Sleep duration as a mediator between an alternating day and night shift work schedule and metabolic syndrome among female hospital employees

The mediating effect of sleep duration on metabolic syndrome severity in adults: a structural equation modeling approach

BACKGROUND

Metabolic syndrome (MetS) is associated to sleep duration. It is crucial to identify factors that disrupt sleep regulation. The study aimed to assess the indirect effect of risk factors related to MetS severity through sleep duration by utilizing a structural equation model (SEM).

METHODS

The study involving 3,935 adults from the baseline data of the Ravansar Non-Communicable Disease (RaNCD) cohort study. MetS severity scores were the outcome variables. SEM was employed to explore the relationships, utilizing IBM SPSS and AMOS version 23.

RESULTS

The mean MetS severity score was higher in women compared to men (0.25 vs. 0.16, P = 0.003). In men, socioeconomic status (SES) has a positive direct effect (β = 0.048) and a negative indirect effect (β=-0.006) on MetS severity. Increased physical activity is directly (β=-0.036) and indirectly (β=-0.093) associated with reducing MetS severity. Nap duration is directly linked to an increase (β = 0.072) but has an indirect effect (β=-0.008) in decreasing MetS severity. In women, SES has a direct (β=-0.020) and indirect (β=-0.001) inverse relationship with MetS severity. Increased physical activity is directly (β=-0.048) and indirectly (β=-0.036) associated with decreasing MetS severity in women. Nap duration is directly associated with an increase in MetS severity (β=-0.018) but indirectly contributes to its reduction (β=-0.002). Sleep duration not only directly affects MetS severity but is also influenced by age, SES, physical activity, obesity and nap duration.

CONCLUSION

Physical activity, SES, and nap duration directly and indirectly effect the MetS severity. Sleep duration was recognized as a mediating variable that supports the indirect effects.

Sleep quality and fatigue among nurses working in high-acuity clinical settings in Saudi Arabia: a cross-sectional study

BACKGROUND

Poor sleep quality is prevalent among nurses worldwide. Around two-thirds of nurses doing shift work are known to experience sleep problems and fatigue. Fatigue and sleep problems are linked to poor performance, impaired alertness, injuries, chronic diseases, compromised healthcare quality, and medical errors, all of which detrimentally impact nurses and threaten patients' safety. This area of research has received insufficient attention in Saudi Arabia; therefore, the purpose of this study was to examine the levels of sleep quality and perceived fatigue and their association among nurses working in acute care settings in comprehensive hospitals in Saudi Arabia.

METHODS

A descriptive cross-sectional study using the Pittsburgh Sleep Quality Index and Chalder Fatigue Scale. Data was obtained via an online questionnaire that was distributed to nurses using the QuestionPro platform through hospital administrators, social media (WhatsApp), and personal contact.

RESULTS

A total of 173 nurses completed the online survey. Most participants reported poor sleep quality (n = 127, 73.4%) and severe perceived fatigue (n = 156, 90.2%). Furthermore, the study revealed a significant correlation between the overall sleep disturbance and fatigue global scores (r = 0.57, P < 0.001), indicating that poor sleep quality was significantly associated with higher fatigue levels among the study sample.

CONCLUSIONS

The current study found a significant association between sleep quality and severe fatigue in nurses working in high acute care settings in Saudi Arabia. It is very clear from the results that nurses are experiencing poor sleep and severe fatigue, which in turn, will negatively impact the nurse's quality of life and patient safety.

Shiftwork sleep disorder and associated factors among nurses working at public hospitals in Harari Regional state and Dire Dawa Administration, Eastern Ethiopia: a cross-sectional study

BACKGROUND

Shiftwork sleep disorder is one of the most common health-related effects of Shiftwork, particularly among healthcare workers. It is a chronic condition that is directly related to a person's work schedule. In Ethiopia, although a mental health strategy is in place, little attention is given to studies that focus on shiftwork sleep disorders among nurses. This study aimed to determine the magnitude of shiftwork sleep disorder and associated factors among nurses working at public hospitals in Harari Regional State and the Dire Dawa Administration.

METHODS

Institutional based cross-sectional study was conducted from June 1-30, 2021 among 392 nurses selected by a simple random sampling technique. A structured interviewer-guided self-administered questionnaire was used for data collection. The International Classification of Sleep Disorders 3rd edition (ICSD-3), Bargen Insomnia Scale (BIS) and Epworth Sleepiness Scale were used to assess shift-work sleep disorder. The data were entered into EpiData and exported to SPSS for analysis. Bivariable logistic regression was used to see the association between the outcome and the explanatory variables. Bivariate and Multivariate analyses were performed, and AOR with 95% CI was used to measure the strength of the association. Those variables with a p-values of < 0.05 were considered as statistically significant.

RESULTS

In this study, the magnitude of shiftwork sleep disorder among nurses was 30.4% (95% CI: 25.4-34.5). Being female (AOR = 2.4, 95% CI: 1.3, 4.2), working an average number of nights > 11 per month in the last 12 months (AOR = 2.5, 95% CI: 1.3, 3.8), and khat use in the last 12 months (AOR = 4.9, 95% CI: 2.9, 8.7) were significantly associated with the shiftwork sleep disorder.

