Shift work and hypertension: Prevalence and analysis of disease pathways in a German car manufacturing company

The effect of shift work on body mass index: A systematic review and meta-analysis of observational studies

CONTEXT

Shift work involves working outside the standard working hours of 9 am to 5 pm Monday to Friday and may include working evening, night, weekend, or rotating shift patterns. Since shift workers sleep less and their circadian rhythms are disrupted, they are reported to have higher body weight than day workers.

OBJECTIVE

This meta-analysis aims to determine whether shift workers (SW) are more prone to higher body mass index (BMI) than their day workers (DW) counterparts. It also addresses the question of whether the duration of shift work exposure, sex, or occupational type affect BMI value.

METHODS

Four databases that is PubMed, EBSCO Host, Scopus, and Web of Science were searched for reports published up to October 2023.

RESULTS

Sixty-three studies involving a total of 693 449 participants met our inclusion criteria. Meta-analyses showed a significant effect of shift work on BMI value (standard mean difference; SMD: 0.10 kg/m2 [95% confidence interval; 95% CI: 0.07; 0.13; p < .001]) as compared with non-shift counterparts. Subgroup analysis revealed that shift work significantly increased BMI for studies where male working on this job schedule (SMD: 0.10 kg/m2 [95% CI: 0.04; 0.17; p = .0018]) for studies where shift workers worked ≥13 years (calculated as the median of shift work experience; SMD: 0.14 kg/m2 [95% CI: 0.10; 0.18; p < .001]) as well as for studies where industrial (SMD: 0.12 kg/m2 [95% CI: 0.05; 0.19; p = .0012]) and other type of occupations were dominated (0.12 kg/m2 [95% CI: 0.07; 0.16; p < .001]).

CONCLUSIONS

We found that in general working on a shift schedule increases BMI as compared with day workers, especially in case of male employed in this job schedule, for shift workers working for long periods of time (≥13 years), and for shift workers employed in industry and other type of occupations(e.g., airline workers, firefighters, police officers, blue collar, security personnel, bus drivers, garbage collectors, railway workers, postal, oil and gas workers).

Tackling Shift Work: Cardiovascular Health in the Auto Industry

Shift work, particularly in the auto industry, presents significant health challenges, notably in how it impacts cardiovascular health due to irregular work schedules and associated sleep disruptions. This prospective study evaluated 4683 workers from a single Romanian automotive enterprise to investigate the relationship between fixed shift work schedules and cardiovascular health outcomes. Our analysis focused on fixed-shift workers, excluding those on rotating shifts to reduce variability and enhance the clarity of the findings. The findings reveal that night shift workers are at a heightened risk of cardiovascular diseases (CVDs) compared to their day shift counterparts. Night shift workers demonstrated a higher CVD incidence (4.3%) compared to day shift workers (2.6%), with an odds ratio (OR) of 1.68 (95% CI: 1.08 to 2.62, p = 0.021). This association remained significant after adjusting for potential confounders, with an adjusted OR of 1.74 (95% CI: 1.09 to 2.75, p = 0.019). Male night shift workers exhibited a significantly higher CVD incidence (4.5%) compared to male day shift workers (3.0%), with an OR of 1.75 (95% CI: 1.07 to 2.89, p = 0.026). Female night shift workers also showed a higher CVD incidence (3.4%) compared to female day shift workers (1.3%), although this was not statistically significant. These findings underscore the urgent need for targeted interventions and effective strategies to mitigate these risks and promote the cardiovascular health and overall well-being of shift workers in the auto industry. This research contributes to a deeper understanding of how non-traditional work schedules affect health and provides a basis for implementing protective measures in occupational settings.

Rotating shift work time is directly associated with excess body adiposity

OBJECTIVE

To analyze the association between changes in body adiposity and length of service on a schedule of rotating shifts.

METHODS

The study was a cross-sectional investigation conducted during the years 2012, 2015, and 2018, involving individuals engaged in rotating shifts at a company involved in iron ore extraction situated within the Iron Quadrangle region of Minas Gerais and the southeastern region of Pará, Brazil. Sociodemographic and behavioral data were collected along with anthropometric parameters in order to calculate body mass index (BMI) and the waist-to-height ratio (WHtR). For data analysis, a multivariate logistic regression was employed to explore potential associations between indicators of body adiposity and the duration of shift work, employing a hierarchical determination model.

RESULTS

The findings showed that in the multivariate model, controlling for confounding factors, workers with 5 to 10, 10 to 15, and more than 15 years of shift work had 41 to 96% greater odds of being overweight (BMI > 25.0 kg/m2), 71 to 82% of having altered neck circumference (> 40 cm), 33 to 120% of altered WC (>102 cm), and 57 to 214% of having altered WHtR (> 0.5 cm).

