Night shift work exposure profile and obesity: Baseline results from a Chinese night shift worker cohort

Investigation of obesity and its related factors among Chinese medical staff: a cross-sectional pilot study

BACKGROUND

Many studies have covered the prevalence of obesity in different populations. However, studies on the prevalence and predictors of obesity among medical staff are lacking. The aim of our study is to investigate the prevalence of obesity among medical staff and to identify the related predictors.

METHODS

Using a snowballing recruitment strategy in the form of an electronic questionnaire, a cross-sectional survey was conducted among 1201 medical staff from cooperative hospitals between January and March 2022. We designed a questionnaire to investigate the participants' demographic, lifestyle, diet, physical activity, and work status.

RESULTS

The overall prevalence of obesity was 8.5%, with males (13.7%) having a greater incidence than females (5.7%) (p < 0.001). Multiple logistic regression analyses showed that alcohol drinking (OR, 2.34; 95% CI 1.23-4.42, p = 0.01), sugar-sweetened beverages consumed > 3/week (OR, 2.50; 95% CI 1.02-6.15, p = 0.046), and working a night shift > 1/week (OR, 2.17; 95% CI 1.02-4.61, p = 0.043) were independent predictive factors for obesity in men. For women, having midnight snack having midnight snack (OR, 2.93;95% CI 1.24-6.96, p = 0.015), good sleep quality (OR, 4.47; 95% CI 1.10-21.70, p = 0.038), and working a night shift > 1/week (OR, 3.62; 95% CI 1.73-7.57, p = 0.001) were independently associated with obesity.

CONCLUSIONS

Obesity presented a low prevalence among medical staff. Alcohol drinking, drinking sugar-sweetened beverages > 3/week, and night shift > 1/week predicted a higher risk of obesity in males. In females, having midnight snack, good sleep quality, and night shift > 1/week were independently associated with obesity.

LEVEL OF EVIDENCE

V, descriptive study.

Relationship Between Rotating Night Shift Work and Anthropometric Markers of Overall and Central Adiposity

Purpose

This study aimed to investigate possible association between rotating night shift (RNS) work and anthropometric markers of overall and central adiposity among male workers.

Methods

Medical records of workers who underwent medical examination at the Occupational Medicine Unit affiliated with Alexandria Faculty of Medicine were reviewed in December 2021 to extract data about RNS, overall adiposity [body mass index (BMI) from 25 to 29.9 kg/m² indicated overweight, while BMI ≥30 kg/m² indicated obesity], central adiposity (waist circumference ≥94 cm). Univariate and multivariate logistic regression were done to model adiposity as a function of potential demographic, lifestyle, and occupational factors.

Results

Data of 647 male workers, including daytime workers (26.9%) and RNS workers (73.1%) who spent 1-5 years, 6-9 years, or ≥10 years working RNS, were analyzed. No association was found between RNS work and overall adiposity (BMI ≥30 kg/m²). In multivariate regression, age, residence, and smoking status were predictors of an increased BMI. Compared with young workers (<30 years old), the odds of an increased BMI (BMI ≥25 kg/m²) were 2.6 and 3.01 times higher among workers who were 30-<40, and 40-<50 years old, respectively [95% CI=(1.35, 5.05) and (1.19, 7.56), respectively]. Workers who lived in urban areas were less likely to have had an increased BMI (OR=0.34, 95% CI=0.16, 0.74). The odds of an increased BMI were 2.14 times higher in workers who never smoked compared with current smokers (95% CI=1.12, 4.11). No association was found between RNS and central adiposity. In multivariate regression, age was the sole predictor of central adiposity.

Conclusion

The study supports the idea that RNS work might not be associated with overall or central adiposity and highlights a possible association between central adiposity and age and association between BMI and age, residence, and smoking behavior. Longitudinal, larger studies are required to explore the relationship between RNS and adiposity.

Association between circadian rhythm and sleep quality among nursing interns: A latent profile and moderation analysis

BACKGROUND

Disturbances in circadian rhythms are common among night-shift workers and result in poor sleep quality. Nevertheless, the heterogeneity of circadian rhythms and their relationship with sleep quality is less explored in nursing interns. Therefore, we aimed to identify the latent subtypes of circadian rhythm, explore their relationship with sleep quality, and evaluate their moderating role between perceived stress and sleep quality in nursing interns.