CONCLUSIONS

The study revealed that about one-third of the nurses had a shiftwork sleep disorder implying a high burden of the problem among nurses in the study setting, which endangers nurses, patients, and the healthcare system. Being female, working an average number of nights > 11 per month in the last 12 months, and khat use showed statistically significantly associated with the shiftwork sleep disorder. Early detection of shiftwork sleep disorder, having a policy on khat use and considering rest/recovery while scheduling work time should be addressed to prevent shiftwork sleep disorder.

Evaluating the Relationship between Circadian Rhythms and Sleep, Metabolic and Cardiovascular Disorders: Current Clinical Evidence in Human Studies

Circadian rhythms are generated by the circadian clock, a self-sustained internal timing system that exhibits 24-h rhythms in the body. Many metabolic, cellular, behavioral and physiological processes are regulated by the circadian clock in coordination with environmental cues. The present study is a comprehensive review of the currently existing evidence concerning the relationship between circadian rhythms and sleep, metabolic, and cardiovascular disorders. We thoroughly searched the online databases PubMed, Scopus, and Web of Science to find the existing clinical studies from the last twenty-three years (2000-2023). Circadian misalignment was found to be associated with an increase in the risk of metabolic disorders, cardiovascular diseases, and obesity, as well as inadequate sleep quality. In this review article, all the included studies had a strength protocol design and all of them were conducted on humans. However, the most common limitations of them were the small sample size and the short time of the intervention. In conclusion, managing the factors that disrupt the optimal function of central and peripheral clocks can help to reduce the risk of metabolic and cardiovascular diseases, improving also sleep quality. Future studies should further explore the underlying mechanisms of the interconnections between circadian clocks and sleep, metabolic, and cardiovascular disorders. This may provide new opportunities for advance chronotherapy approach.

The correlation between testosterone and stroke and the mediating role of blood pressure: The Henan rural cohort study

AIMS

We aimed to investigate the association of serum testosterone with stroke and calculate the proportion explained by blood pressure on this association.

MATERIALS AND METHODS

A total of 6175 subjects were included in this study. Serum testosterone was quantified by liquid chromatography-tandem mass spectrometry. The logistic regression model was used to evaluate the association between serum testosterone and stroke. Linear regression analysis was used to assess the associations of serum testosterone with blood pressure. In addition, mediation analysis was performed to identify the mediation effects of blood pressure on the association of serum testosterone with stroke. Sex-stratified analysis was employed throughout the research.

RESULTS

After adjusting for multiple variables, serum testosterone levels were negatively associated with stroke in males (per 1 unit natural log-transformed, odds ratio (OR) = 0.81, 95% confidence interval (CI): 0.69-0.94; Tertile 3 vs Tertile 1, OR = 0.65, 95% CI:0.44-0.96). Furthermore, blood pressure played a partial mediating role in the relationship between testosterone and stroke in males. The indirect effect/total effect of systolic blood pressure, diastolic blood pressure and mean arterial pressure were 7.37%, 9.54% and 9.22%, respectively. Notably, the relationship between testosterone and stroke and the role of blood pressure in regulating them was not observed in females.

CONCLUSION

This study describes that in rural Chinese males, testosterone can reduce the risk of stroke by affecting blood pressure. To some extent, we provide a new epidemiological evidence for the relationship between testosterone and stroke.

DNA methylation of circadian genes and markers of cardiometabolic risk in female hospital workers: An exploratory study

Night shift work has been linked to increased risk of cardiovascular disease (CVD); however, the underlying mechanisms remain unclear. A compelling yet understudied mechanism involves differential DNA methylation of circadian genes. To investigate the relevance of this mechanism, we conducted an exploratory cross-sectional study of 74 female hospital personnel (38 day workers, 36 night shift workers). Sociodemographic, lifestyle, and health characteristics as well as shift work status and history were determined through self-report. Fasting blood samples were collected to measure markers of cardiometabolic risk and DNA was extracted to measure DNA methylation of 1150 cytosine-guanine (CpG) sites across 22 circadian genes. Associations between methylation levels at individual CpG sites (β-values) and markers of cardiometabolic risk were analyzed while considering effect modification by shift work status. The false discovery rate was applied to account for multiple comparisons (q ≤ 0.20). Two CpG sites [cg06758649 (CRY1) and cg06899802 (CSNK1A1)] were differentially associated with waist circumference and body mass index by shift work status, and eight CpG sites [cg26103512 (CSNK1D), cg03941313 (CSNK1E), cg18217763 (CSNK1E), cg16682686 (DEC1), cg12061096 (RORA), cg10133825 (RORA), cg19652148 (RORA), and cg22904654 (RORA)] were differentially associated with LDL cholesterol concentration by shift work status (all q ≤ 0.20). Our findings suggest that the relationship between DNA methylation of circadian genes and cardiometabolic risk differs by day and night shift worker status, which may contribute to mechanisms of increased risk of CVD observed among night shift workers.