CONCLUSION

The findings suggest that time spent in work has a significant effect on anthropometric indicators of body adiposity, especially if the worker has a previously established comorbidity such as dyslipidemia or hypertension and is frequently exposed to night work.

Chrono-nutrition for hypertension

Despite the advancement in blood pressure (BP) lowering medications, uncontrolled hypertension persists, underscoring a stagnation of effective clinical strategies. Novel and effective lifestyle therapies are needed to prevent and manage hypertension to mitigate future progression to cardiovascular and chronic kidney diseases. Chrono-nutrition, aligning the timing of eating with environmental cues and internal biological clocks, has emerged as a potential strategy to improve BP in high-risk populations. The aim of this review is to provide an overview of the circadian physiology of BP with an emphasis on renal and vascular circadian biology. The potential of Chrono-nutrition as a lifestyle intervention for hypertension is discussed and current evidence for the efficacy of time-restricted eating is presented.

Influence of Shift Work on Arterial Stiffness and Systemic Inflammation: A 3-Year Follow-up Study in Industry

OBJECTIVE

To assess changes in cardiovascular disease risk factors during a 3-year follow-up among 57 rotating shift workers and 29 day workers in industry.

METHODS

We collected demographics by questionnaire, examined blood pressure, heart rate, pulse wave velocity, carotid media thickness, and maximal oxygen uptake. We assessed blood samples for determination of lipids, glycosylated hemoglobin, C-reactive protein, markers of inflammation, and particle concentrations/respirable dust. Baseline comparisons were analyzed using logistic regression (plaque) and linear regression for all other outcomes. We applied mixed models to assess differences in change in health outcomes between the shift workers and the day workers.

RESULTS

At baseline, the adhesion molecules soluble vascular cell adhesion molecule 1 and soluble P-selectin were elevated among the shift workers compared with that of the day workers. There was a significant difference in change in pulse wave velocity between shift workers (1.29-m/s increase) and day workers (0.11-m/s increase) over the 3-year follow-up. Respirable dust levels were below the Norwegian occupational exposure limit.

CONCLUSIONS

Shift work in industry is associated with arterial stiffening reflecting increased risk for future cardiovascular disease. More uncertainly, we found some support for systemic inflammation.

It's About Time: The Circadian Network as Time-Keeper for Cognitive Functioning, Locomotor Activity and Mental Health

A variety of organisms including mammals have evolved a 24h, self-sustained timekeeping machinery known as the circadian clock (biological clock), which enables to anticipate, respond, and adapt to environmental influences such as the daily light and dark cycles. Proper functioning of the clock plays a pivotal role in the temporal regulation of a wide range of cellular, physiological, and behavioural processes. The disruption of circadian rhythms was found to be associated with the onset and progression of several pathologies including sleep and mental disorders, cancer, and neurodegeneration. Thus, the role of the circadian clock in health and disease, and its clinical applications, have gained increasing attention, but the exact mechanisms underlying temporal regulation require further work and the integration of evidence from different research fields. In this review, we address the current knowledge regarding the functioning of molecular circuits as generators of circadian rhythms and the essential role of circadian synchrony in a healthy organism. In particular, we discuss the role of circadian regulation in the context of behaviour and cognitive functioning, delineating how the loss of this tight interplay is linked to pathological development with a focus on mental disorders and neurodegeneration. We further describe emerging new aspects on the link between the circadian clock and physical exercise-induced cognitive functioning, and its current usage as circadian activator with a positive impact in delaying the progression of certain pathologies including neurodegeneration and brain-related disorders. Finally, we discuss recent epidemiological evidence pointing to an important role of the circadian clock in mental health.

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.

Role of circadian rhythm and impact of circadian rhythm disturbance on the metabolism and disease

ABSTRACT

Molecular circadian clocks exist in almost all cells of the organism and operate for approximately 24 h, maintain the normal physiological and behavioral body processes and regulate metabolism of many cells related to a variety of disease states. Circadian rhythms regulate metabolism, mainly including neurotransmitters, hormones, amino acids and lipids. Circadian misalignment is related to metabolic syndromes, such as obesity, diabetes and hypertension, which have reached an alarming level in modern society. We reviewed the mechanism of the circadian clock and the interaction between circadian rhythm and metabolism, as well as circadian rhythm disturbance on the metabolism of hypertension, obesity and diabetes. Finally, we discuss how to use the circadian rhythm to prevent diseases. Thus, this review is a micro to macro discussion from the perspective of circadian rhythm and aims to provide basic ideas for circadian rhythm research and disease therapies.

