Behavioral-Social Rhythms and Cardiovascular Disease Risk in Retired Night Shift Workers and Retired Day Workers

OBJECTIVE

Stability in the timing of key daily routine behaviors such as working/doing housework, sleeping, eating, and engaging in social interactions (i.e., behavioral-social rhythms) contributes to health. This study examined whether behavioral-social rhythms were associated with cardiovascular disease (CVD) risk factors in retired night shift workers and retired day workers and explored whether past night shift work exposure moderated this association.

METHODS

A total of 154 retired older adults participated in this study. Multiple logistic regression models were used to examine associations between behavioral-social rhythms and CVD risk factors. Independent variables included Social Rhythm Metric (SRM)-5 score and actigraphy rest-activity rhythm intradaily variability (IV) and interdaily stability (IS). Dependent variables were metabolic syndrome prevalence and its five individual components.

RESULTS

More regular behavioral-social rhythms were associated with lower odds of prevalent metabolic syndrome (SRM: odds ratio [OR] = 0.57, 95% confidence interval [CI] = 0.35-0.88; IV: OR = 4.00, 95% CI = 1.86-8.58; IS: OR = 0.42, 95% CI = 0.24-0.73) and two of its individual components: body mass index (SRM: OR = 0.56, 95% CI = 0.37-0.85; IV: OR = 2.84, 95% CI = 1.59-5.07; IS: OR = 0.42, 95% CI = 0.26-0.68) and high-density lipoprotein cholesterol (SRM: OR = 0.49, 95% CI = 0.30-0.80; IV: OR = 2.49, 95% CI = 1.25-4.96; IS: OR = 0.35, 95% CI = 0.19-0.66). Past shift work history did not moderate the association between behavioral-social rhythms and metabolic syndrome.

CONCLUSIONS

Behavioral-social rhythms were related to CVD risk factors in retired adults regardless of prior night shift work exposure. Older retired workers may benefit from education and interventions aiming to increase behavioral-social rhythm regularity.

Association Between Augmentation Index and Total Sleep Time in Night Shift Workers

Augmentation index and pulse wave velocity are markers of vascular compromise and independent predictors of cardiovascular risk and mortality. While the link between shift work and heightened cardiovascular risk is established, the intricate genesis of early cardiovascular outcomes in shift workers remains incompletely understood. However, there is evidence that sleep duration plays a role in this regard. Here we evaluate the association of total sleep time with pulse wave velocity, augmentation index, and central blood pressure in night shift workers. This study cross-sectionally evaluated the association of total sleep time evaluated by 10-day monitoring actigraphy with augmentation index, pulse wave velocity, and brachial and central blood pressure evaluated by oscillometry in nursing professionals, 63 shift workers (89% women; age = 45.0 ± 10.5 years), and 17 (100% women; age = 41.8 ± 15.6) day workers. There were no differences in the studied variables between shift workers and day workers. Results of correlation analysis demonstrated that pulse wave velocity, central systolic blood pressure, central diastolic blood pressure, brachial systolic blood pressure, and brachial diastolic blood pressure tended to have significant correlation with each other, while these measures did not have a significant relationship with augmentation index in both groups. However, results of adjusted restricted cubic spline analysis showed a U-shaped-curve association between total sleep time and augmentation index (p < 0.001 for trend) with a nadir at 300-360 min of total sleep time in shift workers. The present study showed that total sleep time, assessed by actigraphy, had a U-shaped association with augmentation index in shift workers, which indicated better characteristics of vascular functionality when sleep time was 5-6 h in the workers studied.

Synergistic interaction between long shifts and short rest periods on depression in shift workers: A cross-sectional study from Korea

BACKGROUND

Long shifts and short rest periods (SRP) between shifts are important factors that greatly affect shift workers' health. However, reports on the psychological effects of shift work, such as depression, have been inconsistent. Therefore, this study aimed to investigate the combined effect of long shifts and SRP on depression in shift workers.

