Night shift work and incidence of diabetes in the Danish Nurse Cohort

Mediation Mendelian randomisation study on the effects of shift work on coronary heart disease and traditional risk factors via gut microbiota

Background

Epidemiological evidence suggests that there is an increased risk of coronary heart disease (CHD) related to jobs involving shift work (JSW), but the causality of and mechanism underlying such a relationship remain unclear. Therefore, we aimed to explore the relationship between JSW and CHD, investigating both causality and potential mediating factors.

Methods

We performed univariate, multivariate, and mediation Mendelian randomisation (MR) analyses using data from large genome-wide association studies focussed on JSW and CHD, as well as data on some CHD risk factors (type 2 diabetes, hypertension, obesity, and lipids measurement) and 196 gut microbiota taxa. Single-nucleotide polymorphisms significantly associated with JSW acted as instrument variables. We used inverse-variance weighting as the primary method of analysis.

Results

Bidirectional MR analysis indicated a robust effect of JSW on increased CHD risk; however, the existence of CHD did not affect the choice of JSW. We identified a mediating effects of type 2 diabetes and hypertension in this relationship, accounting for 11.89% and 14.80% of the total effect of JSW on CHD, respectively. JSW were also causally associated with the risk of type 2 diabetes and hypertension and had an effect on nine microbial taxa. The mediating influence of the Eubacterium brachy group at the genus level explained 16.64% of the total effect of JSW on hypertension. We found limited evidence for the causal effect of JSW on obesity and lipids measurements.

Conclusions

Our findings suggest a causal effect of JSW on CHD, diabetes, and hypertension. We also found evidence for a significant connection between JSW and alterations in the gut microbiota. Considering that certain microbial taxa mediated the effect of JSW on hypertension risk, targeting gut microbiota through therapeutics could potentially mitigate high risks of hypertension and CHD associated with JSW.

Sleep Deprivation and Fatigue among Nurses Working Consecutive Night Shifts: A Prospective Observational Study

PURPOSE

This study aimed to identify changes in sleep patterns and fatigue levels during consecutive night shifts among shift nurses and to determine the association between sleep parameters and increased fatigue levels during work.

METHODS

This prospective observational study employing ecological momentary assessments was conducted using data collected from 98 shift nurses working in Korean hospitals between June 2019 and February 2021. The sleep patterns were recorded using actigraphy. The participants reported their fatigue levels at the beginning and end of each night shift in real time via a mobile link. Linear mixed models were used for the analysis.

RESULTS

Nurses spent significantly less time in bed and had shorter sleep durations during consecutive night shifts than on off-duty days, whereas their wake times after sleep onset were much longer on off-duty days than on on-duty days. Fatigue levels were higher on the second and third night-shift days than on the first night-shift days. A shorter time spent in bed and asleep was associated with a greater increase in fatigue levels at the end of the shift than at the beginning.

CONCLUSION

Nurses experience significant sleep deprivation during consecutive night shifts compared with off-duty days, and this sleep shortage is associated with a considerable increase in fatigue levels at the end of shifts. Nurse managers and administrators must ensure sufficient intershift recovery time during consecutive night shifts to increase the time spent in bed and sleeping.

Relationship between night work and health-related quality of life: an analysis based on profiles and cumulative duration of exposure to night work among French workers in the CONSTANCES cohort

OBJECTIVE

The aim of this study is to estimate the association between night work and health-related quality of life (HRQoL) among French workers. The association between cumulative duration of night work and HRQoL was also investigated.

METHODS

Three career-long night work exposure groups were defined at inclusion in the CONSTANCES cohort: permanent night workers, rotating night workers and former night workers. Day workers with no experience of night work were the reference group. HRQoL was assessed using the Short Form Health Survey (SF-12), in particular the physical component summary (PCS) and mental component summary (MCS) scores, with a higher score indicating better HRQoL. Several linear regression models were built to test the association between night work exposure and HRQoL. The relationship between cumulative duration of night work and HRQoL scores was analyzed using generalised additive models.

RESULTS

The sample consisted of 10,372 participants. Former night workers had a significantly lower PCS score than day workers (β [95% CI]: - 1.09 [- 1.73; - 0.45], p = 0.001), whereas permanent night workers had a significantly higher MCS score (β [95% CI]: 1.19 [0.009; 2.36], p = 0.048). A significant decrease in PCS score from 5 to 20 years of cumulative night work was observed among former night workers.

CONCLUSIONS

Former night workers had poorer physical HRQoL in contrast to permanent and rotating night workers who had similar or even better HRQoL than day workers, suggesting the well-known healthy worker survivor effect. Consequently, both current and former night workers require regular and specific follow-up focused on the physical components of their health.

Cardiovascular risk factors among nurses: A global systematic review and meta-analysis

BACKGROUND

Nurses as the largest group of health workers have a very stressful job which can cause number of diseases specially increase cardiovascular risk factors. This study aims to investigate the overall epidemiology of cardiovascular disease (CVD) risk factors among nurses.

METHOD

We searched all four main databases such as Scopus, PubMed, Embase and Web of Sciences from the beginning of 2000 to March 2022 with appropriate Mesh Terms. We also searched Google scholar. Then we applied inclusion and exclusion criteria and after selection the studies the Newcastle-Ottawa Scale (NOS) was used to assess the methodological quality of included studies. Comprehensive Meta-analysis and R software was used for analysis.

RESULTS

Finally, 22 articles with a total number of 117922 nurses were included. Among all risk factors, sedentary lifestyle and lack of regular physical activity with a prevalence of 46.3% (CI 95%, 26.6-67.2) was regarded as the main prevalent risk factor among nurses. The mean systolic blood pressure (SBP) measured in the study population was 121.31 (CI 95%, 114.73-127.90) and the mean diastolic blood pressure (DBP) was 78.08 (CI 95%, 74.90-81.25). Also family history of cardiovascular disease (41.9%; 95% IC: 29.8-55.1%), being overweight (33.3%; 95% IC: 24.7-43.2%), and alcohol consumption (24.6%; 95% IC: 16.4-35.2%) was found among the participants.

CONCLUSION

Study results revealed that sedentary lifestyle was the main prevalent CVD risk factor among nurses followed by family history of cardiovascular disease, being overweight and alcohol consumption. Furthermore, among nurses with shift works almost all risk factors got higher score representing the worse condition in comparison with day workers' nurses. This study enables learning the associated risk factors of CVD among nurses to facilitate interventional programs with a view to reduce the exposure of nursing staff particularly those who work in shifts to cardiovascular risk factors.

1. WHAT WAS ALREADY KNOWN?

In general, many studies have emphasized the impact of the nursing profession on the incidence of some cardiovascular patients. Also, different shifts of nurses can have a double effect.

2. WHAT ARE THE NEW FINDINGS?

In this study, the mean for sedentary lifestyle was reported to be 46.3% which represented the most prevalent risk factor for cardiovascular risk factors among study population.

3. WHAT IS THEIR SIGNIFICANCE?

This study enables learning the associated risk factors of CVD among nurses to facilitate interventional programs with a view to reduce the exposure of nursing staff particularly those who work in shifts to cardiovascular risk factors. This information can comprise essential tools for health human resource management contributing to advance nursing.

The association between shift work exposure and cognitive impairment among middle-aged and older adults: Results from the Canadian Longitudinal Study on Aging (CLSA)

BACKGROUND

Shift work, especially rotating and night shift work, has been linked to a wide range of detrimental health outcomes. Occupational factors like shift work and their potential impact on cognitive functions have received little attention, and the evidence is inconclusive. The objective of our study is to explore associations between shift work exposure and cognitive impairment indicators based on comparisons with the normative standards from the Canadian population.

METHODS

Cross-sectional analyses were performed using baseline Canadian Longitudinal Study on Aging database, including 47,811 middle-aged and older adults (45-85 years). Three derived shift work variables were utilized: ever exposed to shift work, shift work exposure in longest job, and shift work exposure in current job. Four cognitive function tests were utilized, Rey Auditory Verbal Learning Tests (immediate and delayed) representing memory domain, and Animal Fluency, and Mental Alteration, representing the executive function domain. All cognitive test scores included in study were normalized and adjusted for the participant's age, sex, education and language of test administration (English and French), which were then compared to normative data to create "cognitive impairment' variables. Unadjusted and adjusted multivariable logistic regression models were used to determine associations between shift work variables and cognitive impairment individually (memory and executive function domains), and also for overall cognitive impairment.

