Shift work and diabetes mellitus: a meta-analysis of observational studies

Association of night-shift work with gambling and problem gambling among workers in Japan: A nationwide cross-sectional study

BACKGROUND AND AIMS

Night-shift work disturbs sleep and is associated with poor health conditions among workers. We aimed to investigate the association between night-shift work and gambling among workers and the association between night-shift work and problem gambling in working and gambling participants.

METHODS

This cross-sectional study used data from an online survey conducted between February 6 and 27, 2023 in Japan. A total of 21,134 workers participated in this study, including 9,739 respondents who had gambled in the past year. We estimated the association between night-shift work and gambling among workers and the association between night-shift work and problem gambling among those who gambled at the survey. We defined problem gambling as a score ≥ 8 on the Problem Gambling Severity Index. All estimates were weighted using a nationally representative survey in Japan. We fitted multivariable weighted logistic regression models after adjusting for 14 confounders.

RESULTS

The weighted prevalence of gambling among non-night and night-shift workers was 42.1 % and 55.4 %, respectively. When focusing on workers gambling in the survey, the prevalence of problem gambling among non-night and night-shift workers was 8.8 % and 24.2 %, respectively. The weighted multivariable logistic regression analyses showed that night-shift work was associated with gambling participation among workers (adjusted odds ratio [aOR], 1.39, 95 % confidence interval [CI] 1.25-1.53, p < 0.001). In addition, night-shift work was associated with problem gambling among those who gambled (aOR 1.94, 95 % CI 1.57-2.40, p < 0.001).

CONCLUSIONS

Night-shift work was associated with gambling among workers and with problem gambling among those who gambled.

Microglia, circadian rhythm and lifestyle factors

Microglia, a vital homeostasis-keeper of the central nervous system, perform critical functions such as synaptic pruning, clearance of cellular debris, and participation in neuroinflammatory processes. Recent research has shown that microglia exhibit strong circadian rhythms that not only actively regulate their own immune activity, but also affect neuronal function. Disruptions of the circadian clock have been linked to a higher risk of developing a variety of diseases. In this article we will provide an overview of how lifestyle factors impact microglial function, with a focus on disruptions caused by irregular sleep-wake patterns, reduced physical activity, and eating at the wrong time-of-day. We will also discuss the potential connection between these lifestyle factors, disrupted circadian rhythms, and the role of microglia in keeping brain health.

Effects of (Poly)phenols on Circadian Clock Gene-Mediated Metabolic Homeostasis in Cultured Mammalian Cells: A Scoping Review

Circadian clocks regulate metabolic homeostasis. Disruption to our circadian clocks, by lifestyle behaviors such as timing of eating and sleeping, has been linked to increased rates of metabolic disorders. There is now considerable evidence that selected dietary (poly)phenols, including flavonoids, phenolic acids and tannins, may modulate metabolic and circadian processes. This review evaluates the effects of (poly)phenols on circadian clock genes and linked metabolic homeostasis in vitro, and potential mechanisms of action, by critically evaluating the literature on mammalian cells. A systematic search was conducted to ensure full coverage of the literature and identified 43 relevant studies addressing the effects of (poly)phenols on cellular circadian processes. Nobiletin and tangeretin, found in citrus, (-)-epigallocatechin-3-gallate from green tea, urolithin A, a gut microbial metabolite from ellagitannins in fruit, curcumin, bavachalcone, cinnamic acid, and resveratrol at low micromolar concentrations all affect circadian molecular processes in multiple types of synchronized cells. Nobiletin emerges as a putative retinoic acid-related orphan receptor (RORα/γ) agonist, leading to induction of the circadian regulator brain and muscle ARNT-like 1 (BMAL1), and increased period circadian regulator 2 (PER2) amplitude and period. These effects are clear despite substantial variations in the protocols employed, and this review suggests a methodological framework to help future study design in this emerging area of research.

Sex differences in sleep, circadian rhythms, and metabolism: Implications for precision medicine

The number of individuals experiencing sleep loss has exponentially risen over the past decades. Extrapolation of laboratory findings to the real world suggests that females are more affected by extended wakefulness and circadian misalignment than males are. Therefore, long-term effects such as sleep and metabolic disorders are likely to be more prevalent in females than in males. Despite emerging evidence for sex differences in key aspects of sleep-wake and circadian regulation, much remains unknown, as females are often underrepresented in sleep and circadian research. This narrative review aims at highlighting 1) how sex differences systematically impinge on the sleep-wake and circadian regulation in humans, 2) how sex differences in sleep and circadian factors modulate metabolic control, and 3) the relevance of these differences for precision medicine. Ultimately, the findings justify factoring in sex differences when optimizing individually targeted sleep and circadian interventions in humans.

Effects of Early and Late Time-Restricted Feeding on Parameters of Metabolic Health: An Explorative Literature Assessment

Chrono-nutrition (meal timing) aligns food consumption with one's circadian rhythm. The first meal (e.g., breakfast) likely promotes synchronization of peripheral circadian clocks, thereby supporting metabolic health. Time-restricted feeding (TRF) has been shown to reduce body weight (BW) and/or improve cardiovascular biomarkers. In this explorative literature assessment, 13 TRF randomized controlled trials (RCTs) were selected from PubMed and Scopus to evaluate the effects of early (eTRF: first meal before 10:30 a.m.) and late TRF (lTRF: first meal after 11:30 a.m.) on parameters of metabolic health. Although distinct variations in study design were evident between reports, TRF consistently decreased energy intake (EI) and BW, and improved insulin resistance as well as systolic blood pressure. eTRF seemed to have a greater beneficial effect than lTRF on insulin resistance (HOMA-IR). Importantly, most studies did not appear to consider chronotype in their evaluation, which may have underestimated TRF effects. TRF intervention may be a promising approach for risk reduction of human metabolic diseases. To conclusively determine benefits of TRF and identify clear differences between eTRF and lTRF, future studies should be longer-term (≥8 weeks) with well-defined (differences in) feeding windows, include participants chronotypically matching the intervention, and compare outcomes to those of control groups without any dietary limitations.

"I Am the Last Priority": Factors Influencing Diabetes Management Among South Asian Caregivers in Peel Region, Ontario

OBJECTIVE

In this study we aimed to identify sociocultural and systemic factors influencing diabetes management among South Asian (SA) caregivers in Peel Region, Ontario.

METHODS

Twenty-one semistructured interviews were conducted with SA caregivers using a qualitative descriptive design. Data were analyzed using thematic analysis and intersectionality analysis.

RESULTS

Themes identified included: 1) prioritizing family caregiving over diabetes self-management; 2) labour market impacts on diabetes self-management; and 3) challenges navigating Canadian health and social service systems. SA caregivers described social, economic, and systemic challenges impacting type 2 diabetes management. Systemic factors influencing diabetes management included discrimination and inequities in labour policies and lack of social and health resources funding. Recommendations by caregivers included whole-family, community-based, culturally tailored approaches to diabetes prevention and management strategies.

CONCLUSIONS

Providing support with system navigation, encouraging family-based approaches, and addressing the social determinants of health could be beneficial for supporting SA families with diabetes management and prevention.

BMAL1 deletion protects against obesity and non-alcoholic fatty liver disease induced by a high-fat diet

OBJECTIVES

Obesity and non-alcoholic fatty liver disease (NAFLD) are major health concerns. The circadian rhythm is an autonomous and intrinsic timekeeping system closely associated with energy metabolism and obesity. Thus, this study explored the role of brain and muscle aryl hydrocarbon receptor nuclear translocator-like1 (BMAL1), a circadian clock regulator, in the development of obesity and NAFLD.

METHODS

We generated BMAL1 knockout (BMAL1 KO) mice to imitate circadian rhythm disruption. The study comprised three groups from the same litter: BMAL1 KO mice fed a high-fat diet (to establish obesity and NAFLD phenotypes), wild-type mice fed normal chow, and wild-type mice fed a high-fat diet. The metabolic and NAFLD phenotypes were assessed via physiological measurements and histological examinations. Quantitative polymerase chain reaction and western blotting were used to identify and validate changes in the signaling pathways responsible for the altered NAFLD phenotypes in the wild-type and BMAL1 KO mice.

RESULTS

BMAL1 depletion protected against obesity and metabolic disorders induced by a high-fat diet. BMAL1 depletion also prevented hepatic steatosis and inhibited cluster of differentiation 36 and peroxisome proliferator-activated receptor gamma (i.e., PPARγ) expression.

