Review Article: Night Shift Work, Circadian Disruption, and the Gut Microbiome: Implications for Human Health.

It is known that working in the shift system, especially the night shift, affects physical, mental, and social well-being. We investigated the changes in the inner retinal layers and choroidal layer of the eyes of nurses working night and day shifts using optical coherence tomography (OCT). We also explored the effect of night shift work on metacognition and the relationships between these variables. A total of 79 nurses participated in the study, of whom 40 worked night shifts. The researcher gave the participants sociodemographic information and the Metacognition Questionnaire-30 (MCQ-30) form. Retinal nerve fiber layer (RNFL) thickness, ganglion cell layer (GCL) thickness, inner nuclear layer (INL) thickness, inner plexiform layer (IPL) thickness, central macular thickness (CMT), and subfoveal choroidal thickness (SFCT) were measured with OCT. It was found that the level of metacognitive activity associated with cognitive confidence was higher (p = 0.044) for nurses who worked night shifts and that the level of metacognitive activity associated with cognitive awareness was lower (p = 0.015) for nurses who worked night shifts. RNFL-nasal superior (NS) thickness was lower in night shift workers than the day shift group (p = 0.017). Our study revealed significant relationships between metacognition and the OCT findings among night and day shift workers. Our study revealed that RNFL measurements and metacognitive activity may differ and there may be a relationship between these parameters in nurses who work shifts. Further research is needed to investigate the long-term effects of night shift work on retinal health.

We thank Dr Richard Stevens for his comments (1) on our recent article that showed no increased risk of breast cancer following recent night shift work when compared with recent day shift work (2). This finding was based on linkage of day-by-day information on working hours and breast cancer incidence data. Results are thus less likely to have been biased by differential misclassification than findings from earlier studies relying on self-report (3). We defined a night shift as ≥3 hours of work between 24:00-05:00 hours and a day shift as ≥3 hours work between 6:00-20:00 hours. This day shift definition did not exclude shifts starting before 05:00 or ending after 24:00 hours. However, this affected only 0.02% and 0.3% of all day shifts, respectively. This diminutive misclassification, that is expected to be non-differential, can hardly explain our negative findings. It is suggested that shifts that begin after 07:00 and end before 18:00 would constitute a more sensible baseline comparison group. Since the biological mechanism is not certain, it is not obvious to us if this will be a more appropriate reference than the present. However, we agree that future studies should test how different definitions of shifts affect the risk of breast cancer, which will be possible using this type of data. We only had information on working hours from 2007 and onwards, and night shift work prior to 2007 could have confounded our analyses towards no effect but only if inversely associated with night shift work in 2007 or later. We find this unlikely. Left truncation could also have biased findings towards the null. We therefore supplemented analyses of the total study population with analyses of the one-third of the population with first recorded employment in 2008 or later (the inception population). Even if the mean age was 35.5 years - and many undoubtedly had been working (with and without night shifts) prior to 2008 - this population should be less affected by such selection bias, but we observed similar risk estimates as for the total study population. Taken together, we find that our study provides rather robust evidence of no short-term breast cancer risk following recent night shift work. It must, however, be stressed that data did not allow assessment of a possible long-term risk. Reference 1. Stevens R. Letter ref. Vitisen et al: "Short-term effects of night shift work on breast cancer risk: a cohort study of payroll data". Scand J Work Environ Health. 2017;43(1):95. http://dx.doi.org/10.5271/sjweh.3607 2. Vistisen HT, Garde AH, Frydenberg M, Christiansen P, Hansen AM, Hansen J, Bonde JP, Kolstad HA. Short-term effects of night shift work on breast cancer risk: A cohort study of payroll data. Scand J Work Environ Health. 2017;43(1):59-67. http://dx.doi.org/10.5271/sjweh.3603. 3. Ijaz S, Verbeek J, Seidler A, Lindbohm ML, Ojajarvi A, Orsini N, Costa G, Neuvonen K. Night-shift work and breast cancer--a systematic review and meta-analysis. Scand J Work Environ Health. 2013 Sep 1;39(5):431-47. http://dx.doi.org/10.5271/sjweh.3371.