RESULT

Overall, one in every five individuals (21%) reported having been exposed to some kind of shift work during their jobs. Exposure to night shift work (both current and longest job) was associated with overall cognitive impairment. In terms of domain-based measures, night shift work (longest job) was associated with memory function impairment, and those exposed to rotating shift work (both current and longest job) showed impairment on executive function measures, when compared to daytime workers.

CONCLUSION

This study suggests disruption to the circadian rhythm, due to shift work has negative impact on cognitive function in middle-aged and older adults and this warrants further investigation.

Shift work is associated with an increased risk of type 2 diabetes and elevated RBP4 level: cross sectional analysis from the OHSPIW cohort study

BACKGROUND

Shift work, with its growing prevalence globally, disrupts the body's inherent circadian rhythm. This disruption may escalate the risk of chronic diseasesxacerbate chronic disease risk by dysregulating physiological, behavioral, and psychosocial pathways. This study aimed to evaluate the effect of shift work on type 2 diabetes (T2DM) and Retinol binding protein 4 (RBP4) level.

METHODS

The current study employed a multi-stage stratified cluster sampling technique, examining 1499 oilfield workers from the OHSPIW cohort who participated in occupational health assessments between March 2017 and June 2018.The evaluation involved shift work, sleep quality, T2DM status with questionnaires and plasma RBP4 levels in blood samples. Statistical analysis includes, Chi-square tests, t-tests, multivariate logistic regression analyses, and multivariate linear mixed models.

RESULTS

The prevalence rate of T2DM in shift workers (6.56%) was significantly higher than in day workers (4.21%) (OR = 1.60, 95% CI: 1.01-2.53), with no significant difference found in the family history of diabetes, hypertension, or other chronic heart diseases (P = 0.378). The shift worker (6.89 ± 3.35) also exhibited distinctly higher PSQI scores than day workers (5.99 ± 2.87) (P < 0.001). Adjusting the age, gender, BMI, family income, tobacco smoking, alcohol drinking and PSQI, hailed shift work as a risk factor for T2DM (OR = 1.91, 95% CI: 1.17-3.14). The pairwise comparison revealed significant differences in RBP4 levels across different groups: shift and non-shift workers both with and without T2DM (P < 0.001). The RBP4 level of the shift group without T2DM was higher than the non-shift group without T2DM (P < 0.05). The levels of RBP4 level in shift and non-shift groups with T2DM was higher than those without T2DM (P < 0.05). The multivariate linear mixed model showed that when age, gender, BMI, diabetes, PSQI, family income, smoking and drinking remained unchanged, the RBP4 level of the shift workers increased by an average of 9.51 μg/mL compared with the day workers.

CONCLUSIONS

Shift work is associated with an increased risk of T2DM and high levels of RBP4. Follow-up of RBP4 could facilitateearly detection of T2DM among shift workers.

Association of rotating night shift work, CLOCK, MTNR1A, MTNR1B genes polymorphisms and their interactions with type 2 diabetes among steelworkers: a case-control study

BACKGROUND

The purpose of this study is to investigate the association of rotating night shift work, CLOCK, MTNR1A, MTNR1B genes polymorphisms and their interactions with type 2 diabetes among steelworkers.

METHODS

A case-control study was conducted in the Tangsteel company in Tangshan, China. The sample sizes of the case group and control group were 251 and 451, respectively. The logistic regression, log-linear model and generalized multifactor dimensionality (GMDR) method were used to investigate the interaction between circadian clock gene, melatonin receptor genes and rotating night shift work on type 2 diabetes among steelworkers. Relative excess risk due to interaction (RERI) and attributable proportions (AP) were used to evaluate additive interactions.

RESULTS

Rotating night shift work, current shift status, duration of night shifts, and average frequency of night shifts were associated with an increased risk of type 2 diabetes after adjustment for confounders. Rs1387153 variants in MTNR1B was found to be associated with an increased risk of type 2 diabetes, which was not found between MTNR1A gene rs2119882 locus, CLOCK gene rs1801260 locus and the risk of type 2 diabetes. The association between rotating night shift work and risk of type 2 diabetes appeared to be modified by MTNR1B gene rs1387153 locus (RERI = 0.98, (95% CI, 0.40-1.55); AP = 0.60, (95% CI, 0.07-1.12)). The interaction between MTNR1A gene rs2119882 locus and CLOCK gene rs1801260 locus was associated with the risk of type 2 diabetes (RERI = 1.07, (95% CI, 0.23-1.91); AP = 0.77, (95% CI, 0.36-1.17)). The complex interaction of the MTNR1A-MTNR1B-CLOCK-rotating night shift work model based on the GMDR methods may increase the risk of type 2 diabetes (P = 0.011).

CONCLUSIONS

Rotating night shift work and rs1387153 variants in MTNR1B were associated with an increased risk of type 2 diabetes among steelworkers. The complex interaction of MTNR1A-MTNR1B-CLOCK-rotating night shift work may increase the risk of type 2 diabetes.

Impaired Melatonin Secretion, Oxidative Stress and Metabolic Syndrome in Night Shift Work

Metabolic syndrome has been associated in many studies with working in shifts. Even if the mechanistic details are not fully understood, forced sleep deprivation and exposure to light, as happens during night shifts, or irregular schedules with late or very early onset of the working program, lead to a sleep-wake rhythm misalignment, metabolic dysregulation and oxidative stress. The cyclic melatonin secretion is regulated by the hypothalamic suprachiasmatic nuclei and light exposure. At a central level, melatonin promotes sleep and inhibits wake-signals. Beside this role, melatonin acts as an antioxidant and influences the functionality of the cardiovascular system and of different metabolic processes. This review presents data about the influence of night shifts on melatonin secretion and oxidative stress. Assembling data from epidemiological, experimental and clinical studies contributes to a better understanding of the pathological links between chronodisruption and the metabolic syndrome related to working in shifts.

Relationship of long working hours and night shift working hours with incident diabetes: a retrospective cohort study in Taiwan

PURPOSE

The relationship among long working hours, night shift working hours, and diabetes is still unclear. We aimed to evaluate the association of long working hours and night shift working hours with diabetes among health care workers.

METHODS

We conducted a retrospective cohort study among health care workers in a tertiary medical center in Taiwan from 2002 to 2019. We compared the risk of diabetes among tertiles of total working hours (35-41, 42-45, and ≥46 h per week) and evaluated the relationship between long working hours and diabetes risk. We divided participants into three work patterns: day work only, evening shift workers, and night shift workers. In night shift workers, we further evaluated night shift working hours and incident diabetes using tertiles of night shift working hours (<17, 17-45, and ≥46 h per month). We estimated hazard ratios and 95% confidence intervals for incident diabetes using multivariable Cox proportional hazards models.

RESULTS

The study included 7081 participants. There were 301 incident cases of diabetes during 52,454 person-years. The adjusted hazard ratio (95% confidence interval) for participants who worked greater than or equal to 46 working hours per week was 3.45 (1.27, 9.39) compared with those who worked 35-41 hours. Compared with night shift workers who worked less than 17 h, the adjusted hazard ratios (95% confidence interval) for those who worked 17-45 and ≥46 night shift working hours per month were 2.26 (1.08, 4.75) and 2.60 (1.27, 5.33), respectively.

CONCLUSIONS

Long working hours and night shift working hours increased the risk of diabetes.