CONCLUSIONS

BMAL1 plays an important role in the development of obesity and NAFLD and, thus, is a potential therapeutic target for these conditions.

Plant-based and Early Time-restricted Eating for Prevention and Treatment of Type 2 Diabetes in Adults: A Narrative Review

Type 2 diabetes (T2D) is a significant public health challenge for which effective lifestyle interventions are needed. A growing body of evidence supports the use of both plant-based eating patterns and early time-restricted eating (eTRE) for the prevention and treatment of T2D, but research has not yet explored the potential of these dietary strategies in combination. In this narrative review we assessed the evidence by which plant-based diets, in conjunction with eTRE, could support T2D care. The electronic databases MEDLINE and the Web of Science were searched for relevant articles published throughout the last decade. Observational research has shown that healthy plant-based eating patterns and eTRE are associated with reductions in T2D risk. Interventional trials demonstrated that plant-based diets promote improvements in glycated hemoglobin, insulin resistance, glycemic control, and cardiometabolic risk factors. These changes may be mediated, in part, by reductions in oxidative stress, dietary acid load, and hepatocellular and intramyocellular lipids. The eTRE strategies were also shown to improve insulin resistance and glycemic control, and mechanisms of action included enhanced regulation of circadian rhythm and increased metabolic flexibility. Integrating these dietary strategies may produce additive benefits, mediated by reduced visceral adiposity and beneficial shifts in gut microbiota composition. However, potential barriers to concurrent implementation of these interventions may exist, including social challenges, scheduling constraints, and tolerance. Prospective trials are needed to examine their acceptability and clinical effects.

Hypoglycemic effects and associated mechanisms of resveratrol and related stilbenes in diet

Hyperglycemia has become a global health problem due to changes in diet and lifestyle. Most importantly, persistent hyperglycemia can eventually develop into type II diabetes. While the usage of current drugs is limited by their side effects, stilbenes derived from fruits and herbal/dietary plants are considered as important phytochemicals with potential hypoglycemic properties. Herein, the most common stilbenoids in consumed foods, i.e. resveratrol, pterostilbene, piceatannol, oxyresveratrol, and 2,3,5,4'-tetrahydroxystilbene-2-O-β-glucopyranoside (THSG), are reviewed in this paper. These stilbenes are found to regulate glucose homeostasis via (a) modulation of feeding behaviour and nutrition absorption; (b) restoration of insulin signalling by enhancing insulin production/insulin sensitivity; (c) improvement of gut permeability, gut microbial profile and resulting metabolomes; and (d) amelioration of circadian rhythm disruption. In this review, we have summarized the underlying mechanisms for the hypoglycemic effects of the five most common dietary stilbenoids listed above, providing a comprehensive framework for future study and applications.

Waking Up to the Importance of Sleep in Type 2 Diabetes Management: A Narrative Review

For the first time, the latest American Diabetes Association/European Association for the Study of Diabetes (ADA/EASD) consensus guidelines have incorporated a growing body of evidence linking health outcomes associated with type 2 diabetes to the movement behavior composition over the whole 24-h day. Of particular note, the importance of sleep as a key lifestyle component in the management of type 2 diabetes is promulgated and presented using three key constructs: quantity, quality, and timing (i.e., chronotype). In this narrative review we highlight some of the key evidence justifying the inclusion of sleep in the latest consensus guidelines by examining the associations of quantity, quality, and timing of sleep with measures of glycemia, cardiovascular disease risk, and mortality. We also consider potential mechanisms implicated in the association between sleep and type 2 diabetes and provide practical advice for health care professionals about initiating conversations pertaining to sleep in clinical care. In particular, we emphasize the importance of measuring sleep in a free-living environment and provide a summary of the different methodologies and targets. In summary, although the latest ADA/EASD consensus report highlights sleep as a central component in the management of type 2 diabetes, placing it, for the first time, on a level playing field with other lifestyle behaviors (e.g., physical activity and diet), the evidence base for improving sleep (beyond sleep disorders) in those living with type 2 diabetes is limited. This review should act as a timely reminder to incorporate sleep into clinical consultations, ongoing diabetes education, and future interventions.

Rotating shift work time is directly associated with excess body adiposity

OBJECTIVE

To analyze the association between changes in body adiposity and length of service on a schedule of rotating shifts.

METHODS

The study was a cross-sectional investigation conducted during the years 2012, 2015, and 2018, involving individuals engaged in rotating shifts at a company involved in iron ore extraction situated within the Iron Quadrangle region of Minas Gerais and the southeastern region of Pará, Brazil. Sociodemographic and behavioral data were collected along with anthropometric parameters in order to calculate body mass index (BMI) and the waist-to-height ratio (WHtR). For data analysis, a multivariate logistic regression was employed to explore potential associations between indicators of body adiposity and the duration of shift work, employing a hierarchical determination model.

RESULTS

The findings showed that in the multivariate model, controlling for confounding factors, workers with 5 to 10, 10 to 15, and more than 15 years of shift work had 41 to 96% greater odds of being overweight (BMI > 25.0 kg/m2), 71 to 82% of having altered neck circumference (> 40 cm), 33 to 120% of altered WC (>102 cm), and 57 to 214% of having altered WHtR (> 0.5 cm).

CONCLUSION

The findings suggest that time spent in work has a significant effect on anthropometric indicators of body adiposity, especially if the worker has a previously established comorbidity such as dyslipidemia or hypertension and is frequently exposed to night work.

Circadian Adaptation of Melatonin and Cortisol in Police Officers Working Rotating Shifts

Misalignment of behavior and circadian rhythms due to night work can impair sleep and waking function. While both simulated and field-based studies suggest that circadian adaptation to a nocturnal schedule is slow, the rates of adaptation in real-world shift-work conditions are still largely unknown. The aim of this study was to evaluate the extent of adaptation of 24-h rhythms with 6-sulfatoxymelatonin (aMT6s) and cortisol in police officers working rotating shifts, with a special attention to night shifts. A total of 76 police officers (20 women; aged 32 ± 5.4 years, mean ± SD) from the province of Quebec, Canada, participated in a field study during their 28- or 35-day work cycle. Urine samples were collected for ~32 h before a series of day, evening, and night shifts to assess circadian phase. Before day, evening, and night shifts, 60%-89% of officers were adapted to a day schedule based on aMT6 rhythms, and 71%-78% were adapted based on cortisol rhythms. To further quantify the rate of circadian adaptation to night shifts, initial and final phases were determined in a subset of 37 officers with suitable rhythms for both hormones before and after 3-8 consecutive shifts (median = 7). Data were analyzed with circular and linear mixed-effects models. After night shifts, 30% and 24% of officers were adapted to a night-oriented schedule for aMT6s and cortisol, respectively. Significantly larger phase-delay shifts (aMT6s: -7.3 ± 0.9 h; cortisol: -6.3 ± 0.8 h) were observed in police officers who adapted to night shifts than in non-adapted officers (aMT6s: 0.8 ± 0.9 h; cortisol: 0.2 ± 1.1 h). Consistent with prior research, our results from both urinary aMT6s and cortisol midpoints indicate that a large proportion of police officers remained in a state of circadian misalignment following a series of night shifts in dim-light working environments.

12-week melatonin administration had no effect on diabetes risk markers and fat intake in overweight women night workers

Introduction

Interactions between circadian clocks and key mediators of chronic low-grade inflammation associated with fat consumption may be important in maintaining metabolic homeostasis and may pose a risk for the development of obesity-associated comorbidities, especially type 2 diabetes (T2DM).

Objective

The aims of the present study were to evaluate the effects of melatonin administration on diabetes risk markers according to dietary lipid profile (pro-inflammatory versus anti-inflammatory) in excessive weight night workers, and to determine the effect of administration on fat consumption profile.

Methods

A randomized, controlled, double-blind, crossover clinical trial involving 27 nursing professionals working permanent night shifts under a 12×36-hour system. The melatonin group (12 weeks) used synthetic melatonin (3 mg) only on days off and between shifts, while the placebo group (12 weeks) was instructed to take a placebo, also on days off and between shifts. For inflammatory characteristics, participants were divided into pro-inflammatory (saturated fats, trans fats and cholesterol) and anti-inflammatory (monounsaturated, polyunsaturated fats and EPA + DHA) groups according to fatty acid determinations. At baseline and at the end of each phase, blood glucose, insulin, glycosylated hemoglobin plasma concentrations were collected, and HOMA-IR was calculated.