MATERIALS AND METHODS

In all, 452 nursing interns were recruited between October 2020 and January 2021 from Be Resilient to Nursing Career (BRNC), which is a multicenter, prospective cohort of a career growth program for nursing students. They were assessed using the 10-item Chinese Perceived Stress Scale, Circadian Type Inventory, and Pittsburgh Sleep Quality Index. Latent profile analysis and moderation analysis were performed.

RESULTS

Overall, 72.3% of the nursing interns reported poor sleep quality. We identified three latent subtypes of circadian rhythms, namely, Vigorousness (40.1%), Inadaptability (18.6%), and Flexibility (41.1%). Females (OR = 1.97, 95% Cl: 1.01-3.83, P = 0.047) with normal body mass index (OR = 1.62, 95% CI: 0.95-2.76, P = 0.078) were prone to Flexibility. Circadian rhythm types significantly moderated the association between perceived stress and sleep quality (P < 0.05).

CONCLUSION

Nursing interns suffer from poor sleep. There exists heterogeneity of circadian rhythm subtypes in nursing interns, and attention should be paid to those with Inadaptability type. The association between perceived stress and sleep quality is significantly moderated by circadian rhythm subtypes.

Association of Shift Work with Normal-Weight Obesity in Community-Dwelling Adults

BACKGRUOUND

Shift work is associated with obesity and metabolic syndrome. However, this association in the normal-weight population remains unclear. This study aimed to investigate whether shift work is associated with normal-weight obesity (NWO).

METHODS

From the nationally representative Korea National Health and Nutrition Examination Survey (KNHANES) dataset (2008 to 2011), 3,800 full-time workers aged ≥19 years with a body mass index (BMI) ≤25 kg/m2 were analysed. We defined NWO as BMI ≤25 kg/m2 and body fat percentage ≥25% in men and ≥37% in women. Working patterns were classified into "daytime," "other than daytime," and "shift." Multivariable logistic regression analysis was performed to evaluate the relationship between shift work and NWO.

RESULTS

Shift work was associated with higher odds of NWO than daytime work (adjusted odds ratio [aOR], 1.47; 95% confidence interval [CI], 1.04 to 2.09) and night/evening work (aOR, 1.87; 95% CI, 1.11 to 3.14) after adjustment for type of work, working hours, age, sex, BMI, 25-hydroxyvitamin D levels, homeostatic model assessment for insulin resistance, and other sociodemographic factors. In subgroup analyses, the association between shift work and NWO was more robust in those aged ≥60 years and those working ≥56 hours/week.

CONCLUSION

Shift work was associated with NWO in community-dwelling Korean adults, independent of age, sex, BMI, and other covariates.

Atypical working hours are associated with tobacco, cannabis and alcohol use: longitudinal analyses from the CONSTANCES cohort

BACKGROUND

This study examined prospective associations between atypical working hours with subsequent tobacco, cannabis and alcohol use as well as sugar and fat consumption.

METHODS

In the French population-based CONSTANCES cohort, 47,288 men and 53,324 women currently employed included between 2012 and 2017 were annually followed for tobacco and cannabis use. Among them, 35,647 men and 39,767 women included between 2012 and 2016 were also followed for alcohol and sugar and fat consumption. Three indicators of atypical working hours were self-reported at baseline: working at night, weekend work and non-fixed working hours. Generalized linear models computed odds of substance use and sugar and fat consumption at follow-up according to atypical working hours at baseline while adjusting for sociodemographic factors, depression and baseline substance use when appropriate.

RESULTS

Working at night was associated with decreased smoking cessation and increased relapse in women [odds ratios (ORs) of 0.81 and 1.25], increased cannabis use in men [ORs from 1.46 to 1.54] and increased alcohol use [ORs from 1.12 to 1.14] in both men and women. Weekend work was associated with decreased smoking cessation in women [ORs from 0.89 to 0.90] and increased alcohol use in both men and women [ORs from 1.09 to 1.14]. Non-fixed hours were associated with decreased smoking cessation in women and increased relapse in men [ORs of 0.89 and 1.13] and increased alcohol use in both men and women [ORs from 1.12 to 1.19]. Overall, atypical working hours were associated with decreased sugar and fat consumption.