Modeling the relationship between shift work and cardiometabolic risk through circadian disruption, sleep and stress pathways

The purpose of this study is to elucidate the multiple pathways linking shift work exposure to cardiometabolic risk (CMR) through the intermediates of circadian disruption, sleep disturbances, and stress. A cross-sectional study was conducted at Kingston Health Sciences Center that included female hospital workers, 160 who worked a day-only schedule and 168 who worked rotating days and nights. Participants completed questionnaires, a clinical exam, and wore accelerometers to collect sleep data for 8 days. Participants also collected urine samples at each void during a 24-h collection period, on the day shift for day-only workers and the night shift for rotating shift workers, for cortisol and melatonin measures. We adapted and tested a conceptual model proposed by Knutsson and Boggild for circadian disruption, sleep, and stress mechanistic pathways linking shift work to CMR using structural equation modeling techniques. Status as a rotating shift worker was associated with increased circadian disruption of cortisol and melatonin production compared to day-only workers (P < .001). Increased circadian disruption was associated with an increased CMR (P = .01). Rotating shift work was associated with sleep disturbances (P = .002) and increased job stress (P < .001), but neither was associated with CMR. We conclude that rotating shift work is associated indirectly with increased CMR. This association is mediated by circadian disruption as indicated by attenuated melatonin and cortisol, and flatter cortisol curves.

Disturbance of the Circadian System in Shift Work and Its Health Impact

The various non-standard schedules required of shift workers force abrupt changes in the timing of sleep and light-dark exposure. These changes result in disturbances of the endogenous circadian system and its misalignment with the environment. Simulated night-shift experiments and field-based studies with shift workers both indicate that the circadian system is resistant to adaptation from a day- to a night-oriented schedule, as determined by a lack of substantial phase shifts over multiple days in centrally controlled rhythms, such as those of melatonin and cortisol. There is evidence that disruption of the circadian system caused by night-shift work results not only in a misalignment between the circadian system and the external light-dark cycle, but also in a state of internal desynchronization between various levels of the circadian system. This is the case between rhythms controlled by the central circadian pacemaker and clock genes expression in tissues such as peripheral blood mononuclear cells, hair follicle cells, and oral mucosa cells. The disruptive effects of atypical work schedules extend beyond the expression profile of canonical circadian clock genes and affects other transcripts of the human genome. In general, after several days of living at night, most rhythmic transcripts in the human genome remain adjusted to a day-oriented schedule, with dampened group amplitudes. In contrast to circadian clock genes and rhythmic transcripts, metabolomics studies revealed that most metabolites shift by several hours when working nights, thus leading to their misalignment with the circadian system. Altogether, these circadian and sleep-wake disturbances emphasize the all-encompassing impact of night-shift work, and can contribute to the increased risk of various medical conditions. Here, we review the latest scientific evidence regarding the effects of atypical work schedules on the circadian system, sleep and alertness of shift-working populations, and discuss their potential clinical impacts.

Objective Assessment of Sleep Patterns among Night-Shift Workers: A Scoping Review

In this scoping review of the literature, we identified the types and the parameters of objective measurements to assess sleep patterns among night-shift workers. We conducted a literature search using electronic databases for studies published from 1991 to 2020 and charted and summarized key information. We included 32 studies in the review. Polysomnography was used in 6 studies and wearable sleep detection devices were utilized in 26 studies. The duration of sleep assessment using the wearable devices ranged from 1 day to ≥4 weeks, and more than half of the studies collected data for >2 weeks. The majority of the studies used subjective questionnaires, such as the Karolinska Sleepiness Scale, Epworth Sleepiness Scale, and Pittsburgh Sleep Quality Index, in addition to objective sleep measurements. Total sleep time was the most common parameter, followed by sleep efficiency, sleep onset latency, and time or frequency of being awake. As the utilization of wearable devices to assess the sleep patterns of night-shift workers is expected to increase, further evaluation of device accuracy and precision, optimal data collection period, and key parameters is warranted.

Influence of shift work on rest-activity rhythms, sleep quality, and fatigue of female nurses

Female nurses working rotating shifts must change their daily routines often, which affects their biological circadian rhythms and could cause sleep disorders and fatigue. The objective of this study was to compare the sleep-wake rhythms, sleep quality, and fatigue of female nurses working rotating shifts and fixed day shifts and to analyze the factors that influence their fatigue. Participants comprised a shift worker group of 101 nurses and a day worker group of 76 nurses. Following the collection of basic information of the nurses and their scores in the various constructs of the Pittsburg Sleep Quality Index (PSQI) and the Checklist Individual Strength (CIS) questionnaire, each nurse wore an actigraph for seven consecutive days to collect for analysis the sleep-wake rhythm parameter dichotomy index (I < O) and durations of continuous sleep and wake. Multivariable linear regression was then used to determine whether the influence of various variables on fatigue differed between the two groups. Results revealed that the sleep-wake rhythm parameter I < O of the day worker group was significantly higher than that of the shift worker group (t = 5.08, p < .001). The shift worker group exhibited significantly higher PSQI global scores (t = -2.00, p = .047), longer total sleep time (t = 2.07, p = .040), poorer habitual sleep efficiency (t = -3.06, p = .003), and greater use of sleeping medication (t = -2.90, p = .004) than did the day worker group. Multivariable linear regression was performed to analyze the important predictors of the CIS score in the two groups with body mass index, age, work experience, marital status, educational background, department of employment, shift type at the time of recruitment, sleep-wake rhythm parameter I < O, and quality of sleep as independent variables. Results indicated that in the shift worker group, the overall explanatory power (R²) of the multivariable linear regression model was 22.9% (F = 3.01, p = .003), and only the PSQI global score (β = 0.33, p = .003) influenced the CIS score. In the day worker group, the various variables did not influence the CIS score in the multivariable linear regression model. Although the female nurses working rotating shifts spent more time in bed, their sleep-wake rhythms and sleep quality were poorer than those of the day worker group. Furthermore, the sleep quality of female nurses in the shift worker group had a significant impact on their fatigue. In other words, for female nurses who must work rotating shifts, sleep quality determines whether fatigue can be reduced. The shift-working nurses themselves should implement sleep management, such as avoiding disruptions to their sleep-wake rhythm and improving sleep quality, which should be effective strategies to reduce fatigue.