BackgroundThe destruction of circadian rhythms by night shift work affects major circadian genes, which are known to play a role in advancing or killing the cell cycle through tumor suppressor genes. To find out whether night shift work affects the incidence of colorectal cancer, which was found to be associated with long-term night shift work in previous studies, we surveyed effect of night shift work on colorectal polyps that have a higher incidence than colorectal cancer and can progress to colorectal cancer.MethodsTo examine the correlation between rotating night shifts and colorectal polyps, a survey was conducted with 299 men aged 40–60 years from two university hospitals. We examined lifestyle, work history, work patterns, and colonoscopy results. The differences in prevalence among the groups was compared, and prevalence ratio (PR) was calculated via generalized linear modeling.ResultsThe prevalence of colorectal polyps in night shift and non-shift workers were 53.0% and 33.5%, respectively. After adjusting for age, smoking status, dietary habits, family history of colorectal cancer, obesity, job type, night shift work (PR: 1.13, 95% CI: 1.02–1.25) was a risk factor of colorectal polyps.ConclusionsThe risk of colorectal polyps was greater in night shift workers than non-shift workers. Also risk of colorectal polyp was higher in older group. Our study investigated colorectal polyp instead of colorectal cancer and lacks information about types and gene mutations of colorectal polyps. Further study is needed to clarify effect of night shift work on development of colorectal cancer.

Maintain host health with time-restricted eating and phytochemicals: A review based on gut microbiome and circadian rhythm

Evidence links night shift work to circadian rhythm disruption, causing hormonal and metabolic alterations, as well as increased risk for cardiovascular disease (CVD). This study investigates whether night shift work affects blood glucose variability and dysregulation, potentially driven by circadian misalignment. It also examines whether such disruptions elevate inflammatory markers involved in atherosclerosis and contribute to the exacerbation of CVD risk markers. The study includes 60 participants: rotating night shift workers (day, evening, and night shifts) and day workers (controls) at a pharmaceutical plant. We will assess the effects of night shift work on metabolic and cardiovascular health over three phases: an initial 6-week observational period (phase I), baseline registration of CVD risk factors (phase II), and follow-up assessment of CVD risk factors at 2 years (phase III). Phase I registrations include working hours derived from payroll data, sleep metrics by OURA ring (actigraphy, plethysmography and temperature), continuous assessments of blood glucose using continuous glucose monitor, self-reported food diary and measurements of circadian rhythm markers (monocyte mRNA expression). In phases II and III, blood CVD risk factors such as markers of inflammation, lipids, glycosylated haemoglobin, D-dimer, clinical examination of blood pressure, resting heart rate, arterial stiffness by the means of carotid to femoral pulse wave velocity, carotid intima-media thickness and maximal oxygen uptake (V̇O2max) are measured. To this end, a comprehensive set of methods will be used in a prospective manner to provide new knowledge on shift work-induced glucose regulation and CVD risk factors. All participants provided written informed consent prior to participating in the study, which will adhere to the principles outlined in the Declaration of Helsinki. Ethical approval has been granted by the Norwegian Regional Committee for Medical Research Ethics South-East B (reference # 745702). Dissemination plans include academic and public publications, as well as collaborations with national and regional policy-makers.