CONCLUSIONS

The potential role of atypical working hours on substance use should be considered by public health policy makers and clinicians in information and prevention strategies.

Obesity and Diet Predict Attitudes towards Health Promotion in Pre-Registered Nurses and Midwives

Nurses and midwives are integral to public health promotion; in the UK, they are advised to act as role models by their governing body, but overweight or obesity rates are high. We explored whether obesity and dietary habits are related to attitudes towards healthy role modelling and health promotion practice. A total of 346 pre-registered UK nurses and midwives (92.6% female; 18–53 years) completed an online survey. Items included body composition, dietary habits assessed by the Lifestyle Behaviour Questionnaire (LBQ), attitudes towards being role models for health (RA: role attitudes) and attitudes toward health promotion practice (ATHPP): 33.8% of the sample self-reported as overweight or obese; 67.6% did not consume 5-a-day portions of fruit/veg; 31.5% reported a healthy diet; and 89.6% believed their diet could be healthier. Positive RA was significantly linked to health promotion engagement (HP) (ß = 0.33, p < 0.001). Positive ATHPP was significantly predicted by lower BMI (ß = −0.08, p = 0.078), positive RA (ß = 0.67, p < 0.001), lower HP (ß = −0.25, p < 0.001) and male gender (ß = 0.09, p = 0.02). Greater confidence in patients valuing healthcare professional’s advice was predicted by healthier diet (ß = 0.11, p = 0.03), lower BMI (ß = −0. 16, p < 0.01), more positive RA (ß = 0.14, p < 0.01) as well as HP engagement during training (ß = 0.20, p < 0.01). One’s own motivation to promote health, similarly to ATHPP, was predicted by RA (ß = 0.17, p = 0.001) and previous HP engagement (ß = 0.39, p < 0.001). Findings show that overweight and obesity are prevalent in pre-registered nurses and midwives; the majority did not consume a healthy diet. Individual’s body composition, diet and attitudes towards role modelling are positively associated with their attitudes towards, and confidence in, health promotion practice. Experiences of health promotion practice during training can have either a positive or a negative influence on attitudes. Mentors and educators could actively promote healthy lifestyles for pre-registered nurses and midwives and facilitate more opportunities for health promotion practice during placements, which includes time for reflection.

Influence of Obesity on Heart Rate Variability in Nurses with Age and Shift Type as Moderators

Obesity is a risk factor of cardiovascular disease-related mortality and may be associated with changes in the autonomic nerve activity. Nurses working shifts and caring for patients are under great mental and physical pressure, and research has proven that these can negatively affect the body. The objective of this study was to examine the influence of obesity in nurses on their heart rate variability (HRV) and determine whether age or shift type moderates this influence. A questionnaire survey and HRV measurements were conducted on nurses at a hospital in Taiwan during a routine employee health checkup. HRV analysis was conducted using a noninvasive HRV monitor for five minutes. A total of 242 nurses with a mean age of 28.98 ± 6.56 years were enrolled in this study. An overly large waist circumference (WC) had a negative impact on high frequency (HF), low frequency (LF), and standard deviation of normal-to-normal interval (SDNN), while an overly high body mass index (BMI) had a negative impact on very low frequency (VLF) and SDNN. The interaction term “overly large WC × age” had a negative impact on HF (β = −0.21, p = 0.010) and LF (β = −0.18, p = 0.030), whereas the interaction term “overly high BMI×age” had a negative impact on HF (β = −0.27, p = 0.001), LF (β = −0.19, p = 0.023), and VLF (β = −0.17, p = 0.045). The interaction terms “overly large WC × shift type” and “overly high BMI × shift type” did not influence any HRV parameters. As age increased, so did the degree to which the HF and LF of nurses with an overly large WC were lower than normal, and so did the degree to which the HF, LF, and VLF of nurses with an overly high BMI were lower than normal.

