Night shift work and indicators of cardiovascular risk: A systematic review and meta-analysis

Cardiovascular disease (CVD) is a leading cause of death worldwide, and shift workers have an increased risk of CVD. This comprehensive systematic review and meta-analysis aimed to assess the association between night shift work and cardiovascular risk indicators. A systematic literature search was performed according to the PRISMA 2020 guidelines using Medline, Embase, and Web of Science databases from inception through May 2024. Original manuscripts reporting relevant cardiovascular risk indicators and biomarkers in night shift workers were included. Risk of bias was assessed using the JBI's critical appraisal tools. When applicable, random-effect meta-analyses were performed. If suitable data were not available, a narrative synthesis was performed by combining p-values or vote-counting. Meta-regression analyses were performed to assess the contribution of sex, body mass index, and age as possible modifiers of effect. Evidence was weighed using an adapted GRADE. This study is registered in PROSPERO (CRD42022337285). Of the 8,387 studies identified, 81 were included in the synthesis, comprising 14 cohort and 67 cross-sectional studies. Moderate-confidence evidence was presented demonstrating increased inflammation, dyslipidaemia and impaired cardiac excitability among night shift workers. Dose-dependent effects were reported for these cardiovascular risk indicators, suggesting that the intensity and duration of night shift work contribute to risk of CVD. Furthermore, no association between night shift work and indicators of vascular dysfunction, deregulation of the autonomic nervous system, or altered homeostasis was observed. Considering this, regulatory and preventative initiatives are essential to reduce the cardiovascular risk among night shift workers.

The effects of shift work on sleep quality, diet quality, and obesity-related factors: A male population study

Recent studies suggest that shift working may trigger health issues through disrupted circadian rhythms and altered eating habits. This study aimed to examine the possible associations of shift work with sleep quality, diet quality and obesity-related parameters. This study was conducted with 150 males (75 shift and daytime workers) aged 24-50 years. Dietary intake was determined using the 24-hour recall method, and dietary quality was evaluated using the Healthy Eating Index-2010 (HEI-2010). Anthropometrical measurements and body composition were assessed. The Pittsburgh Sleep Quality Index was used to evaluate sleep quality. Fasting and postprandial glucose and insulin, and fasting lipid levels were analyzed. HOMA-IR was calculated, and blood pressure was measured. The total HEI-2010 score of shift workers (52.6 [45.4-58.8]) was lower than the daytime workers (55.9 [49.1-64.9]) (p = 0.016). Among individuals with good sleep quality, the total HEI-2010 score, seafood and plant proteins, fatty acids, and sodium scores were lower in shift workers compared to others (p < 0.05 for each). Non-obese shift workers had higher body weight, waist circumference, waist/hip ratio, VLDL-cholesterol, triglyceride, postprandial glucose, and insulin levels compared to daytime workers (p < 0.05 for each). This study demonstrates that shift working is associated with lower diet quality independent of sleep quality.

The Impact of Night Work on the Sleep and Health of Medical Staff-A Review of the Latest Scientific Reports

Introduction: Employees working in shifts are exposed to many threats affecting their health, quality of life and safety at work. Those who perform their work only at night are particularly vulnerable. The purpose of the review is to identify risks to the health, quality of life and sleep of shift health workers. Method: A systematic review (SR) was used in the analysis. Electronic databases were searched. The search was limited to the latest studies published in the last five years: 2019-2023. Results: Finally, 36 articles were included in the review. Most authors have shown a link between sleep disturbance or its quality and shift work/night work. Moreover, a three-shift schedule was the most significant factor for poorer subjective sleep quality when compared to other work schedules. Furthermore, many authors have shown a link between shift/night work and health problems, which include cardiometabolic risk, glucose intolerance, breast cancer and immune vulnerability. Conclusions: The research results clearly show a significant impact of night work on the increased risk of sleep disorders and health disturbance. Healthcare workers should be aware of the risks associated with night work in order to take measures preventing sleep/health problems. Shift/night workers should have the opportunity to be screened for disorders linked with their work.