Night Shift Work, Genetic Risk, and Hypertension

BackgroundNight shift work induces physiological and psychological stress by altering sleep and biological rhythms and is associated with hypertension, diabetes, obesity, and cardiovascular diseases. Few studies have been conducted on the control of hypertension and diabetes. This study aimed to examine the effect of night shift work on the control rate of hypertension and diabetes.MethodsSubjects comprised workers aged 20–65 years who underwent specific health examination at a single facility in seven different affiliated examination centers from 1 January to 31 December 2016. Workers were categorised into day workers and night shift workers. Demographic and medical history were taken, and physical examination was done. Blood pressure (BP) and fasting glucose were measured. The control rate of each disease was evaluated based on treatment goals presented in the treatment guidelines of the Korean Society of Hypertension and the Korean Diabetes Association (systolic BP < 140 mmHg and diastolic BP < 90 mmHg; fasting glucose ≤ 130 mg/dL).ResultsAmong 631,418 subjects, 11.2% (70,450) were night shift workers. Of whom 6.1% (4,319) were taking antihypertensive medication and 2.5% (1,775) were taking diabetes medication. Among patients taking antihypertensive medications, the proportion of those whose BP was controlled to suit treatment goals was 81.7% (26,635) of day workers and 77.4% (3,343) of night shift workers, which was significantly different (p < 0.001). Among patients taking diabetes medications, the proportion of those whose blood glucose was controlled to suit treatment goals was 37.4% (4,489) of day workers and 36.5% (647) of night shift workers, but the difference was not significant. The control rates for patients taking antihypertensive medications (odds ratio [OR]: 0.74, 95% confidence interval [CI]: 0.68–0.80) were lower among night shift workers than day workers with adjustment for age, sex, smoking history, alcohol consumption, exercise, and obesity. However, there were no differences in control rates for patients taking diabetes medications (OR: 0.99, 95% CI: 0.87–1.10) between day workers and night shift workers.ConclusionsNight shift work can have an effect on the uncontrolled BP in workers taking antihypertensive medications. Therefore, additional efforts for disease control are necessary for night shift workers with hypertension.

In today's modern world, shift working has become an important part of society and industrial work; prolonged wakefulness is a widespread phenomenon due to which the sleep patterns of individuals are getting disturbed, and many sleep disorders are arising. This study compared the sleep quality and insomnia of the security guards working the day and night shifts. This observational study comprised 100 security guards from Delhi and the NCR region. Self-administered questionnaires, i.e., the Pittsburgh sleep quality index (PSQI) and the Athens Insomnia Scale (AIS), were used to assess sleep quality and insomnia. Fifty questionnaires were filled out by the day shift security guards, and the night shift security guards filled out 50. The data underwent analysis, and a comparison was conducted between security workers on night and day shifts using a Mann-Whitney U test, with a significance level set at p < 0.05. The result revealed a significant difference (95% CI; p < 0.05) for the variables, sleep quality and insomnia when compared between night and day shift working security guards. Among night shift workers, 74% reported issues with sleep quality and 48% experienced insomnia. In comparison, among day shift workers, 58% reported concerns about sleep quality, while 32% reported experiencing insomnia. The study concluded that night-shift working security guards had poorer sleep quality and a higher prevalence of insomnia compared to their day-shift counterparts. These differences are highly significant, highlighting the potential adverse effects of night shift work on sleep health, urging the need for interventions to improve sleep quality and manage insomnia among night shift workers.

This systematic review investigates the bidirectional relationship between alcohol consumption and disrupted circadian rhythms. The goal of this study was to identify (i) the types of circadian rhythm disruptors (i.e. social jet lag, extreme chronotypes, and night shift work) associated with altered alcohol use and (ii) whether sex differences in the consequences of circadian disruption exist. We conducted a search of PubMed, Embase, and PsycINFO exclusively on human research. We identified 177 articles that met the inclusion criteria. Our analyses revealed that social jet lag and the extreme chronotype referred to as eveningness were consistently associated with increased alcohol consumption. Relationships between night shift work and alcohol consumption were variable; half of articles reported no effect of night shift work on alcohol consumption. Both sexes were included as participants in the majority of the chronotype and social jet lag papers, with no sex difference apparent in alcohol consumption. The night shift research, however, contained fewer studies that included both sexes. Not all forms of circadian disruption are associated with comparable patterns of alcohol use. The most at-risk individuals for increased alcohol consumption are those with social jet lag or those of an eveningness chronotype. Direct testing of the associations in this review should be conducted to evaluate the relationships among circadian disruption, alcohol intake, and sex differences to provide insight into temporal risk factors associated with development of alcohol use disorder.