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

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

Is Shift Work Sleep Disorder a Risk Factor for Metabolic Syndrome and Its Components? A Systematic Review of Cross-Sectional Studies

Shift work sleep disorder is prevalent in night shift workers due to prolonged misalignment of the circadian rhythm. Night shift workers comprise a significant portion of the workforce and it is important to study the potential implications on their health. Studies have shown the association of metabolic syndrome (MetS) and the components, that is, obesity, dyslipidemia, hypertension, and insulin resistance, with shift workers. Nocturnal exposure to bright light can affect various physiological processes including melatonin secretion, which is a regulator in insulin synthesis. A systematic review was conducted to identify studies showing the association between shift work and MetS and/or its components, as well as to review the pathophysiology for further investigations. This review follows the guidelines as per the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) checklist 2009. One thousand nine hundred ten records were identified from the PubMed database using both keywords and medical subject headings terms. After applying the inclusion/exclusion and eligibility criteria, 18 observational studies were included in the qualitative synthesis. Quality appraisal was conducted by two investigators independently using the Newcastle/Ottawa Scale, and 11 articles were finalized for the review after scoring 60% and above. Each study measured the different components of MetS and/or the presence of MetS. Statistically significant results were reported for the association between shift work and MetS, shift work and obesity, shift work and dyslipidemia, shift work and hypertension, and shift work and insulin resistance. This review identifies a need to emphasize treatment plans for shift workers to manage not only sleep disorders but other chronic diseases such as MetS, obesity, hypertension, dyslipidemia, and insulin resistance.

Health and wellness in the Australian coal mining industry: A cross sectional analysis of baseline findings from the RESHAPE workplace wellness program

Overweight and obesity has reach pandemic levels, with two-thirds (67%) of adult Australians classified as overweight or obese. As two of the most significant behavioral risk factors for obesity are modifiable (diet and exercise), there exists an opportunity for treatment through workplace health promotion initiatives. As one of Australia’s largest industries with its own unique workplace factors, the mining industry has previously reported higher than population levels of overweight and obesity. This represented an opportune setting to test the RESHAPE workplace wellness program. RESHAPE is an eight-step framework (based on the WHO ‘Health Workplace Framework and Model’) which aims to provide a sustained approach to wellness in the workplace. This paper presents baseline findings from a pilot study that aimed to implement RESHAPE at three mine sites in NSW, Australia, and investigates the issue of overweight and obesity in the coal mining industry. Across three mine sites, 949 coal miners were examined cross-sectionally on a range of workplace, wellness, health, diet, and exercise factors using a paper-based survey. This was a predominantly male sample (90.4%) with the majority (59.2%) of participants aged 25–44 years. Self-reported height and weight measures indicated that less than 20 percent (18.9%) of participants were in a healthy BMI range, while there were effectively equal numbers of overweight (40.9%) and obese (39.1%) participants. Only 3.5% of participants met the daily recommendation for vegetables (5 serves) and shift-workers had greater association with elevated BMI compared to non-shift workers (B = 1.21, 95% CI: 0.23, 2.20, p = 0.016). Poor nutrition is likely to be a key component in elevated levels of overweight and obesity within this industry, with workplace factors compounding challenges workers face in implementing health behavior change. Future studies would benefit from assessing diet and physical activity knowledge in relation to recommendations and serving sizes.

Metabolomic Profiles of Shift Workers and Day Workers: A Cross-Sectional Study

OBJECTIVE

The purpose of this study was to characterize the metabolomic profiles of shift workers and day workers and to discover the effect of shift work on workers' metabolic health.

METHODS

A total of 824 participants aged 25 to 55 years were recruited, and 485 (275 shift workers and 210 day workers) completed the study. The mean age of the shift workers was 37.32 (5.53) years old, and that of day workers was 36.50 (7.83) years old. Serum and salivary samples were collected for the detection of key biochemical indicators (melatonin, cholesterol, and low-density lipoprotein cholesterol) and for metabolome profile analyses.