The Impact of Different Types of Shift Work on Blood Pressure and Hypertension: A Systematic Review and Meta-Analysis

Shift work (SW) encompasses 20% of the European workforce. Moreover, high blood pressure (BP) remains a leading cause of death globally. This review aimed to synthesize the magnitude of the potential impact of SW on systolic blood pressure (SBP), diastolic blood pressure (DBP) and hypertension (HTN). MEDLINE, EMBASE and CENTRAL databases were searched for epidemiological studies evaluating BP and/or HTN diagnosis among shift workers, compared with day workers. Random-effects meta-analyses were performed and the results were expressed as pooled mean differences or odds ratios and 95% confidence intervals (95% CI). The Newcastle-Ottawa Scale was used to assess the risk of bias. Forty-five studies were included, involving 117,252 workers. We found a significant increase in both SBD and DBP among permanent night workers (2.52 mmHg, 95% CI 0.75-4.29 and 1.76 mmHg, 95% CI 0.41-3.12, respectively). For rotational shift workers, both with and without night work, we found a significant increase but only for SBP (0.65 mmHg, 95% CI 0.07-1.22 and 1.28 mmHg, 95% CI 0.18-2.39, respectively). No differences were found for HTN. Our findings suggest that SW is associated with an increase of BP, mainly for permanent night workers and for SBP. This is of special interest given the large number of susceptible workers exposed over time.

Effect of Sleep Disturbances on Blood Pressure

This review summarizes recent literature addressing the association of short sleep duration, shift work, and obstructive sleep apnea with hypertension risk, blood pressure (BP) levels, and 24-hour ambulatory BP. Observational studies demonstrate that subjectively assessed short sleep increases hypertension risk, though conflicting results are observed in studies of objectively assessed short sleep. Intervention studies demonstrate that mild and severe sleep restriction are associated with higher BP. Rotating and night shift work are associated with hypertension as shift work may exacerbate the detrimental impact of short sleep on BP. Further, studies demonstrate that shift work may increase nighttime BP and reduce BP control in patients with hypertension. Finally, moderate to severe obstructive sleep apnea is associated with hypertension, particularly resistant hypertension. Obstructive sleep apnea is also associated with abnormal 24-hour ambulatory BP profiles, including higher daytime and nighttime BP, nondipping BP, and a higher morning surge. Continuous positive airway pressure treatment may lower BP and improve BP dipping. In conclusion, efforts should be made to educate patients and health care providers about the importance of identifying and treating sleep disturbances for hypertension prevention and management. Empirically supported sleep health interventions represent a critical next step to advance this research area and establish causality.

Circadian Rhythm: Potential Therapeutic Target for Atherosclerosis and Thrombosis

Every organism has an intrinsic biological rhythm that orchestrates biological processes in adjusting to daily environmental changes. Circadian rhythms are maintained by networks of molecular clocks throughout the core and peripheral tissues, including immune cells, blood vessels, and perivascular adipose tissues. Recent findings have suggested strong correlations between the circadian clock and cardiovascular diseases. Desynchronization between the circadian rhythm and body metabolism contributes to the development of cardiovascular diseases including arteriosclerosis and thrombosis. Circadian rhythms are involved in controlling inflammatory processes and metabolisms, which can influence the pathology of arteriosclerosis and thrombosis. Circadian clock genes are critical in maintaining the robust relationship between diurnal variation and the cardiovascular system. The circadian machinery in the vascular system may be a novel therapeutic target for the prevention and treatment of cardiovascular diseases. The research on circadian rhythms in cardiovascular diseases is still progressing. In this review, we briefly summarize recent studies on circadian rhythms and cardiovascular homeostasis, focusing on the circadian control of inflammatory processes and metabolisms. Based on the recent findings, we discuss the potential target molecules for future therapeutic strategies against cardiovascular diseases by targeting the circadian clock.

Analysis of changes in cardiac circadian rhythms of RR and QT induced by a 60-day head-down bed rest with and without nutritional countermeasure

PURPOSE

Prolonged weightlessness exposure generates cardiovascular deconditioning, with potential implications on ECG circadian rhythms. Head-down (- 6°) tilt (HDT) bed rest is a ground-based analogue model for simulating the effects of reduced motor activity and fluids redistribution occurring during spaceflight. Our aim was to evaluate the impact of 60-day HDT on the circadianity of RR and ventricular repolarization (QTend) intervals extracted from 24-h Holter ECG recordings, scheduled 9 days before HDT (BDC-9), the 5th (HDT5), 21st (HDT21) and 58th (HDT58) day of HDT, the 1st (R + 0) and 8th (R + 7) day after HDT. Also, the effectiveness of a nutritional countermeasure (CM) in mitigating the HDT-related changes was tested.

METHODS

RR and QTend circadian rhythms were evaluated by Cosinor analysis, resulting in maximum and minimum values, MESOR (a rhythm-adjusted mean), oscillation amplitude (OA, half variation within a night-day cycle), and acrophase (φ, the time at which the fitting sinusoid's amplitude is maximal) values.