METHODS

This cross-sectional study included 3295 shift workers in the sixth Korean Working Conditions Survey. The relative excess risk due to interaction (RERI) was computed to estimate the combined effect of long shifts and SRP on depression.

RESULTS

Depression in shift workers was not significantly associated with long shifts or SRP after adjustment, but the risk was significantly increased when exposed to both factors simultaneously (odds ratio 1.36, 95% confidence interval 1.03-1.79). The RERI between the two factors was statistically significant (p = 0.020), indicating a synergistic interaction with depression. Sensitivity analysis by occupation showed a significant interaction in the combined group of office and service workers (p = 0.034).

CONCLUSIONS

Simultaneous exposure to SRP and long shifts should be avoided when planning shift work schedules or devising health policies for shift workers. Special consideration is needed for healthcare and service workers, who may be particularly vulnerable to negative health impacts due to shift work.

Job burnout among workers with different shift regularity: interactive factors between sleep, depression, and work environment

Object

We investigated burnout and associated factors in non-shift workers (NSWs), shift workers with regular rotating shifts (RRSWs), and shift workers with irregular or unpredictable rotating shifts (IRSWs).

Methods

In total, 5,125 adult workers (1,966 NSWs, 1,936 RRSWs, and 1,223 IRSWs) participated in an online self-reported survey. Job burnout and three dimensions thereof (exhaustion, cynicism, and professional efficacy) were assessed using the Maslach Burnout Inventory-General Survey (MBI-GS). The Center for Epidemiological Studies Depression Scale (CES-D) (depressive symptoms), Pittsburgh Sleep Quality Index (PSQI) (subjective sleep quality), and Korean Occupational Stress Scale (KOSS) (stressful job environment) were also used.

Results

Both types of shift workers scored higher in terms of exhaustion, cynicism, and poor professional efficacy on the MBI-GS compared with NSWs after controlling for age and gender. IRSWs exhibited higher scores on the exhaustion and professional efficacy dimensions of the MBI-GS compared with RRSWs. After controlling for the CES-D and PSQI scores, we found no significant difference in cynicism among the groups. After controlling for the KOSS score, we found no significant difference in professional efficacy. All MBI-GS dimensional scores were correlated significantly with the CES-D, PSQI, and KOSS scores in all three groups.

Conclusion

The job burnout level of rotating shift workers, especially those with irregular shifts, was higher than that of other workers. Cynicism in shift workers may be largely attributable to poor sleep or depression; the poor efficacy of shift workers may be explained by their stressful work environment.

Factors Influencing the Health-Related Quality of Life of Workers According to the Type of Work

This paper describes a descriptive cross-sectional study that was conducted to identify and compare the factors affecting health-related quality of life (HRQoL) according to the type of work. The method involved a secondary analysis of 4131 workers who participated in the first year of the 8th Korea National Health and Nutrition Examination Survey (2019). In this study, a complex sample plan file was created and then weighted and analyzed. For the analyses, frequency, χ2-test, t-test, and linear regression analyses were used for complex sample analysis. Factors that significantly affected the HRQoL of daytime workers were educational background, living with a spouse, regular work, depression for two consecutive weeks, and suicidal thoughts. The explanatory power was 18.9% (p < 0.001). The factor that significantly affected the HRQoL of shift workers was whether they took dietary supplements for 2 weeks or more during the past year, and the explanatory power was 17.6% (p = 0.007). This study confirmed that the factors affecting HRQoL differ according to the type of work. Based on the results of this study, when developing a program to improve the HRQoL of workers, it is necessary to establish a differentiated strategy according to the type of work.