RESULTS

Compared with female day workers, female shift workers had a higher BMI, waist circumference, and hip circumference. Correspondingly, we identified 76 significant metabolites (false discovery rate < 0.05) in shift workers, including L-tryptophan, acylcarnitines, and several fatty acids. Three pathways that presented significant differences were biosynthesis of unsaturated fatty acids, linoleic acid metabolism, and ubiquinone and other terpenoid-quinone biosynthesis.

CONCLUSIONS

Compared with day workers, shift workers were more prone to weight gain and central obesity and were at a higher risk for impaired lipid metabolism with disrupted circadian rhythms.

Rotating night shift work is associated with an increased risk of gastroesophageal reflux disease (GERD) symptoms among workers in China: A cross-sectional study

AIMS OF THE STUDY

Increasing studies suggest a significant association between night shift work and an increased risk of type 2 diabetes, obesity and other metabolic disorders. However, the available evidence of the association of rotating night shift work with gastroesophageal reflux disease (GERD) is limited. Herein, we hypothesised a link between the GERD risk and rotating night shift work among workers in China.

METHODS USED TO CONDUCT THE STUDY

A total of 2027 workers who completed a comprehensive health checkup were included. Logistic regression was used to investigate the link between rotating night shift work and the risk of GERD symptoms. Receiver operating characteristic (ROC) curve analysis was used to assess the multivariable model's diagnostic value for identifying GERD symptoms among workers.

RESULTS OF THE STUDY

In total, 556 (27.4%) individuals had GERD symptoms among 2027 workers. Multivariate analysis showed five independent factors for GERD: rotating night shift work (OR = 3.66, 95% CI: 2.52-5.40), age (OR = 2.53, 95% CI: 1.67-3.78), smoking (OR = 3.70, 95% CI: 2.63-5.21), Helicobacter pylori (H. pylori) infection (OR = 0.68, 95% CI: 0.48-0.96) and obesity (OR = 3.04, 95% CI: 2.43-3.83). A five-variable model based on five independent factors provided an area under a ROC curve (AUROC) of 0.80 (95% CI: 0.78-0.81) for identifying GERD symptoms among workers.

CONCLUSIONS DRAWN FROM THE STUDY AND CLINICAL IMPLICATIONS

Rotating night shift work is independently associated with an increased risk of GERD symptoms. Moreover a five-variable model (rotating night shift work, age, smoking, H pyori infection and obesity) can help identify individuals at high risk for GERD symptoms among workers in China.

Perturbation of the circadian clock and pathogenesis of NAFLD

All living organisms including humans, experience changes in the light exposure generated by the Earth's rotation. In anticipation of this unavoidable geo-physical variability, and to generate an appropriate biochemical response, species of many phyla, including mammals have evolved a nearly 24-hour endogenous timing device known as the circadian clock (CC), which is self-sustained, cell autonomous and is present in every cell type. At the heart of the 'clock' functioning resides the CC-oscillator, an elegantly designed transcriptional-translational feedback system. Notably, the core components of the CC-oscillator not only drive daily rhythmicity of their own synthesis, but also generate circadian phase-specific variability in the expression levels of thousands of target genes through transcriptional, post-transcriptional and post-translational mechanisms. Thereby, this 'clock'-system provides proper chronological coordination in the functioning of cells, tissues and organs. The CC governs many physiologically critical functions. Among these functions, the key role of the CC in maintaining metabolic homeostasis deserves special emphasis. Indeed, the several features of the modern lifestyle (e.g. travel-induced jet lag, rotating shift work, energy-dense food) which, force disruption of circadian rhythms have recently emerged as a major driver to global health problems like obesity, cardiovascular disease and metabolic liver disease such as non-alcoholic fatty liver disease (NAFLD). Here we review, the CC-dependent pathways in different tissues which play critical roles in mediating several critical metabolic functions under physiological conditions and discuss their impact for the development of metabolic disease with a focus on the liver.

