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

Impact of shift work on sleep and fatigue in Maritime pilots

This study examined how objective measures of sleep change across shift-cycles, and the impact of this on sleep quality and fatigue. Forty maritime pilots were recruited from Australian ports. Sleep wake-behaviour (timing and length), and self-reported sleep quality and fatigue, were assessed to determine any impact of roster status and 'on-call' status. On-roster pilots experienced reduced night time sleep duration compared to those off-roster (57 ± 8.8 min), while working on-call also diminished night time sleep duration (126 ± 11.3 min) and quality, compared to workers not on-call. Fatigue scores indicated that participants were not fully recovered prior to commencing rostered night shift, while sleep quality was significantly worse following sleep that occurred after a night shift, compared to after a day shift. These findings potentially support workplace negotiations to change future shift cycles, and to adopt monitoring systems that may mitigate the risk of fatigue-related accidents and chronic health outcomes. Practitioner summary: Long and irregular work hours of maritime pilotage can compromise worker performance and safety. This observational study found that on-roster pilots experience reduced sleep duration compared to those off-roster, while working on-call further diminishes sleep duration and quality. Future workload/fatigue monitoring systems may mitigate fatigue-related accidents and adverse chronic health outcomes. Abbreviations: ANOVA: analysis of variance; ANCOVA: analysis of covariance; BMI: body mass index; CVD: cardiovascular disease; h: hours; mins: minutes; SE: standard error of the mean; SD: standard deviation; SO: sleep opportunities; TST: total sleep time; WASO: wake after sleep onset.

Assessment of Cardiometabolic Health, Diet and Physical Activity in Helicopter Rescue Paramedics

Objective: Shift work is an established risk factor for weight gain, cardiovascular disease, Type II diabetes mellitus, and impaired health-related quality of life (HRQoL). Prolonged exposure to shift work is common in paramedics and other emergency medical service (EMS) providers. Sub-populations of EMS workers may have varying health outcomes when exposed to shift work, but the reasons for this have not been investigated. We sought to describe cardiometabolic health, dietary patterns, physical activity, and health-related quality of life (HRQoL) in a sample of experienced intensive care flight paramedics (ICFPs) working for a Helicopter Emergency Medical Service (HEMS).Methods: Fifteen paramedics (median age 45, IQR 42-48 years) were recruited to undertake a range of health assessments. These included a food frequency questionnaire to assess dietary patterns, sampling of biomarkers to determine cardiometabolic health risk, maximal aerobic capacity assessment via treadmill running and assessment of HRQoL via the SF-36 survey. In an extension of the study protocol, ten of the fifteen participants wore a physical activity monitor for one year.Results: Median (IQR) weight was 79.9 (72.3-89.3) kg, body fat percentage 23.3 (21.9-26.5) %, body mass index (BMI) 25.1 (21.9-27.4) kg.m², and waist to height ratio 0.48 (0.45-0.54). Dietary analyses showed high discretionary food intake. Biomarkers of cardiometabolic health risk were all within normal range. HRQoL was 86.2/100 for physical health and 85.1/100 for mental health. V̇O_2max was 47.0 (43.0-54.6) mL.kg^-1.min^-1. The ten participants that wore activity monitors completed 11,235 (8334-15,380) steps per day and undertook 50 (12-98) minutes per day/350 (84-686) minutes per week of moderate to vigorous physical activity. The least amount of physical activity was conducted on day shifts.Conclusions: For ICFPs included in this study, HRQoL, cardiometabolic and physical activity outcomes are representative of good health. Although shift work influences the amount of physical activity, ICFPs exceeded minimum recommendations even when rostered to duty. Despite lengthy careers in EMS, ICFPs demonstrate an excellent health profile that is likely due to high physical activity levels and healthy BMI. This information may be useful in guiding health interventions in the wider EMS workforce.

Relationship between the night shift work and thyroid disorders: A systematic review and meta-analysis

OBJECTIVES

The night shift workers were reported to have health consequences, ranging from mild, as cluster headache, to severe, as heart attacks and hormonal irregularities. This study is aimed to perform a systematic review and meta-analyze of the association between the night shift work and the thyroid disorders.

METHODS

We comprehensively searched eight databases, including PubMed and Google Scholar for the relevant articles. This systematic review and meta-analysis were conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-analysis (PRISMA) statement.

RESULTS

We finally included six papers involving 4074 participants. Four papers were eligible for meta-analysis involving 1864 night shift workers and 2017 day shift workers. We against found that thyroid stimulating hormone (TSH) is significantly higher in the night shift group compared to the day shift group.

CONCLUSIONS

The higher TSH among the night shift workers is attributed to disruption of the circadian rhythm and sleep/wake cycle, with subsequent eating disorders. We proposed that more attention should be paid to the working pattern and the related health consequences.

Health Effects of Night and Irregular Shiftwork: A Longitudinal Cohort Study of US Workers

OBJECTIVES

Evidence suggests that shiftwork results in adverse occupational health outcomes. This paper contributes to the literature by estimating the separate health effects of night and irregular shiftwork on a longitudinal panel of US workers.

METHODS

Data from a 20-year panel of worker surveys from the 1979 National Longitudinal Survey of Youth were used to predict self-reported health limitations related to night and irregular shiftwork using a series of random effects logit models.

RESULTS

Separate and combined specifications of shiftwork as night and irregular effort significantly increase the odds of health limitations compared with working a regular daytime schedule, with more pronounced effects for irregular work (odds ratio [OR] = 1.09 to 1.52) over night shift (OR = 1.03 to 1.14).

CONCLUSIONS

The results suggest that both night and irregular shiftwork may have important negative implications on occupational health, with the deleterious effects particularly pronounced for irregularly scheduled work effort.