Unhealthy Food Choices among Healthcare Shift Workers: A Cross-Sectional Study

Shift healthcare workers are a group particularly exposed to an increased risk of poor eating habits and are affected by many diseases. The aim of the study was to evaluate the dietary patterns (DPs), including the Polish-adapted Mediterranean Diet (Polish-aMED®) score, and dietary fat intake in association with the shift work of healthcare workers. This cross-sectional study involved 445 healthcare workers from the West Pomeranian in Poland. Dietary data were collected using an FFQ-6®. A posteriori DPs were derived with a Principal Component Analysis (PCA). The Polish-aMED® score and the individual’s percentage of energy from dietary fat (Pfat) were calculated. Healthcare shift work compared to the daily work was associated with approximately 2-times higher odds of adherence to the ‘Meat/fats/alcohol/fish’ DP in the upper tertile (OR: 2.38; 95% Cl: 1.27−4.47; p < 0.01) and higher Pfat >35% of total energy intake (OR: 1.73; 95% Cl: 1.06−2.83; p < 0.05). Healthcare shift work compared to the daily work was associated with approximately 50% lower odds of adherence to the ‘Pro-healthy’ DP in the middle tertile (OR: 0.48; 95% Cl: 0.26−0.89; p < 0.05) and a higher level of the Polish-aMED® score (OR: 0.57; 95% Cl: 0.33−0.98; p < 0.05), as well as lower odds of the constants of mealtime (OR: 0.54; 95% Cl: 0.33−0.89; p < 0.05). The obtained findings highlight the unhealthy food choices among shift healthcare workers. Thus, to avoid the negative health consequences, there is a need for nutritional education for healthcare workers, especially those working shifts.

The Effect of Sleep Quality and Mental Fatigue on the Learning Rate of Shift Workers with Fast Shift Work Rotation

Background

Modern industrial societies are always prone to errors and accidents due to complex devices, multitasking, and shift work jobs. Therefore, behavioral tests in learning and memory are necessary to evaluate employees' perceptions to examine the brain's information processing and the physiological and psychological aspects of memory disorders.

Materials and Methods

In this study, the effect of fast shift rotation, sleep quality, and mental fatigue on individuals' learning and memory was investigated using a maze device. Participants were divided into two groups (regular daytime workers and shift workers). The quality of sleep was assessed using the Pittsburgh Sleep Quality Index (PSQI), and the rate of mental fatigue was evaluated using a checklist published by the Japan Industrial Safety and Health Association.

Results

Learning time and the number of learning errors at the beginning and end of the morning shifts and night shifts had a significant relationship (P value <0.0001). However, there was no meaningful relationship between sleep quality and time and the number of learning errors in day workers and shift workers.

Conclusion

The results indicated that although shift workers experience rapid shift rotation, they are still exposed to this circadian sleep change's side effects such as general physical fatigue, sensory-neurological fatigue, poor perceived sleep quality, daily dysfunction, difficulty in learning, and memory. They show a significant difference compared to people working on a regular workday.

Rostering in Air Traffic Control: A Narrative Review

Most Air Traffic Controllers (ATCOs) must cover uninterrupted work shifts for 24 h a day, seven days a week. The proper planning of a shift schedule requires consideration of at least three elements: the specific characteristics of the controller task, the physiological needs of the operator, and the definition of rest periods within rostering. We reviewed the literature for providing comprehensive guidance on the main requirements for the construction of a shift schedule for ATCOs. Our considerations are organized according to a rationale reflecting the most important criteria for the construction of the schedule: namely, the organization of rest periods conceptualized as intervals between cycles of shifts, intervals between individual shifts, and breaks within the shift. The suggested parameters could be used to construct shift schedules within a variation margin that depends on individual contexts of application.

Circadian Disruption and Occupational Toxicants Exposure Affecting the Immunity of Shift Workers During SARS CoV-2 Pandemic

In several regions of the world, the recent Coronavirus Disease-2019 (COVID-19) pandemic outbreak increased morbidity and mortality. The pandemic situation disrupted many workers' previously established lifestyles. The main aim of the present review was to describe the circadian disruption and occupational toxicant exposure affecting the immunity of shift workers during the SARS CoV-2 pandemic. We retrieved pertinent published literature from the Google Scholar, PubMed, and Scopus databases. In the present review, we discuss the circadian rhythm involving the hypothalamic-pituitary-adrenal (HPA) axis at the molecular level, its disruption, occupational toxicant exposure causing immunomodulatory effects, and the role of immunity during the SARS CoV-2 pandemic. The severity of the progression of the viral infection depends on multiple factors affecting immunity. Hence, shift workers may need to be aware of those factors such as circadian rhythm disruption as well as occupational toxicant exposure. The timing of shift workers' energy intake is also important concerning the shift of the workers. The information in the present review may be important for all workers who are at risk during the pandemic. In the absence of any published literature related to association of circadian rhythm disruption with occupational toxicant exposure, the present review may have greater importance.