Association between Occupational Characteristics and Overweight and Obesity among Working Korean Women: The 2010-2015 Korea National Health and Nutrition Examination Survey

Associations between several occupational characteristics and obesity are not fully elucidated in Korean working populations, especially in females. This study investigated associations between occupational characteristics and overweight/obesity among Korean women. Data on 2090 female workers (the mean age was 38.8 ± 0.2 years), extracted from Korean National Health and Nutrition Examination Surveys in 2010-2015, were analyzed and showed that 6.8% of subjects were underweight, 50.8% had normal weight, 20.1% were overweight, and 22.2% were individuals with obesity. Multiple regression analysis was performed to examine associations between occupational characteristics and overweight/obesity, after controlling for demographic, behavioral, and health-related characteristics. The reference group was normal weight. Working hours were strongly associated with overweight/obesity. The odds ratio (OR) of obesity in women who worked for ≥60 hours per week was 2.68 (95% confidence interval: [CI] 2.13-3.36) compared with those who worked for <40 hours. Night/shift workers were 1.21 times (95% confidence interval: [CI] 1.01-1.45) more likely to experience obesity than day or evening workers. In conclusion, obesity rates increase among female workers with longer working hours and those who work at night or in shifts. Occupational characteristics should be considered in the prevention of obesity among working women.

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

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

Eating Behavior (Duration, Content, and Timing) Among Workers Living under Different Levels of Urbanization

Urbanization has contributed to extended wakefulness, which may in turn be associated with eating over a longer period. Here, we present a field study conducted in four groups with different work hours and places of living in order to investigate eating behavior (duration, content, and timing). Anthropometric measures were taken from the participants (rural (n = 22); town (n = 19); city-day workers (n = 11); city-night workers (n = 14)). In addition, a sociodemographic questionnaire was self-answered and 24-h food recalls were applied for three days. The 24-h food recalls revealed that fat intake varied according to the groups, with the highest consumption by the city-day workers. By contrast, city-day workers had the lowest intake of carbohydrate, whereas the rural group had the highest. In general, all groups had some degree of inadequacy in food consumption. Eating duration was negatively correlated with total energy intake, fat, and protein consumption in the rural and town groups. There was a positive correlation between body mass index and eating duration in both city groups. The rural group had the earliest start time of eating, and this was associated with a lower body mass index. This study suggested that food content and timing, as well as eating duration, differed according to place of living, which in turn may be linked to lifestyle.

Job-Related Characteristics and Obesity in Australian Employees: Evidence From a Longitudinal Nationally Representative Sample

OBJECTIVE

This study aimed to examine the longitudinal association between 9 job-related characteristics and obesity among Australian employees using a nationally representative sample.

DESIGN

Longitudinal research design.

SETTING

Workplace.

PARTICIPANTS

This study was conducted by pooling 2 cross-sectional surveys of nationally representative longitudinal data collected across 2-time points in 2013 and 2017. This study limited the sample to current employees aged 15 to 64 years. The total number of observation included in the analysis is 16 980 of 11 521 employees.

MEASURES

The outcome variable is weight status and the main exposure variables are 9 job-related characteristics (work hours per week, work schedule, job type, employment contract type, firm size, supervisory responsibility, paid sick leave, self-perceived job stress, and self-perceived job insecurity). Generalized estimating equation logistic regression was employed to explore the association between job-related characteristics and obesity.

RESULTS

This study found that 59% of Australian employees were either overweight or obese. Employees working more than 40 hours per week were 1.11 times (odds ratio [OR]: 1.11, 95% confidence interval [CI]: 1.03-1.21) and 1.07 times (OR: 1.07, 95% CI: 1.01-1.13) more prone to become overweight and obese, respectively, compared to their counterparts who work 31 to 40 hours per week. The study also revealed that self-perceived job insecurity was positively associated with obesity (OR: 1.03, 95% CI: 1.02-1.04). However, this study did not find evidence that work schedule, job type, employment contract, firm size, supervisory role, paid sick leave, and self-perceived job stress were associated with obesity.

CONCLUSIONS

Working more than 40 hours per week and self-perceived job insecurity were significantly associated with obesity among Australian employees. A better understanding of why prolonged work hours and self-perceived job insecurity are associated with obesity may help policy makers to implement workplace wellness policies and for employers to take measures to tackle the obesity problem of their employees.

