Disease In Shift Workers Research Articles

Nonalcoholic Fatty Liver Disease in Shift Workers and Its Effect on Peripheral Nerve Conduction: A Cross-Sectional Study.

Introduction Nonalcoholic fatty liver disease (NAFLD) presents as a multisystem disorder, heightening the risk of developing type 2 diabetes mellitus (T2DM) and cardiovascular diseases (CVDs). Occupation emerges as a significant factor influencing the occurrence of NAFLD. Research indicates that individuals engaged in shift work face an elevated risk of NAFLD, alongside obesity and T2DM, attributed to disruptions in their circadian rhythm, which precipitate hepatic steatosis and inflammation. Remarkably, peripheral neuropathy has been observed in conjunction with advanced liver disorders and NAFLD in the general population. However, the correlation between NAFLD and peripheral neuropathy remains unestablished in shift workers. Objective To identify NAFLD in seemingly healthy rotating shift workers and assess any potential impact of NAFLD on nerve function in this demographic. Methods This cross-sectional study involved 73 apparently healthy nonalcoholic security guards (aged 35 to 60 years) working in rotating shifts. The study included a comprehensive assessment, beginning with a medical history, an evaluation of physical activity, and anthropometric measurements. Confirmation of NAFLD was achieved through abdominal ultrasonography (USG), followed by the analysis of biochemical parameters. Motor and sensory nerve conduction studies (NCS) were conducted on participants with normal vitamin B12 levels using the Aleron electromyograph (EMG) machine (Recorders and Medicare Systems Private Ltd, Budanpur, India). The evaluation encompassed the Median and Common Peroneal motor nerves, as well as Median and Sural sensory nerves. Recorded parameters for motor nerves included distal motor latency (DML), compound muscle action potential (CMAP) amplitude, conduction velocity (CV), and F-wave minimum latency (F-wave), while sensory nerve parameters comprised sensory onset latency (SOL), sensory nerve action potential (SNAP) amplitude, and CV. Results Among 73 healthy security guards working in rotating shifts, 76.1% were diagnosed with NAFLD through abdominal ultrasound. Following participant withdrawals and exclusions due to vitamin B12 deficiency, a comparison of NCS parameters between NAFLD (n=24) and Non-NAFLD (n=12) groups revealed no significant disparities in motor or sensory parameters, except for a slightly diminished CMAP amplitude in the peroneal nerve of NAFLD subjects (8.21±2.83mV vs ±10.22±2.30 mV, p< 0.040). However, these differences fell within normal ranges, indicating no notable impact on peripheral nerve conduction in the presence of NAFLD. Conclusion The results indicate a high prevalence of NAFLD among individuals working rotating shifts. Moreover, the investigation suggests that despite the presence of NAFLD, there is no discernible influence on motor and sensory peripheral nerve conduction, particularly in common peroneal, median, and sural nerves.

Effect of oral melatonin treatment on insulin resistance and diurnal blood pressure variability in night shift workers. A double-blind, randomized, placebo-controlled study

BackgroundNight shift work is associated with sleep disturbances, obesity, and cardiometabolic diseases. Disruption of the circadian clock system has been suggested to be an independent cause of type 2 diabetes and cardiovascular disease in shift workers. We aimed to improve alignment of circadian timing with social and environmental factors with administration of melatonin. MethodsIn a randomized, placebo-controlled, prospective study, we analysed the effects of 2 mg of sustained-release melatonin versus placebo on glucose tolerance, insulin resistance indices, sleep quality, circadian profiles of plasma melatonin and cortisol, and diurnal blood pressure profiles in 24 rotating night shift workers during 12 weeks of treatment, followed by 12 weeks of wash-out. In a novel design, the time of melatonin administration (at night or in the morning) depended upon the shift schedule. We also compared the baseline profiles of the night shift (NS) workers with 12 healthy non-night shift (NNS)-working controls. ResultsWe found significantly impaired indices of insulin resistance at baseline in NS versus NNS (p < 0.05), but no differences in oral glucose tolerance tests nor in the diurnal profiles of melatonin, cortisol, or blood pressure. Twelve weeks of melatonin treatment did not significantly improve insulin resistance, nor did it significantly affect diurnal blood pressure or melatonin and cortisol profiles. Melatonin administration, however, caused a significant improvement in sleep quality which was significantly impaired in NS versus NNS at baseline (p < 0.001). ConclusionsRotating night shift work causes mild-to-moderate impairment of sleep quality and insulin resistance. Melatonin treatment at bedtime improves sleep quality, but does not significantly affect insulin resistance in rotating night shift workers after 12 weeks of administration.

Shift Work is Associated with an Elevated White Blood Cell Count: A Systematic Review and Meta-Analysis.

