Association between shift work and obesity according to body fat percentage in Korean wage workers: data from the fourth and the fifth Korea National Health and Nutrition Examination Survey (KNHANES 2008-2011)

The effect of shift work on body mass index: A systematic review and meta-analysis of observational studies

CONTEXT

Shift work involves working outside the standard working hours of 9 am to 5 pm Monday to Friday and may include working evening, night, weekend, or rotating shift patterns. Since shift workers sleep less and their circadian rhythms are disrupted, they are reported to have higher body weight than day workers.

OBJECTIVE

This meta-analysis aims to determine whether shift workers (SW) are more prone to higher body mass index (BMI) than their day workers (DW) counterparts. It also addresses the question of whether the duration of shift work exposure, sex, or occupational type affect BMI value.

METHODS

Four databases that is PubMed, EBSCO Host, Scopus, and Web of Science were searched for reports published up to October 2023.

RESULTS

Sixty-three studies involving a total of 693 449 participants met our inclusion criteria. Meta-analyses showed a significant effect of shift work on BMI value (standard mean difference; SMD: 0.10 kg/m2 [95% confidence interval; 95% CI: 0.07; 0.13; p < .001]) as compared with non-shift counterparts. Subgroup analysis revealed that shift work significantly increased BMI for studies where male working on this job schedule (SMD: 0.10 kg/m2 [95% CI: 0.04; 0.17; p = .0018]) for studies where shift workers worked ≥13 years (calculated as the median of shift work experience; SMD: 0.14 kg/m2 [95% CI: 0.10; 0.18; p < .001]) as well as for studies where industrial (SMD: 0.12 kg/m2 [95% CI: 0.05; 0.19; p = .0012]) and other type of occupations were dominated (0.12 kg/m2 [95% CI: 0.07; 0.16; p < .001]).

CONCLUSIONS

We found that in general working on a shift schedule increases BMI as compared with day workers, especially in case of male employed in this job schedule, for shift workers working for long periods of time (≥13 years), and for shift workers employed in industry and other type of occupations(e.g., airline workers, firefighters, police officers, blue collar, security personnel, bus drivers, garbage collectors, railway workers, postal, oil and gas workers).

Characteristics Associated with Bone Loss after Spinal Cord Injury: Implications for Hip Region Vulnerability

BACKGRUOUND

In individuals with spinal cord injury (SCI), bone loss progresses rapidly to the area below the level of injury, leading to an increased risk of fracture. However, there are limited data regarding SCI-relevant characteristics for bone loss and the degree of bone loss in individuals with SCI compared with that in non-SCI community-dwelling adults.

METHODS

Data from men with SCI who underwent dual-energy X-ray absorptiometry at the National Rehabilitation Center (2008 to 2020) between 12 and 36 months after injury were collected and analyzed. Community-dwelling men were matched 1:1 for age, height, and weight as the control group, using data from the Korea National Health and Nutrition Examination Survey (KNHANES, 2008 to 2011).

RESULTS

A comparison of the SCI and the matched control group revealed significantly lower hip region T-scores in the SCI group, whereas the lumbar spine T-score did not differ between groups. Among the 113 men with SCI, the paraplegia group exhibited significantly higher Z-scores of the hip region than the tetraplegia group. Participants with motor-incomplete SCI showed relatively preserved Z-scores of the hip region compared to those of the lumbar region. Moreover, in participants with SCI, the percentage of skeletal muscle displayed a moderate positive correlation with femoral neck Z-scores.

CONCLUSION

Men with SCI exhibited significantly lower bone mineral density of the hip region than community-dwelling men. Paraplegia rather than tetraplegia, and motor incompleteness rather than motor completeness were protective factors in the hip region. Caution for loss of skeletal muscle mass or increased adiposity is also required.