Conclusion

Melatonin administration for 12 weeks had no effect on T2DM risk markers according to dietary lipid profile (pro-inflammatory or anti-inflammatory potential) in excessive weight night workers. Among the limitations of the study include the fact that the low dose may have influenced the results expected in the hypothesis, and individual adaptations to night work were not evaluated. The insights discussed are important for future research investigating the influence of melatonin and fats considered anti- or pro-inflammatory on glucose and insulin homeostasis related to night work.

Attention to Innate Circadian Rhythm and the Impact of Its Disruption on Diabetes

Novel strategies are required to reduce the risk of developing diabetes and/or clinical outcomes and complications of diabetes. In this regard, the role of the circadian system may be a potential candidate for the prevention of diabetes. We reviewed evidence from animal, clinical, and epidemiological studies linking the circadian system to various aspects of the pathophysiology and clinical outcomes of diabetes. The circadian clock governs genetic, metabolic, hormonal, and behavioral signals in anticipation of cyclic 24-hour events through interactions between a "central clock" in the suprachiasmatic nucleus and "peripheral clocks" in the whole body. Currently, circadian rhythmicity in humans can be subjectively or objectively assessed by measuring melatonin and glucocorticoid levels, core body temperature, peripheral blood, oral mucosa, hair follicles, rest-activity cycles, sleep diaries, and circadian chronotypes. In this review, we summarized various circadian misalignments, such as altered light-dark, sleep-wake, rest-activity, fasting-feeding, shift work, evening chronotype, and social jetlag, as well as mutations in clock genes that could contribute to the development of diabetes and poor glycemic status in patients with diabetes. Targeting critical components of the circadian system could deliver potential candidates for the treatment and prevention of type 2 diabetes mellitus in the future.

Association between disruption of circadian activity rhythms and obesity

This cross-sectional study aimed to elucidate the association between disruption of circadian activity rhythms and obesity-related indices. This study included 69 older participants (male, n = 36; female, n = 33), and disruption of circadian activity rhythms in daily life was assessed using the cosinor method based on physical activity data. The daily physical activity data were fitted to a cosine curve to estimate the peak phase (acrophase), and the difference in the peak phase (time) for each day was determined. The standard deviation (SD) of the mean peak phase differences over 6 days was obtained. The higher the SD value, the more disturbed the circadian rhythm of activity. Based on the calculated values, the samples were divided into tertiles (small, medium, and large). A significant positive correlation was found between Log SD and body fat percentage on the disruption of circadian activity rhythms and obesity-related indices. In addition, positive associations were observed among body mass, body mass index, and Log SD. However, these associations were not observed in women. These results suggest that disruption of circadian activity rhythms is associated with obesity-related indices and may differ according to sex.

Archaic Introgression Shaped Human Circadian Traits

When the ancestors of modern Eurasians migrated out of Africa and interbred with Eurasian archaic hominins, namely, Neanderthals and Denisovans, DNA of archaic ancestry integrated into the genomes of anatomically modern humans. This process potentially accelerated adaptation to Eurasian environmental factors, including reduced ultraviolet radiation and increased variation in seasonal dynamics. However, whether these groups differed substantially in circadian biology and whether archaic introgression adaptively contributed to human chronotypes remain unknown. Here, we traced the evolution of chronotype based on genomes from archaic hominins and present-day humans. First, we inferred differences in circadian gene sequences, splicing, and regulation between archaic hominins and modern humans. We identified 28 circadian genes containing variants with potential to alter splicing in archaics (e.g., CLOCK, PER2, RORB, and RORC) and 16 circadian genes likely divergently regulated between present-day humans and archaic hominins, including RORA. These differences suggest the potential for introgression to modify circadian gene expression. Testing this hypothesis, we found that introgressed variants are enriched among expression quantitative trait loci for circadian genes. Supporting the functional relevance of these regulatory effects, we found that many introgressed alleles have associations with chronotype. Strikingly, the strongest introgressed effects on chronotype increase morningness, consistent with adaptations to high latitude in other species. Finally, we identified several circadian loci with evidence of adaptive introgression or latitudinal clines in allele frequency. These findings identify differences in circadian gene regulation between modern humans and archaic hominins and support the contribution of introgression via coordinated effects on variation in human chronotype.

Alignment Between 24-h Light-Dark and Activity-Rest Rhythms Is Associated With Diabetes and Glucose Metabolism in a Nationally Representative Sample of American Adults

OBJECTIVE

The alignment between environmental stimuli (e.g., dark, light) and behavior cycles (e.g., rest, activity) is an essential feature of the circadian timing system, a key contributor to metabolic health. However, no previous studies have investigated light-activity alignment in relation to glycemic control in human populations.

RESEARCH DESIGN AND METHODS

The analysis included ∼7,000 adults (aged 20-80 years) from the National Health and Nutrition Examination Survey (NHANES) (2011-2014) with actigraphy-measured, multiday, 24-h activity and light data. We used phasor analysis to derive phasor magnitude and phasor angle, which measures coupling strength and phase difference between the activity-rest and light-dark cycles, respectively. We used multinomial logistic regression and multiple linear regression to study phasor magnitude and phasor angle in relation to diabetes (primary outcome) and multiple secondary biomarkers of glycemic control.

RESULTS

Lower alignment strength (i.e., a shorter phasor magnitude) and more delayed activity relative to the light cycle (i.e., a larger phasor angle) were both associated with diabetes. Specifically, compared with individuals in the quintiles indicating the most proper alignment (Q5 for phasor magnitude and Q1 for phasor angle), those in the quintiles with the most impaired alignment had a >70% increase in the odds of diabetes for phasor magnitude (odds ratio 1.76 [95% CI 1.39, 2.24]) and for phasor angle (1.73 [1.34, 2.25]). Similar associations were observed for biomarkers for glucose metabolism. The results were generally consistent across diverse sociodemographic and obesity groups.

CONCLUSIONS

The alignment pattern between 24-h activity-rest and light-dark cycles may be a critical factor in metabolic health.

Shiftwork, long working hours and markers of inflammation in a national US population-based sample of employed black and white men and women aged ≥45 years

OBJECTIVES

Work schedule demands contribute to circadian disruption and may influence health via an inflammatory response. We examined the impact of shiftwork and long work hours on inflammation in a national US sample.

METHODS

Participants included 12 487 employed black and white men and women aged ≥45 years enrolled in the REasons for Geographic and Racial Differences in Stroke Study who completed an occupational questionnaire (2011-2013) and clinical examination (2013-2016). Cross-sectional associations between shiftwork and work hours with log-transformed high-sensitivity C reactive protein (CRP) and white blood cell (WBC) count were examined by multiple linear regression analysis, overall and by race-sex subgroups.

RESULTS

Overall, rotating shift workers had higher log-CRP concentration compared with day workers (β=0.09, 95% CI:0.02 to 0.16) and findings for WBC were null. Black women had the highest geometric mean CRP (2.82 mg/L), while white men had the highest WBC (6.35×109/L). White men who worked afternoons had higher log-CRP compared with those who worked days (β=0.20, 95% CI: 0.08 to 0.33). Black men engaged in shiftwork <10 years working ≥55 hours/week had higher log-CRP and log-WBC compared with those working days <55 hours/week (β=0.33, 95% CI: 0.02 to 0.64 and β=0.10, 95% CI: 0.003 to 0.19). Among shift workers, non-retired white women working forward and backward shift rotations had higher log-CRP compared with those working forward only (β=0.49, 95% CI: 0.02 to 0.96).

CONCLUSIONS

Shift workers had higher inflammatory markers compared with day workers and race-sex disparities should be examined further. These findings highlight a potential biological pathway linking work schedule demands and chronic disease.

Exploring Australian night shift workers' food experiences within and outside of the workplace: a qualitative photovoice study

OBJECTIVE

Night shift workers are at a 20 to 40 % increased risk of metabolic diseases, which may be associated with their disrupted eating patterns. This qualitative study explores factors that influence night shift workers' eating habits, within and outside of the workplace, to identify target areas for health promotion strategies.

PARTICIPANTS AND SETTING

Eligible participants resided in Australia, working at least three overnight shifts per month.

DESIGN

The photovoice method was used, whereby participants were asked to take photos that represent their typical eating habits. These photos were incorporated as prompts in a semi-structured interview, which explored factors influencing eating habits on night shifts and days-off and perceptions and enablers to healthy eating.

