada koji su klasificirani u četiri kategorije učinaka: na biološke funkcije, radnu efikasnost, društvene / obiteljske aspekte života te na zdravlje. Dan je sustavni pregled dosadašnjih istraživanja zdravstvenih problema smjenskih radnika u čijoj je osnovi narušavanje cirkadijurnih ritmova organizma koju nameće smjenski / noćni rad. Zdravstveni problemi koji se dovode u vezu sa smjenskim radom su ovi: problemi sa spavanjem, gastrointestinalne i kardiovaskularne bolesti, karcinom, problemi s reproduktivnim funkcijama žena te lošije psihičko zdravlje.

U radu se također raspravlja o toleranciji smjenskog rada. Pri tome je kao teoretski okvir povezanosti smjenskog rada i negativnih zdravstvenih posljedica rabljen procesni model koji su postavili Smith i suradnici 1999. Poseban naglasak stavljen je na individualne i organizacijske faktore o kojima ovisi mogućnost prilagodbe na smjenski rad te tolerancija takvog rada. Značajni prediktori tolerancije smjenskog rada su: dob, spol, jutarnjost-večernjost, rigidnost-fleksibilnost u navikama spavanja, obiteljska situacija, higijena spavanja te zdrava prehrana. S obzirom na rezultate istraživanja koji upućuju na povezanost nekih karakteristika organizacije smjenskog rada s tolerancijom prema smjenskom radu, kao što su: broj radnih smjena i trajanje smjene, broj sukcesivnih noćnih smjena, regularnost smjena, brzina i smjer rotacije smjena, preporučene su intervencijske strategije u organizaciji smjenskog rada.