Development and Internal Validation of Risk Assessment Models for Chronic Obstructive Pulmonary Disease in Coal Workers

Coal workers are more likely to develop chronic obstructive pulmonary disease due to exposure to occupational hazards such as dust. In this study, a risk scoring system is constructed according to the optimal model to provide feasible suggestions for the prevention of chronic obstructive pulmonary disease in coal workers. Using 3955 coal workers who participated in occupational health check-ups at Gequan mine and Dongpang mine of Hebei Jizhong Energy from July 2018 to August 2018 as the study subjects, random forest, logistic regression, and convolutional neural network models are established, and model performance is evaluated to select the optimal model, and finally a risk scoring system is constructed according to the optimal model to achieve model visualization. The training set results show that the logistic, random forest, and CNN models have sensitivities of 78.55%, 86.89%, and 77.18%; specificities of 85.23%, 92.32%, and 87.61%; accuracies of 81.21%, 85.40%, and 83.02%; Brier scores of 0.14, 0.10, and 0.14; and AUCs of 0.76, 0.88, and 0.78, respectively, and similar results are obtained for the test set and validation set, with the random forest model outperforming the other two models. The risk scoring system constructed according to the importance ranking of random forest predictor variables has an AUC of 0.842; the evaluation results of the risk scoring system shows that its accuracy rate is 83.7% and the AUC is 0.827, and the established risk scoring system has good discriminatory ability. The random forest model outperforms the CNN and logistic regression models. The chronic obstructive pulmonary disease risk scoring system constructed based on the random forest model has good discriminatory power.

Enhancing the metabolic benefits of exercise: Is timing the key?

Physical activity represents a potent, non-pharmacological intervention delaying the onset of over 40 chronic metabolic and cardiovascular diseases, including type 2 diabetes, coronary heart disease, and reducing all-cause mortality. Acute exercise improves glucose homeostasis, with regular participation in physical activity promoting long-term improvements in insulin sensitivity spanning healthy and disease population groups. At the skeletal muscle level, exercise promotes significant cellular reprogramming of metabolic pathways through the activation of mechano- and metabolic sensors, which coordinate downstream activation of transcription factors, augmenting target gene transcription associated with substrate metabolism and mitochondrial biogenesis. It is well established that frequency, intensity, duration, and modality of exercise play a critical role in the type and magnitude of adaptation; albeit, exercise is increasingly considered a vital lifestyle factor with a critical role in the entrainment of the biological clock. Recent research efforts revealed the time-of-day-dependent impact of exercise on metabolism, adaptation, performance, and subsequent health outcomes. The synchrony between external environmental and behavioural cues with internal molecular circadian clock activity is a crucial regulator of circadian homeostasis in physiology and metabolism, defining distinct metabolic and physiological responses to exercise unique to the time of day. Optimising exercise outcomes following when to exercise would be essential to establishing personalised exercise medicine depending on exercise objectives linked to disease states. We aim to provide an overview of the bimodal impact of exercise timing, i.e. the role of exercise as a time-giver (zeitgeber) to improve circadian clock alignment and the underpinning clock control of metabolism and the temporal impact of exercise timing on the metabolic and functional outcomes associated with exercise. We will propose research opportunities that may further our understanding of the metabolic rewiring induced by specific exercise timing.

Experiences and perceptions of nurses working night shift: a qualitative systematic review

OBJECTIVE

The objective of this review was to examine the available evidence on the experiences and perceptions of nurses working the night shift within any specialty in the acute care, subacute, or long-term care setting.

INTRODUCTION

Nurses are required for around-the-clock patient care. Night shift nurses can experience detrimental effects because of their work hours, which disrupt their normal circadian rhythm. Understanding nurses' experiences and perceptions when working night shift will facilitate the development of strategies to minimize the potential negative effects of working at night. In examining nurses' experiences and perceptions of working night shift, there is scope to explore how to improve night shift nurses' practice environment and job satisfaction, which will then translate to improved nurse and patient outcomes.

INCLUSION CRITERIA

This review included qualitative studies focused on the experiences and perceptions of registered nurses and licensed practical nurses who work the night shift or rotate between day and night shift.

METHODS

This review followed the JBI methodology for systematic reviews of qualitative evidence. The methodology used was consistent with the a priori protocol. Studies included in this review were those published in full text, English, and between 1983 (when the seminal work on hospitals that attract and retain nurses was published) and February 2021, when the search was completed. The main databases searched for published and unpublished studies included MEDLINE, CINAHL, Embase, PsycINFO, and Web of Science.From the search, two reviewers independently screened the studies against the inclusion criteria, and then papers selected for inclusion were assessed for methodological quality. Qualitative data were extracted from the included papers independently by the four reviewers. Results from each reviewer were discussed and clarified to reach agreement. The extracted findings were pooled and examined for shared meaning, coded, and grouped into categories. Common categories were grouped into meta-synthesis to produce a comprehensive set of synthesized findings. The final synthesized findings were graded using the ConQual approach to determine the level of confidence (trust) users may have in the value of the synthesized findings.

RESULTS

Thirty-four papers, representing 33 studies, met the criteria for inclusion. The studies were conducted in 11 countries across six continents, with a total of 601 participants. From these, a total of 220 findings were extracted and combined to form 11 categories based on similarity in meaning, and three syntheses were derived: i) The "Other" Shift: the distinctiveness of night nursing; ii) Juggling sleep and all aspects of life when working nights; and iii) Existing in the Twilight Zone: battling the negative impact of sleep deprivation consumes nurses who strive to keep patients, self, and others safe.

CONCLUSIONS

The major conclusions from this review are the uniqueness of working the night shift and the sleep deprivation of night nurses. Organizational strategies and support are needed for those working this shift, which will enhance nurse and patient safety.

SYSTEMATIC REVIEW REGISTRATION NUMBER

PROSPERO CRD42019135294.

The role of light pollution in mammalian metabolic homeostasis and its potential interventions: A critical review

Irregular or unnatural artificial light causes severe environmental stress on the survival and health of organisms, which is rapidly becoming a widespread new type of environmental pollution. A series of disruptive behaviors to body homeostasis brought about by light pollution, including metabolic abnormalities, are likely to be the result of circadian rhythm disturbances. Recently, the proposed role of light pollution in metabolic dysregulation has accelerated it into an emerging field. Hence, the regulatory role of light pollution in mammalian metabolic homeostasis is reviewed in this contribution. Light at night is the most widely affected type of light pollution, which disrupts metabolic homeostasis largely due to its disruption of daily food intake patterns, alterations of hormone levels such as melatonin and glucocorticoids, and changes in the rhythm of inflammatory factor production. Besides, light pollution impairs mammalian metabolic processes in an intensity-, photoperiod-, and wavelength-dependent manner, and is also affected by species, gender, and diets. Nevertheless, metabolic disorders triggered by light pollution are not irreversible to some extent. Potential interventions such as melatonin supplementation, recovery to the LD cycle, time-restricted feeding, voluntary exercise, wearing blue light-shied goggles, and bright morning light therapy open a bright avenue to prevent light pollution. This work will help strengthen the relationship between light information and metabolic homeostasis and provide new insights for the better prevention of metabolic disorders and light pollution.

Nurses' steps, distance traveled, and perceived physical demands in a three-shift schedule

BACKGROUND

The physical job demands of hospital nurses are known to be very high. Although many studies have measured the physical activities of nurses subjectively using questionnaires, it remains necessary to quantify and measure nurses' physical activity at work using objective indicators. This study was conducted to address this gap in the literature by analyzing nurses' physical activity using both objective measurements and subjective perceptions. The number of steps, distance traveled, and actual work hours were measured during work, and the influence of related factors was analyzed.

METHODS

Using a cross-sectional design, survey and activity tracking data were collected from nurses who worked in three shifts in two tertiary hospitals located in the capital region of South Korea. The participants comprised 117 nurses working in four different units (medical ward, surgical ward, intensive care unit, emergency room), and data from 351 shifts were used in the final analysis. Between-group differences in the main variables were analyzed using the t-test, the Mann-Whitney test, analysis of variance, or the Kruskal-Wallis test, as appropriate. The relationships were examined through multiple linear regression analysis.

RESULTS

The average number of steps and distance traveled were greatest for nurses working in the emergency room, followed by the intensive care unit, surgical ward, and medical ward (in descending order). Younger nurses and those with shorter unit experience tended to have the greatest number of steps and distance traveled.

CONCLUSION

Using activity trackers, this study derived physical activity measures such as number of steps and distance traveled, enabling an objective examination of physical activity during shifts. Nurses' level of physical activity differed depending on the type of nursing unit, nurses' age, and unit experience. These results suggest the need for support programs that are specific to the job demands of specific nursing units.

Influence of occupational exposure on hyperuricemia in steelworkers: a nested case-control study

BACKGROUND

Occupational exposure may be associated with an increased risk of developing hyperuricemia. This study sheds lights on the association between occupational exposure and hyperuricemia in steelworkers.