Night shift work and the risk of metabolic syndrome: Findings from an 8-year hospital cohort

Objectives

Studies concerning the risk of metabolic syndrome associated with night work have shown inconsistent findings, due to imprecise working time data and cross-sectional design. We used register-based daily working time data to examine the risk of incident metabolic syndrome associated with night shift work.

Methods

Working time data collected between 2010 and 2018 of 5775 Taiwanese hospital workers were used to identify night shift workers and to calculate the number of night shifts. Metabolic syndrome was identified by annual occupational health examination results, which were linked to the working time data. Logistic regression models and generalized estimating equations were used to examine the association between night shift work and metabolic syndrome and the 5 components of metabolic syndrome.

Results

Night shift work is associated with a higher risk of developing metabolic syndrome (adjusted OR = 1.36, 95% CI = 1.04 to 1.78) and high waist circumference (adjusted OR = 1.27, 95% CI = 1.07 to 1.78) compared to day work. Among night shift workers, increased number of night shifts was associated with high blood pressure (adjusted OR = 1.15, 95% CI = 1.01 to 1.31).

Conclusions

Night shift work is associated with metabolic risk factors. Long-term effects of circadian rhythm disruption on metabolic disturbances needs to be further studied.

Impact of stress and coping strategies on insomnia among Polish novice nurses who are employed in their field while continuing their education: a cross-sectional study

OBJECTIVES

To determine to what degree particular coping strategies mediate the association between stress and insomnia in novice nurses who are employed while continuing their education and how type of education moderate the relationships between workplace stress, coping strategies and insomnia.

METHODS

A descriptive cross-sectional study was performed using an online questionnaire, which was completed by 159 novice registered nurses. The questionnaire comprised four components: Athens Insomnia Scale, Perceived Stress at Work (based on Perceived Stress Scale), Brief-Coping Orientation to Problem Experienced (COPE)and metrics with sociodemographic data questions.

RESULTS

Stress was found to be a significant predictor of insomnia among novice nurses. After adjusting the coping strategy, work stress ceased to be a significant predictor of insomnia. Among the strategies, the significant predictors that increased severity insomnia were acceptance, denial and self-blame. Predictors that decreased severity insomnia were use of emotional support and venting. Furthermore, the relationship between both active coping and self-distraction strategies and insomnia was significant for part-time students.

CONCLUSIONS

Insomnia is significant phenomena among novice nurses and are exacerbated by increased stress in the workplace. Choosing appropriate coping strategies for stress that are dependent on the individuals' activities significantly reduce the severity of insomnia caused by work stress.

Association of apolipoprotein Cs with new-onset type 2 diabetes mellitus: findings from the Chinese multi-provincial cohort study

OBJECTIVES

Apolipoprotein Cs (apoCs), especially apoC-II and apoC-III, as the components of triglyceride-rich lipoproteins, play a key role in the pathophysiology of diabetes. However, prospective studies examining direct associations between apoCs and diabetes are not reproducible. The aim of this study was to evaluate the impact of apoCs on the risk of developing diabetes in a middle-aged population, and to explore possible mediators responsible for the relationship between apoCs and diabetes.

DESIGN

Prospective cohort study.

SETTING

Community-based study carried out in Beijing.

METHODS

ApoCs were measured in 1085 participants aged 45-74 years and free of type 2 diabetes mellitus (T2DM) at baseline from the Chinese Multi-Provincial Cohort Study-Beijing Project. Multivariate logistic regression was performed to examine the association of apoCs with a 5-year risk of new-onset T2DM. The impacts of triglycerides, insulin and high-sensitivity C reactive protein (hs-CRP) on the association between apoC-III and the risk of T2DM were explored by a mediation test.

RESULTS

During the 5 years of follow-up, 97 (8.9%) participants developed T2DM. ApoC-III was significantly associated with the risk of developing T2DM after multivariable adjustment (OR=1.40; 95% CI 1.07 to 1.82). This association was mainly mediated by triglyceride levels with a significant indirect effect (OR 1.61; 95% CI 1.19 to 2.18), followed by hs-CRP and insulin.

CONCLUSIONS

Our findings demonstrated that higher serum apoC-III was independently associated with increased 5-year risk of new-onset T2DM in the Chinese population, and triglyceride plays a crucial role in mediating this relationship. More attention should be paid to preventive strategies of T2DM targeting apoC-III.

Rotating between day and night shifts: Factors influencing sleep patterns of hospital nurses

AIMS AND OBJECTIVES

This study aimed to investigate sleep patterns of hospital nurses using a wearable electronic device and determine the influence of rotating day and night shifts and lifestyle factors on their sleep efficiency.

BACKGROUND

Nurses working in shifts are vulnerable to sleep disturbances. However, little is known about the influence of rotating day and night shift schedules and healthy lifestyle on nurses' daily sleep patterns.