RESULTS

Ten participants completed the study. Thematic analysis generated four main themes, which were mapped onto the Social Ecological Model (SE Model). Aligned with the SE Model, our results show night shift workers' eating habits are influenced by intrapersonal, interpersonal and (work) organisational levels. Participants reported that at work, appropriate food preparation facilities are required to enable healthy food choices. Poor shift work rostering leads to prolonged fatigue on days-off, limiting their ability and motivation to engage in healthy eating. Consequently, night shift workers seem to require additional supports from their social networks and enhanced food literacy skills, in order to adopt/ maintain healthy eating behaviours.

CONCLUSIONS

Night shift work creates individual and environmental barriers to healthy eating, which are present during and outside of work. Health promotion strategies for this population should include multiple approaches to address these barriers.

Associations of meal timing, number of eating occasions and night-time fasting duration with incidence of type 2 diabetes in the NutriNet-Santé cohort

BACKGROUND

Food intake plays a pivotal role in regulating circadian rhythms, which modulate glucose and lipid homeostasis. However, studies investigating the association of meal timing and type 2 diabetes (T2D) incidence are lacking. The objective of this study was to investigate the longitudinal associations of meal timing, number of eating occasions and night-time fasting duration with incidence of T2D.

METHODS

In total, 103 312 adults [79% women, mean age at baseline = 42.7 (SD = 14.6)] from the NutriNet-Santé cohort (2009-21) were included. Participants' meal timings and frequency were assessed using repeated 24-h dietary records and averaged from the first 2 years of follow-up (5.7 records/participant). Associations of meal timing, number of eating occasions and night-time fasting duration with incidence of T2D were assessed by using multivariable Cox proportional hazard models adjusted for known risk factors.

RESULTS

During a median follow-up of 7.3 years, 963 new cases of T2D were ascertained. Compared with participants habitually having a first meal before 8AM, those eating after 9AM had a higher incidence of T2D (HR = 1.59, 95% CI 1.30-1.94). Time of last meal was not associated with T2D incidence. Each additional eating episode was associated with a lower incidence of T2D (HR = 0.95, 95% CI 0.90-0.99). Night-time fasting duration was not associated with T2D incidence, except in participants having breakfast before 8AM and fasting for >13 h overnight (HR = 0.47, 95% CI 0.27-0.82).

CONCLUSIONS

In this large prospective study, a later first meal was associated with a higher incidence of T2D. If confirmed in other large-scale studies, an early breakfast should be considered in preventing T2D.

Association of shift work with oxidative stress and alteration of fasting plasma glucose level in Chinese adults

OBJECTIVE

This study aimed to assess the association of shift work with blood glucose and the mediating role of oxidative stress.

METHODS

Fasting plasma glucose (FPG) and urinary concentrations of oxidative stress biomarkers (8-hydroxy-2'-deoxyguanosine [8-OHdG], 4-hydroxy-2-nonenal-mercapturic acid, and 8-iso-prostaglandin F2α [8-isoPGF2α ]) were measured among 831 participants.

RESULTS

Positive dose-response relationships among shift work duration,  FPG (ptrend  < 0.001), and abnormal glucose regulation (AGR; ptrend  = 0.035) were found. Compared with participants without shift work, three-shift work was associated with a higher level of FPG (percentage change: 6.49%, 95% CI: 4.21%-8.83%) and a higher prevalence of impaired fasting glucose (odds ratio: 1.886, 95% CI: 1.114-3.192) and AGR (odds ratio: 1.929, 95% CI: 1.197-3.111). A dose-response relationship was found between shift work duration and 8-OHdG (ptrend  = 0.002) and 8-isoPGF2α (ptrend  = 0.019). Urinary 8-OHdG and 8-isoPGF2α partially mediated the association between shift work duration and FPG levels and the prevalence of impaired fasting glucose and AGR, with mediating proportions ranging from 4.77% to 20.76%.

CONCLUSIONS

These findings suggest that shift work is positively associated with blood glucose, and the association is partially mediated by oxidative stress.

Archaic Introgression Shaped Human Circadian Traits

Introduction

When the ancestors of modern Eurasians migrated out of Africa and interbred with Eurasian archaic hominins, namely Neanderthals and Denisovans, DNA of archaic ancestry integrated into the genomes of anatomically modern humans. This process potentially accelerated adaptation to Eurasian environmental factors, including reduced ultra-violet radiation and increased variation in seasonal dynamics. However, whether these groups differed substantially in circadian biology, and whether archaic introgression adaptively contributed to human chronotypes remains unknown.

Results

Here we traced the evolution of chronotype based on genomes from archaic hominins and present-day humans. First, we inferred differences in circadian gene sequences, splicing, and regulation between archaic hominins and modern humans. We identified 28 circadian genes containing variants with potential to alter splicing in archaics (e.g., CLOCK, PER2, RORB, RORC), and 16 circadian genes likely divergently regulated between present-day humans and archaic hominins, including RORA. These differences suggest the potential for introgression to modify circadian gene expression. Testing this hypothesis, we found that introgressed variants are enriched among eQTLs for circadian genes. Supporting the functional relevance of these regulatory effects, we found that many introgressed alleles have associations with chronotype. Strikingly, the strongest introgressed effects on chronotype increase morningness, consistent with adaptations to high latitude in other species. Finally, we identified several circadian loci with evidence of adaptive introgression or latitudinal clines in allele frequency.

Conclusions

These findings identify differences in circadian gene regulation between modern humans and archaic hominins and support the contribution of introgression via coordinated effects on variation in human chronotype.

Evaluation of the "Shifting Weight using Intermittent Fasting in night-shift workers" weight loss interventions: a mixed-methods protocol

Introduction

Shift workers are at a greater risk for obesity-related conditions. The impacts of working at night presents a challenge for designing effective dietary weight-loss interventions for this population group. The Shifting Weight using Intermittent Fasting in night-shift workers (SWIFt) study is a world-first, randomized controlled trial that compares three weight-loss interventions. While the trial will evaluate the effectiveness of weight-loss outcomes, this mixed-methods evaluation aims to explore for who weight-loss outcomes are achieved and what factors (intervention features, individual, social, organisational and wider environmental) contribute to this.

Methods

A convergent, mixed-methods evaluation design was chosen where quantitative and qualitative data collection occurs concurrently, analyzed separately, and converged in a final synthesis. Quantitative measures include participant engagement assessed via: dietary consult attendance, fulfillment of dietary goals, dietary energy intake, adherence to self-monitoring, and rates for participant drop-out; analyzed for frequency and proportions. Regression models will determine associations between engagement measures, participant characteristics (sex, age, ethnicity, occupation, shift type, night-shifts per week, years in night shift), intervention group, and weight change. Qualitative measures include semi-structured interviews with participants at baseline, 24-weeks, and 18-months, and fortnightly audio-diaries during the 24-week intervention. Interviews/diaries will be transcribed verbatim and analyzed using five-step thematic framework analysis in NVivo. Results from the quantitative and qualitative data will be integrated via table and narrative form to interrogate the validity of conclusions.

Discussion

The SWIFt study is a world-first trial that compares the effectiveness of three weight-loss interventions for night shift workers. This mixed-methods evaluation aims to further explore the effectiveness of the interventions. The evaluation will determine for who the SWIFt interventions work best for, what intervention features are important, and what external factors need to be addressed to strengthen an approach. The findings will be useful for tailoring future scalability of dietary weight-loss interventions for night-shift workers.Clinical trial registration: This evaluation is based on the SWIFt trial registered with the Australian New Zealand Clinical Trials Registry [ACTRN 12619001035112].