Prediction of risk of coronary artery disease based on the Framingham risk score in association with shift work among nurses

Objectives. This study aimed to determine the prediction of risk of coronary artery disease (CAD) based on the Framingham risk score (FRS) in association with shift work among nurses.Methods. This cross-sectional and descriptive-analytic study was conducted with nurses working in three hospitals located in Abadan, southwest Iran. The sample size was 120 participants, divided into 60 shift workers and 60 day workers (non-shift workers). Demographic data and medical and occupational history were collected through a checklist and interviews. CAD risk assessment tools used to estimate the 10-year cardiovascular disease (CVD) risk included the FRS. Data were analysed by Mann-Whitney U test, χ² test and one-way analysis of variance (ANOVA) using SPSS version 22.0.Results. There were statistically significant differences between blood pressure (BP), total cholesterol (TC), body mass index (BMI) and shift work (p ≤ 0.001). There was a statistically significant difference between prevalence of CAD risk and shift work based on the FRS (p = 0.04).Conclusion. The study findings showed that shift work is a risk factor for CAD disturbances. Therefore, particular follow-up of shift workers should be recommended for screening and preventing CAD.

The Effect of Shiftwork on Body Composition: A Comparative Cross-sectional Study Among Health Care Workers

OBJECTIVE

This study compared the body composition parameters between shiftworkers and nonshiftworkers in a hospital setting in Sri Lanka.

METHODS

A comparative cross-sectional study was carried out among a sample of 78 health care workers, recruited by a stratified random sampling technique. Subjects underwent anthropometric and bioimpedentiometric analysis for body composition parameters.

RESULTS

The mean (SD) body fat percentage (BF%) of shiftworking women (40.8 [SD, 6.8%]) was significantly higher than day-working women (36.7% [SD, 5.9%]) ( P < 0.05). Mean BF% between day and shift groups did not significantly differ (33.0% [SD, 6.9%] vs 32.4% [SD, 10.7%]). Body mass index and waist circumference were significantly higher among shiftworking women ( P < 0.05), whereas male workers showed the opposite trend.

CONCLUSION

Prolonged exposure to shiftwork was associated with a higher BF%. Therefore, interventions for shiftworkers must be addressed, focusing on improving body composition.

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.

Shift Work and Obesity Risk-Are There Sex Differences?

PURPOSE OF REVIEW

Shift work is prevalent among the working population and is linked to an array of adverse health outcomes. This review summarizes current evidence on the relation between shift work and risk of obesity, with a particular emphasis on potential sex differences.

RECENT FINDINGS

Observational data strongly point towards an association between shift work and heightened risk of prevalent and incident obesity, and particularly abdominal obesity. Circadian misalignment and unhealthy lifestyle behaviors are the primary culprits mediating such association. As it pertains to sex differences in the impact of shift work on obesity, few studies have examined this aspect, and findings are conflicting. Shift work is an important risk factor for obesity, with likely multiple biological and behavioral mediators. However, whether there is a sex-dependent vulnerability to the obesogenic effects of shift work is unclear. This area presents opportunities for future research.

Sox2 Ablation in the Suprachiasmatic Nucleus Perturbs Anxiety- and Depressive-like Behaviors

Mood disorders negatively impact the lives of hundreds of millions of individuals worldwide every year, yet the precise molecular mechanisms by which they manifest remain elusive. Circadian dysregulation is one avenue by which mood disorders are thought to arise. SOX2 is a transcription factor that is highly expressed in the murine suprachiasmatic nucleus (SCN), the circadian master clock, and has been recently found to be an important regulator of Per2, a core component of the molecular clock. Genetic ablation of the Sox2 gene in GABAergic neurons selectively impacts SCN neurons, as they are one of very few, if not the only, GABAergic populations that express Sox2. Here, we show that GABAergic-restricted ablation of Sox2 results in anxio-depressive-like phenotypes in mice as observed in the elevated plus maze, forced swim test, tail suspension test, and sucrose preference test. We further observe a reduction in basal and/or forced swim-induced c-Fos expression, a marker of neuronal activation, in the nucleus incertus, arcuate nucleus, and dentate gyrus of Sox2 conditional knockout (cKO) mice. Given the restricted disruption of SOX2 expression in the SCN of Sox2 cKO mice, we propose that their mood-associated phenotypes are the consequence of a dysregulated central clock that is unable to communicate appropriately timed signals to other brain nuclei that regulate affective behaviors.