Circadian regulation of liver metabolism: experimental approaches in human, rodent, and cellular models

Circadian rhythms are endogenous oscillations with approximately a 24-h period that allow organisms to anticipate the change between day and night. Disruptions that desynchronize or misalign circadian rhythms are associated with an increased risk of cardiometabolic disease. This review focuses on the liver circadian clock as relevant to the risk of developing metabolic diseases including nonalcoholic fatty liver disease (NAFLD), insulin resistance, and type 2 diabetes (T2D). Many liver functions exhibit rhythmicity. Approximately 40% of the hepatic transcriptome exhibits 24-h rhythms, along with rhythms in protein levels, posttranslational modification, and various metabolites. The liver circadian clock is critical for maintaining glucose and lipid homeostasis. Most of the attention in the metabolic field has been directed toward diet, exercise, and rather little to modifiable risks due to circadian misalignment or disruption. Therefore, the aim of this review is to systematically analyze the various approaches that study liver circadian pathways, targeting metabolic liver diseases, such as diabetes, nonalcoholic fatty liver disease, using human, rodent, and cell biology models.NEW & NOTEWORTHY Over the past decade, there has been an increased interest in understanding the intricate relationship between circadian rhythm and liver metabolism. In this review, we have systematically searched the literature to analyze the various experimental approaches utilizing human, rodent, and in vitro cellular approaches to dissect the link between liver circadian rhythms and metabolic disease.

Consequences of Shift Work and Night Work: A Literature Review

Nonstandard work schedules such as shift work and night work tend to trigger problems for workers in different areas. To illustrate the diversity of areas affected and the relative interest of the scientific community, we conducted a literature review of the effects of shift work and night work on workers. In particular, we intended to identify the main variables addressed in the field of health, the family sphere, and the organizational context. The literature review was carried out using the Web of Science with the following terms: "shift work", "rotating shifts", and "night work". Inclusion criteria incorporated empirical studies and articles written in Portuguese or English published in 2019. We selected 129 of the 619 articles identified. Regarding the impacts of shift work and night work, there existed a high discrepancy of focus between the three defined areas: health, family life, and organizational context. Specifically, health-related variables were the most studied (83.4%), followed by organizational variables (9.2%), and, lastly, family variables (7.4%). Based on these results, it is essential to extend the study of the two underrepresented impacts to other crucial areas, not only for the worker but also for organizations.

Association of industrial work schedules with development of metabolic syndrome, insulin resistance, and serum adipokine concentrations

Background

Association of work schedule in industrial workers with the progression of metabolic syndrome, insulin resistance, and serum adipokine concentrations is incompletely explored.

Objective

To determine the association of work schedule with the progression of metabolic syndrome, insulin resistance, and adipokine concentrations in industrial workers.

Methods

In a cross-sectional study design of industrial workers we compared metabolic syndrome, insulin resistance, and adipokines concentration between workers in the day shift (n = 52), rotational shift (n = 21), and night shift (n = 15). The international Diabetes Federation criteria were used to diagnose metabolic syndrome. We used a homeostatic model assessment of insulin resistance (HOMA-IR). Serum insulin, leptin, and adiponectin concentrations were measured using enzyme-linked immunosorbent assays. Serum glucose, triglyceride, and high-density lipoprotein cholesterol (HDL-C) concentrations were monitored using Prietest clinical chemistry reagents.

Results

The proportional difference in metabolic syndrome (0.31, 95% confidence interval [CI] 0.036-0.587, P = 0.026), median difference of leptin (0.61, 95% CI 0.186-1.034, P = 0.005), and leptin-to-adiponectin ratio (LAR; 0.45, 95% CI 0.235-0.665, P < 0.001) was significantly higher, and serum adiponectin was lower (-2.00, 95% CI -4.197 to 0.197, P = 0.07) in the night-shift workers compared with that of day-shift workers. Among rotational-shift workers, the proportional difference between metabolic syndrome (0.14, 95% CI -0.098 to 0.378, P = 0.25), median difference of leptin (0.25, 95% CI -0.124 to 0.624, P = 0.19), and LAR (0.09, 95% CI -0.099 to 0.279, P = 0.35) was higher, and serum adiponectin concentration was lower (-0.73, 95% CI -2.660 to 1.208, P = 0.46) compared with that of day-shift workers; however, the altered differences were not significant. We observed a higher proportion of difference in HOMA-IR in shift workers (night and rotation) than in day-shift workers.

Conclusion

Night-shift workers are vulnerable to a higher risk of metabolic syndrome, HOMA-IR, and adipokine changes.

Longterm effects of rotational night shift work on expression of circadian genes and its association with postprandial triglyceride levels - A pilot study