The Effect of Commencing Rotating Shift Work on Diet and Body Composition Changes in Graduate Paramedics: A Longitudinal Mixed Methods Study

Objectives: Diet quality often changes as shift workers adjust to atypical work schedules, however, limited research exists examining the early effects of starting rotating shift work on diet and body composition. This study explored dietary behavior changes occurring in graduate paramedics during the first year of exposure to rotating shift work, and investigated dietary intake, diet quality and anthropometric changes over two years. Methods: Participants from a graduate paramedic cohort in Melbourne, Australia were approached after two years of shift work for study inclusion. Using a mixed method study approach, the qualitative component comprised individual in-depth interviews to explore perceived dietary behavior changes experienced over the first year of shift work. Interview transcripts were thematically analyzed and guided by the COM-B model (capability, opportunity, motivation, and behavior) and theoretical domains framework (TDF). Diet quality and dietary intake were quantitatively assessed by the Australian Eating SurveyTM at baseline, one year, and two years, along with body weight, waist circumference, and body mass index (BMI) to monitor changes. Results: Eighteen participants were included in the study. From the interviews, participants reported: 1. food choices are driven by wanting to fit in with coworker food habits, 2. food choices and mealtimes are unpredictable and 3. paramedics try to make healthy food choices but give in to less healthy options. While daily energy intake and diet quality scores did not differ in the first two years of shift work, daily energy from takeaway foods significantly increased (mean difference (MD): 2.96% EI; 95% CI: 0.44 - 5.48; p = 0.017) and increases in weight (MD: 2.96 kg; 95% CI: 0.89-5.04; p = 0.003), BMI (MD: 1.07 kg/m2; 95% CI: 0.26 - 1.87; p = 0.006) and waist circumference (MD: 5.07 cm; 95% CI: 1.25-8.89; p = 0.006) were also evident at two years. Conclusions: This study contributes new information on dietary changes and the current early trajectory of unintentional weight gain and takeaway reliance occurring within a graduate paramedic cohort over two years of shift work. To reduce the unintended metabolic consequences commonly observed with rotating shift schedules, workplaces could improve access to healthier food options and enable behavioral support/education to address nutrition-related health risks.

Circadian Dysfunction in Adipose Tissue: Chronotherapy in Metabolic Diseases

Essential for survival and reproduction, the circadian timing system (CTS) regulates adaptation to cyclical changes such as the light/dark cycle, temperature change, and food availability. The regulation of energy homeostasis possesses rhythmic properties that correspond to constantly fluctuating needs for energy production and consumption. Adipose tissue is mainly responsible for energy storage and, thus, operates as one of the principal components of energy homeostasis regulation. In accordance with its roles in energy homeostasis, alterations in adipose tissue's physiological processes are associated with numerous pathologies, such as obesity and type 2 diabetes. These alterations also include changes in circadian rhythm. In the current review, we aim to summarize the current knowledge regarding the circadian rhythmicity of adipogenesis, lipolysis, adipokine secretion, browning, and non-shivering thermogenesis in adipose tissue and to evaluate possible links between those alterations and metabolic diseases. Based on this evaluation, potential therapeutic approaches, as well as clock genes as potential therapeutic targets, are also discussed in the context of chronotherapy.

Circadian control of Nocturnin and its regulatory role in health and disease

Circadian rhythms are generated by intrinsic 24-h oscillations that anticipate the extrinsic changes associated with solar day. A conserved transcriptional-translational feedback loop generates these molecular oscillations of clock genes at the organismal and the cellular levels. One of the recently discovered outputs of circadian clock is Nocturnin (Noct) or Ccrn4l. In mice, Noct mRNA is broadly expressed in cells throughout the body, with a particularly high-amplitude rhythm in liver. NOCT belongs to the EEP family of proteins with the closest similarity to the CCR4 family of deadenylases. Multiple studies have investigated the role of Nocturnin in development, adipogenesis, lipid metabolism, inflammation, osteogenesis, and obesity. Further, mice lacking Noct (Noct KO or Noct-/-) are protected from high-fat diet-induced obesity and hepatic steatosis. Recent studies had provided new insights by investigating various aspects of Nocturnin, ranging from its sub-cellular localization to identification of its target transcripts. However, a profound understanding of its molecular function remains elusive. This review article seeks to integrate the available literature into our current understanding of the functions of Nocturnin, their regulatory roles in key tissues and to throw light on the existing scientific lacunae.

The circadian rhythm: an influential soundtrack in the diabetes story

Type 2 Diabetes Mellitus (T2DM) has been the main category of metabolic diseases in recent years due to changes in lifestyle and environmental conditions such as diet and physical activity. On the other hand, the circadian rhythm is one of the most significant biological pathways in humans and other mammals, which is affected by light, sleep, and human activity. However, this cycle is controlled via complicated cellular pathways with feedback loops. It is widely known that changes in the circadian rhythm can alter some metabolic pathways of body cells and could affect the treatment process, particularly for metabolic diseases like T2DM. The aim of this study is to explore the importance of the circadian rhythm in the occurrence of T2DM via reviewing the metabolic pathways involved, their relationship with the circadian rhythm from two perspectives, lifestyle and molecular pathways, and their effect on T2DM pathophysiology. These impacts have been demonstrated in a variety of studies and led to the development of approaches such as time-restricted feeding, chronotherapy (time-specific therapies), and circadian molecule stabilizers.

A State-of-Art Review of the Vicious Circle of Sleep Disorders, Diabetes and Neurodegeneration Involving Metabolism and Microbiota Alterations

In the context of neurodegenerative disorders, cognitive decline is frequently reported in older population. Recently, numerous metabolic pathways have been implicated in neurodegeneration, including signaling disruption of insulin and other glucose-regulating hormones. In fact, Alzheimer's disease has now been considered as "type-3 diabetes". In this review, we tried to clarify the role of sleep impairment as the third major player in the complex relationship between metabolic and neurodegenerative diseases. Altered sleep may trigger or perpetuate these vicious mechanisms, leading to the development of both dementia and type 2 diabetes mellitus. Finally, we analyzed these reciprocal interactions considering the emerging role of the gut microbiota in modulating the same processes. Conditions of dysbiosis have been linked to circadian rhythm disruption, metabolic alterations, and release of neurotoxic products, all contributing to neurodegeneration. In a future prospective, gut microbiota could provide a major contribution in explaining the tangled relationship between sleep disorders, dementia and diabetes.

Shift Work and Metabolic Syndrome Updates: A Systematic Review

Shift work can cause circadian cycles disturbances and misaligns the endogenous rhythms. The physiological variables are driven by the circadian system and, its misalignment, can impair the metabolic functions. Thus, the main objective of this study was to evaluate the metabolic alterations as a result of shift work and night work reported in articles published in the last 5 years, using the eligibility criteria both gender and indexed articles in English language. In order to execute this work, we perform a systematic review according to PRISMA guidelines and searched about Chronobiology Disorders and Night Work, both related to metabolism, in Medline, Lilacs, ScienceDirect and Cochrane. Cross-sectional, cohort and experimental studies with low risk of bias were included. We found a total of 132 articles, and, after the selection process, 16 articles remained to be analyzed. It was observed that shift work can cause circadian misalignment and, consequently, some metabolic parameters alterations such as an impaired glycemic control and insulin functioning, cortisol phase release, cholesterol fractions imbalance, changes in morphological indexes and melatonin secretion. There are some limitations, such as heterogenicity in used databases and the 5 years restriction period, because the effects of sleep disturbance may have been reported earlier. In conclusion, we suggest that shift work interferes with the sleep-wake cycle and eating patterns, which cause crucial physiological alterations that, together, can lead to metabolic syndrome.

Sexual dimorphism in the response to chronic circadian misalignment on a high-fat diet

Longitudinal studies associate shiftwork with cardiometabolic disorders but do not establish causation or elucidate mechanisms of disease. We developed a mouse model based on shiftwork schedules to study circadian misalignment in both sexes. Behavioral and transcriptional rhythmicity were preserved in female mice despite exposure to misalignment. Females were protected from the cardiometabolic impact of circadian misalignment on a high-fat diet seen in males. The liver transcriptome and proteome revealed discordant pathway perturbations between the sexes. Tissue-level changes were accompanied by gut microbiome dysbiosis only in male mice, biasing toward increased potential for diabetogenic branched chain amino acid production. Antibiotic ablation of the gut microbiota diminished the impact of misalignment. In the United Kingdom Biobank, females showed stronger circadian rhythmicity in activity and a lower incidence of metabolic syndrome than males among job-matched shiftworkers. Thus, we show that female mice are more resilient than males to chronic circadian misalignment and that these differences are conserved in humans.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Influence of Shift Work on Arterial Stiffness and Systemic Inflammation: A 3-Year Follow-up Study in Industry

OBJECTIVE

To assess changes in cardiovascular disease risk factors during a 3-year follow-up among 57 rotating shift workers and 29 day workers in industry.

METHODS

We collected demographics by questionnaire, examined blood pressure, heart rate, pulse wave velocity, carotid media thickness, and maximal oxygen uptake. We assessed blood samples for determination of lipids, glycosylated hemoglobin, C-reactive protein, markers of inflammation, and particle concentrations/respirable dust. Baseline comparisons were analyzed using logistic regression (plaque) and linear regression for all other outcomes. We applied mixed models to assess differences in change in health outcomes between the shift workers and the day workers.