Sleep quality does not mediate the negative effects of chronodisruption on body composition and metabolic syndrome in healthcare workers in Ecuador

BACKGROUND AND AIMS

The objective of the present work was to determine to what extent sleep quality may mediate the association between chronodisruption (CD) and metabolic syndrome (MS), and between CD and body composition (BC).

METHODOLOGY

Cross-sectional study which included 300 adult health workers, 150 of whom were night shift workers and thereby exposed to CD. Diagnosis of MS was made based on Adult Treatment Panel III criteria. Sleep quality was measured using the Pittsburgh Sleep Quality Index. Body mass index (BMI), fat mass percentage, and visceral fat percentage were measured as indicators of body composition (BC). Data were analyzed using logistic, linear regression and structural equation models.

RESULTS

The odds of health workers exposed to CD to suffer MS was 22.13 (IC₉₅ 8.68-66.07) when the model was adjusted for age, gender, physical activity and energy consumption. CD was also significantly associated with an increase in fat mass and visceral fat percentages, but not to BMI. Surprisingly, there was not enough evidence supporting the hypothesis that sleep quality contributes to the association between CD and MS or between CD and BC.

CONCLUSIONS

Sleep quality does not mediate the negative effects of CD on MS nor on BC.

Circadian dysynchrony among nurses performing shift work at a tertiary care teaching hospital: a preliminary study

BACKGROUND

Circadian rhythm is intracellular molecular mechanisms, influenced by environmental factors such as light, noise, mealtime, and sleep pattern. Shift work affects the sleep pattern, mealtime and psychological aspects of workers. This study aims to compare the effect of shift work on circadian dysynchrony among nurses in two different groups based on the duration of shift work.

MATERIAL AND METHOD

It was a cross-sectional, preliminary study done at a tertiary care teaching hospital in North India. The study enrolled 170 nurses (aged <35 years) performing shift duties for last 3 years (group-1) and 1 year (group-2) respectively in a 1:1 ratio. Tools used to collect data were case reporting form (demographic and clinical variables, anthropometric measures), Hamilton Anxiety Rating Scale, and Pittsburg Sleep Quality Index.

RESULTS

Mean age of participants was 27.39±2.89 vs. 26.14±2.45 in group 1 and 2. We found significant positive correlation of duration of shift work with diastolic blood pressure (DBP) (P=0.000), systolic blood pressure (SBP) (P=0.001), body fat % (P=0.019), weight (P=0.034), hip circumference (HC) (P=0.000) and also significant difference between means of DBP (P=0.001) and HC (P=0.003) in both groups. Whereas bad sleep quality was found in 79% and 66% of participants in group 1 and 2 respectively, the prevalence of moderate to severe anxiety in groups 1 and 2 was 60% and 37% respectively.

CONCLUSION

Long duration of shift work increases the risk of developing cardiometabolic risk factors as a consequence of circadian dysynchrony and varies with the duration of shift work.

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.

Application of multiple-group latent growth model to determine the effect of shift work on body mass index among petrochemical industries staff

Background: Shift work can be defined as work activity scheduled in which employees work outside standard daytime hours. Some reports have shown that shift work is associated with several health problems. The main objective of this research was to explore the effect of shift work on body mass index (BMI) over time among Iranian petroleum industry staff.

Methods: This longitudinal study sample was consisted of 3,686 (1,872 day workers and 1,814 shift workers) petrochemical industries staff in Mahshahr, southwest of Iran, from 2012 to 2015. The weight and height of these staff were measured using standard techniques and equipment. Multiple-group latent growth curve modeling was used to determine the effect of shift working on BMI trajectories over this period of time via Mplus software, version 6.0.