DESIGN

Descriptive correlational design.

METHODS

Thirty-two hospital nurses working in shifts and 32 hospital nurses not working in shifts participated in data collection. Their sleep patterns were measured for six consecutive days using Fitbit Charge 3^™ , and information on alcohol consumption, exercise, and eating habits were assessed using a questionnaire. Data were analysed using repeated measures analysis of variance with post hoc Scheffe's test and hierarchical multiple regression analysis. The study was conducted in accordance with the STROBE guideline.

RESULTS

Overall, nurses working on rotating day and night shifts had significantly shorter total sleep time, longer sleep onset latency, and lower sleep efficiency than those not working in shifts. In particular, nurses working for 3 or 4 consecutive night shifts had significantly shorter total sleep time, lower sleep efficiency and longer sleep onset latency than those working for 0-2 consecutive night shifts. Rotating day and night shifts and alcohol consumption significantly influenced sleep efficiency.

CONCLUSIONS

A work schedule of ≥3 consecutive night shifts and the habit of alcohol consumption before bed time influence nurses' sleep efficiency.

RELEVANCE TO CLINICAL PRACTICE

Given the poor sleep pattern among nurses working in shifts, particularly those working on ≥2 consecutive night shifts, it is necessary to develop an optimal shift schedule and a program to promote healthy lifestyle among hospital nurses.

The relationship between chronotype and sleep behavior during rotating shift work: a field study

Shift work, an essential part of our 24/7 society, inevitably leads to displacement of the habitual sleep period and thereby to misalignment of the internal circadian timing system with the rest-activity cycle and the environment. How interindividual differences in circadian organization affect sleep duration and timing during rotating shift work is not fully understood. The objective of this study was to assess the effect of chronotype, shift type, and their interaction on actigraphy-based sleep behavior in 74 police officers (20 women and 54 men; age [mean ± SD]: 32.1 ± 5.4 years) involved in rotating shift work throughout a 28- to 35-day work cycle consisting of morning, evening, and night shifts. Using linear mixed modeling, we found that chronotype was associated with sleep duration depending on the shift type: increasing morningness was correlated with longer sleep duration during series of consecutive morning shifts, while increasing eveningness was correlated with longer sleep duration during series of evening shifts. During series of night shifts, increasing eveningness was associated with a longer duration of the main sleep episode, but this relationship was attenuated and no longer significant when naps were taken into account due to increased napping in morning chronotypes during series of night shifts. Providing a detailed within-subject characterization of sleep behavior across a complete work cycle consisting of morning, evening, and night shifts, this study advances the understanding of the relationship between chronotype and sleep in rotating shift workers and supports the implementation of work schedules that take into account chronobiological principles.

Association between shift work or long working hours with metabolic syndrome: a systematic review and dose-response meta-analysis of observational studies

This meta-analysis investigates the relationship between both shift work and long working hours and risk of developing metabolic syndrome (MetS). PubMed, EMBASE, and Web of Science databases were searched from the outset to December 10, 2019. Two reviewers independently screened studies, extracted data, and assessed the risk of bias of included studies. A total of 36 (30 cross-sectional, 5 cohort, and a nested case-control) studies, involving 274,263 participants, were included. The pooled odds ratio of shift work and development of MetS was 1.35 (95% confidence interval: 1.24-1.48), and the pooled odds ratio of long working hours and development of MetS was 1.19 (95% confidence interval: 0.97-1.46). In the subgroup analysis stratified by gender, the pooled odds ratios for male and female shift workers were 1.25 (95% confidence interval: 1.14-1.37) and 1.47 (95% confidence interval: 1.18-1.82), respectively. The dose-response (number of years of shift work and development of MetS) analysis showed the pooled odds ratio for 5 years of shift work was 1.07 (95% confidence interval: 1.05-1.09) and for 10 years of shift work 1.11 (95% confidence interval: 1.06-1.15). Our meta-analysis confirmed shift work is significantly associated with risk of metabolic syndrome, but the relationship between long working hours and MetS was not substantiated. Additionally, there was a nonlinear dose-response relationship between the number of years of shift work and risk of MetS, showing positive relationship to about 20 years of shift work but not for longer than 20 years. Prospective cohort studies regarding specific shift work schedules are needed to confirm these results.

Acute and chronic sleep deprivation in residents: Cognition and stress biomarkers

OBJECTIVES

Insufficient sleep affects circadian hormonal profiles and inflammatory markers and may modulate attention, executive functioning and decision-making. Medical professionals and specifically resident physicians, who are involved in long-term nightshift schedules during their post-graduate training, are prone to acute and chronic sleep deprivation and disruption, putting them at risk for making medical errors. The aim of the study was to evaluate the impact of chronic and acute-on-chronic sleep deprivation and disruption among residents on selected physiological and cognitive measures.

METHODS

Thirty-three medical and surgical residents were evaluated twice - at baseline and after a 26-hour shift. Eighteen young attending physicians who did not engage in nightshift schedules served as controls and were evaluated once. Measures included morning cortisol and high-sensitivity C-reactive protein (hs-CRP), computerised tests of attention and behaviour, the Behaviour Rating Inventory of Executive Function, a risk-taking questionnaire and the Pittsburgh Sleep Quality Index.