METHOD

A nested case-control study was conducted within a cohort of workers in steel companies to explore the association between occupational exposure and hyperuricemia. The case group consisted of a total of 641 cases of hyperuricemia identified during the study period, while 641 non-hyperuricemia subjects with the same age and gender distribution were randomly selected from the cohort as the control group.

RESULTS

The incidence rate of hyperuricemia among workers in the steel company was 17.30%, with an incidence density of 81.32/1,000 person-years. In comparison to the reference group, the risks of developing hyperuricemia for steelworkers undergoing ever shifts, current shifts, heat exposure, and dust exposure were 2.18 times, 1.81 times, 1.58 times and 1.34 times higher respectively. The odds ratios (ORs) and 95% confidence intervals (CIs) were 1.87(1.12-3.13) and 2.02(1.21-3.37) for the cumulative number of days of night work at 0-1,972.80 and ≥ 1,972.80 (days), respectively. Compared to the group with the cumulative heat exposure of 0 (°C/year), the ORs (95% CI) for the risk of developing hyperuricemia in the groups with the cumulative heat exposure of 0-567.83 and ≥ 567.83 (°C/year) were 1.50(1.02-2.22) and 1.64(1.11-2.43), respectively. The OR (95% CI) for the risk of developing hyperuricemia was 1.56(1.05-2.32) at the cumulative dust exposure of ≥ 30.02 (mg/m³/year) compared to that at the cumulative dust exposure of 0 (mg/m³/year). Furthermore, there was a multiplicative interaction between heat exposure and dust exposure in the development of hyperuricemia.

CONCLUSION

Shift work, heat, and dust are independent risk factors for the development of hyperuricemia in steelworkers. Additionally, there is a multiplicative interaction between heat exposure and dust exposure in the development of hyperuricemia. Interventions for shift work, heat and dust may help to reduce the incidence rate of hyperuricemia and improve the health of steelworkers.

Work Conditions of Italian Nurses and Their Related Risk Factors: A Cohort Investigatory Study

(1) Background: Nursing is a satisfying employment pathway, as nurses preserve lives, but it is also considered one of the most stressful care professions. Nursing is a lifesaving and highly satisfying profession, yet it is considered one of the most stressful occupations. This study aimed to assess differences in anxiety, depression and stress states among nurses according to gender, work history, shift and body mass index (BMI) characteristics. (2) Methods: An online questionnaire was addressed to all Italian nurses during May 2022, investigating anxiety, depression and stress conditions according to the Depression, Anxiety and Stress Scale-21 Items (DASS-21) and sampling characteristics, such as sex, work experience, shift and BMI values. (3) Results: A total of 408 Italian nurses answered the questionnaire. Significant differences between the following were reported: anxiety levels and work experience, since nurses employed over 6 years reported higher anxiety levels than their younger colleagues (p = 0.035); depression levels and sex (p = 0.017), as females reported higher depression levels than males; and also between depression levels and BMI levels (p = 0.003), as 5.90% of overweight and 2.50% of obese participants reported extremely severe depression. By considering stress levels according to sampling characteristics, significant differences were registered according to BMI levels (p < 0.001), as overweight subjects reported higher stress levels (7.40%) than the other subgroups. Finally, significant associations were recorded between anxiety, depression and stress conditions with sex, work experience, shift and BMI. (4) Conclusions: The data were in agreement with the current literature, indicating that nurses might take care not only of their patients but also of themselves, in both the physical and mental aspects.

Associations of chronotype and sleep patterns with metabolic syndrome in the Hispanic community health study/study of Latinos

Sleep duration, sleep efficiency, and sleep timing have been shown to have potential effects on metabolic functions relevant to circadian rhythms. It is not clear if the impact of sleep patterns on metabolic risk factors is through sociocultural and environmental factors or circadian misalignment. We investigated the associations of sleep patterns, chronotype, and social jet lag with metabolic syndrome among non-shift worker Hispanic/Latino adults. We used cross-sectional data from the Sueño Ancillary Study of The Hispanic Community Health Study/Study of Latinos (HCHS/SOL). Data from a subsample of 2189 participants aged 18-64 years were used in the analysis. Mean nightly sleep duration, mean sleep onset time, mean sleep offset time, mean sleep midpoint time, sleep efficiency, sleep variability (standard deviation (SD) of sleep duration, and SD of sleep midpoint), and time spent above light exposure threshold (1000 lux) in a day were assessed by wrist actigraphy (Acti-watch Spectrum). Chronotype was determined by the reduced Morningness-Eveningness Questionnaire. Medical conditions including dyslipidemia, hypertension, and diabetes mellitus were determined from a fasting blood specimen and physical exam at the baseline visit. To determine whether sleep patterns, light levels, chronotype, and social jetlag are associated with metabolic syndrome, multivariable logistic regression models were fitted, including variables with P < .15 in the univariate analysis. The results of the multivariable analysis demonstrated that in participants older than 40 years, intermediate chronotype (vs early) was significantly associated with a higher risk of metabolic syndrome (Odds ratio (95%CI): 1.33 (1.04,1.7)), while later chronotype (vs. early) in participants younger than 40 years was significantly associated with a lower risk of metabolic syndrome (Odds ratio (95%CI): 0.37 (0.14, 0.96)). Also, higher sleep efficiency was significantly associated with decreased odds of metabolic syndrome (Odds ratio (95%CI): 0.98 (0.96, 0.99)). Nightly sleep duration was not significantly different between two groups of participants with and without metabolic syndrome in multivariable analyses. There was no significant association between social jet lag and metabolic syndrome in multivariable analysis (p = .286). Moreover, there was no significant association between chronotype and social jet lag in multivariable analysis. The association between metabolic syndrome and chronotype is age-dependent. While early chronotype is associated with metabolic syndrome in younger individuals, it tended to be associated with lower odds for metabolic syndrome in older individuals.

The association between shift work exposure and the variations in age at natural menopause among adult Canadian workers: results from the Canadian Longitudinal Study on Aging (CLSA)

OBJECTIVE

A wide range of negative health outcomes have been associated with shift work (SW) particularly night and rotating SW. However, little is known about effects of SW exposure on reproductive health outcomes. The objective of our study is to prospectively investigate the association between SW exposure and the variations in age at natural menopause among adult Canadian workers.

METHODS

Secondary data analyses were performed using the Canadian Longitudinal Study on Aging database. Premenopausal women (N = 3,688) at baseline were followed prospectively for 3 years. Three derived variables were used to measure SW primary exposure: 1) ever exposed to SW, 2) SW exposure in current job, and 3) SW exposure in the longest job. Cox proportional hazard regression models were used to evaluate risk of variations in age at natural menopause after adjusting for potential confounders.

RESULT

One out of five women (20%) reported to be ever exposed to SW during their jobs. Overall, women who were ever exposed to SW were significantly associated with a delayed onset of menopause compared with daytime workers (hazard ratios [HR] = 0.77, 95% CI, 0.61-0.98). Particularly, when compared with daytime workers, rotating shift worker in the current and longest job were significantly related to delayed onset of menopause (HR = 0.64, 95% CI, 0.46-0.89 and HR = 0.65, 95% CI, 0.49-0.86), respectively.

CONCLUSION

Our results suggest a relationship between rotating shift and delayed onset of menopause. We speculate that disruptive circadian stimuli may play a role in menopausal onset and this warrants further investigation.

VIDEO SUMMARY

http://links.lww.com/MENO/A940.

Induction of internal circadian desynchrony by misaligning zeitgebers

24-h rhythms in physiology and behaviour are orchestrated by an endogenous circadian clock system. In mammals, these clocks are hierarchically organized with a master pacemaker residing in the hypothalamic suprachiasmatic nucleus (SCN). External time signals—so-called zeitgebers—align internal with geophysical time. During shift work, zeitgeber input conflicting with internal time induces circadian desynchrony which, in turn, promotes metabolic and psychiatric disorders. However, little is known about how internal desynchrony is expressed at the molecular level under chronodisruptive environmental conditions. We here investigated the effects of zeitgeber misalignment on circadian molecular organisation by combining 28-h light–dark (LD-28) cycles with either 24-h (FF-24) or 28-h feeding-fasting (FF-28) regimes in mice. We found that FF cycles showed strong effects on peripheral clocks, while having little effect on centrally coordinated activity rhythms. Systemic, i.e., across-tissue internal circadian desynchrony was profoundly induced within four days in LD-28/FF-24, while phase coherence between tissue clocks was maintained to a higher degree under LD-28/FF-28 conditions. In contrast, temporal coordination of clock gene activity across tissues was reduced under LD-28/FF-28 conditions compared to LD-28/FF-24. These results indicate that timed food intake may improve internal synchrony under disruptive zeitgeber conditions but may, at the same time, weaken clock function at the tissue level.