Results: The mean (±SD) age of the shift workers and day workers were 38.96 (±8.36) and 43.33 (±8.35) years, respectively. Findings from the modeling approach showed that the slope of BMI in shift workers on average was 0.14 kg/m2 greater than the day workers in years under study (p<0.001).

Conclusion: The findings of the current study suggest that shift work can be considered as a potential risk indicator for higher weight gain in petrochemical staff. Hence, health policy-makers should organize health screening programs and periodical checkups to find high-risk staff and control unhealthy lifestyle factors in these industries.

Healthy Diet and Reduction of Chronic Disease Risks of Night Shift Workers

BACKGROUND

The large increase in epidemiological studies on night shift work is due to the important effects of night shift work on workers' health and psychophysical wellbeing. The short-term effects-insomnia, difficulties in managing work and private life, lower work performance, and more work and extra-work accidents-are easily studied. However, there are several long-term effects that are difficult to study because of the need for detailed exposure assessment and the long latency periods of these diseases.

OBJECTIVE

The aim was to collect epidemiologic evidence of diseases in night shift workers, describing their biological pathways and a set of dietary guidelines.

METHODS

This is a review on diet and health effects in night shift workers.

RESULTS

Significant increases in the rate ratios and hazard ratios of different diseases were associated with modified eating behaviours and poor eating habits among night shift workers. Night shift work is a risk factor for disruption of the circadian rhythms and for some genetic deregulation because it produces the inversion of the sleep/wake cycle and modifies the alternation between activity and rest.

CONCLUSION

A healthy diet and improved dietary practices, together with other factors, can reduce shift workers' chronic disease risk. The literature showed the importance of eating behaviour in order to prevent diseases in these workers; therefore, educational programmes are necessary to encourage several important lifestyle changes. The target of our future research will be the role of food components in some dietetic habits for the prevention of disease in night shift workers.

Sex differences in the circadian misalignment effects on energy regulation

Shift work causes circadian misalignment and is a risk factor for obesity. While some characteristics of the human circadian system and energy metabolism differ between males and females, little is known about whether sex modulates circadian misalignment effects on energy homeostasis. Here we show-using a randomized cross-over design with two 8-d laboratory protocols in 14 young healthy adults (6 females)-that circadian misalignment has sex-specific influences on energy homeostasis independent of behavioral/environmental factors. First, circadian misalignment affected 24-h average levels of the satiety hormone leptin sex-dependently (P < 0.0001), with a ∼7% decrease in females (P < 0.05) and an ∼11% increase in males (P < 0.0001). Consistently, circadian misalignment also increased the hunger hormone ghrelin by ∼8% during wake periods in females (P < 0.05) without significant effect in males. Females reported reduced fullness, consistent with their appetite hormone changes. However, males reported a rise in cravings for energy-dense and savory foods not consistent with their homeostatic hormonal changes, suggesting involvement of hedonic appetite pathways in males. Moreover, there were significant sex-dependent effects of circadian misalignment on respiratory quotient (P < 0.01), with significantly reduced values (P < 0.01) in females when misaligned, and again no significant effects in males, without sex-dependent effects on energy expenditure. Changes in sleep, thermoregulation, behavioral activity, lipids, and catecholamine levels were also assessed. These findings demonstrate that sex modulates the effects of circadian misalignment on energy metabolism, indicating possible sex-specific mechanisms and countermeasures for obesity in male and female shift workers.

Effect of night shift work on the control of hypertension and diabetes in workers taking medication

Background

Night shift work induces physiological and psychological stress by altering sleep and biological rhythms and is associated with hypertension, diabetes, obesity, and cardiovascular diseases. Few studies have been conducted on the control of hypertension and diabetes. This study aimed to examine the effect of night shift work on the control rate of hypertension and diabetes.