RESULTS

RR and QTend MESOR increased at HDT5, and the OA was reduced along the HDT period, mainly due to the increase of the minima. At R + 0, QTend OA increased, particularly in the control group. The φ slightly anticipated during HDT and was delayed at R + 0.

CONCLUSION

60-Day HDT affects the characteristics of cardiac circadian rhythm by altering the physiological daily cycle of RR and QTend intervals. Scheduled day-night cycle and feeding time were maintained during the experiment, thus inferring the role of changes in the gravitational stimulus to determine these variations. The applied nutritional countermeasure did not show effectiveness in preventing such changes.

Shift Workers Have Higher Blood Pressure Medicine Use, But Only When They Are Short Sleepers: A Longitudinal UK Biobank Study

Background

Some, but not all, studies report associations between shift work and hypertension, suggesting that particular subgroups may be at risk. We examined moderating effects of sleep duration and circadian preference on the relationship between shift work and new blood pressure (BP) medicine use at follow‐up.

Methods and Results

Baseline and 5‐year follow‐up data from the UK Biobank cohort (N=9200) were used to generate logistic regression models for shift workers and nonshift workers. The moderating effects of sleep duration (short ≤6 hours; adequate 7–8 hours; long ≥9 hours) and circadian preference (morning “larks;” intermediate; evening “owls”) at baseline were examined with new BP medicine use at follow‐up, adjusting for age, sex, race, education, employment, urban/rural, cardiovascular disease family history, depression, alcohol intake, physical activity, diet, smoking, and body mass index. The sample was predominately middle aged (55.3±7.4), female (57.3%), and white (97.9%). Most reported adequate sleep duration (7–8 hours, 73.7%) and were intermediate type (65.3%); 8.0% were shift workers at baseline. Only 6.5% reported new BP medicine use at follow‐up. Short sleep duration was a significant moderator of new BP medicine use in shift workers. Among short sleepers, shift workers had a 2.1‐fold increased odds of new BP medicine use compared with nonshift workers (odds ratio=2.08, 95% CI=1.21–3.58, P=0.008). In those reporting adequate (odds ratio=0.82, 95% CI=0.54–1.25, P=0.35) and long sleep (odds ratio=0.64, 95% CI=0.11–3.54, P=0.60), this relationship was protective but nonsignificant. Interaction between circadian preference and shift work on BP medicine use was nonsignificant.

Conclusions

Shift workers with short sleep duration may be at risk for hypertension.

Metabolic syndrome in shift healthcare workers

Background:

Shift work including night shifts is generally associated with chronic misalignment between the endogenous circadian timing system and behavior cycles, leading to metabolic disorders including metabolic syndrome (MS).

Objectives:

The purpose of this research was to analyze the latest developments in assessing and managing the occupational risk of MS in shift-healthcare workers (HCWs).

Methods:

According to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement, the authors used MEDLINE/Pubmed to perform a systematic review of literature from January 2008 to December 2018.

Results:

Six studies were selected; the topics, discussed in order of frequency from highest to lowest, were: risk assessment, occurrence rates, and risk management. The main occupational determinants for MS were the cumulative shift work including night shifts and the number of nights worked per month per worker. With regard to cumulative lifetime exposure to shift work, the findings of our review suggest a dose–response relationship between increasing years of shift work history and MS in shift-HCWs.

Conclusions:

The findings suggest the need to better investigate the impact of sleep deprivation in the assessment of MS risk in shift-HCWs and clarify the role of such variables as confounders, mediators, or effect modifiers. Moreover, to date the data regarding management interventions focused on the risk of MS are inconsistent and therefore a special effort is required to detect strategic ways to minimize the likelihood of MS occurring in shift-HCWs.

Snap-fit assembly and upper limb functional limitations in automotive production workers: a nested case-control study

OBJECTIVES

The use of snap-fits in car-part assembling has developed into an industrial standard. Cross-sectional evidence indicates, however, that this assembling process might adversely affect workers' upper limb function. The objective of this study was to analyze incident cases of upper limb functional limitations (ULFL) in relation to exposure to snap-fit assembly.

METHODS

We performed a nested case-control study within a population of 5139 blue-collar automotive production workers. Cases with ULFL detected during follow-up were matched with controls based on employment duration and investigated on their exposure to snap-fit assembly. By conditional logistic regression, we modeled the risk for ULFL according to person-years of exposure to snap-fit assembly, adjusted for gender and baseline BMI.