RESULTS

Residents, but not attendings, reported chronic sleep disruption and deprivation. Residents at baseline exhibited reduced morning cortisol levels and elevated hs-CRP levels, compared to attendings. Residents at baseline had impaired global executive function compared to attendings. A nightshift with acute sleep deprivation further reduced residents' executive function. Residents at baseline and after a nightshift demonstrated increased impulsivity and slower processing time than attendings. Residents and attendings did not differ in risk-taking tendencies which were assessed in a separate cohort.

CONCLUSIONS

In a real-life setting, resident physicians exhibit increased low-grade systemic inflammation (hs-CRP) and impaired HPA-axis function. Their chronic sleep curtailment is associated with greater impulsivity, slower cognitive processing, and impaired executive function. Future research is warranted to understand how improving working schedule by increasing sleep duration may minimise the short-term and potential long-term risks to physicians in training.

A systematic review and meta-analysis of the association between shift work and metabolic syndrome: The roles of sleep, gender, and type of shift work

This study was conducted to investigate the association between shift work and metabolic syndrome (MetS) and quantify the roles of sleep, gender, and type of shift work. We searched online databases, including PubMed, Scopus, and Web of Science on November 17, 2019. Of the 821 articles identified, 38 observational studies (27 cross-sectional, 10 cohorts, and one nested case-control), conducted on 128,416 participants, met our eligibility criteria. The pooled Odds ratio (OR) and 95% Confidence interval (CI) of MetS in shift-versus day-workers were estimated as 1.14 (1.07, 1.21) and 1.11 (1.06, 1.17) for the unadjusted and adjusted models. This association remained significant only for the studies with a cross-sectional design. There was a significantly higher odds of MetS in the studies conducted only on females (1.13 [1.06, 1.20]) or males (1.12 [1.02, 1.21]). The pooled adjusted OR (95% CI) for the studies without and with sleep adjustment was calculated as 1.14 (1.08, 1.21) and 1.29 (1.06, 1.52). We observed that rotating shift workers had stronger odds of MetS than the other shift workers. In conclusion, our findings revealed the significant odds of an association between shift work and MetS and different effects for sleep, gender, and type of shift work.

BMI differences between different genders working fixed day shifts and rotating shifts: a literature review and meta-analysis

The objective of this study was to perform a systematic literature review and meta-analysis to understand the BMI differences between different genders working fixed day shifts and rotating shifts. The Pubmed, Medline, and Embase databases were searched using set keywords, thereby producing 42 studies. Study quality was assessed using appraisal criteria from the Joanna Briggs Institute (JBI), and meta-analysis was performed using Comprehensive Meta-Analysis Software (CMA) version 3. The indices were the means and standard deviations of BMI values from different genders working fixed day shifts and rotating shifts. The participants of the studies included a total of 43,193 individuals working rotating shifts and 185,875 individuals working fixed day shifts. The pooling effect size (SMD, standardized mean difference) presented was 0.19. The 95% confidence interval ranged from 0.10 to 0.281. The meta-regression analysis results showed that women had higher BMI values than men, the difference was statistically significant (p <.001). The heterogeneity test indicated statistically significant differences (p <.05), and the percentage of heterogeneity (I square) was 97.91%, which indicates that a high degree of heterogeneity exists among studies. A subgroup analysis by gender was conducted. For women, the pooling effect size was 0.25, and the 95% confidence interval ranged from 0.20 to 0.30. For men, the pooling effect size was 0.19, and the 95% confidence interval ranged from 0.05 to 0.33. This meta-analysis found that both women and men working rotating shifts have significantly higher BMI values than those working fixed day shifts. Finally, we divided the data into a cross-sectional group and a cohort group based on study design, and a meta-regression analysis conducted after controlling for age and nature of work variables revealed that in the cohort study, women presented higher BMI values than men, and the difference was statistically significant (p =.010). Thus, in terms of long-term effects, these results indicate that working rotating shifts exerts a greater impact on the BMI of women.

Feeding Rhythms and the Circadian Regulation of Metabolism

The molecular circadian clock regulates metabolic processes within the cell, and the alignment of these clocks between tissues is essential for the maintenance of metabolic homeostasis. The possibility of misalignment arises from the differential responsiveness of tissues to the environmental cues that synchronize the clock (zeitgebers). Although light is the dominant environmental cue for the master clock of the suprachiasmatic nucleus, many other tissues are sensitive to feeding and fasting. When rhythms of feeding behavior are altered, for example by shift work or the constant availability of highly palatable foods, strong feedback is sent to the peripheral molecular clocks. Varying degrees of phase shift can cause the systemic misalignment of metabolic processes. Moreover, when there is a misalignment between the endogenous rhythms in physiology and environmental inputs, such as feeding during the inactive phase, the body's ability to maintain homeostasis is impaired. The loss of phase coordination between the organism and environment, as well as internal misalignment between tissues, can produce cardiometabolic disease as a consequence. The aim of this review is to synthesize the work on the mechanisms and metabolic effects of circadian misalignment. The timing of food intake is highlighted as a powerful environmental cue with the potential to destroy or restore the synchrony of circadian rhythms in metabolism.

Contribution of serum lipids as effect modifiers to a relationship between mean arterial pressure and coronary heart disease in Chinese rural population: the Henan Rural Cohort Study

OBJECTIVES

The aim of this study was to evaluate the relationship between mean arterial pressure (MAP) and coronary heart disease (CHD) in Chinese rural population. In addition, we hypothesised that this relationship might be mediated by some degree of serum lipids.