Evaluating "The REST of your Life," a workplace health program to improve employee sleep, health, energy, and productivity

Purpose Sleep is critical for employee health, well-being, and productivity. Our purpose is to evaluate a sleep-focused interactive workplace health promotion program. Design We evaluate sleep and mental health before and after exposure to the program using a pre/post quasi-experimental pilot study design with surveys administered at baseline and 1-, 6-, and 12-months post-exposure (Phase 1). We design program evaluation surveys for dissemination when the program is offered broadly to hospital employees (Phase 2). Setting The study was conducted at a large teaching hospital in the Southeast U.S. in 2016. Subjects Subjects were full-time hospital employees. Intervention The program was presented to subjects in one four-hour interactive session. Measures In Phase 1 (n=55), surveys included the validated Apnea Risk Evaluation System (ARES), Dysfunctional Beliefs About Sleep (DBAS), Generalized Anxiety Disorder-7 (GAD-7), Pittsburgh Sleep Quality Index (PSQI), and Patient Health Questionnaire (PHQ-9). Phase 2 (n=3,935) utilized program evaluation surveys. Analysis We compare survey responses between pre- and post-program using ANOVA with post-hoc tests. Results Statistically significant improvement in all sleep and mental health domains was demonstrated. In Phase 2, 81.9% reported "strongly agree" to willingness to recommend the program to co-workers. Conclusion We demonstrate improvement in employee sleep and mental health after exposure to a novel workplace health promotion program to improve sleep.

The Association Between the Number of Consecutive Night Shifts and Insomnia Among Shift Workers: A Multi-Center Study

Objectives: There is a need to determine the optimal limit of consecutive night shift work to reduce insomnia caused by the accumulation of sleep problems among night shift workers. This study aimed to investigate the prevalence of insomnia caused by consecutive night shifts and evaluate the night shift duration that worsens insomnia the most, using a large amount of medical examination data. Methods: Night shift profiles and baseline demographics data of three hospitals were collected from January 2015 to December 2017. For subjects who had been examined more than once at the same institution, information corresponding to the most recent date was used. Multivariate logistic regression was performed to estimate odds ratios (ORs) and 95% confidence intervals (CIs). Pooled ORs were calculated by using the results of the three institutions. Results: Of the 33,669 participants, 31.3% were female. The average age was 41.1 ± 11.1 years and the prevalence of insomnia was 38.7% (n = 13,025). After adjusting for potential confounders and compared to workers who reported not working in consecutive night shifts, odds of insomnia were greatest among workers reporting working three consecutive nights (OR 2.65, 95% CI 1.97-3.56) followed by those working two nights (OR 1.81, 95% CI 1.45-2.26), five nights (OR 1.78, 95% CI 1.56-2.03), and four nights (OR 1.68, 95% CI 1.55-1.82). Conclusion: Our study demonstrates a significant relationship between consecutive night shift and insomnia with multicenter examination data, using common data model. This study could be a basis for establishing policies and guidelines that improve night shift workers' health.