RESULTS

Overall, 64 ULFL cases were detected during a follow-up of 20610.8 person-years (3.1 cases per 1000 person-years). Cases, matched with an average of 4 controls, had significantly longer exposure duration to snap-fit assembly compared with controls (M = 1.15 person-years, SD = 1.68 person-years vs. M = 0.41 person-years, SD = 1.25 person-years). One person-year of exposure to snap-fit assembly was associated with an approximate 20% risk increase of developing ULFLs (OR 1.23, 95% CI 1.08-1.39).

CONCLUSIONS

We confirm an association between accumulated exposure to snap-fits in car-part assembling and upper limb musculoskeletal disorders. Company physicians should thus be vigilant to symptoms of musculoskeletal disorders of the upper limbs in snap-fit assembly and support the development of threshold values for snap-fit insertion forces.

Common Sleep, Psychiatric, and Somatic Problems According to Work Schedule: an Internet Survey in an Eastern European Country

PURPOSE

A wide range of health problems was investigated, aiming to identify the presence and severity of a set of self-reported and common sleep, psychiatric, and somatic health problems among working professionals in four different shift schedules (morning, evening, rotating, and day) in several cities in Romania.

METHODS

A heterogeneous sample of 488 workers of different professions completed online a battery of tests, namely the Basic Nordic Sleep Questionnaire, the Parasomnia Questionnaire, the Epworth Sleepiness Scale, and the Patient Health Questionnaire, designed to identity symptoms of insomnia, sleepiness, snoring, parasomnia, as well as of depression, anxiety, eating, somatoform, and alcohol use disorders, respectively. The timing and the duration of the sleep, along with the presence of high blood pressure and type 2 diabetes mellitus were also inquired. The prevalence of the different health problems in relation to the type of shift schedule was evaluated with the Pearson Chi-square test. ANOVA was used to calculate the significance of the difference between the means, while associations with different health problems were estimated by binary logistic regression.

RESULTS

The most common mental health problems were depression (26%), insomnia (20%), alcohol misuse (18%), and anxiety (17%). No significant differences based on the type of shift in terms of health problems were found, except for high blood pressure and symptoms of panic disorder that were more frequently reported by the workers in early morning shifts. Together with the workers in rotating shifts, they also reported increased sleepiness, poorer sleep quality, and shorter sleep duration. In contrast, the workers in evening shifts reported less severe health problems and longer sleep duration.

CONCLUSIONS

Working in early morning shifts was found to be associated with poorer health outcomes, while working in rotating and early morning shifts with more severe sleep-related problems.

Night and rotational work exposure within the last 12 months and risk of incident hypertension

Objectives Shift work, such as alternating day and nights, causes chronobiologic disruptions which may cause an increase in hypertension risk. However, the relative contributions of the components of shift work ‒ such as shift type (eg, night work) and rotations (ie, switching of shift times; day to night) ‒ on this association are not clear. To address this question, we constructed novel definitions of night work and rotational work and assessed their associations with risk of incident hypertension. Methods A cohort of 2151 workers at eight aluminum manufacturing facilities previously studied for cardiovascular disease was followed from 2003 through 2013 for incident hypertension, as defined by ICD-9 insurance claims codes. Detailed time-registry data was used to classify each worker's history of rotational and night work. The associations between recent rotational work and night work in the last 12 months and incident hypertension were estimated using adjusted Cox proportional hazards models. Results Elevated hazard ratios (HR) were observed for all levels of recent night work (>0-5, >5-50, >50-95, >95-100%) compared with non-night workers, and among all levels of rotational work (<1, 1-10, >10-20, >20-30, and >30%) compared with those working <1% rotational work. In models for considering the combination of night and rotational work, workers with mostly night work and frequent rotations (≥50% night and ≥10% rotation) had the highest risk of hypertension compared to non-night workers [HR 4.00, 95% confidence interval (CI )1.69-9.52]. Conclusions Our results suggest recent night and rotational work may both be associated with higher rates of incident hypertension.

The Effect of Shift Work on Urogenital Disease: a Systematic Review

PURPOSE OF REVIEW

Non-standard shift work schedules negatively impact the overall health of shift workers, and several studies have shown that shift work, specifically, is detrimental to urogenital health. The aims of this study are to systematically review the literature and determine the effect of shift work on the outcomes of hypogonadism, male infertility, lower urinary tract symptoms, and urogenital cancers.

RECENT FINDINGS

Recent evidence supports associations between non-standard shift work and an increase in the frequency of prostate cancer and the severity of erectile dysfunction, lower urinary tract symptoms, and hypogonadal symptoms, as well as worsening of semen parameters and fertility. These associations are strengthened by the presence of shift work sleep disorder (SWSD) which affects up to 20% of shift workers. No studies have assessed the impact of shift work on the frequency or severity of nephrolithiasis, interstitial cystitis, pelvic pain, prostatitis, or urinary tract infections. Non-standard shift work has been associated with a variety of negative health outcomes and urologic complications, especially with concurrent shift work sleep disorder. Recognition of these elevated risks among shift workers can aid in more effective screening for urologic conditions.