Mitochondria's role in sleep: Novel insights from sleep deprivation and restriction studies

OBJECTIVES/METHODS

The biology underlying sleep is not yet fully elucidated, but it is known to be complex and largely influenced by circadian rhythms. Compelling evidence supports of a link among circadian rhythms, sleep and metabolism, which suggests a role for mitochondria. These organelles play a significant role in energy metabolism via oxidative phosphorylation (OXPHOS) and several mitochondrial enzymes display circadian oscillations. However, the interplay between mitochondria and sleep is not as well-known. This review summarises human and animal studies that have examined the role of mitochondria in sleep. Literature searches were conducted using PubMed and Google Scholar.

RESULTS

Using various models of sleep deprivation, animal studies support the involvement of mitochondria in sleep via differential gene and protein expression patterns, OXPHOS enzyme activity, and morphology changes. Human studies are more limited but also show differences in OXPHOS enzyme activity and protein levels among individuals who have undergone sleep deprivation or suffer from different forms of insomnia.

CONCLUSIONS

Taken altogether, both types of study provide evidence for mitochondria's involvement in the sleep-wake cycle. We briefly discuss the potential clinical implications of these studies.

Shift work and the onset of type 2 diabetes: results from a large-scale cohort among Japanese workers

AIMS

Data are limited regarding how shift work is linked to the development of type 2 diabetes, especially among workers at high risk of diabetes. We examined the risk of diabetes according to shift-work conditions over several years among Japanese adults.

METHODS

This prospective study enrolled 17,515 workers (age 40-78 years). Shift work was self-reported at annual health examinations over time from 2004 to 2017 and categorized as shift workers or non-shift workers. Diabetes was defined as fasting plasma glucose, random glucose, HbA1c, and self-reported use of antidiabetic medications. The association of shift work and diabetes was quantified using Cox regression.

RESULTS

During a follow-up of 8.1 years in median, 2071 incident cases of diabetes were documented. Compared with non-shift work, shift work showed a significantly elevated hazard ratios of developing diabetes. Shift work showed a 19% (95% confidence intervals: 3-37%) higher hazard ratios for diabetes, after adjustment for demographic-, cardiometabolic-, and work-related factors. Further adjustment for lifestyle factors and body mass index did not materially change this association (a 16% increase; 95% confidence intervals, 1-34%). This relationship was replicated among workers with prediabetes.

CONCLUSIONS

Engaging in shift work may increase the risk of developing diabetes independently of lifestyle factors and body mass index, even among prediabetic workers.

The Effects of Shift Work on Cardio-Metabolic Diseases and Eating Patterns

Energy metabolism is tightly linked with circadian rhythms, exposure to ambient light, sleep/wake, fasting/eating, and rest/activity cycles. External factors, such as shift work, lead to a disruption of these rhythms, often called circadian misalignment. Circadian misalignment has an impact on some physiological markers. However, these proxy measurements do not immediately translate into major clinical health outcomes, as shown by later detrimental health effects of shift work and cardio-metabolic disorders. This review focuses on the effects of shift work on circadian rhythms and its implications in cardio-metabolic disorders and eating patterns. Shift work appears to be a risk factor of overweight, obesity, type 2 diabetes, elevated blood pressure, and the metabolic syndrome. However, past studies showed discordant findings regarding the changes of lipid profile and eating patterns. Most studies were either small and short lab studies, or bigger and longer cohort studies, which could not measure health outcomes in a detailed manner. These two designs explain the heterogeneity of shift schedules, occupations, sample size, and methods across studies. Given the burden of non-communicable diseases and the growing concerns about shift workers' health, novel approaches to study shift work in real contexts are needed and would allow a better understanding of the interlocked risk factors and potential mechanisms involved in the onset of metabolic disorders.

Quality of Life (QoL) among Health Care Workers with Diabetes Mellitus: A Literature Review

OBJECTIVE

This scoping literature review explores the impact of diabetes mellitus (DM) on the health-related quality of life (HRQoL) of health care workers (HCWs). HCWs play a vital role in the global health care system, with the COVID-19 pandemic demonstrating their effectiveness and worth beyond any doubt. However, HCWs are among the most vulnerable members of the health care system because they are most susceptible to stress, exhaustion, and occupational health risks.

METHOD

The review was conducted in 2021 and included articles published in English in the past five years that explore diabetic HCWs' QoL and studies intended to assess the relationship between work stress and DM. In total, 27 relevant articles were found that satisfied the inclusion criteria and were critically and thematically analyzed.

RESULTS

Most DM studies have focused on the clinical management of patients, but researchers have paid little attention to the high-risk group of HCWs with diabetes. In addition to fulfilling their job mandate, HCWs are burdened with various sociological stressors that affect their QoL.

CONCLUSION

This literature review suggests DM has a significant impact on QoL in the work-life context. However, there is limited evidence to demonstrate the impact of DM on the QoL of HCWs. Thus, further research is needed in this area to improve the provision of integrated care.

Relationship between rotating shift work and white blood cell count, white blood cell differential count, obesity, and metabolic syndrome of nurses

This study investigated the relationship between working rotating shifts and white blood cell (WBC) count, WBC differential count (DC), obesity, and metabolic syndrome of nurses. Samples were obtained from a total of 720 nurses who had received health checkups at a large teaching hospital in Taiwan. Among these nurses, 500 worked rotating shifts, and the remaining 220 nurses worked fixed daytime shifts. We used binary logistic regression to identify the risk factors of obesity or metabolic syndrome. The results indicate that nurses working rotating shifts had a significantly higher WBC count than those working fixed daytime shifts. WBC count was an independent factor relating to an overly large waist circumference or overly high body mass index (BMI) of nurses. For every 10³/μL increase in WBC count, the risk of waist circumference exceeding 90 cm and 80 cm respectively in male and female nurses increased by 46%, and for every 10³/μL increase in WBC count, the risk of a BMI 24 kg/m² in nurses increased by 50%. Similarly, WBC count and work type were independent factors influencing the metabolic syndrome of nurses. For every 10³/μL increase in WBC count, the risk of metabolic syndrome occurring in nurses increased by 65%. Nurses working rotating shifts were at a 3.34 times greater risk of having metabolic syndrome than those working fixed daytime shifts. The mean age of our participants was 29.54 years old, and only approximately 4% of the participants had metabolic syndrome. Among these nurses, we found that high WBC was correlated with an overly large waist circumference and overly high BMI. Furthermore, the nurses working rotating shifts may have been at greater risk of metabolic syndrome than those working fixed daytime shifts, and increases in WBC were also associated with the occurrence of metabolic syndrome.

Circadian rhythm and gestational diabetes: working conditions, sleeping habits and lifestyle influence insulin dependency during pregnancy

OBJECTIVE

Management of gestational diabetes (GDM) is currently changing toward a more personalized approach. There  is a growing number of GDM patients requiring only a single dose of basal insulin at night to achieve glucose control. Well-known risk factors like obesity, parity and family history have been associated with GDM treatment requirements. Sleep quality and lifestyle factors interfering with the circadian rhythm are known to affect glucose metabolism. The aim of this study was to investigate the impact of such lifestyle factors on insulin requirement in GDM patients, in particular on long-acting insulin to control fasting glucose levels.

RESEARCH DESIGN AND METHODS

A total of 805 patients treated for GDM between 2012 and 2016 received a study questionnaire on lifestyle conditions. Sleep quality and work condition categories were used for subgroup analysis. Independent effects on treatment approaches were evaluated using multivariate regression.