Salivary Biomarkers and Work-Related Stress in Night Shift Workers

Work organization, such as shifts and night work, can interfere with the perception of work-related stress and therefore on the development of pathological conditions. Night shift work, particularly, can have a negative impact on workers’ wellbeing by interfering with the biological sphere. The aim of this study is to evaluate the associations between work activities, shift work effects and stress-related responses in 106 dock workers enrolled in southeast Italy. Dock workers’ tasks consist of complex activities that seemed to affect more sleep quality than work-related stress. An analysis of salivary biomarkers such as cortisol, α-amylase, melatonin and lysozyme was performed along with validated psycho-diagnostic questionnaires. Alpha-amylase showed a significant negative correlation with the effort/reward imbalance score; thus, the measurement of salivary α-amylase is proposed as a sensitive and non-invasive biomarker of work-related stress. This study may provide new insights into developing strategies for the management of night shift work. Salivary biomarkers should be further investigated in the future in order to develop simple and effective tools for the early diagnosis of work-related stress or its outcomes.

Internet-Based Individualized Cognitive Behavioral Therapy for Shift Work Sleep Disorder Empowered by Well-Being Prediction: Protocol for a Pilot Study

Background

Shift work sleep disorders (SWSDs) are associated with the high turnover rates of nurses, and are considered a major medical safety issue. However, initial management can be hampered by insufficient awareness. In recent years, it has become possible to visualize, collect, and analyze the work-life balance of health care workers with irregular sleeping and working habits using wearable sensors that can continuously monitor biometric data under real-life settings. In addition, internet-based cognitive behavioral therapy for psychiatric disorders has been shown to be effective. Application of wearable sensors and machine learning may potentially enhance the beneficial effects of internet-based cognitive behavioral therapy.

Objective

In this study, we aim to develop and evaluate the effect of a new internet-based cognitive behavioral therapy for SWSD (iCBTS). This system includes current methods such as medical sleep advice, as well as machine learning well-being prediction to improve the sleep durations of shift workers and prevent declines in their well-being.

Methods

This study consists of two phases: (1) preliminary data collection and machine learning for well-being prediction; (2) intervention and evaluation of iCBTS for SWSD. Shift workers in the intensive care unit at Mie University Hospital will wear a wearable sensor that collects biometric data and answer daily questionnaires regarding their well-being. They will subsequently be provided with an iCBTS app for 4 weeks. Sleep and well-being measurements between baseline and the intervention period will be compared.

Results

Recruitment for phase 1 ended in October 2019. Recruitment for phase 2 has started in October 2020. Preliminary results are expected to be available by summer 2021.

Conclusions

iCBTS empowered with well-being prediction is expected to improve the sleep durations of shift workers, thereby enhancing their overall well-being. Findings of this study will reveal the potential of this system for improving sleep disorders among shift workers.

Trial Registration

UMIN Clinical Trials Registry UMIN000036122 (phase 1), UMIN000040547 (phase 2); https://tinyurl.com/dkfmmmje, https://upload.umin.ac.jp/cgi-open-bin/ctr_e/ctr_view.cgi?recptno=R000046284

International Registered Report Identifier (IRRID)

DERR1-10.2196/24799

Sleep and Association With Cardiovascular Risk Among Midwestern US Firefighters

INTRODUCTION

Cardiovascular disease is the leading cause of on-duty fatalities among U.S. firefighters. Research has demonstrated that many modifiable risk factors are contributors to the high prevalence of cardiometabolic risk factors. The current study aimed to assess whether sleep is associated with cardiometabolic risk factors among Indianapolis firefighters. The findings could support improving sleep hygiene in this population.

MATERIAL AND METHODS

This cross-sectional study was conducted from the baseline data of eligible firefighters enrolled in "Feeding America's Bravest", a Mediterranean diet lifestyle intervention within the Indiana Fire Departments. Participants' sleep quality was categorized as "good" (≤ 8 points) or "bad" (>8 points) by a sleep quality questionnaire based on some questions from Pittsburgh Sleep Quality Index. In addition, firefighters' sleep duration was stratified based on the number of hours slept per night (≤6 as "short sleep" or >6 hours as normal). Linear and logistic regression models were used to examine the association of sleep with cardiometabolic risk factors.