The white blood cell (WBC) count increases significantly in reaction to infections and certain chronic diseases. Shift employment increases the risk for chronic low-grade inflammation and the progression of several chronic diseases. The objective of this study was to systematically evaluate the evidence from studies on total and differential WBC counts in shift employees. A literature search was performed in PubMed®, Web of Science, and Scopus databases using keywords for research published before March 1, 2022. A meta-analysis was conducted for total and differential WBC counts using a random-effects approach. A total of 25 studies covering a sample of 37,708 day and shift employees were included in this review. The studies represented America, Europe, East Asia, and Middle East. A significant increase in the total counts (×109/L) of WBC [mean difference (MD) = 0.43; 95% confidence interval (CI): 0.34-0.52; P < 0.001], lymphocytes (MD = 0.16; 95% CI: 0.02-0.30; P = 0.02), monocytes (MD = 0.04; 95% CI: 0-0.07; P = 0.03), and eosinophils (MD = 0.01; 95% CI: 0-0.01; P = 0.03) was observed in shift workers compared to the day counterparts. However, neutrophils and basophils were not significantly different between the groups. Shift work significantly increases the total and differential blood counts in peripheral circulation. Therefore, total and differential WBC counts represent a relatively inexpensive biomarker for diagnostics and prognostics of diseases in shift workers.

CrossTalk opposing view: Insufficient sleep is not responsible for increased risk of metabolic disease in shift workers.

CrossTalk opposing view: Insufficient sleep is not responsible for increased risk of metabolic disease in shift workers.

CrossTalk proposal: Insufficient sleep is responsible for increased risk of metabolic disease in shift workers.

CrossTalk proposal: Insufficient sleep is responsible for increased risk of metabolic disease in shift workers.

Shift Work and Cardiovascular Disease

Shift work has become a necessity in many industries; however, the shift work system disrupts the endogenous circadian rhythm by changing the sleep-wake cycle and can prepare the ground for cardiovascular diseases. Shift workers are at risk of some chronic disorders such as hypertension, elevated serum lipids and body weight, cardiovascular conditions, including coronary artery disease, acute myocardial infarction, and stroke and metabolic syndrome. Furthermore, it is thought that changes occur in the concentrations of melatonin, cortisol, ghrelin, and leptin due to the night shift work, and this is associated with the change in the circadian rhythm. In this condition, reconsidering some precautions can reduce the risk of cardiovascular disease. Recently, it has been shown that exercise can be effective in reducing the risk of cardiovascular disease in shift workers. The aim of this review is to determine the relationship with cardiovascular diseases and shift work system.

Human seasonal and circadian studies in Antarctica (Halley, 75°S)

Living for extended periods in Antarctica exposes base personnel to extremes of daylength (photoperiod) and temperature. At the British Antarctic Survey base of Halley, 75°S, the sun does not rise for 110 d in the winter and does not set for 100 d in summer. Photoperiod is the major time cue governing the timing of seasonal events such as reproduction in many species. The neuroendocrine signal providing photoperiodic information to body physiology is the duration of melatonin secretion which reflects the length of the night: longer in the short days of winter and shorter in summer. Light of sufficient intensity and spectral composition serves to suppress production of melatonin and to set the circadian timing and the duration of the rhythm. In humans early observations suggested that bright (>2000 lux) white light was needed to suppress melatonin completely. Shortly thereafter winter depression (Seasonal Affective Disorder or SAD) was described, and its successful treatment by an artificial summer photoperiod of bright white light, sufficient to shorten melatonin production. At Halley dim artificial light intensity during winter was measured, until 2003, at a maximum of approximately 500 lux in winter. Thus a strong seasonal and circadian time cue was absent. It seemed likely that winter depression would be common in the extended period of winter darkness and could be treated with an artificial summer photoperiod. These observations, and predictions, inspired a long series of studies regarding human seasonal and circadian status, and the effects of light treatment, in a small overwintering, isolated community, living in the same conditions for many months at Halley. We found little evidence of SAD, or change in duration of melatonin production with season. However the timing of the melatonin rhythm itself, and/or that of its metabolite 6-sulphatoxymelatonin (aMT6s), was used as a primary marker of seasonal, circadian and treatment changes. A substantial phase delay of melatonin in winter was advanced to summer phase by a two pulse 'skeleton' bright white light treatment. Subsequently a single morning pulse of bright white light was effective with regard to circadian phase and improved daytime performance. The circadian delay evidenced by melatonin was accompanied by delayed sleep (logs and actigraphy): poor sleep is a common complaint in Polar regions. Appropriate extra artificial light, both standard white, and blue enriched, present throughout the day, effectively countered delay in sleep timing and the aMT6s rhythm. The most important factor appeared to be the maximum light experienced. Another manifestation of the winter was a decline in self-rated libido (men only on base at this time). Women on the base showed lower aspects of physical and mental health compared to men. Free-running rhythms were seen in some subjects following night shift, but were rarely found at other times, probably because this base has strongly scheduled activity and leisure time. Complete circadian adaptation during a week of night shift, also seen in a similar situation on North Sea oil rigs, led to problems readapting back to day shift in winter, compared to summer. Here again timed light treatment was used to address the problem.Sleep, alertness and waking performance are critically dependent on optimum circadian phase. Circadian desynchrony is associated with increased risk of major disease in shift workers. These studies provide some groundwork for countering/avoiding circadian desynchrony in rather extreme conditions.