A nationally representative study of law enforcement shiftwork and health outcomes

The purpose of this study was to estimate the effect of past and current rotating shift assignments on U.S. law enforcement officers' health outcomes. In a nationally representative sample of 2,867 officers, with an oversample of female officers, we estimated models of sleep quality and fatigue, physical health outcomes, and psychological health outcomes. Further, we examined individual and agency-level factors associated with officers who reported currently working a rotating shift, to investigate what patterns there may be in shift assignments. A history of rotating shift assignments was positively associated with lower sleep quality, and with hypertension, diabetes, and high cholesterol, but not with gastrointestinal disorders, perceived stress, emotional well-being, or suicidality. The associations of shiftwork with health outcomes did not vary by gender. Demographic characteristics did not predict current rotating shift assignments, but a longer history of shiftwork and more working hours did predict a current shift assignment. Attention to mitigating shift system designs as well as the effect of cumulative years of working a rotating shift for the benefit of officer health outcomes is warranted.

Prevalence of Diagnosed Diabetes Among Employed US Adults by Demographic Characteristics and Occupation, 36 States, 2014 to 2018

OBJECTIVE

To assess the prevalence of diagnosed diabetes among employed US adults from 36 states by occupation group using data from 2014 to 2018 Behavioral Risk Factor Surveillance System.

METHODS

Prevalence of diabetes was calculated by 22 broad and 93 detailed occupation groups among a sample of 366,633 employed respondents. Wald chi-square values were used to determine the significance of associations between diabetes and occupation groups after adjusting for sex, age, and race/ethnicity.

RESULTS

The prevalence of diabetes was 6.4% among employed US adults. The three broad occupation groups with the highest adjusted prevalence of diabetes were protective services (8.9%), farming, fishing, and forestry (8.8%), and community and social services (8.4%).

CONCLUSIONS

Prevalence of diabetes differed by occupation. Work-related factors (eg, shift work, job stress) should be further examined in relation to risk of developing diabetes.

The role of circadian rhythm stability and amplitude in musculoskeletal disorder prevalence and work-family conflict

Aim

This study aimed to investigate the effect of circadian rhythm stability and amplitude on musculoskeletal disorder prevalence and work–family conflict among nurses.

Design

This cross‐sectional study was conducted on 386 nurses working in three hospitals, in Shahroud, Iran.

Method

The data were collected using the Circadian Rhythm Inventory, Nordic Musculoskeletal Disorders, and Carlson Work‐Family Conflict questionnaires.

Results

The highest prevalence of musculoskeletal disorders was reported in the lower back (68.4%), upper back (65.5%) and shoulders (53.6%), respectively. No significant relation was found between circadian rhythm stability and amplitude, and musculoskeletal disorders prevalence. The nurses who could not overcome drowsiness reported more Work Interference with Family (WIF), Family Interference with Work (FIW) (time‐based) and FIW (strain‐based) compared to the nurses who overcame drowsiness. In addition, the appropriate nurses for shift work experienced less WIF, FIW (behavioural‐based) and WIF (strain‐based) compared to the nurses who could not work overtime or at night.

Chronotype and cardio metabolic health in obesity: does nutrition matter?

The aim of the study was to investigate the association of chronotype categories with type 2 diabetes mellitus (T2DM) and cardiovascular diseases (CVD) in 172 middle-aged adults (71.5% females; 51.8 ± 15.7 years). Anthropometric parameters, lifestyle habits, adherence to the Mediterranean Diet (MD), sleep quality, chronotype and the presence of T2DM and CVD were studied. Chronotype was classified as morning in 58.1% of subjects, evening in 12.8% and intermediate in 28.1%. Subjects with evening chronotype followed an unhealthier lifestyle than other chronotypes; indeed, they significantly performed less regular activity and were more frequently smokers. Furthermore, they had significantly higher risk to have T2DM [Odds Ratio (OR)=3.36 95% confidence interval (CI) 1.14-35.42; p = 0.03] and CVD [Odds Ratio (OR)= 5.89 95% CI 1.14-30.60; p = 0.035](CI) 2.24-407.54); p = 0.01] compared to morning chronotype after adjustment for gender, body mass index (BMI), sleep quality and adherence to the MD. The confidence intervals were wide, indicating that the sample size was too small. Thus, these data need to be replicated in a larger sample size. In addition, nutritional assessment was limited since only PREDIMED questionnaire was carried out. However, the main strengths of this study included a random sample and a population-based approach, although the cross-sectional design cannot establish causality. Although study population was unbalanced per gender and smoking and age group representing only middle-aged people,we adjusted the statistical analysis for potential confounding factors. In conclusion, the evening chronotype has an increased risk to be associated to T2DM and CVD.

Astrocyte Clocks and Glucose Homeostasis

The endogenous timekeeping system evolved to anticipate the time of the day through the 24 hours cycle of the Earth's rotation. In mammals, the circadian clock governs rhythmic physiological and behavioral processes, including the daily oscillation in glucose metabolism, food intake, energy expenditure, and whole-body insulin sensitivity. The results from a series of studies have demonstrated that environmental or genetic alterations of the circadian cycle in humans and rodents are strongly associated with metabolic diseases such as obesity and type 2 diabetes. Emerging evidence suggests that astrocyte clocks have a crucial role in regulating molecular, physiological, and behavioral circadian rhythms such as glucose metabolism and insulin sensitivity. Given the concurrent high prevalence of type 2 diabetes and circadian disruption, understanding the mechanisms underlying glucose homeostasis regulation by the circadian clock and its dysregulation may improve glycemic control. In this review, we summarize the current knowledge on the tight interconnection between the timekeeping system, glucose homeostasis, and insulin sensitivity. We focus specifically on the involvement of astrocyte clocks, at the organism, cellular, and molecular levels, in the regulation of glucose metabolism.