Night work is related to higher global and central adiposity in Brazil: National Health Survey, 2013

BACKGROUND

Night work can disturb the natural circadian rhythm, leading to disruptions in metabolic rate and subsequent overall gain weight or even more harmful abdominal adiposity. Our aims were to investigate the associations between night work frequency and markers of overall and central obesity.

METHODS

We conducted a cross-sectional analysis of data from the Brazilian National Health Survey on over 35 500 current workers. Exposure to current night work was composed of three categories: daytime work (reference category), less than one night per week, and more than two nights per week. The body mass index and waist circumference were used as adiposity markers. Logistic and multinomial regression models were used, with adjustment for demographic characteristics, work conditions, self-related health, and health-related behaviors.

RESULTS

After complete adjustment, individuals who worked two or more nights a week had higher odds of overweight (odds ratio [OR]: 1.20, 95% CI: 1.04-1.38), obesity (OR: 1.38, 95% CI: 1.17-1.64) and increased waist circumference (OR: 1.27, 95% CI: 1.10-1.46) than daytime workers.

CONCLUSIONS

Night work was significantly associated with measures of adiposity. Changes in working conditions, such as controlling the numbers of nights worked per week or promoting workplaces with healthy meals and the opportunity to perform physical exercise at work, could be suggested.

Association between shift work and obesity in a large sample of Iranian steel industry workers

Obesity is associated with several chronic diseases, and previous research suggests that shift work could be associated with the risk of overweight and obesity, but the results remain inconclusive. Furthermore, only a few studies report related findings for industrial workforce with high job-related stress. The aim of this cross-sectional study was to see if such association exists in a large sample of 3063 industrial workers in a developing country. The sample was selected among 16,000 steel company workers through multistage cluster sampling. We took anthropometric measurements, including body mass index (BMI), waist circumference (WC), and waist-to-hip ratio (WHR). Information about potential confounders was collected with a self-administered questionnaire. The association between shift work and both general and abdominal obesity was established with multinomial and binary logistic regression analysis. The study sample consisted of 1683 (54.9 %) rotational shift workers and 1380 (45.1 %) day workers. Shift work was significantly associated with higher risk of overweight after adjusting for the impacts of potential confounders (OR=1.2; 95 % CI:1.04-1.4) but not with abdominal obesity. This study established that shift work was an independent risk factor for overweight in industrial shift workers. Modification of working schedules is recommended, particularly for prolonged, continuous shift work.

Urinary bisphenol A and incidence of metabolic syndrome among Chinese men: a prospective cohort study from 2013 to 2017

OBJECTIVES

Experimental studies suggested that bisphenol A (BPA) exposure increased the risk of metabolic syndrome (MetS) through the mechanism of insulin resistance. All previous epidemiological studies of BPA and MetS were cross-sectional studies, and their findings were mixed. This study aims to provide further evidence on the association between urinary BPA and risk of MetS using a prospective cohort study in China.

METHODS

The study population was from the Shenzhen Night shift workers' cohort. A total of 1227 male workers were recruited from the baseline survey in 2013 and then followed until 2017. Modified Adult Treatment Panel III criteria were used to identify the cases of MetS. Urinary BPA concentration was assessed using high-performance liquid chromatography-tandem mass spectrometry, and it was categorised into three subgroups by tertiles to obtain the adjusted HR (aHR) and 95% CI using Cox proportional hazard model.

RESULTS

During 4 years of follow-up, 200 subjects developed MetS. Compared with the lowest urinary BPA subgroup, a weakly increased risk of MetS was suggested among those with the middle (aHR=1.19, 95% CI 0.87 to 1.63) and high level of urinary BPA (aHR=1.16, 95% CI 0.84 to 1.59); however, the significant association with MetS was restricted primarily to the smokers, showing a positive gradient with urinary BPA (middle level: aHR=2.40, 95% CI 1.13 to 5.08; high level: aHR=2.87, 95% CI 1.38 to 5.98; p trend= 0.010).

CONCLUSION

This prospective cohort study provided further evidence that exposure to BPA may increase the risk of MetS, and this association was further positively modified by cigarette smoking.