Modeling the Influence of Seasonal Differences in the HPA Axis on Synchronization of the Circadian Clock and Cell Cycle

Synchronization of biological functions to environmental signals enables organisms to anticipate and appropriately respond to daily external fluctuations and is critical to the maintenance of homeostasis. Misalignment of circadian rhythms with environmental cues is associated with adverse health outcomes. Cortisol, the downstream effector of hypothalamic-pituitary-adrenal (HPA) activity, facilitates synchronization of peripheral biological processes to the environment. Cortisol levels exhibit substantial seasonal rhythmicity, with peak levels occurring during the short-photoperiod winter months and reduced levels occurring in the long-photoperiod summer season. Seasonal changes in cortisol secretion could therefore alter its entraining capabilities, resulting in a season-dependent modification in the alignment of biological activities with the environment. We develop a mathematical model to investigate the influence of photoperiod-induced seasonal differences in the circadian rhythmicity of the HPA axis on the synchronization of the peripheral circadian clock and cell cycle in a heterogeneous cell population. Model simulations predict that the high-amplitude cortisol rhythms in winter result in the greatest entrainment of peripheral oscillators. Furthermore, simulations predict a circadian gating of the cell cycle with respect to the expression of peripheral clock genes. Seasonal differences in cortisol rhythmicity are also predicted to influence mitotic synchrony, with a high-amplitude winter rhythm resulting in the greatest synchrony and a shift in timing of the cell cycle phases, relative to summer. Our results highlight the primary interactions among the HPA axis, the peripheral circadian clock, and the cell cycle and thereby provide an improved understanding of the implications of circadian misalignment on the synchronization of peripheral regulatory processes.

Associations of rotational shift work and night shift status with hypertension: a systematic review and meta-analysis

BACKGROUND

The reported risks of hypertension (HTN) in rotating shift and night shift workers are controversial. The objective of this meta-analysis was to assess the association between shift work status and HTN.

METHODS

A literature search was performed using MEDLINE, EMBASE and Cochrane Database from inception through October 2016. Studies that reported odds ratios (OR) comparing the risk of HTN in shift workers were included. A prespecified subgroup analysis by rotating shift and night shift statuses were also performed. Pooled OR and 95% confidence interval (CI) were calculated using a random-effect, generic inverse variance method. The protocol for this study is registered with International Prospective Register of Systematic Reviews; no. CRD42016051843.

RESULTS

Twenty-seven observational studies (nine cohort and 18 cross-sectional studies) with a total of 394 793 individuals were enrolled. The pooled ORs of HTN in shift workers in cohort and cross-sectional studies were 1.31 (95% CI, 1.07-1.60) and 1.10 (95% CI, 1.00-1.20), respectively. When meta-analysis was restricted only to cohort studies in rotating shift, the pooled OR of HTN in rotating shift workers was 1.34 (95% CI, 1.08-1.67). The data regarding night shift and HTN in cohort studies was limited. The pooled OR of HTN in night shift workers in cross-sectional studies was 1.07 (95% CI, 0.85-1.35).

CONCLUSION

Based on the findings of our meta-analysis, shiftwork status may play an important role in HTN, as there is a significant association between rotating shift work and HTN. However, there is no significant association between night shift status and risk of HTN.

The Relationship Between Shift Work and Men's Health

BACKGROUND

More than 21 million Americans and nearly 20% of the U.S. workforce are shift workers. Non-standard shift work, defined as work that falls outside of 6 am-6 pm, can lead to poor diet, exercise, and sleep habits that lead to decreased productivity, increased workplace accidents, and a variety of negative health outcomes.

AIM

To investigate the associations between shift work exposure and chronic medical conditions such as metabolic syndromes, cardiovascular disease, gastrointestinal disturbances, and depression as well as urologic complications including hypogonadism, male infertility, lower urinary tract symptoms, and prostate cancer with a focus on the effects of shift work sleep disorder (SWSD) on the severity of these negative health outcomes.

METHODS

We reviewed the literature examining effects of shift work and SWSD on general and urologic health.

OUTCOMES

We produced a summary of effects of shift work on health with focus on the increased risk of negative health outcomes in non-standard shift workers, particularly those with SWSD, when compared to daytime workers or workers without SWSD.

RESULTS

Studies have associated non-standard shift work schedules and poor health outcomes, including increased risks of diabetes mellitus, dyslipidemia, hypertension, heart disease, peptic ulcer disease, and depression, in shift workers. However, few studies have focused on the role that shift work plays in men's urologic health. Current evidence supports associations between non-standard shift work and increased hypogonadal symptoms, poor semen parameters, decreased fertility, lower urinary tract symptoms, and prostate cancer. These associations are strengthened by the presence of SWSD, which affects up to 20% of shift workers. Unfortunately, interventions, such as planned naps, timed light exposure, melatonin, and sedative hypnotics, aimed at alleviating excessive nighttime sleepiness and daytime insomnia in non-standard shift workers experiencing SWSD, are limited and lack strong evidence to support their efficacy.