RESULTS

At baseline, the adhesion molecules soluble vascular cell adhesion molecule 1 and soluble P-selectin were elevated among the shift workers compared with that of the day workers. There was a significant difference in change in pulse wave velocity between shift workers (1.29-m/s increase) and day workers (0.11-m/s increase) over the 3-year follow-up. Respirable dust levels were below the Norwegian occupational exposure limit.

CONCLUSIONS

Shift work in industry is associated with arterial stiffening reflecting increased risk for future cardiovascular disease. More uncertainly, we found some support for systemic inflammation.

Overall Clinical Features of Type 2 Diabetes Mellitus With Respect to Gender

Introduction Since patients with type 2 diabetes are frequently misdiagnosed, provided inappropriate management, or poorly controlled, it is important to comprehend the wide range of clinical signs and symptoms associated with diabetes. Therefore, this study evaluated the overall clinical manifestations of patients with type 2 diabetes patients with respect to gender. Methods This was a multicenter, cross-sectional study that was conducted at various hospitals, using a non-probability sampling technique. The duration of the study was about six months, from January 1, 2022 to June 30, 2022. The study included 590 type 2 diabetes patients, ranging in age from 35 to 70 years. Age, gender, socioeconomic status, health status, co-morbidities, and diabetes symptoms were documented. A chi-square was applied to determine the association between overall symptoms associated with type 2 diabetes and gender. An independent t-test was applied to determine the significance level between means of demographic parameters. Results The study findings showed that out of 590 patients with diabetes, 310 (52.5%) were males and 280 (47.5%) were females. The male and female mean ages were 57.46±14.93 and 50.38±14.85 years, respectively, with a statistically significant gender difference (p<0.001). The prevalence of renal manifestation in type 2 patients with diabetes revealed a significant relationship (p<0.05) for both genders. The prevalence of ocular manifestations revealed a significant relationship with both genders (p<0.05) in terms of distortion and blurred vision. The prevalence of ocular manifestations revealed a significant relationship observed with both genders (p<0.05) in terms of shortness of breath, dyspnea severity, and severity of chest pain. Conclusion This study concluded that women with type 2 diabetes mellitus have a significantly higher frequency of muscular pain, urinary symptoms, neurological symptoms, and dermatological manifestations than men. In contrast, respiratory symptoms were significantly more pronounced in males than in females. The presence of comorbidities such as dyslipidemia significantly increased the probability of developing type 2 diabetes in both genders.

Meal-timing patterns and chronic disease prevalence in two representative Austrian studies

PURPOSE

This study aimed at describing meal-timing patterns using cluster analysis and explore their association with sleep and chronic diseases, before and during COVID-19 mitigation measures in Austria.

METHODS

Information was collected in two surveys in 2017 (N = 1004) and 2020 (N = 1010) in representative samples of the Austrian population. Timing of main meals, nighttime fasting interval, last-meal-to-bed time, breakfast skipping and eating midpoint were calculated using self-reported information. Cluster analysis was applied to identify meal-timing clusters. Multivariable-adjusted logistic regression models were used to study the association of meal-timing clusters with prevalence of chronic insomnia, depression, diabetes, hypertension, obesity and self-rated bad health status.

RESULTS

In both surveys, median breakfast, lunch and dinner times on weekdays were 7:30, 12:30 and 18:30. One out of four participants skipped breakfast and the median number of eating occasions was 3 in both samples. We observed correlation between the different meal-timing variables. Cluster analysis resulted in the definition of two clusters in each sample (A17 and B17 in 2017, and A20 and B20 in 2020). Clusters A comprised most respondents, with fasting duration of 12-13 h and median eating midpoint between 13:00 and 13:30. Clusters B comprised participants reporting longer fasting intervals and later mealtimes, and a high proportion of breakfast skippers. Chronic insomnia, depression, obesity and self-rated bad health-status were more prevalent in clusters B.

CONCLUSIONS

Austrians reported long fasting intervals and low eating frequency. Meal-timing habits were similar before and during the COVID-19-pandemic. Besides individual characteristics of meal-timing, behavioural patterns need to be evaluated in chrono-nutrition epidemiological studies.

Dietary Patterns under the Influence of Rotational Shift Work Schedules: A Systematic Review and Meta-Analysis

Workers employed in rotating shift schedules are at a higher metabolic risk compared with those in regular day and fixed shift schedules; however, the contribution of diet is unclear. This systematic review aimed to investigate how rotating shift work schedules affect dietary energy intake and dietary patterns compared with regular day and fixed shift schedules. In addition, intraperson energy intake and dietary pattern comparisons within rotating shift schedules were investigated. Database searches were conducted on MEDLINE, Cochrane, CINAHL, PSYCinfo, EMBASE, and Scopus, in addition to manual search of bibliographic references, to identify articles. Two separate meta-analyses compared dietary intake between day work and rotating shift work schedules and within the rotational shift work group (morning/day and night shifts). Differences in dietary patterns were synthesized narratively. Thirty-one studies (n = 18,196 participants) were included in the review, and meta-analyses were conducted with 24-hour mean energy intake data from 18 (n = 16,633 participants) and 7 (n = 327 participants) studies, respectively. The average 24-hour energy intake of rotating shift workers was significantly higher than that of workers in regular daytime schedules [weighted mean difference (WMD): 264 kJ; 95% confidence interval (CI): 70, 458 kJ; P < 0.008; I² = 63%]. However, the mean difference in 24-hour energy intake between morning/day shifts compared with night shifts within rotational shift schedules was not statistically significant (WMD: 101 kJ; 95% CI: -651, 852 kJ; P = 0.79; I² = 77%). Dietary patterns of rotating shift workers were different from those of day workers, showing irregular and more frequent meals, increased snacking/eating at night, consumption of fewer core foods, and more discretionary foods. This review highlights that dietary intake in rotational shift workers is potentially higher in calories and features different eating patterns as a consequence of rotating shift work schedules. This review was registered at PROSPERO as ID 182507.

Meal timing variability of rotating shift workers throughout a complete shift cycle and its effect on daily energy and macronutrient intake: a field study

PURPOSE

To evaluate the meal timing variability of rotating shift workers throughout a complete shift schedule and its effect on daily energy and macronutrient intake.

METHODS

Thirty male shift-workers from a mining company were evaluated in a complete rotation shift cycle over 240 consecutive hours (10 days; two days of morning shifts, two days of evening shifts, 24 h free, two days of night shifts and three days off). Food intake related variables [meal timing, energy (kcal) and macronutrient intake (%)] were assessed by 24 h recall by a trained nutritionist. Mixed models were used to analyze the variation in meal timing and energy and macronutrient intake throughout the shift cycle, as well as the interaction between shift and time ranges (00:00-03:59, 04:00-07:59, 08:00-11:59, 12:00-15:59, 16:00-19:59, 20:00-23:59).

RESULTS

The first meal of the day was earlier on night shifts [D6 (3:44 ± 0:33) and D7 (5:52 ± 0:42)] compared to the other shifts (p < 0.001), except for D4 (evening shift; 5:51 ± 0:47) versus D7 (p = 0.999). Night shifts also showed a shorter night fasting (D5-D6, 9.3 h; D6-D7, 9.6 h) than most other nights (p < 0.05), except for the fasting between D1-D2 (11.3 h) and D3-D4 (11.2 h) (p > 0.05). There was no difference in 24 h energy intake throughout the shift cycle (p = 0.065). The analysis of interaction between shift and time ranges showed that night shift (D6) presented a higher intake of energy (441.5 ± 48.4 kcal), percentage of energy (D6: 17.8 ± 1.8%), fat (17.6 ± 2.0%), carbohydrate (17.0 ± 1.7%) and protein (16.4 ± 1.8%) between 00:00 and 03:59 compared with the other shift days (p < 0.05).

CONCLUSION

Night shifts seem to contribute to a longer eating window than other shifts. Moreover, there is a higher energy and macronutrients intake during night shifts, which reduces the night fast period and could have implications for metabolic dysregulation.

Outdoor light at night, genetic predisposition and type 2 diabetes mellitus: A prospective cohort study

BACKGROUND

According to animal and human epidemiologic studies, exposure to outdoor light at night (LAN) may cause circadian disruption, which may disturb sleep quality and lead to incident type 2 diabetes mellitus (T2DM).