Abnormalities of lipid metabolism in the form of high fasting as well as postprandial triglyceride levels immediately after night shift work and under simulated night shift conditions have been reported in the literature. Whether dysregulation of circadian genes in the long term is associated with abnormal triglyceride metabolism has not been previously investigated. This pilot study aimed to investigate the long-term effect of rotational night shift work on the expression of circadian genes among healthcare workers and to ascertain the association between the expression of circadian genes and postprandial triglyceride and insulin resistance parameters. The study was conducted on two groups of healthcare workers (n = 20/group). Group 1 included day shift workers who had not done night shift duty during the past one year or ever. Group 2 included healthcare workers doing rotational night shift duties (≥4 night shift duties/month). Fasting blood samples were collected at 08:00 h to study the expression of circadian genes CLOCK, NPAS2, BMAL1, CRY1, CRY2, PER1, PER2, PER3, REVERBα, and biochemical parameters after which a standardized fat challenge test was done to measure postprandial triglyceride levels. Study of Group 2 individuals was conducted after a minimum of one week after the last night shift duty. Expression of CLOCK, NPAS2, PER1, PER3, and REV-ERBα genes was higher in Group 2 compared to Group 1 subjects, and expression of BMAL1 and CRY1 genes were lower in Group 2 compared to Group 1. Several of these genes showed significant correlations with postprandial triglyceride and insulin resistance parameters in Group 2 but not in Group 1 subjects. The present study showed altered expression of several circadian genes in healthcare workers involved in rotational night shift duties associated with postprandial triglyceride and insulin resistance parameters. This study therefore suggests that long term circadian gene dysregulation could have serious metabolic consequences in individuals engaged in rotational night shift duties.

Family history of diabetes determines the association of HOMA-IR with fasting and postprandial triglycerides in individuals with normal glucose tolerance

BACKGROUND

Individuals with family history of diabetes carry nearly double the risk of diabetes than those without. However, the mechanism for this increased risk of diabetes in them is not fully understood.

OBJECTIVE

To study fasting and postprandial triglyceride levels in individuals with normal glucose tolerance (NGT) who had family history of diabetes and to ascertain their association with insulin resistance.

METHODS

Fasting triglyceride levels and HOMA-IR were compared in 671 NGT individuals with and without a family history of diabetes. A standardized fat challenge test was also done in one tenth of individuals of each group and postprandial triglyceride responses were compared between them. Association of HOMA-IR with fasting and postprandial triglyceride levels was ascertained through pearson's coefficient of correlation.

RESULTS

Individuals with family history of diabetes had significantly higher HOMA-IR (P < 0.001) and significantly higher postprandial triglyceride AUC (P = 0.04) after standardized fat meal despite having similar fasting triglyceride levels (P = 0.51) as those without family history of diabetes. Fasting as well as postprandial triglyceride levels significantly correlated with HOMA-IR (r = 0.35, P < 0.001 and r = 0.39, P = 0.04) only in those with a positive family history of diabetes but not in those without. Triglyceride levels mediated the associations of BMI (Δ β = -0.053) and waist circumference (Δ β = -0.075) with HOMA-IR.

CONCLUSION

Triglyceride levels, both in the fasting and the postprandial state are associated with insulin resistance in NGT individuals with a family history of diabetes but not in those without.

Shift work, and particularly permanent night shifts, promote dyslipidaemia: A systematic review and meta-analysis

BACKGROUND AND AIMS

Shift work is common worldwide and linked to deleterious cardiovascular effects that might be underlined by dyslipidemia. The aim of this systematic review and meta-analysis is to determine the impact of shiftwork on dyslipidemia.

METHODS

Searching in PubMed, Cochrane Library, Science Direct and Embase databases without language restriction on 15 February 2020, included studies that describe blood lipids levels or a risk measure in shift workers compared with fixed-day workers (controls). Differences by study-level characteristics were estimated using stratified meta-analysis by type of shift work, and meta-regression to examine relations between dyslipidemia and demographic, lifestyle and work characteristics. Estimates were pooled using random-effect meta-analysis.

RESULTS

We included a total of 66 articles, representing 197,063 workers. Shift work globally increased the levels of triglycerides (overall SMD = 0.09; 95CI 0.05 to 0.13; p < 0.001), and globally decreased the levels of c-HDL (-0.08; 95CI -0.12 to -0.03; p = 0.001). Permanent night shift workers were an at-risk type of shift for dyslipidemia with significantly higher blood levels of total cholesterol (0.22; 95CI 0.01 to 0.42; p = 0.043) and triglycerides (0.18; 0.03 to 0.33; p = 0.017), and significantly lower blood levels of c-HDL (-0.16; 95CI -0.32 to 0.00; p = 0.05). Permanent night shift workers were more at-risk for total cholesterol than rotating 3 × 8 shift workers (Coefficient 0.22; 95CI 0.01 to 0.42; p = 0.038) and rotating 2 × 12 shift workers (0.24; 0.02 to 0.46; p = 0.037), and more at-risk for triglycerides than rotating day shift workers (0.21; 95CI 0.03 to 0.38; p = 0.023). Results were non-significant for c-LDL, nor depending on type of shifts.

CONCLUSIONS

Shift work, and particularly permanent night shift, is associated with dyslipidaemia via elevated total cholesterol and triglycerides, and reduced HDL-cholesterol. Our current study provides a practical and valuable strengthening of the evidence-base required for preventive health initiatives and workplace reform.