RESULTS

A total of 258 firefighters were included. Bad sleepers had higher weight, greater waist circumference, higher body mass index (BMI), and increased body fat (all p<0.01) compared to good sleepers. Similarly, participants with short sleep duration were heavier (p<0.02), had greater BMI (p<0.02) and increased body fat (p<0.04) compared with participants with normal sleep duration. Both bad and short sleepers had a higher prevalence of hypertension and obesity (p <0.05).

CONCLUSIONS

Our study supports that both sleep quality and quantity are associated with cardiometabolic risk among firefighters.

Nutritional and Behavioral Approaches to Body Composition and Low-Grade Chronic Inflammation Management for Older Adults in the Ordinary and COVID-19 Times

As more insight is gained into personalized health care, the importance of personalized nutritional and behavioral approaches is even more relevant in the COVID-19 era, in addition to the need for further elucidation regarding several diseases/conditions. One of these concerning body composition (in this context; bone, lean and adipose tissue) is osteosarcopenic adiposity (OSA) syndrome. OSA occurs most often with aging, but also in cases of some chronic diseases and is exacerbated with the presence of low-grade chronic inflammation (LGCI). OSA has been associated with poor nutrition, metabolic disorders and diminished functional abilities. This paper addresses various influences on OSA and LGCI, as well as their mutual action on each other, and provides nutritional and behavioral approaches which could be personalized to help with either preventing or managing OSA and LGCI in general, and specifically in the time of the COVID-19 pandemic. Addressed in more detail are nutritional recommendations for and roles of macro- and micronutrients and bioactive food components; the microbiome; and optimal physical activity regimens. Other issues, such as food insecurity and nutritional inadequacy, circadian misalignment and shift workers are addressed as well. Since there is still a lack of longer-term primary studies in COVID-19 patients (either acute or recovered) and interventions for OSA improvement, this discussion is based on the existing knowledge, scientific hypotheses and observations derived from similar conditions or studies just being published at the time of this writing.

Eating Duration throughout a Rotating Shift Schedule: A Case Study

OBJECTIVE

The impact of the rotation between different shifts and free days within a short period of time on the food consumption is poorly addressed in the literature. Our objective was to characterize the eating duration (ED) over 10 d of clockwise rotating and to associate it with the intake of energy and macronutrients.

METHODS

Thirty male shift-workers from a mining company were evaluated over a complete rotation shift schedule of 10 consecutive days (2 d of morning shifts, 2 d of afternoon shifts, 24 h free-day, 2 d of night shifts, and three free days). ED was defined as the interval between the first meal after awaking and last meal before sleep onset. Sleep/wake periods and food intake were evaluated by actigraphy and 24 h recalls, respectively. Generalized models were used to analyze the variation in ED and its association with nutrient intake over the shift schedule.

RESULTS

ED periods showed significant variations throughout shift rotation and were associated with energy intake. The highest energy intake (3410 ± 235 kcal) and longest ED (20.7 ± 1.2 h) were found on Day 5, the day between afternoon and night shifts, and a part of Day 6 (night shift), i.e., in the longest period of wakefulness and the shortest sleep duration (4.7 ± 0.3 h) (p < 0.05 for all). The lowest energy intake (1284 ± 125 kcal) and shortest ED (4.96 ± 0.7 h) (p < 0.05) occurred after the last night shift (Day 7). The balance between the percentage of macronutrients did not differ statistically between the ED periods.

CONCLUSIONS

In general, longer periods of wakefulness showed greater energy intake, demonstrating the tendency of workers to eat around the clock during their shift. Even with the energy intake variation, the balance of macronutrients remained the same over the ED periods. Despite the need of confirmation in future studies, these results suggest that the management of ED period could be considered in the nutritional approach of shift workers.

Cardiovascular and metabolic risk factors of shift workers within the automotive industry

Background

Previous research highlighted the importance of identifying the modifiable risk factors among shift workers in specific industries to take effective preventative and therapeutic steps to decrease the risks associated with non-communicable chronic diseases.