RESULTS

In total, 235 (29.2%) questionnaires returned. Women reporting poor sleep conditions had higher pre-pregnancy weight and BMI, heavier newborns, more large for gestational age newborns and higher rates of hyperbilirubinemia. Treatment requirements were related to sleep and work condition categories. Multivariate regression for 'Basal' insulin-only treatment revealed an adjOR 3.4 (CI 1.23-9.40, p  <  0.05) for unfavorable work conditions and adjOR 4.3 (CI 1.28-14.50, p  <  0.05) for living with children.

CONCLUSIONS

Our findings suggest that external stressors like unfavorable work conditions and living with children are independently associated with the necessity of long-acting insulin at night in GDM patients. Thus, fasting glucose levels of pregnant women presenting with such lifestyle conditions may be subject to close monitoring.

Nurses' experiences and preferences around shift patterns: A scoping review

Objective

To explore the evidence on nurses’ experiences and preferences around shift patterns in the international literature.

Data sources

Electronic databases (CINHAL, MEDLINE and Scopus) were searched to identify primary studies up to April 2021.

Methods

Papers reporting qualitative or quantitative studies exploring the subjective experience and/or preferences of nurses around shift patterns were considered, with no restrictions on methods, date or setting. Key study features were extracted including setting, design and results. Findings were organised thematically by key features of shift work.

Results

30 relevant papers were published between 1993 and 2021. They contained mostly qualitative studies where nurses reflected on their experience and preferences around shift patterns. The studies reported on three major aspects of shift work: shift work per se (i.e. the mere fact of working shift), shift length, and time of shift. Across all three aspects of shift work, nurses strive to deliver high quality of care despite facing intense working conditions, experiencing physical and mental fatigue or exhaustion. Preference for or adaptation to a specific shift pattern is facilitated when nurses are consulted before its implementation or have a certain autonomy to self-roster. Days off work tend to mitigate the adverse effects of working (short, long, early or night) shifts. How shift work and patterns impact on experiences and preferences seems to also vary according to nurses’ personal characteristics and circumstances (e.g. age, caring responsibilities, years of experience).

Conclusions

Shift patterns are often organised in ways that are detrimental to nurses’ health and wellbeing, their job performance, and the patient care they provide. Further research should explore the extent to which nurses’ preferences are considered when choosing or being imposed shift work patterns. Research should also strive to better describe and address the constraints nurses face when it comes to choice around shift patterns.

Shift work and incidence of psychiatric disorders: The Danish Nurse Cohort study

BACKGROUND

Research on health effects of shift work has especially focused on somatic diseases, such as breast cancer and cardiometabolic disease, while less attention has been given to the association between shift work and mental health.

METHODS

We used information on 19 964 female nurses (≥44 years) from the Danish Nurse Cohort, who reported current work schedule (day, evening, night, or rotating) at recruitment (1993/1999). In 5102 nurses who participated in both cohort waves, we defined persistent night shift work as working night shift in 1993 and 1999. We used Cox regression models to calculate hazard ratios (HRs) and 95% confidence intervals (CIs), adjusting for relevant confounders. Through linkage of cohort participants to national registers, we defined incidence of mood and neurotic disorders as first hospital contact or redeemed prescription until November 2018.

RESULTS

We found association between night shift work with mood disorders (HR = 1.31; 95%CI = 1.17-1.47) and neurotic disorders (1.29; 1.17-1.42), compared to day work. Associations were enhanced in nurses with persistent night shift work (1.85; 1.43-2.39 and 1.62; 1.26-2.09 for mood and neurotic disorders, respectively) and in nurses with specialist confirmed mood (1.69; 1.24-2.29) and neurotic (1.72; 1.22-2.44) disorders. Nurses with preexisting psychiatric disorders and full-time work seemed most susceptible.

CONCLUSIONS

Night shift work is associated with increased risk of major psychiatric disorders. The novel suggestive findings of vulnerable groups, including nurses with a history of psychiatric disorders and full-time workers, are based on a limited number of cases, and further research is needed to confirm the results.

Experiences and perceptions of nurses working night shift: a qualitative systematic review protocol

OBJECTIVE

The objective of this qualitative systematic review is to examine the available evidence on the experiences of nurses working the night shift within any specialty in the acute care, subacute, or long-term care setting.

INTRODUCTION

Nurses are required for round-the-clock patient care, and night shift nurses can experience detrimental effects as a result of their work hours. Understanding nurses' experiences when working night shift will facilitate the development of strategies to minimize the potential negative effects of working at night. In examining nurses' perceptions of working night shift, there is scope to explore how to improve night shift nurses' practice environment and job satisfaction, which will then translate to improved patient outcomes.

INCLUSION CRITERIA

This review will consider qualitative studies that include registered nurses and licensed practical nurses who work night shift or rotate between day and night shift. Night supervisors and advanced practice nurses will be excluded due to the potential for dissimilar experiences and resources within those groups. The search will be limited to studies published in English from 1983 to the present.

METHODS

The search strategy is designed to locate both published and unpublished qualitative studies by searching academic databases for published studies, gray literature, and hand searching reference lists. The study selection, critical appraisal, data extraction, and synthesis for this systematic review will be conducted in accordance with the JBI methodology for systematic reviews of qualitative evidence.

SYSTEMATIC REVIEW REGISTRATION NUMBER

PROSPERO CRD42019135294.

Sleep-Related Problems in Night Shift Nurses: Towards an Individualized Interventional Practice

Rotating shifts (mostly 8- or 12-h) are common among nurses to ensure continuity of care. This scheduling system encompasses several adverse health and performance consequences. One of the most injurious effects of night-time shift work is the deterioration of sleep patterns due to both circadian rhythm disruption and increased sleep homeostatic pressure. Sleep problems lead to secondary effects on other aspects of wellbeing and cognitive functioning, increasing the risk of errors and workplace accidents. A wide range of interventions has been proposed to improve the sleep quality of nurses and promote an increase in attention levels. In recent years, particular attention has been paid to individual and environmental factors mediating the subjective ability to cope with sleep deprivation during the night shift. Given the predictive role of these factors on the negative impact of a night shift, an individualized intervention could represent an effective countermeasure by ensuring suitable management of shift schedules. Therefore, the aims of this mini-review are to: (a) provide an updated overview of the literature on sleep problems in night shift nurses and their adverse consequences; and (b) critically analyze the psychosocial factors that mediate the negative impact of shift work with the ultimate goal of defining an effective countermeasure based on an individualized approach.

Dose-Response Relationship between Night Work and the Prevalence of Impaired Fasting Glucose: The Korean Worker's Special Health Examination for Night Workers Cohort

Many studies have been conducted regarding the association between night work and diabetes, but the association between impaired fasting glucose (IFG) and night work is still unclear. The aim of this study was to evaluate this association using the Special Health Examination (SHEW) for Korean night workers. Laboratory, questionnaire, and physical examination data were collected for 80,077 manual workers between 2014 and 2016 from Korea Medical Institute, and associations of the data with IFG were evaluated using a multivariate logistic regression model. The odds ratios for IFG among those who worked night shifts for 2~5 years, 5~12 years, and 12 years or over (ref: <2 years) after adjusting for abdominal obesity were 1.14 (0.90–1.45), 1.41 (1.10–1.81), and 1.75 (1.41–2.19), respectively. A dose–response relationship was identified between the duration of night work and the prevalence of IFG (p for trend <0.05). A dose relationship remained significant when a subgroup of non-obese participants was analyzed. We identified an association and a dose–response relationship between the number of years of night work and IFG. To prevent the development of diabetes in night workers, we suggest that they should be pre-emptively screened and treated from the stage of IFG.

Clocks, cancer, and chronochemotherapy

The circadian clock coordinates daily rhythmicity of biochemical, physiologic, and behavioral functions in humans. Gene expression, cell division, and DNA repair are modulated by the clock, which gives rise to the hypothesis that clock dysfunction may predispose individuals to cancer. Although the results of many epidemiologic and animal studies are consistent with there being a role for the clock in the genesis and progression of tumors, available data are insufficient to conclude that clock disruption is generally carcinogenic. Similarly, studies have suggested a circadian time-dependent efficacy of chemotherapy, but clinical trials of chronochemotherapy have not demonstrated improved outcomes compared with conventional regimens. Future hypothesis-driven and discovery-oriented research should focus on specific interactions between clock components and carcinogenic mechanisms to realize the full clinical potential of the relationship between clocks and cancer.