DESIGN

This is a cross-sectional study.

SETTING

The participants were from the Henan Rural Cohort Study, initiated in five rural areas (Tongxu county of Kaifeng city, Yima county of Sanmenxia city, Suiping county of Zhumadian city, Xinxiang county of Xinxiang city and Yuzhou county of Xuchang city) in Henan Province, China, during July 2015 and September 2017.

PARTICIPANTS

The study included 39 020 subjects aged 18-79 years as current research population.

OUTCOME MEASURES

Systolic blood pressure (SBP) and diastolic blood pressure (DBP) were measured using an electronic sphygmomanometer. MAP was calculated by one-third SBP plus two-thirds DBP. The study used restricted cubic splines and logistic regression models to evaluate the ORs and 95% CIs. Mediation analysis using bootstrap was performed to examine the contribution of serum lipids to MAP-related CHD.

RESULTS

The adjusted OR (95% CI) for the highest MAP quartile with the risk of CHD was 1.45 (1.24 to 1.69) compared with the lowest quartile. Simultaneously, each 1-SD increment in MAP was significantly associated with a 12% increased risk of CHD. A linear dose-response relationship between MAP and CHD was found (p value for non-linear=0.1169) in the fully adjusted model. We further reported that 36.07% of proportion explained risk of CHD was mediated through serum lipids.

CONCLUSIONS

Increased MAP was a significant marker of CHD in Chinese rural population. Meanwhile, the relationship was mediated by some degree of serum lipids, and triglyceride was the strongest mediator.

TRIAL REGISTRATION NUMBER

Henan Rural Cohort study has been registered at Chinese Clinical Trial Register (ChiCTR-OOC-15006699) and the stage it relates to is Post-results.

Night-Shift Work Duration and Risk of Colorectal Cancer According to IRS1 and IRS2 Expression

BACKGROUND

We hypothesized that the risk of colorectal cancer in night-shift workers might be different according to insulin receptor substrate status.

METHODS

Among 77,470 eligible women having night work assessed in the Nurses' Health Study, we documented a total of 1,397 colorectal cancer cases, of which 304 or 308 had available data on IRS1 and IRS2, respectively. We used duplication-method Cox proportional hazards regression analysis for competing risks to calculate HRs and 95% confidence intervals (CI) for each colorectal cancer subtype. We measured tumor IRS1 or IRS2 expression by immunohistochemistry (IHC).

RESULTS

Compared with women who never worked night shifts, those working ≥15 years night shifts had a marginal trend of increased overall risk of colorectal cancer (P _trend = 0.06; multivariable HR = 1.20; 95% CI, 0.99-1.45). Longer duration of night-shift work was associated with a higher risk of IRS2-positive tumors (multivariable HR = 2.69; 95% CI, 1.48-4.89; P _trend = 0.001, ≥15 years night shifts vs. never) but not with IRS2-negative tumors (multivariable HR = 0.90; 95% CI, 0.54-1.51; P _trend = 0.72; P _{heterogeneity} for IRS2 = 0.008). Similarly, the corresponding multivariable HRs were 1.81 for IRS1-positive tumors (95% CI, 0.94-3.48; P _trend = 0.06) and 1.13 for IRS1-negative tumors (95% CI, 0.71-1.80; P _trend = 0.56; P _{heterogeneity} for IRS1 = 0.02).

CONCLUSIONS

Our molecular pathologic epidemiology data suggest a potential role of IRS in mediating carcinogenesis induced by night-shift work.

IMPACT

Although these findings need validation, rotating night shift might increase colorectal cancer risk in women with abnormal insulin receptor pathways.

The Manitoba Personalized Lifestyle Research (TMPLR) study protocol: a multicentre bidirectional observational cohort study with administrative health record linkage investigating the interactions between lifestyle and health in Manitoba, Canada

INTRODUCTION

Lifestyle factors, such as diet, physical activity and sleep, are associated with the development of many chronic diseases. The objective of The Manitoba Personalized Lifestyle Research study is to understand how these lifestyle factors interact with each other and with other factors, such as an individual's genetics and gut microbiome, to influence health.

METHODS

An observational study of adults, with extensive phenotyping by objective health and lifestyle assessments, and retrospective assessment of early life experiences, with retrospective and prospective utilisation of secondary data from administrative health records.

STUDY POPULATION

A planned non-random convenience sample of 840 Manitobans aged 30-46 recruited from the general population, stratified by sex (equal men and women), body mass index (BMI; 60% of participants with a BMI>25 kg/m²) and geography (25% from rural areas). These stratifications were selected based on Manitoba demographics.

MEASUREMENTS

Lifestyle factors assessed will include dietary pattern, physical activity, cardiovascular fitness, and sleep. Factors such as medical history, socioeconomic status, alcohol and tobacco consumption, cognition, stress, anxiety, and early life experiences will also be documented. A maternal survey will be performed. Body composition and bone density will be measured by dual energy X-ray absorptiometry. Blood pressure, pulse wave velocity, and augmentation index will be measured on two consecutive days. Chronic disease risk biomarkers will be measured in blood and urine samples. DNA will be extracted for genetic analysis. A faecal sample will be collected for microbiome analysis. Participants may provide their Manitoba personal health information number to link their study data with administrative health records.