METHODS

We followed 283,374 persons from 2006 through 2020. Outdoor LAN exposure was estimated using satellite data for individual address with 500 m² scale buffer during follow-up. Incidence of T2DM was confirmed by hospital inpatient records. We identified potential confounders by a directed acyclic graph, including demographic, genetic, individual and regional level socioeconomic status, and environmental risk factors, and calculated hazard ratios (HRs) and 95% confidence intervals (CIs) through time-varying Cox proportional hazard model. Furthermore, we examined the association of outdoor LAN with a defined health sleep scores and moderation of genetic predisposition and shift work on the relationship of outdoor LAN and incident T2DM.

RESULTS

We identified 7,775 incident T2DM cases over 3,027,505 person-years. Higher outdoor LAN exposures were significantly associated with higher risk of T2DM. The estimated HR for incident T2DM with an interquartile range (IQR: 11.22 nW/cm²/sr) increase in outdoor LAN was 1.05 (95%CI: 1.01, 1.09) in the fully adjusted model. Participants who lived in the highest quarter of outdoor LAN area were more likely to develop T2DM (HR: 1.14,95%CI: 1.02, 1.27). Besides, those who were exposed to higher levels of outdoor LAN had poorer sleep quality. No moderation role of PRS on outdoor LAN-induced T2DM observed both on the multiplicated and additive scale. The hazards of outdoor LAN were observed in those who never owned a night shift work.

CONCLUSION

Although further work is required to clarify potential mechanisms, our findings indicate that exposure to residential outdoor LAN may contribute to T2DM risk and low sleep quality.

Circadian Rhythms Disrupted by Light at Night and Mistimed Food Intake Alter Hormonal Rhythms and Metabolism

Availability of artificial light and light-emitting devices have altered human temporal life, allowing 24-hour healthcare, commerce and production, and expanding social life around the clock. However, physiology and behavior that evolved in the context of 24 h solar days are frequently perturbed by exposure to artificial light at night. This is particularly salient in the context of circadian rhythms, the result of endogenous biological clocks with a rhythm of ~24 h. Circadian rhythms govern the temporal features of physiology and behavior, and are set to precisely 24 h primarily by exposure to light during the solar day, though other factors, such as the timing of meals, can also affect circadian rhythms. Circadian rhythms are significantly affected by night shift work because of exposure to nocturnal light, electronic devices, and shifts in the timing of meals. Night shift workers are at increased risk for metabolic disorder, as well as several types of cancer. Others who are exposed to artificial light at night or late mealtimes also show disrupted circadian rhythms and increased metabolic and cardiac disorders. It is imperative to understand how disrupted circadian rhythms alter metabolic function to develop strategies to mitigate their negative effects. In this review, we provide an introduction to circadian rhythms, physiological regulation of homeostasis by the suprachiasmatic nucleus (SCN), and SCN-mediated hormones that display circadian rhythms, including melatonin and glucocorticoids. Next, we discuss circadian-gated physiological processes including sleep and food intake, followed by types of disrupted circadian rhythms and how modern lighting disrupts molecular clock rhythms. Lastly, we identify how disruptions to hormones and metabolism can increase susceptibility to metabolic syndrome and risk for cardiovascular diseases, and discuss various strategies to mitigate the harmful consequences associated with disrupted circadian rhythms on human health.

The Effect of Night Shifts on 24-h Rhythms in the Urinary Metabolome of Police Officers on a Rotating Work Schedule

Shift workers face an increased risk of metabolic health problems, but the direct metabolic response to working nights is not fully understood. The aim of this study was to investigate the effect of night shifts on the 24-h urinary metabolome of shift workers. Eleven police officers working rotating shifts completed two 24-h laboratory visits that took place before and after they worked 7 consecutive nights. Sleep and meals were scheduled on a day schedule in the first visit and then on a night schedule (i.e., sleep and meals shifted by approximately 12 h) in the second visit. Targeted metabolomic analysis was performed on urine samples collected throughout these laboratory visits. Differential rhythmicity analysis was used to compare 24-h rhythms in urinary metabolites in both conditions. Our results show that on the day schedule, 24-h rhythms are present in the urinary levels of the majority of metabolites, but that this is significantly reduced on the night schedule, partly due to loss of organic acid rhythmicity. Furthermore, misalignment of 24-h metabolite rhythms with the shifted behavioral cycles in the night schedule was observed in more than half of the metabolites that were rhythmic in both conditions (all acylcarnitines). These results show that working nights alters the daily rhythms of the urinary metabolome in rotating shift workers, with the most notable impact observed for acylcarnitines and organic acids, 2 metabolite classes involved in mitochondrial function. Further research is warranted to study how these changes relate to the increased metabolic risks associated with shift work.

Distribution of working hour characteristics by race, age, gender, and shift schedule among U.S. manufacturing workers

Shift work is a common occupational exposure, however, few studies have examined aspects of shift work beyond night work and long hours, such as rotational patterns or weekend work, which may contribute to poor health through disruption of the body's circadian rhythms. In this manuscript, we calculated the prevalence of working hour characteristics using algorithms for type (e.g., day), duration, intensity, rotational direction, and social aspects (e.g., weekend work) in a nationwide cohort of American manufacturing workers (N = 23,044) between 2003 and 2014. Distributions of working hour characteristics were examined by schedules (e.g., permanent day, day/night) and demographics, and were cross-classified in a matrix to examine co-occurrence. Approximately 55% of shifts may cause circadian rhythm disruption as they were non-day shifts or day shifts with a quick return or rotation, or were 13 h or longer. Older workers, female workers, and White workers worked permanent day shifts most often, while workers of color worked more day/night schedules. Night and evening shifts had more frequent shift rotations, quick returns, and longer hours than day shifts. Yet, day shifts, which are presumed to have little negative circadian impact, may cause circadian rhythm disruption as long hours, quick returns and rotations also occurred within day shifts.

Metabolomic profiles in night shift workers: A cross-sectional study on hospital female nurses

Background and aim

Shift work, especially including night shifts, has been found associated with several diseases, including obesity, diabetes, cancers, and cardiovascular, mental, gastrointestinal and sleep disorders. Metabolomics (an omics-based methodology) may shed light on early biological alterations underlying these associations. We thus aimed to evaluate the effect of night shift work (NSW) on serum metabolites in a sample of hospital female nurses.

Methods

We recruited 46 nurses currently working in NSW in Milan (Italy), matched to 51 colleagues not employed in night shifts. Participants filled in a questionnaire on demographics, lifestyle habits, personal and family health history and work, and donated a blood sample. The metabolome was evaluated through a validated targeted approach measuring 188 metabolites. Only metabolites with at least 50% observations above the detection limit were considered, after standardization and log-transformation. Associations between each metabolite and NSW were assessed applying Tobit regression models and Random Forest, a machine-learning algorithm.

Results

When comparing current vs. never night shifters, we observed lower levels of 21 glycerophospholipids and 6 sphingolipids, and higher levels of serotonin (+171.0%, 95%CI: 49.1-392.7), aspartic acid (+155.8%, 95%CI: 40.8-364.7), and taurine (+182.1%, 95%CI: 67.6-374.9). The latter was higher in former vs. never night shifters too (+208.8%, 95%CI: 69.2-463.3). Tobit regression comparing ever (i.e., current + former) and never night shifters returned similar results. Years worked in night shifts did not seem to affect metabolite levels. The Random-Forest algorithm confirmed taurine and aspartic acid among the most important variables in discriminating current vs. never night shifters.

Conclusions

This study, although based on a small sample size, shows altered levels of some metabolites in night shift workers. If confirmed, our results may shed light on early biological alterations that might be related to adverse health effects of NSW.

Circadian rhythms in cardiac metabolic flexibility

Numerous aspects of cardiovascular physiology (e.g., heart rate, blood pressure) and pathology (e.g., myocardial infarction and sudden cardiac death) exhibit time-of-day-dependency. In association with day-night differences in energetic demand and substrate availability, the healthy heart displays remarkable metabolic flexibility through temporal partitioning of the metabolic fate of common substrates (glucose, lipid, amino acids). The purpose of this review is to highlight the contribution that circadian clocks provide toward 24-hr fluctuations in cardiac metabolism and to discuss whether attenuation and/or augmentation of these metabolic rhythms through adjustment of nutrient intake timing impacts cardiovascular disease development.