Light at Night and Risk of Pancreatic Cancer in the NIH-AARP Diet and Health Study

Circadian disruption may play a role in carcinogenesis. Recent research suggests that light at night (LAN), a circadian disruptor, may be a risk factor for cancer. Moreover, LAN has been linked to obesity and diabetes, two risk factors for pancreatic ductal adenocarcinoma (PDAC). Here we examine the relationship between LAN and PDAC in an epidemiologic study of 464,371 participants from the NIH-AARP Diet and Health Study. LAN was estimated from satellite imagery at baseline (1996), and incident primary PDAC cases were ascertained from state cancer registries. Cox proportional hazards models were used to estimate HRs and two-sided 95% confidence intervals (CI) for the association between quintiles of LAN and PDAC in the overall population stratified by sex. Over up to 16.2 years of follow-up, a total of 2,502 incident PDAC were identified in the cohort. Higher estimated LAN exposure was associated with an elevated PDAC risk. Compared with those living in areas in the lowest LAN quintile, those in areas in the highest quintile had a 27% increase PDAC risk [HR (95% CI), 1.24 (1.03-1.49)], with similar risk for men [1.21 (0.96-1.53)] and women [1.28 (0.94-1.75)]. In addition, stronger associations were observed in normal and overweight groups compared with the obese group (P interaction = 0.03). Our results support the hypothesis that LAN and circadian disruption may be risk factors for PDAC. SIGNIFICANCE: Our study suggests that higher LAN is a risk factor for pancreatic cancer, contributing to the growing literature that demonstrates the potentially adverse health effects of light pollution.

The mediating role of lifestyle in the relationship between shift work, obesity and diabetes

PURPOSE

Shift work has been related to obesity and diabetes, but the potential mediating role of lifestyle is yet unknown. Our aim was to investigate this mediating role of physical activity, diet, smoking, and sleep quality in the relationships between shift work, and obesity and diabetes.

METHODS

In this cross-sectional study, 3188 shift workers and 6395 non-shift workers participated between 2013 and 2018 in periodical occupational health checks. Weight and height were objectively measured to calculate obesity (BMI ≥ 30 kg/m²). Diabetes status, physical activity, diet, smoking, and sleep quality were assessed using standardized questionnaires. Structural equation models adjusted for relevant confounders were used to analyze the mediating role of lifestyle in the relationships between shift work, and obesity and diabetes.

RESULTS

Shift workers were more often obese (OR: 1.37, 95% CI 1.16-1.61) and reported more often to have diabetes (OR:1.35, 95% CI 1.003-1.11) than non-shift workers. Shift workers had lower physical activity levels, ate fruit and vegetables less often, smoked more often, and had poorer sleep quality (p < 0.05). Mediation analysis revealed that shift workers had a higher odds of obesity (OR: 1.07, 95% CI 1.01-1.15) and diabetes (OR: 1.13, 95% CI 1.02-1.27) mediated by poorer sleep quality. Lower physical activity levels (OR: 1.11, 95% CI 1.05-1.19) and lower intake of fruit and vegetables (OR: 1.04, 95% CI 1.01-1.15) were also mediators in the relationship between shift work and obesity, but not in the relationship between shift work and diabetes (p ≥ 0.05).

CONCLUSION

These results imply that interventions targeting diet, physical activity and in particular sleep problems specifically developed for shift workers could potentially reduce the adverse health effects of shift work.

Pregnancy-induced changes in β-cell function: what are the key players?

Maternal metabolic adaptations during pregnancy ensure appropriate nutrient supply to the developing fetus. This is facilitated by reductions in maternal peripheral insulin sensitivity, which enables glucose to be available in the maternal circulation for transfer to the fetus for growth. To balance this process and avoid excessive hyperglycaemia and glucose intolerance in the mother during pregnancy, maternal pancreatic β-cells undergo remarkable changes in their function including increasing their proliferation and glucose-stimulated insulin secretion. In this review we examine how placental and maternal hormones work cooperatively to activate several signalling pathways, transcription factors and epigenetic regulators to drive adaptations in β-cell function during pregnancy. We also explore how adverse maternal environmental conditions, including malnutrition, obesity, circadian rhythm disruption and environmental pollutants, may impact the endocrine and molecular mechanisms controlling β-cell adaptations during pregnancy. The available data from human and experimental animal studies highlight the need to better understand how maternal β-cells integrate the various environmental, metabolic and endocrine cues and thereby determine appropriate β-cell adaptation during gestation. In doing so, these studies may identify targetable pathways that could be used to prevent not only the development of pregnancy complications like gestational diabetes that impact maternal and fetal wellbeing, but also more generally the pathogenesis of other metabolic conditions like type 2 diabetes.

Acute metabolic effects of melatonin-A randomized crossover study in healthy young men

Melatonin regulates circadian rhythm, but may also have effects on glucose homeostasis. A common G-allele in the MTNR1B locus has been associated with an increased risk of type 2 diabetes (T2DM). We aimed to examine acute effects of high doses of melatonin on glucose metabolism with attention to MTNR1B genotype. Twenty men were examined in a double-blinded, randomized crossover study on two nonconsecutive days with four doses of 10 mg oral melatonin or placebo. Insulin sensitivity and insulin secretion were assessed by an intravenous glucose tolerance test (IVGTT) and a hyperinsulinaemic-euglycaemic clamp (HEC). Blood samples were drawn to determine the metabolic profile and MTNR1B rs10830963 genotype. Indirect calorimetry and blood pressure measurements were also performed. Insulin sensitivity index was significantly reduced on the melatonin day (P = .028) in the whole group and in homozygous carriers of the rs10830963 C-allele (P = .041). Glucose during the IVGTT was unaffected, but there was a tendency towards lower insulin and C-peptide levels in the first minutes after glucose administration in G-allele carriers. Systolic blood pressure decreased and lipid oxidation increased significantly on the melatonin day in rs10830963 G-allele carriers. Overall, our study reports that acute administration of melatonin in supra-physiological doses may have a negative impact on insulin sensitivity. Clinical trial registration number (clinicaltrial.gov): NCT03204877.

Effect of Sleep Disturbances on Blood Pressure

This review summarizes recent literature addressing the association of short sleep duration, shift work, and obstructive sleep apnea with hypertension risk, blood pressure (BP) levels, and 24-hour ambulatory BP. Observational studies demonstrate that subjectively assessed short sleep increases hypertension risk, though conflicting results are observed in studies of objectively assessed short sleep. Intervention studies demonstrate that mild and severe sleep restriction are associated with higher BP. Rotating and night shift work are associated with hypertension as shift work may exacerbate the detrimental impact of short sleep on BP. Further, studies demonstrate that shift work may increase nighttime BP and reduce BP control in patients with hypertension. Finally, moderate to severe obstructive sleep apnea is associated with hypertension, particularly resistant hypertension. Obstructive sleep apnea is also associated with abnormal 24-hour ambulatory BP profiles, including higher daytime and nighttime BP, nondipping BP, and a higher morning surge. Continuous positive airway pressure treatment may lower BP and improve BP dipping. In conclusion, efforts should be made to educate patients and health care providers about the importance of identifying and treating sleep disturbances for hypertension prevention and management. Empirically supported sleep health interventions represent a critical next step to advance this research area and establish causality.