Compliance with Recommendations on Work Schedule for Shift Nurses in South Korea

Background

A well-designed shift schedule has been reported to have a positive effect on improving health problems associated with shift work. This study aimed to identify compliance with the 17 recommendations on work schedule (WSRs) for shift nurses and related factors.

Methods

The descriptive study was conducted with 182 nurses who worked in three shifts for more than 1 year at superior general and general hospitals in three regions. Data were collected with self-administered questionnaire and 13-week work schedule tables, and analyzed with both person- and cycle-based compliance.

Results

Person-based compliance was 11.77 among 17 items in total. However, no one completely complied with WSRs of “no work on weekends” and which showed the lowest cycle-based compliance (22.3%). Compliance with some WSRs was related to hospital type, proportion of nurses in school and having standards on work schedule at institutional level.

Conclusion

Compliance with WSRs of shift nurses in Korea is still unsatisfactory, and one day off after night shift and work on weekend are quite common. Hospitals should keep the standards on work schedule, monitor compliance with standards, and try to introduce modified shift systems to improve the current problems.

Gut microbiota: closely tied to the regulation of circadian clock in the development of type 2 diabetes mellitus

Type 2 diabetes mellitus (T2DM), a worldwide epidemic disease, has caused tremendous economic and social burden, but the pathogenesis remains uncertain. Nowadays, the impact of unrhythmic circadian clock caused by irregular sleep and unhealthy diet on T2DM has be increasingly studied. However, the contribution of the endogenous circadian clock system to the development of T2DM has not yet been satisfactorily explored. It is now becoming clear that the gut microbiota and the circadian clock interact with each other to regulate the host metabolism. Considering all these above, we reviewed the literature related to the gut microbiota, circadian clock, and T2DM to elucidate the idea that the gut microbiota is closely tied to the regulation of the circadian clock in the development of T2DM, which provides potential for gut microbiota-directed therapies to ameliorate the effects of circadian disruptions linked to the occurrence and development of T2DM.

Melatonin in Wine and Beer: Beneficial Effects

Melatonin is a hormone secreted in the pineal gland with several functions, especially regulation of circadian sleep cycle and the biological processes related to it. This review evaluates the bioavailability of melatonin and resulting metabolites, the presence of melatonin in wine and beer and factors that influence it, and finally the different benefits related to treatment with melatonin. When administered orally, melatonin is mainly absorbed in the rectum and the ileum; it has a half-life of about 0.45–1 h and is extensively inactivated in the liver by phase 2 enzymes. Melatonin (MEL) concentration varies from picograms to ng/mL in fermented beverages such as wine and beer, depending on the fermentation process. These low quantities, within a dietary intake, are enough to reach significant plasma concentrations of melatonin, and are thus able to exert beneficial effects. Melatonin has demonstrated antioxidant, anticarcinogenic, immunomodulatory and neuroprotective actions. These benefits are related to its free radical scavenging properties as well and the direct interaction with melatonin receptors, which are involved in complex intracellular signaling pathways, including inhibition of angiogenesis and cell proliferation, among others. In the present review, the current evidence on the effects of melatonin on different pathophysiological conditions is also discussed.

Night work and incidence of Parkinson's disease in the Danish Nurse Cohort

OBJECTIVES

Evidence on the association between night work and Parkinson's disease (PD) is sparse and conflicting, calling for more definitive studies.

METHODS

We included 20 138 female nurses from the Danish Nurse Cohort without PD who at baseline in 1993 and/or 1999 reported their most common current work schedule (day, evening, night, and rotating (a combination of at least two of these)), including information on lifetime cumulative duration (years) of each shift in a 2009 follow-up survey. We obtained information on PD hospital contacts and PD medication until November 2018 via linkage to the Danish National Patient (inpatient from 1977 and outpatient contacts from 1995 onwards) and Prescription Registers starting in 1995. We defined the incidence of PD as the first-ever hospital contact due to PD, or the first-ever redeemed levodopa prescription, whichever came first. We used Cox regression models to calculate HRs and 95% CIs, adjusting for age, smoking status, coffee consumption and use of hormone replacement therapy.

RESULTS

We found no significant difference in PD risk among nurses who reported working evening (HR=0.86; 95% CI=0.55 to 1.34), night (HR=1.26; 95% CI=0.79 to 2.02) or rotating shifts (HR=0.83; 95% CI=0.56 to 1.21) at cohort baseline in 1993 or 1999, when compared with permanent day workers. Similarly, persistency of shift work (working the same work schedule for 6+ years) or duration of shift work was not associated with PD risk.

CONCLUSIONS

Overall, there was little evidence for an association between various shift work schedules including night work and PD in this cohort of middle-aged female nurses.

Lifetime night work exposure and the risk of type 2 diabetes: results from the longitudinal study of adult health (ELSA-Brasil)

The aim of this research project was to test the effects of lifetime night work exposure on type 2 diabetes (T2DM) risk. The Brazilian Longitudinal Study of Adult Health (ELSA-Brasil) is a prospective cohort study of chronic conditions, such as diabetes and cardiovascular disease. The participants (N = 15105) were recruited (2008-2010) at five public universities and one research institute in six cities in Brazil. Participants from the first wave (2008-2010) were followed up for a mean of 3.8 years. Current analyses comprise 4671 women and 3965 men. Hazard ratios (HR) were estimated using Cox regression models. Crude T2DM incidence rates were 2.26 and 1.44 per 100 person-years, respectively, for women and men who reported ≥ 10 years' working nights. In women, ≥ 10 years of night work was associated with a higher risk of T2DM (HR 1.46 [95% CI: 1.03; 2.08]), after adjusting for age, education, work hours, and BMI. The additional adjustment for physical activity attenuated the association (HR 1.36 [95% CI: 0.94; 1.96]). In men, the results were not statistically significant (HR = 0.65 [95% CI: 0.40; 1.07]). The findings indicate the effects of lifetime night work on T2DM incidence seem to be greater among women than men.

Association between circadian disruption and diseases: A narrative review

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

Shift work and incidence of dementia: A Danish Nurse Cohort study

INTRODUCTION

A few studies suggest that working night and rotating shifts increase the risk of dementia. We examined the association between shift work and the incidence of dementia in a cohort of female Danish nurses.

METHODS

We linked Danish Nurse Cohort participants, who reported work schedules (day, evening, night, rotating shifts) in 1993 and/or 1999 and their duration in 2009, to Danish registers to obtain information on dementia hospitalizations and prescription medication until November 2018.

RESULTS

Among 6048 nurses who reported work schedules in 1993 and 1999, nurses working night shifts ≥6 years had higher dementia incidence (hazard ratio: 2.43, 95% confidence interval: 1.39 to 4.23) than those working day shifts ≥6 years. Among 8059 nurses who reported shift work duration, nurses working night shifts ≥6 years had higher dementia incidence than those working night shifts <1 year (1.47, 1.06 to 2.06).

DISCUSSION

Persistent night shift work may increase the risk of dementia.

After-Effects of Time-Restricted Feeding on Whole-Body Metabolism and Gene Expression in Four Different Peripheral Tissues

OBJECTIVE

Epidemiological studies show that shift workers are at increased risk for type 2 diabetes. As modern societies increasingly require shift work, it seems crucial to determine whether there are long-lasting health effects of rotational shifts.

METHODS

This study examined the after-effects of 4 weeks of time-restricted feeding (TRF) during the light period (= light-fed) in rats, an animal model for shift work. This study also included a TRF-dark (= dark-fed) control group. The aligned and misaligned feeding times of light and dark feeding are associated with poor and good health outcomes, respectively. Several physiological measures were monitored continuously; blood, liver, brown adipose tissue, and soleus and gastrocnemius muscle were collected following 11 days of ad libitum (AL) feeding after ending the TRF.

RESULTS

In the dark-fed animals, the day/night differences in food intake, activity, and respiratory exchange ratio were still enhanced at the end of the experiment. Light-fed animals displayed the smallest day/night differences for these measures, as well as for body temperature. In both the light- and dark-fed animals, rhythms in plasma glucose, nonesterified fatty acids, and gene expression had not fully recovered after 11 days of AL feeding. Importantly, the effects on gene expression were both tissue and gene dependent.