Association of shift work with incident dementia: a community-based cohort study

BACKGROUND

Some observational studies had found that shift work would increase risks of metabolic disorders, cancers, and cardiovascular diseases, but there was no homogeneous evidence of such an association between shift work and incident dementia. This study aimed to investigate whether shift work would increase the risk of dementia in a general population.

METHODS

One hundred seventy thousand seven hundred twenty-two employed participants without cognitive impairment or dementia at baseline recruited between 2006 and 2010 were selected from the UK Biobank cohort study. Follow-up occurred through June 2021. Shift work status at baseline was self-reported by participants and they were categorized as non-shift workers or shift workers. Among shift workers, participants were further categorized as night shift workers or shift but non-night shift workers. The primary outcome was all-cause dementia in a time-to-event analysis, and the secondary outcomes were subtypes of dementia, including Alzheimer's disease, vascular dementia, and other types of dementia.

RESULTS

In total, 716 dementia cases were observed among 170,722 participants over a median follow-up period of 12.4 years. Shift workers had an increased risk of all-cause dementia as compared with non-shift workers after multivariable adjustment (hazard ratio [HR], 1.30, 95% confidence interval [CI], 1.08-1.58); however, among shift workers, night shift work was not associated with the risk of dementia (HR, 1.04, 95% CI, 0.73-1.47). We found no significant interaction between shift work and genetic predisposition to dementia on the primary outcome (P for interaction = 0.77).

CONCLUSIONS

Shift work at baseline was associated with an increased risk of all-cause dementia. Among shift workers, there was no significant association between night shift work and the risk of dementia. The increased incidence of dementia in shift workers did not differ between participants in different genetic risk strata for dementia.

A nomogram for predicting lung-related diseases among construction workers in Wuhan, China

Objective

To develop a prediction nomogram for the risk of lung-related diseases (LRD) in construction workers.

Methods

Seven hundred and fifty-two construction workers were recruited. A self- designed questionnaire was performed to collected relevant information. Chest X-ray was taken to judge builders' lung health. The potential predictors subsets of the risk of LRD were screened by the least absolute shrinkage and selection operator regression and univariate analysis, and determined by using multivariate logistic regression analysis, then were used for developing a prediction nomogram for the risk of LRD. C-index, calibration curve, receiver operating characteristic curve, decision curve analysis (DCA) and clinical impact curve analysis (CICA) were used to evaluation the identification, calibration, predictive ability and clinical effectiveness of the nomogram.

Results

Five hundred and twenty-six construction workers were allocated to training group and 226 to validation group. The predictors included in the nomogram were symptoms, years of dust exposure, work in shifts and labor intensity. Our model showed good discrimination ability, with a bootstrap-corrected C index of 0.931 (95% CI = 0.906-0.956), and had well-fitted calibration curves. The area under the curve (AUC) of the nomogram were (95% CI = 0.906-0.956) and 0.945 (95% CI = 0.891-0.999) in the training and validation groups, respectively. The results of DCA and CICA indicated that the nomogram may have clinical usefulness.

Conclusion

We established and validated a novel nomogram that can provide individual prediction of LRD for construction workers. This practical prediction model may help occupational physicians in decision making and design of occupational health examination.

Erfüllte Gegenwart und Rhythmus des Lebens

Der Zusammenhang von Zeit und gutem Leben wurde bereits für eine Reihe medizinischer Disziplinen und Praktiken herausgearbeitet. Doch welche Rolle spielt die Zeitlichkeit des guten Lebens für die Medizin insgesamt? Das ist die leitende Frage dieses Artikels. Dabei wird das gute Leben als sinnvolles Leben verstanden. In diesem Sinne wird für eine zweifache medizinische Relevanz der Zeitlichkeit des guten Lebens argumentiert: Erstens besteht der Sinn medizinischer Behandlungen in der Ermöglichung erfüllter Gegenwart. Zweitens kann und sollte ebendies u. a. durch die Wahrung und Wiederherstellung der chronobiologischen Rhythmen geschehen.

Time for Exercise? Exercise and Its Influence on the Skeletal Muscle Clock

Circadian rhythms drive our daily behaviors to coincide with the earth's rotation on an approximate 24-h cycle. The circadian clock mechanism present in nearly every cell is responsible for our circadian rhythms and is comprised of a transcriptional-translational feedback loop in mammals. The central clock resides in the hypothalamus responding to external light cues, whereas peripheral clocks receive signals from the central clock and are also sensitive to cues from feeding and activity. Of the peripheral clocks, the skeletal muscle clock is particularly sensitive to exercise which has shown to be an important time-cue with the ability to influence and adjust the muscle clock phase in response to exercise timing. Since the skeletal muscle clock is also involved in the expression of tissue-specific gene expression-including glucoregulatory genes-this might suggest a role for exercise timing as a therapeutic strategy in metabolic diseases, like type 2 diabetes. Notably, those with type 2 diabetes have accompanied disruptions in their skeletal muscle clock mechanism which may also be related to the increased risk of type 2 diabetes seen among shift workers. Therefore, the direct influence of exercise on the skeletal muscle clock might support the use of exercise timing to provide disease-mitigating effects. Here, we highlight the potential use of time-of-day exercise as a chronotherapeutic tool within circadian medicine to improve the metabolic profile of type 2 diabetes and support long-term glycemic control, potentially working through the skeletal muscle clock and circadian physiology.

What do we know about the effect of night-shift work on cardiovascular risk factors? An umbrella review

Objective

To evaluate the existing evidence on the effect of night-shift work and its subtypes (permanent and rotating) on cardiovascular risk factors: diabetes, lipid disorders, being overweight, hypertension, smoking habits, sedentariness, and occupational psychosocial stressors.

Method

A Web of Sciences and Cochrane review library search was conducted to identify systematic reviews with or without meta-analysis dealing with the quantification of the link between night-shift work and the studied cardiovascular risk factors in working populations. We used the AMSTAR 2 to evaluate the quality of each review. The main results of the included systematic reviews were compiled in a summary structured around the different cardiovascular risk factors.

Results

After selection, 33 systematic reviews were included: nine for diabetes, four for lipid disorders, nine for being overweight, four for hypertension, two for smoking habits, three for occupational psychosocial stressors and two for sedentariness. The results confirmed an excess risk of diabetes of about 10% regardless of the type of night work. A stated excess risk of being overweight at around 25% was also highlighted for shift workers overall, which could reach 38% among night-shift workers. An increased risk of obesity, estimated at 5% for night-shift workers and at 18% for rotating shift workers, was observed. An excess risk of hypertension was estimated at around 30% when considering the broad definition of shift work and when night periods were included in rotating shifts. The literature provided inconsistent results for the link between lipid disorders and night-shift work. Shift workers appeared to be more likely to smoke. The link between shift work and occupational psychosocial stressors was scarcely explored in the available studies. Sedentariness was scarcely considered in systematic reviews, which prevents any firm conclusions.

Conclusion

The consequences of night work in terms of diabetes, being overweight/obesity and hypertension are established. Monitoring of these cardiovascular risk factors for these night-shift workers could be implemented by practitioners. In contrast, the links with lipid disorders, sedentariness, smoking habits, and occupational psychosocial stressors warrant further investigation.

Systematic review registration

https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42021275212, PROSPERO (ID CRD42021275212).

Eating Patterns among Emergency Medical Service Providers in the United States: A Qualitative Interview Study

Emergency medical service (EMS) providers experience demanding work conditions in addition to shift work, which increases risk for nutrition related chronic disease such as metabolic syndrome, diabetes, obesity, and cardiovascular disease. The high stress, emergent, and unpredictable nature of EMS may interfere with healthy eating patterns on and off shift, however little is known about how these conditions impact dietary patterns among EMS providers. This study aimed to understand factors impacting dietary patterns through semi-structured interviews with 40 EMS providers throughout the United States. Interviews were conducted virtually via Zoom video conference. Inductive coding was used to identify themes throughout the interviews. Salient factors mentioned in the interviews included hunger, fatigue, stress, coworker influence, ambulance posting, geographical location, agency policy, and culture. Factors were grouped into 4 domains: physiological factors, psychosocial factors, physical environment, and organizational environment, represented by an adapted version of the social ecological model of health behaviors to include factors influencing eating patterns specific to EMS, which may contribute to overall health. Various barriers to healthy eating exist within EMS, and future studies should explore interventions at each level of our proposed model to improve conditions and reduce nutrition related disease risk in this essential population.