Dose-Response Relationship between Night Work and the Prevalence of Impaired Fasting Glucose: The Korean Worker's Special Health Examination for Night Workers Cohort

Many studies have been conducted regarding the association between night work and diabetes, but the association between impaired fasting glucose (IFG) and night work is still unclear. The aim of this study was to evaluate this association using the Special Health Examination (SHEW) for Korean night workers. Laboratory, questionnaire, and physical examination data were collected for 80,077 manual workers between 2014 and 2016 from Korea Medical Institute, and associations of the data with IFG were evaluated using a multivariate logistic regression model. The odds ratios for IFG among those who worked night shifts for 2~5 years, 5~12 years, and 12 years or over (ref: <2 years) after adjusting for abdominal obesity were 1.14 (0.90–1.45), 1.41 (1.10–1.81), and 1.75 (1.41–2.19), respectively. A dose–response relationship was identified between the duration of night work and the prevalence of IFG (p for trend <0.05). A dose relationship remained significant when a subgroup of non-obese participants was analyzed. We identified an association and a dose–response relationship between the number of years of night work and IFG. To prevent the development of diabetes in night workers, we suggest that they should be pre-emptively screened and treated from the stage of IFG.

Cross-species physiological interactions of endocrine disrupting chemicals with the circadian clock

Endocrine disrupting chemicals (EDCs) are endocrine-active chemical pollutants that disrupt reproductive, neuroendocrine, cardiovascular and metabolic health across species. The circadian clock is a transcriptional oscillator responsible for entraining 24-hour rhythms of physiology, behavior and metabolism. Extensive bidirectional cross talk exists between circadian and endocrine systems and circadian rhythmicity is present at all levels of endocrine control, from synthesis and release of hormones, to sensitivity of target tissues to hormone action. In mammals, a range of hormones directly alter clock gene expression and circadian physiology via nuclear receptor (NR) binding and subsequent genomic action, modulating physiological processes such as nutrient and energy metabolism, stress response, reproductive physiology and circadian behavioral rhythms. The potential for EDCs to perturb circadian clocks or circadian-driven physiology is not well characterized. For this reason, we explore evidence for parallel endocrine and circadian disruption following EDC exposure across species. In the reviewed studies, EDCs dysregulated core clock and circadian rhythm network gene expression in brain and peripheral organs, and altered circadian reproductive, behavioral and metabolic rhythms. Circadian impacts occurred in parallel to endocrine and metabolic alterations such as impaired fertility and dysregulated metabolic and energetic homeostasis. Further research is warranted to understand the nature of interaction between circadian and endocrine systems in mediating physiological effects of EDC exposure at environmental levels.

Shiftwork and Alcohol Consumption: A Systematic Review of the Literature

INTRODUCTION

Shiftwork can be a risk factor for a number of different somatic and psychological health conditions, especially sleep disorders. Shiftworkers sleep less than dayworkers, and 20-40% of them suffer from difficulties initiating and maintaining sleep, which result in reduced capacity for work and social life. A common coping strategy might be the use of alcohol, which presents a health and safety hazard as it further impairs sleep quality and exacerbates sleepiness in the workplace. This review aimed to assess the extent of such possible connections.

METHODS

We performed a systematic search of the scientific literature on shiftwork and alcohol consumption in PubMed, PsycInfo, and Cochrane Library. Only original studies comparing shiftworkers with non-shiftworkers were included. The recommendations of the Preferred Reporting Items of Systematic Reviews and Meta-Analyses were followed.

RESULTS

Fourteen articles are included in this review. Six studies report some kind of connection between shift- or nightwork and alcohol consumption, especially as a sleep aid. Conflicting or negative results are reported by 3 studies.

DISCUSSION

Shiftwork, especially working at night and in rotation shifts, is associated with binge drinking disorder in different professions. The reasons for pathological consumption of alcohol can be self-medication of sleep problems or coping with stress and psychosocial problems typical for shiftwork. Nurses aged over 50 years represent one important risk group. These results can be important for preventive programs against sleep disorders, including measures other than drinking alcohol as a sleep aid in the workplace of shiftworkers.

Feasibility of text message sleep assessment in African American and Latino patients with type 2 diabetes

STUDY OBJECTIVES

Text messaging (TM) may provide an inexpensive and convenient method for self-reported sleep assessment. This pilot study evaluated the feasibility of a TM sleep diary among a racial/ethnic minority population with uncontrolled type 2 diabetes.

METHODS

A convenience sample of 40 participants with uncontrolled type 2 diabetes was recruited. Participants wore an Actiwatch (Philips Spectrum Plus, Philips Respironics, Murrysville, Pennsylvania) for 7 consecutive days during both wake and sleep intervals and completed a daily TM sleep diary including 10 questions adapted from the Consensus Sleep Diary. The relationships between sleep measures from TMs and actigraphy were explored through Bland-Altman plots and correlations.

RESULTS

Of the 40 participants enrolled, 34 were African American and 6 were Latino. The mean age was 52.2 years (standard deviation = 8.2), and the mean hemoglobin A1c was 9.0% (standard deviation = 1.5). All but 1 participant attempted to complete the TM sleep diary. With a maximum of 70 TM replies possible, the median number of responses per participant was 66 (interquartile range = 59.5-69). Actigraphy and TM measures were related for total sleep time (median = 382 vs 393 min, respectively [r = .71; P < .01]), sleep onset latency (median = 31.4 vs 27.5 min [r = .61; P < .01]), time in bed (433.3 vs 489.3 min [r = .74; P < .01]), and sleep efficiency (77% vs 86% [r = .45; P = .005]). The measure of wake after sleep onset was higher from actigraphy than from TM, with a weak relationship between the 2 measures (median 47.9 vs 6.0 min [r = .31; P = .05]).