Night shift work is associated with cardiovascular disease, but its associations with cardiovascular disease biomarkers are unclear. We investigated these associations in a study of female nurses. We used data from the Nurses' Health Study II for total cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein (HDL) cholesterol, triglycerides, C-reactive protein (CRP), and fibrinogen. The sample sizes for our analysis ranged from 458 (fibrinogen) to 3574 (total cholesterol). From questionnaires, we determined the number of night shifts worked in the 2 weeks before blood collection and total years of rotating night shift work. We used quantile regression to estimate differences in biomarker levels by shift work history, adjusting for potential confounders. Nurses working 1 to 4 recent night shifts had median HDL cholesterol levels 4.4 mg/dL (95% confidence interval [CI]: 0.3, 7.5) lower than nurses without recent night shifts. However, working ≥5 recent night shifts and years of rotating night shift work were not associated with HDL cholesterol. There was no association between recent night shifts and CRP, but median CRP levels were 0.1 (95% CI: 0.0, 0.2), 0.2 (95% CI: 0.1, 0.4), and 0.2 (95% CI: 0.0, 0.4) mg/L higher among nurses working rotating night shifts for 1 to 5, 6 to 9, and ≥10 years compared with nurses never working rotating night shifts. These associations were attenuated when excluding postmenopausal women and women taking statins. We observed no associations between night shift work and other biomarkers. We found suggestive evidence of adverse short-term and long-term effects of night shift work on select cardiovascular disease biomarkers.

Background: Night shift work has an impact on the health of factory workers. One of the impacts of night shift work is the risk of hypertension and disturbed sleep patterns. The purpose of this study was to determine how big the effect of night shift work on hypertension and sleep patterns in factory workers.Subjects and Method: This was a meta-analysis and systematic study with the population: factory workers. Intervention: night shift work. Comparation: morning and afternoon shift work. Outcome: hypertension and sleep patterns. The article search process was carried out according to the PRISM Flow Diagram and searched through several indexes such as PubMed, ScienceDirect, Google Schoolar, and Springer Link with the search keywords “Night Shift” AND “Hypertension” AND “Sleep” AND “Worker”. The articles used are articles from 2013-2022 and are written in English.Results: A total of 11 articles originating from the Asian continent (China, Indonesia, South Korea, Malaysia, and Japan) were considered suitable for meta-analysis. From the results of data analysis that has been carried out, it is known that factory workers who work night shifts have a risk of experiencing hypertension (aOR= 3.43; 95% CI= 2.48 to 4.72; p&lt;0.001), and disturbed sleep patterns (aOR= 3.63; 95% CI= 2.66 to 4.95; p&lt;0.001) compared with morning and afternoon shift workers and the results were statistically significant.Conclusion: Night shifts can increase the risk of hypertension and sleep disturbances in factory workers. Keywords: Night shift, hypertension, sleep pattern, factory worker Correspondence:Amanda Kesli Ramadhani. Masters Program in Public Health, Universitas Sebelas Maret, Jl. Ir. Sutami No.36, Kentingan, Jebres, Surakarta 57126, Central Java. Email. amandakesly@yahoo.com. Mobile: 085692832776.

Are night shift workers at an increased risk for COVID-19?

Night shift work is associated with increased breast cancer risk, but the molecular mechanisms are not well-understood. The objective of this study was to explore the relationship between night shift work parameters (current status, duration/years, and intensity) and methylation in circadian genes as a potential mechanism underlying the carcinogenic effects of night shift work. A cross-sectional study was conducted among 74 female healthcare employees (n = 38 day workers, n = 36 night shift workers). The Illumina Infinium MethylationEPIC beadchip was applied to DNA extracted from blood samples to measure methylation using a candidate gene approach at 1150 CpG loci across 22 circadian genes. Linear regression models were used to examine the association between night shift work parameters and continuous methylation measurements (β-values) for each CpG site. The false-discovery rate (q = 0.2) was used to account for multiple comparisons. Compared to day workers, current night shift workers demonstrated hypermethylation in the 5ʹUTR region of CSNK1E (q = 0.15). Individuals that worked night shifts for ≥10 years exhibited hypomethylation in the gene body of NR1D1 (q = 0.08) compared to those that worked <10 years. Hypermethylation in the gene body of ARNTL was also apparent in those who worked ≥3 consecutive night shifts a week (q = 0.18). These findings suggest that night shift work is associated with differential methylation in core circadian genes, including CSNK1E, NR1D1 and ARNTL. Future, larger-scale studies with long-term follow-up and detailed night shift work assessment are needed to confirm and expand on these findings.