Aim

The aim of this study was to investigate the prevalence of cardiovascular and metabolic disease risk factors among shift workers within the automotive industry.

Setting

This study was conducted at a car manufacturing company in the Eastern Cape Province of South Africa.

Methods

The study employed a cross-sectional quantitative design. Body mass index was calculated, and the American College for Sports Medicine classification for normal weight, overweight and obesity was used to assess the weight status of the workers. Fasting blood glucose and cholesterol as well as blood pressure (BP) were also measured.

Results

Seventy-five automotive shift workers participated in the research. Twenty-three per cent of the participants had no risk factors, 30.6% had one risk factor, 34.7% had two risk factors and only 5.3% exhibited four risk factors. Sixty-six percent of participants were classified as either pre-obese or obese, while 55% were hypertensive. Systolic BP (r = 0.258; p < 0.05), diastolic BP (r = 0.342; p < 0.01), cholesterol (r = 0.258; p < 0.05) and age (r = 0.271; p < 0.05) significantly correlated with body mass index.

Conclusion

This study highlights the prevalence of risk factors for cardiovascular diseases among employees in the automotive industry. However, it does not show any risk factors for metabolic diseases.

Assessment of work-related stress by using salivary cortisol level examination among early morning shift workers

OBJECTIVE

Early morning shifts have a negative effect on the hypothalamic-pituitary-adrenal axis. The aim of this study was to comprehensively assess the extent of occupational stress in early shift workers of the car industry by using salivary cortisol as an objective marker during a workday and on a day off.

METHODS

For this cross-sectional epidemiological type of study, a survey included 55 suitable volunteers from the car industry. Five saliva samples were collected according to the following schedule: during one work day in the morning, during the morning shift from 6 a.m. - 2 p.m., then after the shift was completed, 3 hours after work and in the evening before going to sleep. Control samples were taken from the same participants on a day off. Radioimmunoanalysis was used as the main analytical method, and the effect of factors and between-factor interactions on the levels of salivary cortisol during the workday were assessed using an ANOVA model.

RESULTS

The cortisol diurnal rhythm was as expected, with the highest values in the morning and declining to the lowest values in the evening hours. Concentrations of salivary cortisol showed higher values during the workday, especially higher concentrations of evening cortisol and attenuated cortisol slope. Based on the results, irregular shift work has a greater increase in cortisol excretion after waking in the morning and a slower progressive recovery of the organism during the workday. In addition, cortisol levels were significantly higher in older women than in older men but did not differ in younger subjects.

CONCLUSIONS

Salivary cortisol levels are a suitable objective marker of stress and can be used as a good predictor of occupational stress by public health services for the purposes of primary prevention.

Hemoglobin Changes After Long-Term Intermittent Work at High Altitude

Chronic high altitude hypoxia leads to an increase in red cell numbers and hemoglobin concentration. However, the effects of long-term intermittent hypoxia on hemoglobin concentration have not fully been studied. The aim of this study was to evaluate hemoglobin levels in workers commuting between an elevation of 3,800 m (2-week working shift) and lowland below 1,700 m (2 weeks of holiday). A total of 266 healthy males, aged from 20 to 69 years (mean age 45.9 ± 0.6 years), were included into this study. The duration of intermittent high altitude exposure ranged from 0 to 21 years. Any cardiac or pulmonary disorder was excluded during annual check-ups including clinical examination, clinical lab work (blood cell count, urine analysis, and biochemistry), ECG, echocardiography, and pulmonary function tests. The mean hemoglobin level in workers was 16.2 ± 0.11 g/dL. Univariate linear regression revealed an association of the hemoglobin levels with the years of exposure. Hemoglobin levels increased 0.068 g/dL [95% CI: 0.037 to 0.099, p < 0.001] for every year of intermittent high altitude exposure. Further, after adjusting for other confounding variables (age, living at low or moderate altitude, body mass index, and occupation) using multivariable regression analysis, the magnitude of hemoglobin level changes decreased, but remained statistically significant: 0.046 g/dL [95% CI: 0.005 to 0.086, p < 0.05]. Besides that, a weak linear relationship between hemoglobin levels and body mass index was revealed, which was independent of the years of exposure to high altitude (0.065 g/dL [95% CI: 0.006 to 0.124, p < 0.05]). We concluded that hemoglobin levels have a linear relationship with the exposure years spent in intermittent hypoxia and body mass index.