Circadian rhythm disruption is associated with an increased risk of sarcopenia: a nationwide population-based study in Korea

Reduced sleep quality is associated with an increased risk of sarcopenia. However, the potential effects of disturbing the regular circadian rhythm, as occurs with shift work, on the risk of sarcopenia have not been established. Data from 9105 workers from the 2008–2011 Korean National Health and Nutrition Examination Survey were analyzed. Sarcopenia, measured by dual-energy X-ray absorptiometry, was defined as one standard deviation below the mean of the appendicular skeletal muscle/body mass index value of a young reference group. Compared to the group that had never experienced shift work, the odds ratio (OR) for sarcopenia with a 95% confidence interval (95% CI) for the shift work group was 1.7 (1.5–1.9); the association remained even after adjusting for confounding variables, including age, sex, total fat mass, insulin resistance profile, smoking, alcohol intake, diet, and physical activity. The results of the subgroup analysis indicated that the highest risk of sarcopenia was among workers engaging in shift work with an irregular schedule (OR 1.8, 95% CI 1.3–2.4). Disruption of circadian rhythm by shift work was associated with increased risk of sarcopenia. Intervention strategies are needed to prevent sarcopenia in shift workers.

The circadian clock and liver function in health and disease

Each day, all organisms are subjected to changes in light intensity because of the Earth's rotation around its own axis. To anticipate this geo-physical variability, and to appropriately respond biochemically, most species, including mammals, have evolved an approximate 24-hour endogenous timing mechanism known as the circadian clock (CC). The 'clock' is self-sustained, cell autonomous and present in every cell type. At the core of the clock resides the CC-oscillator, an exquisitely crafted transcriptional-translational feedback system. Remarkably, components of the CC-oscillator not only maintain daily rhythmicity of their own synthesis, but also generate temporal variability in the expression levels of numerous target genes through transcriptional, post-transcriptional and post-translational mechanisms, thus, ensuring proper chronological coordination in the functioning of cells, tissues and organs, including the liver. Indeed, a variety of physiologically critical hepatic functions and cellular processes are CC-controlled. Thus, it is not surprising that modern lifestyle factors (e.g. travel and jet lag, night and rotating shift work), which force 'circadian misalignment', have emerged as major contributors to global health problems including obesity, non-alcoholic fatty liver disease and steatohepatitis. Herein, we provide an overview of the CC-dependent pathways which play critical roles in mediating several hepatic functions under physiological conditions, and whose deregulation is implicated in chronic liver diseases including non-alcoholic steatohepatitis and alcohol-related liver disease.

Night shift work and abnormal liver function: is non-alcohol fatty liver a necessary mediator?

OBJECTIVES

Accumulated evidence implies that night shift work may trigger liver dysfunction. Non-alcoholic fatty liver (NAFL) is suggested to be a necessary mediator in this process. This study aimed to examine the relationship between night shift work and elevated level of alanine transaminase (e-ALT) of workers and investigate the potential mediation effect of NAFL.

METHODS

This study included all male workers from the baseline survey of a cohort of night shift workers. Information on demographics, lifestyle and lifetime working schedule was collected by face-to-face interview. Liver sonography was used to identify NAFL cases. Serum ALT level was detected by an automatic biochemical analyser. e-ALT was defined as ALT >40 U/L. Logistic regression models were used to evaluate ORs, and mediation analysis was employed to examine the mediation effect.

RESULTS

Among 4740 male workers, 39.5% were night shift workers. Night shift workers had an increased risk of e-ALT (OR, 1.19, 95% CI 1.00 to 1.42). With the increase in night shift years, the OR of e-ALT increased from 1.03 (95% CI 0.77 to 1.36) to 1.60 (95% CI 1.08 to 2.39) among workers without NAFL. A similar trend was not found among workers with NAFL. In addition, no significant mediation effect of NAFL in the association between night shift work and e-ALT was found.

CONCLUSIONS

Night shift work is positively associated with abnormal liver function, in particular among workers without NAFL. Shift work involving circadian disruption is likely to exert a direct effect on liver dysfunction rather than rely on the mediation effect of NAFL.