CONCLUSIONS

TM is a novel and feasible method for sleep assessment in racial/ethnic minority adults with uncontrolled type 2 diabetes.

Shiftwork and Light at Night Negatively Impact Molecular and Endocrine Timekeeping in the Female Reproductive Axis in Humans and Rodents

Shiftwork, including work that takes place at night (nightshift) and/or rotates between day and nightshifts, plays an important role in our society, but is associated with decreased health, including reproductive dysfunction. One key factor in shiftwork, exposure to light at night, has been identified as a likely contributor to the underlying health risks associated with shiftwork. Light at night disrupts the behavioral and molecular circadian timekeeping system, which is important for coordinated timing of physiological processes, causing mistimed hormone release and impaired physiological functions. This review focuses on the impact of shiftwork on reproductive function and pregnancy in women and laboratory rodents and potential underlying molecular mechanisms. We summarize the negative impact of shiftwork on female fertility and compare these findings to studies in rodent models of light shifts. Light-shift rodent models recapitulate several aspects of reproductive dysfunction found in shift workers, and their comparison with human studies can enable a deeper understanding of physiological and hormonal responses to light shifts and the underlying molecular mechanisms that may lead to reproductive disruption in human shift workers. The contributions of human and rodent studies are essential to identify the origins of impaired fertility in women employed in shiftwork.

Time for Novel Strategies to Mitigate Cardiometabolic Risk in Shift Workers

Circadian disruption induced by shift work is robustly associated with obesity, diabetes, and cardiovascular disease in humans. Less well-known are the mechanisms underlying these associations, and the effectiveness of strategies to reduce cardiometabolic risk in the shift work population. In this review, the different ways in which shift work can deteriorate cardiometabolic health, and how to use this information to reflect on various risk-mitigating strategies, is discussed. While individual strategies appear promising in animal studies, the multifactorial disease risk in shift workers likely requires a multidisciplinary approach. Therefore, the need for individually-tailored combined lifestyle interventions, that could be essential in reducing cardiometabolic disorders in the large population of shift workers in our 24/7 society, is argued.

Employment factors associated with daily time management in working people with type 2 diabetes

AIM

To determine the employment factors associated with daily time management in working people with type 2 diabetics.

METHODS

A questionnaire survey was administered to 277 working people with type 2 diabetes. It included a daily time management scale, and questions about age, gender, hemoglobin A1c levels, shift work, managerial position, and average working hours. Multiple regression analysis was used to assess the relationship between daily time management and each factor, adjusted for age, gender, and hemoglobin A1c.

RESULTS

Responses were obtained from 220 individuals. Daily time management was associated with managerial position (being a manager) and working hours. Shift work was associated with "adjustment of life rhythms" and managerial position was associated with "adjustment of work" and "goal setting and behaviors consistent with personal values". Hours of work were associated with "adjustment of life rhythms" and "time control".

CONCLUSION

When providing support on time management to working people with type 2 diabetes mellitus, any assessment should consider the availability of shift work, whether they are in a managerial position and working hours.

The importance of 24-h metabolism in obesity-related metabolic disorders: opportunities for timed interventions

Various metabolic processes in the body oscillate throughout the natural day, driven by a biological clock. Circadian rhythms are also influenced by time cues from the environment (light exposure) and behaviour (eating and exercise). Recent evidence from diurnal- and circadian-rhythm studies indicates rhythmicity in various circulating metabolites, insulin secretion and -sensitivity and energy expenditure in metabolically healthy adults. These rhythms have been shown to be disturbed in adults with obesity-related metabolic disturbances. Moreover, eating and being (in)active at a time that the body is not prepared for it, as in night-shift work, is related to poor metabolic outcomes. These findings indicate the relevance of 24-h metabolism in obesity-related metabolic alterations and have also led to novel strategies, such as timing of food intake and exercise, to reinforce the circadian rhythm and thereby improving metabolic health. This review aims to deepen the understanding of the influence of the circadian system on metabolic processes and obesity-related metabolic disturbances and to discuss novel time-based strategies that may be helpful in combating metabolic disease.

[Association between the practice of physical activity of different types and the use of insulin in adult and elderly diabetics in Brazil]

The scope of this paper was to verify the association between the practice of physical activity of different types and the use of insulin in adults and the elderly. This is a cross-sectional population-based study with data from the survey entitled Surveillance of risk factors and protection for chronic diseases by telephone (VIGITEL 2013). The sample consisted of individuals aged ≥18 years, living in the 27 Brazilian capitals and diagnosed with diabetes. The practice of physical activity in commuting, the home, leisure, work and the use of insulin were self-reported. Binary logistic regression was used in crude and adjusted analyses for sociodemographic factors. Of the 4,593 subjects with diabetes, insulin use was reported by 16.2% and 25.5% of adults and the elderly, respectively. The practice of physical activity in the home (OR: 0.61, 95%CI: 0.40; 0.94) and at work (OR: 0.38, 95%CI: 0.18; 0.78) were associated with the lowest use of insulin among the elderly. There was a tendency to reduce insulin use as the number of physically active domains increased among the elderly (p = 0.003). The conclusion drawn was that physical activity practiced alone or in a cumulative way in different domains was associated with lower insulin use among the elderly.

Cross-sectional and Prospective Associations of Rest-Activity Rhythms With Metabolic Markers and Type 2 Diabetes in Older Men

OBJECTIVE

Disruption of rest-activity rhythms is cross-sectionally associated with metabolic disorders, including type 2 diabetes, yet it remains unclear whether it predicts impaired glucose metabolism and homeostasis. The aim of this study is to examine the cross-sectional and prospective associations between rest-activity rhythm characteristics and glycemic measures in a cohort of older men.

RESEARCH DESIGN AND METHODS

Baseline rest-activity rhythms were derived from actigraphy with use of extended cosine model analysis. With subjects fasting, glucose, insulin, and HOMA of insulin resistance (HOMA-IR) were measured from blood at baseline and after ∼3.5 years. Type 2 diabetes was defined based on self-report, medication use, and fasting glucose.