CONCLUSIONS

Our data indicate that rotational shift workers may have an increased risk of long-lasting disturbed rhythms in several physiological measures after a period of shift work. Clearly, such disturbances may harm their health.

Relationship between night shift work, eating habits and BMI among nurses in Lebanon

Background

The objective of this cross-sectional study was to evaluate the relationships between night shift work, eating habits and body mass index (BMI) among Lebanese nurses.

Methods

A total of 307 nurses were randomly selected from five hospitals located in Beirut. Data about demographic and professional characteristics, anthropometric measures, dietary habits and intakes were collected through a validated questionnaire. To study the relationship between night shift work, eating habits and BMI, chi-square test, t-test and logistic regressions were used.

Results

The majority of nurses (78. 2%) had irregular meals timing with a significant decrease in the number of complete meals consumed during the day and an increase in the number of snacks consumed during night (p < 0. 05). The most consumed snacks during night shifts were sweets and potato chips. The findings highlighted that BMI and waist circumference significantly increased with the number of years of work (r = 0.175; p < 0.05) and the cumulative number of night shifts hours over the entire work history (r = 0.135/p < 0. 05).

Conclusion

Night shift work is positively associated with abnormal eating patterns and BMI among Lebanese nurses. However the increase in BMI is not related to eating habits.

Systematic review of shift work and nurses' health

BACKGROUND

Nursing is characterized by a working articulation in shifts to ensure continuity of care throughout the 24 h. However, shift work and the resulting desynchronization of circadian rhythms may have adverse effects on nurses' health.

AIMS

To describe the effects of shift work and desynchronization of circadian rhythms on nurse's health.

METHODS

Databases: PubMed, Cinahl, Scopus, Embase and Ilisi. Search terms (free terms, MeSH): 'nurses', 'shiftwork', 'nightwork', 'sleep disorder, circadian rhythm', 'work schedule tolerance', 'breast neoplasm', 'metabolic syndrome X', 'metabolic cardiovascular syndrome', 'Cardiovascular disease', 'stress', 'diabetes'. We included all randomized controlled trials, observational studies, reviews and papers studying nurses' shift work. Quality assessment of the retrieved papers was verified according to Dixon-Woods checklist.

RESULTS

Twenty-four articles were analyzed. Literature review has shown that shift work involves an alteration in psychophysical homeostasis, with a decrease in performance. It is an obstacle for social and family relationships, as well as a risk factor for stress, sleep disorders, metabolic disorders, diabetes, cardiovascular disorders and breast cancer.

CONCLUSIONS

An organized ergonomic turnaround can be less detrimental to the health of nurses and more beneficial for the healthcare providers. Therefore, we suggest organizing studies to assess whether improving nurses' health would lead to a reduction in miscarriages, absenteeism and work-related stress.

Habitual late sleep initiation is associated with increased incidence of type 2 diabetes mellitus in Korean adults: the Korean Genome and Epidemiology Study

STUDY OBJECTIVES

Although sleep duration and quality were significant risk factors of type 2 diabetes (T2D), the impact of sleep initiation time on the development of T2D has not been studied in large longitudinal studies.

METHODS

A total of 3689 participants without diabetes aged 40-69 years at baseline were enrolled from the Korean Genome and Epidemiology Study and followed up for 12 years. Participants were categorized based on habitual sleep initiation time by questionnaire as follows: 20:00-22:59 (early sleepers, ES, n = 766), 23:00-00:59 (usual sleepers, US, n = 2407), and 1:00-5:59 (late sleepers, LS, n = 516). Incident T2D was identified biennially by fasting plasma glucose or 2-hour glucose after 75-g oral glucose loading or use of anti-diabetes medication.

RESULTS

During follow-up, 820 cases of T2D were documented and the LS group showed the highest increase in insulin resistance. Hazard ratio (HR) (95% confidence interval) for T2D of LS compared to ES was 1.34 (1.04-1.74) after adjustment for covariates including sleep duration. The impact of late sleep on the development of T2D was more evident in older individuals (≥65 years at baseline) (HR = 4.24 [1.42-12.68] in older LS vs. older ES, HR = 1.27 [1.00-1.62] in younger LS vs. younger ES, pinteraction = 0.002). In addition, LS with low insulin secretion and sensitivity showed an approximately fivefold increased risk for T2D compared to ES with high insulin secretion and sensitivity.

CONCLUSIONS/INTERPRETATION

Habitual late sleep initiation is a significant risk factor for T2D in Koreans, especially in people with lower insulin sensitivity, lower β-cell function, and older age.

Perceptions of the impact of non-standard work schedules on health in Australian graduates: an exploratory study

Non-standard working hours are associated with negative health outcomes. However, little is known about the early years of exposure to non-standard work hours, or whether workers new to these work schedules perceive their work as impacting their health. This limits our ability to develop meaningful intervention strategies for transitioning into non-standard work hour schedules. This exploratory study investigated whether recent Australian graduates in various non-standard workhour schedules perceive that their work schedule negatively impacts their health. The responses of 120 graduates within four years of completing their tertiary qualification collected from an online survey were analysed. Graduates were asked whether they perceived their work arrangements as impacting their health. Significantly more of those who were engaged in non-standard work schedules or worked beyond contracted hours perceived their working arrangements as having an impact on their health. This study highlights the importance of studying workers' perceptions of the impact of work hours on health, particularly when workers may be experiencing good global health but be at risk for negative health outcomes in future.

Circadian misalignment alters insulin sensitivity during the light phase and shifts glucose tolerance rhythms in female mice

Shift work and jet lag, characterized by circadian misalignment, can disrupt several physiological activities, but whether they affect the rhythm of glucose uptake and insulin sensitivity remain unclear. In the present study, female C57BL/6J mice were maintained for four weeks under the condition of 8-hour phase advance and delay every 3–4 days to mimic shift work. Intraperitoneal glucose tolerance test (IPGTT) and intraperitoneal insulin tolerance test (IPITT) were performed repeatedly at Zeitgeber time (ZT) 0, ZT6, ZT12, and ZT18. Glucose-stimulated insulin secretion (GSIS) test was performed at ZT6. We found that the average level of daily glucose tolerance did not decrease but the phase of glucose tolerance advanced by 2.27 hours and the amplitude attenuated by 20.4% in shift work mice. At ZT6, IPITT showed blood glucose at 30 min after insulin injection decreased faster in shift work mice (−3.50±0.74mmol/L, −61.58±7.89%) than that in control mice (−2.11±1.10mmol/L, −33.72±17.24%), but IPGTT and GSIS test showed no significant difference between the two groups. Food intake monitor showed that the feeding time of shift work mice continued to advance. Restricting feed to a fixed 12-hour period alleviated the increase of insulin sensitivity induced by shift-work. We also observed that an increase of blood glucose and liver glycogen at ZT0, as well as a phase advance of liver clock genes and some glucose metabolism-related genes such as forkhead box O1 (Foxo1) and peroxisome proliferator activated receptor alpha (Pparα) in shift work mice. Our results showed that light change-simulated shift work altered insulin sensitivity during the light phase and shifted glucose tolerance rhythms in female mice, suggesting a causal association between long-term shift work and type 2 diabetes.

Does night work affect age at which menopause occurs?

PURPOSE OF REVIEW

To delineate the current state of evidence on the impact of night shift work on age at natural menopause.

RECENT FINDINGS

The only direct evidence is from a single observational study, which indicates that women who work night shifts are at moderately higher risk for earlier menopause and that this risk is more pronounced among younger women. Underlying biological mechanisms have yet to be sufficiently substantiated. A long-held line of inquiry, most strongly propagated by the observed link between night shift work and female breast cancer, is the 'Light at Night' hypothesis, which suggests melatonin-mediated circadian disruption as a potential regulator of reproductive signaling in women. Supporting evidence is found from observations of changes in endogenous melatonin production among night working women or in response to light exposure, and corresponding changes in endogenous ovarian hormone levels and modulated menstrual patterns, among other indications of altered central ovulation-governing processes. Susceptibility to night shift work may be modified by chronotype.

SUMMARY

This review summarizes the literature related to night work and ovulatory regulation in humans, prioritizing population-based evidence to provide motivation for the study of circadian disruption and night shift work as a regulator of menopausal timing.