CONCLUSIONS

Non-standard shift work has been associated with a variety of negative health outcomes and urologic complications, especially with concurrent SWSD. Recognition of these increased risks among shift workers can potentially aid in more effective screening of chronic health and urologic conditions. Non-pharmacologic treatment of SWSD focuses on behavioral therapy and sleep hygiene while melatonin, hypnotics, and stimulants are used to alleviate insomnia and excessive sleepiness of SWSD. Further research into both pharmacologic and non-pharmacologic therapies for SWSD is needed to establish more definitive guidelines in the treatment of SWSD in order to increase productivity, minimize workplace accidents, and improve quality of life for shift workers. Deng N, Kohn TP, Lipshultz LI, et al. The Relationship Between Shift Work and Men's Health. Sex Med Rev 2018;6:446-456.

Interaction effect of job insecurity and role ambiguity on psychological distress in Japanese employees: a cross-sectional study

Purpose

We examined the interaction effect of job insecurity (JI) and role ambiguity (RA) on psychological distress in Japanese employees.

Methods

Overall, 2184 male and 805 female employees from two factories of a manufacturing company in Japan completed a self-administered questionnaire comprising the scales measuring JI (Job Content Questionnaire), RA (National Institute for Occupational Safety and Health Generic Job Stress Questionnaire), psychological distress (K6 scale), and potential confounders (i.e., age, education, family size, occupational class, and work shift). Taking psychological distress as a dependent variable, hierarchical multiple regression analyses were conducted by gender and employment status (i.e., permanent and non-permanent employees). An interaction term of JI × RA was included in the model.

Results

After adjusting for potential confounders, the main effects of JI and RA on psychological distress were significant regardless of gender or employment status. Furthermore, the significant interaction effect of JI × RA on psychological distress was observed among permanent male employees (β = 0.053, p = 0.010). Post hoc simple slope analyses showed that the simple slope of JI was greater at higher levels of RA (i.e., one standard deviation [SD] above the mean) (β = 0.300, p < 0.001) compared to lower levels of RA (i.e., one SD below the mean) (β = 0.212, p < 0.001). On the other hand, the interaction effect of JI × RA was not significant among permanent or non-permanent female employees.

Conclusions

The present study suggests that higher levels of RA strengthen the association of JI with psychological distress, at least among Japanese permanent male employees.

The Circadian Clock and Human Health

Epidemiological studies provided the first evidence suggesting a connection between the circadian clock and human health. Mutant mice convincingly demonstrate the principle that dysregulation of the circadian system leads to a multitude of pathologies. Chrono-medicine is one of the most important upcoming themes in the field of circadian biology. Although treatments counteracting circadian dysregulation are already being applied (e.g., prescribing strong and regular zeitgebers), we need to comprehend entrainment throughout the body's entire circadian network before understanding the mechanisms that tie circadian dysregulation to pathology. Here, we attempt to provide a systematic approach to understanding the connection between the circadian clock and health. This taxonomy of (mis)alignments on one hand exposes how little we know about entrainment within any organism and which 'eigen-zeitgeber' signals are used for entrainment by the different cells and tissues. On the other hand, it provides focus for experimental approaches and tools that will logically map out how circadian systems contribute to disease as well as how we can treat and prevent them.

Prevalence of Hypertension in Professional Drivers (from the RACER-ABPM Study)

Professional drivers are a group exposed to many cardiovascular risk factors. Nonsystematic working hours, stress, low physical activity, and unhealthy dietary habits are common among professional drivers. These translate into high risk of cardiovascular disease. The aim of the current analysis was to establish the prevalence of arterial hypertension in a group of continuous professional drivers. The RACER (Risk of Adverse Cardiovascular Events among professional dRivers in Poland) study is a prospective study focused on assessing cardiovascular risk factors in professional drivers. Patients included in the study were screened for the classical and nonclassical cardiovascular risk factors and had an ambulatory blood pressure monitoring (ABPM) performed. Of the RACER study population, 144 drivers were included into the RACER-ABPM study. Of this group 135 (95.7%) were male at mean age of 50.2 ± 9.3 years, with mean body mass index of 32.3 ± 3.0 kg/m². In 21.3% of patients, family history of cardiovascular disease was noted, 28.1% were current smokers, and 2.9% had diabetes mellitus. Arterial hypertension was previously diagnosed in 39 patients (27.9%). In ABPM, the mean 24-hour blood pressure (BP) values were 130.3 ± 14.3 and 80.9 ± 9.9 for systolic and diastolic BP, respectively, and 46.1% of patients could be categorized as dippers. Based on the ABPM results, arterial hypertension was diagnosed in 104 of patients (73.8%). Patients with hypertension tend to be more often male and have a family history of cardiovascular disease. In conclusion, arterial hypertension is highly prevalent in professional drivers. Also abnormal day-to-night BP value patterns are often seen in this group.