Night shift work and inflammatory markers in male workers aged 20-39 in a display manufacturing company.

BackgroundThis study aimed to determine the association between shift work and inflammatory markers, which are independent risk factors of cardiovascular diseases, in male manual workers at a display manufacturing company.MethodsThis study was conducted between June 1 and July 31, 2015 on 244 male manual workers aged 20–39 years old at a display manufacturing company and investigated age, marital status, education level, alcohol consumption habit, smoking habit, regular exercise habit, sleep duration, sleep debt, sleep insufficiency, past medical history, current and past shift work experience, duration of shift work, and weekly work hours through face-to-face interviews using structured questionnaires and performed blood tests. Study participants were divided into daytime, former shift, and current shift workers based on the work schedule. Chi-square tests and one-way analyses of variance were performed to compare inflammatory markers and cardiovascular disease risk factors, and analyses of covariance were conducted after adjusting for variables potentially affecting inflammatory markers.ResultsHigh-sensitivity C-reactive protein (hs-CRP; mean ± standard deviation) levels in daytime, former shift, and current shift workers were 0.65 ± 0.43, 0.75 ± 0.43, and 0.86 ± 0.72 mg/L, respectively (p = 0.029). The leukocyte count (mean ± standard deviation) was 5,556 ± 1,123, 6,210 ± 1,366, and 6,530 ± 1,216 cells/μL, respectively (p < 0.001). Both hs-CRP level and leukocyte count were significantly higher in current shift workers than in daytime workers, and leukocyte count was higher in former shift workers than in daytime workers. After adjusting for variables potentially affecting inflammatory markers, hs-CRP levels (adjusted mean ± standard deviation) in daytime and current shift workers were 0.59 ± 0.06 and 0.92 ± 0.07 mg/L, respectively (p = 0.002). The leukocyte count (adjusted mean ± standard deviation) was 5,557 ± 124 and 6,498 ± 144 cells/μL, respectively (p < 0.001).ConclusionsA significant association between shift work and increases in inflammatory markers was confirmed. Because chronic low-grade inflammation plays an important role in the development of cardiovascular diseases, regular follow-up of inflammatory markers as a marker of cardiovascular diseases in shift workers may serve as an early indicator in predicting the effects of shift work on health.

Assessment of plasma homocysteine levels in shift healthcare workers

Previous studies have indicated an association between shift work and cardiovascular disease. Increased plasma homocysteine levels has been proposed as a cardiovascular risk factor independent of other conventional risk factors. Our aim is to verify the usefulness of plasma homocysteine as a screening test to prevent cardiovascular diseases in shift workers. Thirty rotating shift nurses and 28 daytime nurses have been submitted during 18 months to regular taking of arterial pressure and body weight. Venous blood was drawn to measure glycaemia, triglycerides, plasma cortisol level, HDL cholesterol, blood cell count, alanine-aminotransferase, aspartate-aminotransferasi, gamma-GT, and plasma homocysteine. No increase in average plasma homocysteine in rotating shift nurses, nor a higher frequency in hyperomocisteinemia than in daytime workers was found. A significant difference was observed in body weight and systolic blood pressure (p<0.05), which resulted higher in rotating shift workers than in daytime workers. A significant increase was observed in alanine-aminotransferase (ALT) among shift workers (p<0.05). Plasma homocysteine measurement should not be employed as a screening test for the prevention of cardiovascular disease in rotating shift workers.

KLF15 Establishes the Landscape of Diurnal Expression in the Heart.

Circadian rhythms offer temporal control of anticipatory physiologic adaptations in animals. In the mammalian cardiovascular system, the importance of these rhythms is underscored by increased cardiovascular disease in shift workers, findings recapitulated in experimental animal models. However, a nodal regulator that allows integration of central and peripheral information and coordinates cardiac rhythmic output has been elusive. Here, we show that kruppel-like factor 15 (KLF15) governs a biphasic transcriptomic oscillation in the heart with a maximum ATP production phase and a remodeling and repair phase corresponding to the active and resting phase of a rodent. Depletion of KLF15 in cardiomyocytes leads to a disorganized oscillatory behavior without phasic partition despite an intact core clock. Thus, KLF15 is a nodal connection between the clock and meaningful rhythmicity in the heart.