This review summarizes the evidence concerning effects of night shift work on women's reproductive health, specifically difficulty in conceiving and miscarriage. We distinguish between fixed night shift and rotating night shift, as the population subgroups exposed, the social and biological mechanisms, and the magnitude of effects are likely to differ; of note, women working fixed night shift are known to have high tolerance for this schedule. We identified two relevant systematic reviews with meta-analyses and five additional studies. Night shift work may give rise to menstrual cycle disturbances, but effect sizes are imprecise. Endometriosis may be elevated in night shift workers, but evidence is only preliminary. Adequate data are lacking to assess associations between night shift work and infertility or time to pregnancy. The weight of evidence begins to point to working at night, whether in fixed or rotating shifts, as a risk factor for miscarriage. There are many methodological problems with this literature, with substantial variation in the definitions of night shift and schedule types making comparisons between studies difficult and pooling across studies questionable. Nevertheless, there appears to be grounds for caution and counselling where women have concerns about night shift work and their reproductive health.

Background &amp; objective: Night shift work has well-known adverse effects on health like sleep disturbances and other medical conditions including thyroid diseases. Various studies have revealed that the effect of night shift work on healthis mainly related to its interference with circadian rhythm, which can also influence thyroid hormone levels in accordance with sleep patterns. Therefore, night work can modify thyroid function and increase the risk of thyroid disorders. The present study was therefore conducted to evaluate the impact of the night shift work on the thyroid function status of female nurses in a tertiary care hospital. Methods: This case-control study was conducted in the Department of Physiology, Dhaka Medical College, Dhaka over a period of 1 year from January 2021 to December 2021. All female nurses (in the age range of 25-50 years) working at Dhaka Medical College in different shifts were the study population. Of them, the case group consisted of 90 female nurses who worked the night shift in different wards from 8.00 pm. to 8.00 am and the control group consisted of 90female nurses who worked the morning shift in the Outpatient Department (OPD) from 8.00 am to 2.00 pm. However, nurses with a personal or family history of sleep disorder, taking medications that may interfere with sleep, history of diabetes mellitus, bronchial asthma, or diagnosed with any kind of thyroid disease, such as Hashimoto’s thyroiditis, and pregnant nurses were excluded from the study. While the exposure variable was shift-work, the outcome variable was thyroid function status, evaluated in terms of serum FT4, FT3, and TSH and the presence of thyroid disorders. Results: The cases and controls were almost alike in terms of age, BMI, and blood pressure. The mean age of the case and the control groups were between 34 and 35 years with no significant difference between the groups. While serum levels of free thyroxine (FT4) and free triiodothyronine (FT3) were somewhat reduced in the case group than those in the control group, the serum TSH was significantly elevated in the former group than that in the latter group – a picture typical of subclinical hypothyroidism. Overt hypothyroidism was also higher in the former group than that in the latter group. Subclinical and clinical hyperthyroidism was found in 2(2.2%) and 3(3.3%) subjects of the control group only. Overall, 60% of the cases had some form of thyroid disorders as opposed to 15% of the controls with the risk of having thyroid disorders in night shift nurses being &gt; 8(95% CI = 4.1 – 17.5) times higher than that in morning shift nurses(p &lt; 0.001). Conclusions: The study concluded that night shift nurses may have a higher risk of developing subclinical hypothyroidism due to significantly higher levels of TSH and normal FT3, and FT4 levels. About two-fifths of the nurses working night shifts are at increased risk of having thyroid disorders, primarily subclinical hypothyroidism. Ibrahim Card Med J 2022; 12 (2): 40-45