ETHICS AND DISSEMINATION

Ethics approval has been obtained from the University of Manitoba Health Research Ethics Board (protocol # HS18951; 05/01/2016). Data analysis, release of results and publication of manuscripts are scheduled to start in early 2019. Additional information at www.TMPLR.ca.

TRIAL REGISTRATION NUMBER

NCT03674957; Pre-results.

Metabolic syndrome in shift healthcare workers

Background:

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

Objectives:

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

Methods:

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

Results:

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

Conclusions:

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

The Role of Microbiome in Insomnia, Circadian Disturbance and Depression

Good sleep and mood are important for health and for keeping active. Numerous studies have suggested that the incidence of insomnia and depressive disorder are linked to biological rhythms, immune function, and nutrient metabolism, but the exact mechanism is not yet clear. There is considerable evidence showing that the gut microbiome not only affects the digestive, metabolic, and immune functions of the host but also regulates host sleep and mental states through the microbiome-gut-brain axis. Preliminary evidence indicates that microorganisms and circadian genes can interact with each other. The characteristics of the gastrointestinal microbiome and metabolism are related to the host's sleep and circadian rhythm. Moreover, emotion and physiological stress can also affect the composition of the gut microorganisms. The gut microbiome and inflammation may be linked to sleep loss, circadian misalignment, affective disorders, and metabolic disease. In this review article, we discuss various functions of the gut microbiome and how its activities interact with the circadian rhythms and emotions of the host. Exploring the effects of the gut microbiome on insomnia and depression will help further our understanding of the pathogenesis of mental disorders. It is therefore important to regulate and maintain a normal gastrointestinal micro-ecological environment in patients when treating mental disorders.

Impact of Shift Work on the Circadian Timing System and Health in Women

Women who do shift work are a sizable part of the workforce. Shift workers experience circadian misalignment due to shifted sleep periods, with potentially far-reaching health consequences, including elevated risk of sleep disturbances, metabolic disorders, and cancer. This review provides an overview of the circadian timing system and presents the sex differences that can be observed in the functioning of this system, which may account for the lower tolerance to shift work for women compared with men. Recent epidemiologic findings on female-specific health consequences of shift work are discussed.

A dose-response association of night sleep duration with hypertension in a Chinese rural population: the Henan Rural Cohort Study

The purpose of the study was to determine if there was a relationship between night sleep duration and hypertension, and to evaluate as to whether blood lipid levels played a role in this relationship. A total of 37,317 participants aged 18-79 years were included in this study. Night sleep duration was classified as <5, 5-, 6-, 7-, 8-, 9-, and ≥10 hours. Logistic regression and restricted cubic spline analysis was carried out to evaluate the association of sleep duration with hypertension. Compared with reference sleep duration (7 hours), in males, the multivariate odds ratios (ORs) (95% confidence interval [95% CI]) of the groups with longest sleep duration (≥10 hours) and shortest sleep duration (<5 hours) for hypertension was 1.52 (1.25-1.84) and 1.07 (0.80-1.44), respectively. Similarly, the longest sleep duration was associated with diagnosed hypertension (1.21, 1.00-1.45) in females. The OR for an indirect effect of sleep duration through low-density lipoprotein cholesterol (LDL-C) on hypertension was 1.085 (95% CI 1.038-1.137). Overall, a 3.5% possibility of hypertension being associated with sleep duration was attributable to LDL-C. In summary, a relationship between sleep duration and hypertension was observed in this rural population. LDL-C appeared to partially mediate the effect of sleep duration on hypertension in males.

Sleep problems in shift nurses: A brief review and recommendations at both individual and institutional levels

AIMS

The purposes of this article are (a) to review briefly the current literature on shift nurses' sleep patterns, sleep quality, and the existing interventions implemented in nursing settings; and (b) to propose solutions that target individual nurses, nurse managers, and health care organisations to improve sleep health in shift nurses.

BACKGROUND

Sleep problems among shift nurses have been recognized increasingly as a significant issue at both the individual and organisational levels. However, the solutions are not well known.

DESIGN

Narrative review.

METHODS

A literature search was conducted using the following databases: CINAHL, PubMed, Embase, and Google Scholar from 1986 to 2016, to include original papers that reported studies on shift nurses' sleep problems and interventions.

RESULTS

Thirteen papers were included in this review, which all indicated associations between shift nurses' sleep problems and current intervention practices. Despite the higher prevalence of sleep problems in shift nurses compared to the general population, current interventional practices only focus on bright-light exposure, nap breaks, shift schedule rearrangement, and behavioural interventions.

CONCLUSIONS

To address shift nurses' poor sleep quality, we proposed two levels of approach for consideration-the individual level and the management/institutional level. The recommendations include: improving sleep hygiene; providing a low-stimulation sleep environment; conducting rigorous intervention studies to evaluate the effectiveness of a variety of therapies to deal with shift nurses' sleep disturbances; increasing awareness of sleep health of shift nurses; establishing a flexible rotating work schedule; and putting in place policies such as a 15-30 min nap break, social support, and a suitable working environment.

IMPLICATIONS FOR NURSING MANAGEMENT

With better awareness and understanding of shift nurses' sleep behaviours, effective interventions can be employed to improve shift nurses' sleep patterns and sleep quality to promote better emotional and health outcomes.