RESULTS

In the cross-sectional analysis (n = 2,450), lower 24-h amplitude-to-mesor ratio (i.e., mean activity-adjusted rhythm amplitude) and reduced overall rhythmicity were associated with higher fasting insulin and HOMA-IR (all P _trend < 0.0001), indicating increased insulin resistance. The odds of baseline type 2 diabetes were significantly higher among those in the lowest quartile of amplitude (Q1) (odds ratio [OR]_{Q1 vs. Q4} 1.63 [95% CI 1.14, 2.30]) and late acrophase group (OR_{late vs. normal} 1.46 [95% CI 1.04, 2.04]). In the prospective analysis (n = 861), multiple rest-activity characteristics predicted a two- to threefold increase in type 2 diabetes risk, including a lower amplitude (OR_{Q1 vs. Q4} 3.81 [95% CI 1.45, 10.00]) and amplitude-to-mesor ratio (OR 2.79 [95% CI 1.10, 7.07]), reduced overall rhythmicity (OR 3.49 [95% CI 1.34, 9.10]), and a late acrophase (OR 2.44 [1.09, 5.47]).

CONCLUSIONS

Rest-activity rhythm characteristics are associated with impaired glycemic metabolism and homeostasis and higher risk of incident type 2 diabetes.

Sickness absenteeism, work performance, and healthcare use due to respiratory infections for shift and non-shift workers

This study aimed to compare sickness absenteeism, work performance, and healthcare use due to respiratory infections, as well as general sickness absenteeism and work performance between shift and non-shift workers. In this study, 589 shift and non-shift workers employed in hospitals were included. For 6 months, participants kept a daily record of their influenza-like illness/acute respiratory infection (ILI/ARI) symptoms using a diary application. After an episode of ILI/ARI symptoms ended, participants (n = 531) were questioned about their sickness absenteeism (occurrence and duration in hours), work performance (on a 10 point scale), and healthcare use during the ILI/ARI episode. At the end of the 6 months follow-up, participants (n = 498) were also asked about general sickness absenteeism and work performance in the past 4 weeks. Mixed-model and regression analyses were used to compare absenteeism, work performance, and healthcare use between shift and non-shift workers. No differences were found in sickness absenteeism [Odds Ratio (OR) = 1.00 (95%‒Confidence Interval (CI): 0.61‒1.64)] and work performance [Regression coefficient (B) = -0.19 (95%‒CI: -0.65‒0.26)] due to ILI/ARI between shift and non-shift workers. In addition, healthcare use due to ILI/ARI was similar between shift and non-shift workers. Furthermore, similar general sickness absenteeism rates and work performance levels were found between shift and non-shift workers. As this is the first study that examined the associations with shift work due to ILI/ARI, further studies are needed to confirm our findings.

Lifetime night work exposure and the risk of type 2 diabetes: results from the longitudinal study of adult health (ELSA-Brasil)

The aim of this research project was to test the effects of lifetime night work exposure on type 2 diabetes (T2DM) risk. The Brazilian Longitudinal Study of Adult Health (ELSA-Brasil) is a prospective cohort study of chronic conditions, such as diabetes and cardiovascular disease. The participants (N = 15105) were recruited (2008-2010) at five public universities and one research institute in six cities in Brazil. Participants from the first wave (2008-2010) were followed up for a mean of 3.8 years. Current analyses comprise 4671 women and 3965 men. Hazard ratios (HR) were estimated using Cox regression models. Crude T2DM incidence rates were 2.26 and 1.44 per 100 person-years, respectively, for women and men who reported ≥ 10 years' working nights. In women, ≥ 10 years of night work was associated with a higher risk of T2DM (HR 1.46 [95% CI: 1.03; 2.08]), after adjusting for age, education, work hours, and BMI. The additional adjustment for physical activity attenuated the association (HR 1.36 [95% CI: 0.94; 1.96]). In men, the results were not statistically significant (HR = 0.65 [95% CI: 0.40; 1.07]). The findings indicate the effects of lifetime night work on T2DM incidence seem to be greater among women than men.

Association between circadian disruption and diseases: A narrative review

Circadian rhythms play an important role in a wide range of human physiology and pathology. Individuals increasingly experience situations such as night-shift work schedules, likely leading to circadian disruption. Recent studies have also demonstrated that patients with other diseases often show symptoms of circadian disruption as manifested by the sleep-wake cycle and other biological rhythms. Circadian disruption often results in changes to the phase, period, and amplitude of the sleep-wake cycle, melatonin rhythm, and core body temperature. Several cardiometabolic, psychiatric, and neurodegenerative diseases are closely related to circadian disruption. Several interventions are also available, including phototherapy, exogenous melatonin, and exercise. The cumulative findings suggest that circadian disruption can increase risk for some cardiometabolic diseases. Circadian disruption also acts as a concomitant symptom of several psychiatric and neurodegenerative diseases. More attention should be paid to evaluating the impact of circadian disruption on these related diseases, as well as the benefits of the mitigation interventions for both circadian disruption and related diseases.

Eating Duration throughout a Rotating Shift Schedule: A Case Study

OBJECTIVE

The impact of the rotation between different shifts and free days within a short period of time on the food consumption is poorly addressed in the literature. Our objective was to characterize the eating duration (ED) over 10 d of clockwise rotating and to associate it with the intake of energy and macronutrients.

METHODS

Thirty male shift-workers from a mining company were evaluated over a complete rotation shift schedule of 10 consecutive days (2 d of morning shifts, 2 d of afternoon shifts, 24 h free-day, 2 d of night shifts, and three free days). ED was defined as the interval between the first meal after awaking and last meal before sleep onset. Sleep/wake periods and food intake were evaluated by actigraphy and 24 h recalls, respectively. Generalized models were used to analyze the variation in ED and its association with nutrient intake over the shift schedule.