Decreased concentration of serum melatonin in nighttime compared with daytime female medical technologists in South Korea

Working during the night can disrupt the normal circadian rhythm by altering the melatonin level. A low level of melatonin is associated with an increased risk of cancer, possibly by decreasing the expression of tumor-suppressor genes, such as p53. To determine whether nighttime work is associated with melatonin level in serum as well as the expression of related genetic markers, we enrolled 100 female nighttime medical technologists employed at a hospital in South Korea. Melatonin concentration and melatonin receptor 1 (MT1) expression were significantly lower in nighttime than in daytime workers (1.84 pg/mL versus 4.04 pg/mL; 1.16 versus 1.61, respectively). However, p53 expression showed no difference between the groups. In summary, nighttime work could be an important risk factor for circadian disruption, but not a direct risk factor for cancer in medical technologists in South Korea.

Are Supplementation of Omega-3 and Ascorbic Acid Effective in Reducing Oxidative Stress and Depression among Depressed Shift Workers?

BACKGROUND

This study assessed the effect of supplementation of omega-3 fatty acids and ascorbic acid alone and in combination on the level of lipid peroxidation (malondialdehyde, MDA concentration), total antioxidant capacity (TAC) and depression scores in depressed rotational shift workers in the Tehran Shahid Tondgoyan Oil refinery.

MATERIAL AND METHODS

In this randomized, double-blind, placebo-controlled trial, 136 men who met the inclusion and exclusion criteria and had a Beck Depression Inventory (BDI) score ≥ 10 were selected. Among the participants, 33 received omega-3 fatty acid soft gel (1000 mg twice daily) with vitamin C (250 mg twice daily) (group 1), 31 took omega-3 fatty acid supplements and vitamin C placebo (group 2), 30 took omega-3 fatty acid supplement placebo and vitamin C (group 3), and 32 received omega-3 fatty acid supplement placebo and vitamin C placebo (group 4) for 2 months. Measured were serum MDA, TAC concentrations, and BDI scores at baseline and after 2 months.

RESULTS

This study showed that the BDI score was reduced significantly in all 4 groups, however, the level of decrease was more in the omega-3 fatty acid (alone) supplementation group (mean 6.29 score decrease) (p < 0.001). MDA level decreased significantly in groups with omega-3 fatty acids (mean 0.78 μmol/L ± 1.64 μmol/L decrease) (p = 0.014) or vitamin C supplementation alone (mean 0.74 μmol/L ± 1.55 μmol/L decrease) (p = 0.014), but not in combination.

CONCLUSIONS

Supplementation of omega-3 fatty acids alone and not in combination with vitamin C had a better impact on depression and MDA level pronounced in depressed male shift workers.

Circadian Activity Rhythms and Sleep in Nurses Working Fixed 8-hr Shifts

Shift work is associated with adverse health outcomes. The aim of this study was to explore the effects of shift work on circadian activity rhythms (CARs) and objective and subjective sleep quality in nurses. Female day-shift (n = 16), evening-shift (n = 6), and night-shift (n = 13) nurses wore a wrist actigraph to monitor the activity. We used cosinor analysis and time-frequency analysis to study CARs. Night-shift nurses exhibited the lowest values of circadian rhythm amplitude, acrophase, autocorrelation, and mean of the circadian relative power (CRP), whereas evening-shift workers exhibited the greatest standard deviation of the CRP among the three shift groups. That is, night-shift nurses had less robust CARs and evening-shift nurses had greater variations in CARs compared with nurses who worked other shifts. Our results highlight the importance of assessing CARs to prevent the adverse effects of shift work on nurses' health.