Short sleep duration increases the risk of chronic kidney disease in shift workers.

To investigate the association of sleep duration and shift work with development of chronic kidney disease (CKD) in Japanese workers. A total of 3600 participants without CKD were observed for an average of 4.4 years. The Cox proportional-hazards regression model was used to estimate hazard ratios and 95% confidence intervals of the risk of CKD associated with sleep duration and shift work. Sleep duration and shift work showed no significant association with the risk of CKD. Nevertheless, when the results were stratified by shift work status, short sleep duration was associated with a significantly higher risk of CKD among shift workers (hazard ratio = 3.60; 95% confidence interval: 1.52 to 10.68). Short sleep duration was a risk factor for early CKD but only among shift workers.

Effects of circadian disruption on the cardiometabolic system

The presence of day-night variations in cardiovascular and metabolic functioning is well known. However, only recently it has been shown that cardiovascular and metabolic processes are not only affected by the behavioral sleep/wake cycle but are partly under direct control of the master circadian pacemaker located in the suprachiasmatic nucleus (SCN). Heart rate, cardiac autonomic activity, glucose metabolism and leptin-involved in appetite control-all show circadian variation (i.e., under constant behavioral and environmental conditions). This knowledge of behavioral vs. circadian modulation of cardiometabolic function is of clinical relevance given the morning peak in adverse cardiovascular incidents observed in epidemiological studies and given the increased risk for the development of diabetes, obesity, and cardiovascular disease in shift workers. We will review the evidence for circadian control of cardiometabolic functioning, as well its sensitivity to light and melatonin, and discuss potential implication for therapy.

Methodological Aspects of Shift-Work Research

A major issue in shift-work research is to understand the possible ways in which shift work can impact performance and health. Nearly all body functions, from those of the cellular level to those of the entire body, are circadian rhythmic. Disturbances of these rhythms as well as the social consequences of odd work hours are of importance for the health and well-being of shift workers. This article reviews a number of common methodological issues which are of relevance to epidemiological studies in this area of research. It discusses conceptual problems regarding the use of the term “shift work,” and it underscores the need to develop models that explain the mechanisms of disease in shift workers.

Changes in frequency of premature complexes and heart rate variability related to shift work

OBJECTIVESTo investigate whether an increased risk of cardiovascular disease might be caused by increased arrhythmogeneity and by unfavourable changes in autonomic cardiac control the changes in the occurrence of premature...

Shift work modifies the circadian patterns of heart rate variability in nurses

Objective: The influence of shifting the work–sleep cycle on the circadian rhythm of cardiac autonomic activity was investigated by the spectral analysis of heart rate variability (HRV). Methods: The subjects were 10 healthy Japanese female nurses aged 33±3 (S.D.) years. The subjects underwent ambulatory 24-h electrocardiogram (ECG) recordings on the days of day shift (working from 08:00 to 17:00 h) and night shift (working from 21:40 to 08:40 h). Variables of the frequency domain of HRV were calculated for three activity states (work, awake but not working, and sleep). Results: The mean values of HRV variables over 24 h were not different between day shift and night shift. For both shifts, variables related to the sympathetic control (low frequency component in normalized units and low/high frequency component ratio) were the largest during the work period and the smallest during the sleep period, while an opposite order was present for variables related to the vagal control (high frequency component in absolute value and normalized units). HRV variables in each activity state were not different between the two shifts. Conclusions: The circadian rhythm of cardiac autonomic activity is largely modified by the level of physical activity regardless of the clock hour, which may have clinical implications when studying the circadian fluctuations of the onset of cardiovascular disease in shift workers.

Absenteeism of shift and day workers with special reference to peptic ulcer.

The causes and duration of sickness absences have been registered for workers in 30 plants of 17 member companies of The Japan Chemical Fibers and Textile Association (JCFTA). Diseases that caused absence were classified into 38 categories by plant physicians according to a simplified version of the International Classification of Diseases, and recorded monthly in the central file of JCFTA. Using 1982 data for 26, 324 male manufacturing workers including 13, 472 shift workers, incidences (inception rate) of diseases that caused absence and days lost due to them were studied in order to evaluate the effect of shift work. The incidence of peptic ulcer was significantly higher (rate ratlo=1.6) among shift workers as compared with day workers. The incidences of days lost due to other diseases in shift workers were almost equal to or lower than those in day workers.