RESULTS

ED periods showed significant variations throughout shift rotation and were associated with energy intake. The highest energy intake (3410 ± 235 kcal) and longest ED (20.7 ± 1.2 h) were found on Day 5, the day between afternoon and night shifts, and a part of Day 6 (night shift), i.e., in the longest period of wakefulness and the shortest sleep duration (4.7 ± 0.3 h) (p < 0.05 for all). The lowest energy intake (1284 ± 125 kcal) and shortest ED (4.96 ± 0.7 h) (p < 0.05) occurred after the last night shift (Day 7). The balance between the percentage of macronutrients did not differ statistically between the ED periods.

CONCLUSIONS

In general, longer periods of wakefulness showed greater energy intake, demonstrating the tendency of workers to eat around the clock during their shift. Even with the energy intake variation, the balance of macronutrients remained the same over the ED periods. Despite the need of confirmation in future studies, these results suggest that the management of ED period could be considered in the nutritional approach of shift workers.

Contrasting impact of rural, versus urban, living on glucose metabolism and blood pressure in Uganda

Background: The burden of cardiometabolic diseases, including cardiovascular diseases and diabetes, is increasing in sub-Saharan Africa and this has been linked to urbanisation. Helminths, through their immunomodulatory properties, may protect against these disorders. We hypothesised that the rural environment protects against cardiometabolic diseases and that helminths may influence rural-urban disparity of cardiometabolic disease risk. Methods: We compared metabolic parameters of individuals aged ≥10 years living in rural, high-helminth-transmission and urban, lower-helminth-transmission settings in Uganda. Cross-sectional surveys were conducted in rural Lake Victoria island fishing communities and in urban sub-wards in Entebbe municipality. Helminth infection and outcomes, including insulin resistance (computed using the homeostatic model assessment of insulin resistance [HOMA-IR]), fasting blood glucose, fasting blood lipids, blood pressure, body mass index (BMI), waist and hip circumference, were assessed. Results: We analysed 1,898 rural and 930 urban participants. Adjusting for BMI, exercise, smoking, alcohol intake, age and sex, urban residents had lower mean fasting glucose (adjusted mean difference [95%CI] 0.18 [-0.32, -0.05] p=0.01) and HOMA-IR (-0.26 [-0.40, -0.11] p=0.001) but higher blood pressure (systolic, 5.45 [3.75, 7.15] p<0.001; diastolic, 1.93 [0.57, 3.29] p=0.006). Current helminth infection did not explain the observed differences. Conclusions: In the Ugandan context, living in rural fishing communities may protect against hypertension but worsen glucose metabolism.

Association between sleep duration and impaired fasting glucose according to work type in non-regular workers: data from the first and second year (2016, 2017) of the 7th Korean National Health and Nutrition Examination (KNHANE) (a cross-sectional study)

Background

We aimed to find the relationship between sleep duration and impaired fasting glucose according to working type in non-regular workers using the 2016 and 2017 Korean National Health And Nutrition Examination (KNHANE, 7th revision).

Method

In the 1st and 2nd year (2016, 2017) of the 7th KNHANE, 16,277 people participated. Minors were excluded because this study was intended for individuals aged 19 years and older. As this study was based on wage workers, unemployment, self-employed workers, employers, unpaid family workers, and those who have insufficient answers such as unknown or no response were excluded. Regular workers were excluded because this study was intended for non-regular workers. Finally, a total of 2,168 people were included in the survey, except those who had been diagnosed with diabetes, had a fasting blood glucose level of 126 mg/dL or higher, or taking hypoglycemic agents or receiving insulin injections. To find the relationship between sleep duration and impaired fasting glucose according to work type in non-regular workers, multiple logistic regression analysis was performed by adjusting the general and occupational characteristics after stratification according to work type. All statistical analyses were performed using the SPSS software (version 26.0; SPSS Inc., Chicago, IL, USA).

Results

In the case of insufficient sleep duration in irregular female workers, the odds ratio (OR) of impaired fasting glucose was statistically insignificant, but in the case of insufficient sleep duration in irregular male workers who have shift work, the odds ratio (OR) of impaired fasting glucose was significantly higher than that of sufficient sleep duration (Model 1, OR: 3.05, 95% confidence interval [CI]: 1.18–7.90; Model 2, OR: 2.81, 95% CI: 1.08–7.29).

Conclusions

Our findings demonstrate that insufficient sleep duration was associated with an increase in fasting blood glucose levels in non-regular male workers working shifts. This means that non-regular workers are in desperate need for adequate sleep and health care. We hope that our study will help improve the health of non-regular workers and more systematic and prospective follow-up studies will be conducted to further improve the health of non-regular workers.

The moderating role of lifestyle, age, and years working in shifts in the relationship between shift work and being overweight

PURPOSE

This study aimed to investigate the relationship between the moderating role of lifestyle, age, and years working in shifts and, shift work and being overweight.

METHODS

Cross-sectional data were used of 2569 shift and 4848 non-shift production workers who participated between 2013 and 2018 in an occupational health check. Overweight (BMI ≥ 25 kg/m2) was calculated using measured weight and height; lifestyle was assessed by questionnaires. Multiple-adjusted logistic regression with interaction terms between shift work and potential moderators assessed multiplicative interaction; the relative excess risk due to interaction assessed additive interaction (synergism).

RESULTS

Shift work was significantly related to being overweight (OR 1.53, 95% CI 1.33 1.76). The strength of this association did not differ by level of sleep quality, fruit and vegetable intake, and physical activity (p ≥ 0.05). Additive and multiplicative interaction by smoking status was present (p < 0.01), with a stronger relationship between shift work and being overweight among non-smokers compared to smokers. Older age as well as more years of exposure to shift work were, independently from each other, related to a stronger relationship between shift work and being overweight (multiplicative interaction p < 0.05).

CONCLUSION

Shift work was to a similar extent related to being overweight among those with a healthy and unhealthy lifestyle. This does, however, not imply that shift workers can behave unhealthy without any harm. Based on the evident health benefits of a healthy lifestyle, it is still recommended to get sufficient quality of sleep and to meet the recommended level of daily physical activity and, fruit and vegetable intake.