Shift Work Is Associated with Metabolic Syndrome in Young Female Korean Workers

Background

Shift work is associated with health problems, including metabolic syndrome. This study investigated the association between shift work and metabolic syndrome in young workers.

Methods

A total of 3,317 subjects aged 20–40 years enrolled in the 2011–2012 Korean National Health and Nutrition Examination Survey were divided into shift and day workers. We conducted a cross-sectional study and calculated odds ratios using multivariate logistic regression analysis in order to examine the association between shift work and metabolic syndrome.

Results

The prevalence of metabolic syndrome was 14.3% and 7.1% among male and female shift workers, respectively. After adjusting for confounding factors, shift work was associated with metabolic syndrome in female workers (odds ratio, 2.53; 95% confidence interval, 1.12 to 5.70).

Conclusion

Shift work was associated with metabolic syndrome in young women. Timely efforts are necessary to manage metabolic syndrome in the workplace.

Twenty-four-hour work shifts, increased job demands, and elevated blood pressure in professional firefighters

PURPOSE

To investigate whether working conditions (number of 24-h shifts, number of calls, sedentary work, job strain, effort-reward imbalance, and physical demands) are associated with elevated blood pressure and hypertension among professional firefighters.

METHODS

A total of 330 (321 males and 9 females) firefighters were chosen for this study among the Southern California firefighters who participated in a work and obesity project. Working conditions were measured with a firefighter-specific occupational health questionnaire. Blood pressure was clinically assessed, and hypertension was defined according to the contemporary standard classification.

RESULTS

About 11 % of the firefighters had hypertension. Fifty percent of the hypertensive firefighters (mostly mild hypertensive) had uncontrolled high blood pressure. Hypertension was more prevalent in male, older, and high-rank firefighters and firefighter who reported low numbers of daily calls. In male firefighters who were normotensive or hypertensive without taking anti-hypertensive medication, additional 24-h shifts in the past month increased the risk of elevated diastolic blood pressure (DBP) than those who reported a standard work schedule (eight to eleven 24-h shifts). Particularly, firefighters who reported sixteen 24-h shifts had 5.0 mmHg higher DBP (p < 0.01). Body mass index attenuated the association between number of shifts and blood pressure to some extent. Firefighters who reported "increased job demands over the past years" had 3.0 mmHg (p = 0.06) higher systolic blood pressure. Other working conditions were not associated with elevated blood pressure and hypertension.

CONCLUSIONS

Many additional 24-h shifts and increased job demands were risk factors for elevated blood pressure in male firefighters. Optimal collective and individual workload and improved hypertension management are warranted for enhancing the cardiovascular health of firefighters.

Snap-fits and upper limb functional limitations in German automotive workers

BACKGROUND

The use of snap-fit fasteners in automotive assembly has increased in the last 10 years. Their impact on musculoskeletal function of the upper limbs in assembly workers is not well described.

AIMS

To investigate the association between snap-fit assembly and upper limb functional limitations (ULFLs) in workers after a large-scale expansion of snap-fit assembly by a German automotive company.

METHODS

Cross-sectional data on blue-collar production workers' exposure to snap-fit assembly and ULFLs were collected from medical check-ups and company registers. The association between duration of snap-fit assembly and ULFLs, and the dose-response relationship between the two were analysed using logistic regression, adjusted for body mass index, gender and employment duration before snap-fit exposure.

RESULTS

The study group included 10722 workers. Within the company, 8.4, 6.9 and 10.3% were exposed to snap-fit 1-12, 13-24 and ≥25 months, respectively. After adjusting for confounders, snap-fit exposure for 1-12 months [odds ratio (OR) = 1.59, 95% confidence interval (CI) 0.88-2.88] and 13-24 months (OR = 1.48, 95% CI 0.76-2.88) was not statistically significantly associated with ULFLs compared with an unexposed group. However, exposure to ≥25 months of snap-fit assembly was statistically significant associated with ULFLs showing >2-fold risk (OR = 2.44, 95% CI 1.52-3.92). No clear dose-response relationship was found.

CONCLUSIONS

Our study suggests a negative long-term impact from snap-fit assembly on workers' upper limb function. Company physicians should be vigilant for signs of upper limb musculoskeletal disorders among workers exposed to snap-fit assembly.