Methods

Subjects comprised workers aged 20–65 years who underwent specific health examination at a single facility in seven different affiliated examination centers from 1 January to 31 December 2016. Workers were categorised into day workers and night shift workers. Demographic and medical history were taken, and physical examination was done. Blood pressure (BP) and fasting glucose were measured. The control rate of each disease was evaluated based on treatment goals presented in the treatment guidelines of the Korean Society of Hypertension and the Korean Diabetes Association (systolic BP < 140 mmHg and diastolic BP < 90 mmHg; fasting glucose ≤ 130 mg/dL).

Results

Among 631,418 subjects, 11.2% (70,450) were night shift workers. Of whom 6.1% (4,319) were taking antihypertensive medication and 2.5% (1,775) were taking diabetes medication. Among patients taking antihypertensive medications, the proportion of those whose BP was controlled to suit treatment goals was 81.7% (26,635) of day workers and 77.4% (3,343) of night shift workers, which was significantly different (p < 0.001). Among patients taking diabetes medications, the proportion of those whose blood glucose was controlled to suit treatment goals was 37.4% (4,489) of day workers and 36.5% (647) of night shift workers, but the difference was not significant. The control rates for patients taking antihypertensive medications (odds ratio [OR]: 0.74, 95% confidence interval [CI]: 0.68–0.80) were lower among night shift workers than day workers with adjustment for age, sex, smoking history, alcohol consumption, exercise, and obesity. However, there were no differences in control rates for patients taking diabetes medications (OR: 0.99, 95% CI: 0.87–1.10) between day workers and night shift workers.

Conclusions

Night shift work can have an effect on the uncontrolled BP in workers taking antihypertensive medications. Therefore, additional efforts for disease control are necessary for night shift workers with hypertension.

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.

Is shift work associated with a higher risk of overweight or obesity? A systematic review of observational studies with meta-analysis

Background

An increasing number of original studies suggest that exposure to shift work could be associated with the risk of overweight and obesity, but the results remain conflicted and inconclusive. This study aimed to quantitatively synthesize available epidemiological evidence on the association between shift work and the risk of overweight and obesity by a meta-analysis.

Methods

The authors searched PubMed, Embase and the reference lists of all included studies up to April 2017, with a verification search in December 2017. Inclusion criteria were original studies that reported odds ratios, relative risks or hazard ratios (ORs, RRs or HRs, respectively) of at least one outcome of overweight or obesity. Summary risk estimates were calculated by random-effect models.

Results

Twenty-six studies (7 cohort studies, 18 cross-sectional studies and 1 case-control study) involving 311 334 participants were identified. Among these studies, the cut-off points of overweight and obesity varied greatly, so the heterogeneity was substantial; however, the results were stable. Shift work was found to be positively associated with the risk of overweight [RR: 1.25; 95% confidence interval (95% CI): 1.08-1.44] and obesity (RR: 1.17; 95% CI: 1.12-1.22).

Conclusions

Individuals involved in shift work are more likely to become overweight or obese. Appropriate preventive interventions in the organization of shift schedules according to ergonomic criteria would allow shift workers to avoid potential health impairment.

The Impact of Obesity in the Workplace: a Review of Contributing Factors, Consequences and Potential Solutions

This narrative review summarized findings from previous reviews and the most recently published studies, regarding the following: (1) the association between two occupational risk factors-shift work and sedentary work-and obesity, (2) the effects of obesity on workplace productivity and (3) the effectiveness of workplace interventions aimed at preventing or reducing obesity. Despite some inconsistencies in findings, there is convincing evidence that shift work increases the risk of obesity, while most studies did not show a significant association between sedentary work and obesity. Overweight and obesity were found to be associated with absenteeism, disability pension and overall work impairment, whilst evidence of their relationship with presenteeism, unemployment and early retirement was not consistent. Due to the vast heterogeneity in the types of workplace-based interventions to prevent or treat obesity, no sound conclusions can as yet be drawn about their overall effectiveness and best practice recommendations for their implementation.