Healthy Behaviors through Behavioral Design-Obesity Prevention

Evidence for behavior modification for improved health outcomes was evaluated for nutrition, physical activity (PA), and indoor environmental quality (IEQ). The databases searched included LISTA, PubMed, and Web of Science, with articles rated using an a priori baseline score of 70/100 to establish inclusion. The initial search produced 52,847 articles, 63 of which were included in the qualitative synthesis. Thirteen articles met inclusion for nutrition: cafeteria interventions, single interventions, and vending interventions. Seventeen articles on physical activity were included: stair use, walking, and adjustable desks. For IEQ, 33 articles met inclusion: circadian disruption, view and natural light, and artificial light. A narrative synthesis was used to find meaningful connections across interventions with evidence contributing to health improvements. Commonalities throughout the nutrition studies included choice architecture, increasing the availability of healthy food items, and point-of-purchase food labeling. Interventions that promoted PA included stair use, sit/stand furniture, workplace exercise facilities and walking. Exposure to natural light and views of natural elements were found to increase PA and improve sleep quality. Overexposure to artificial light may cause circadian disruption, suppressing melatonin and increasing risks of cancers. Overall, design that encourages healthy behaviors may lower risks associated with chronic disease.

Ticking for Metabolic Health: The Skeletal-Muscle Clocks

To be prepared for alternating metabolic demands occurring over the 24-hour day, the body preserves information on time in skeletal muscle, and in all cells, through a circadian-clock mechanism. Skeletal muscle can be considered the largest collection of peripheral clocks in the body, with a major contribution to whole-body energy metabolism. Comparison of circadian-clock gene expression between skeletal muscle of nocturnal rodents and diurnal humans reveals very common patterns based on rest/active cycles rather than light/dark cycles. Rodent studies in which the circadian clock is disrupted in skeletal muscle demonstrate impaired glucose handling and insulin resistance. Experimental circadian misalignment in humans modifies the skeletal-muscle clocks and leads to disturbed energy metabolism and insulin resistance. Preclinical studies have revealed that timing of exercise over the day can influence the beneficial effects of exercise on skeletal-muscle metabolism, and studies suggest similar applicability in humans. Current strategies to improve metabolic health (e.g., exercise) should be reinvestigated in their capability to modify the skeletal-muscle clocks by taking timing of the intervention into account.

Synergistic Effect of Feeding Time and Diet on Hepatic Steatosis and Gene Expression in Male Wistar Rats

OBJECTIVE

Eating out of phase with the endogenous biological clock alters clock and metabolic gene expression in rodents and can induce obesity and type 2 diabetes mellitus. Diet composition can also affect clock gene expression. This study assessed the combined effect of diet composition and feeding time on (1) body composition, (2) energy balance, and (3) circadian expression of hepatic clock and metabolic genes.

METHODS

Male Wistar rats were fed a chow or a free-choice high-fat, high-sugar (fcHFHS) diet, either ad libitum or with food access restricted to either the light or dark period. Body weight, adiposity, and hepatic fat accumulation as well as hepatic clock and metabolic mRNA expression were measured after 5 weeks of the diet. Energy expenditure was measured using calorimetric cages.

RESULTS

Animals with access to the fcHFHS diet only during the light period showed more hepatic fat accumulation than fcHFHS dark-fed animals despite less calories consumed. In contrast, within the chow-fed groups, light-fed animals showed the lowest hepatic fat content, but they also showed the lowest caloric intake. Locomotor activity and heat production followed feeding times, except in the fcHFHS light-fed group. Hepatic clock and metabolic gene expression rhythms also followed timing of food intake. Yet, in the fcHFHS light-fed animals, clock gene expression appeared 3 hours advanced compared with chow light-fed animals, an effect not observed in the fcHFHS dark-fed animals.

CONCLUSIONS

An fcHFHS diet consumed in the light period promotes hepatic fat accumulation and advances clock gene expression in male Wistar rats, likely because of a mismatch between energy intake and expenditure.

Diurnal Regulation of Peripheral Glucose Metabolism: Potential Effects of Exercise Timing

Diurnal oscillations in energy metabolism are linked to the activity of biological clocks and contribute to whole-body glucose homeostasis. Postprandially, skeletal muscle takes up approximately 80% of circulatory glucose and hence is a key organ in maintenance of glucose homeostasis. Dysregulation of molecular clock components in skeletal muscle disrupts whole-body glucose homeostasis. Next to light-dark cycles, nonphotic cues such as nutrient intake and physical activity are also potent cues to (re)set (dys)regulated clocks. Physical exercise is one of the most potent ways to improve myocellular insulin sensitivity. Given the role of the biological clock in glucose homeostasis and the power of exercise to improve insulin sensitivity, one can hypothesize that there might be an optimal time for exercise to maximally improve insulin sensitivity and glucose homeostasis. In this review, we aim to summarize the available information related to the interaction of diurnal rhythm, glucose homeostasis, and physical exercise as a nonphotic cue to correct dysregulation of human glucose metabolism.

Working time characteristics and long-term sickness absence among Danish and Finnish nurses: A register-based study

BACKGROUND

Working time regimes in Denmark and Finland share many similarities such as nursing personnel working in highly irregular shift systems. Yet, there are also differences for example in policy on when and how the employers are compensated for sickness absence.

OBJECTIVE

We aimed to investigate the association between different working hour characteristics and long-term sickness absence and whether these associations differed within various age groups in two large datasets of nursing personnel from Denmark and Finland.

DESIGN

Based on objective payroll data we used Poisson regression models to calculate incidence rate ratios with 95% confidence intervals to prospectively assess the risk of long-term sickness absence in relation to annual working hour characteristics. The analyses were adjusted for age, sex, short-term sickness absence, and weekly working hours.

SETTING(S)

Danish and Finnish nursing personnel.

PARTICIPANTS

31,729 Danish and 6970 Finnish nursing personnel with ≥ 0.5 Whole-Time Equivalent, registered in the database ≥ 1 year, 18-67 years of age with less than 30 days sickness absence in baseline year 2008.

METHODS

Working hour characteristics were assessed for 2008: time of day; day; evening; night. Duration of shift; long shifts (9-12 h); very long shifts (12-24 h); quick returns (< 11 h between two shifts); long weeks (> 40 h/week); very long weeks (> 48 h/week); and consecutive night shifts (≥ 5 night shifts). Long-term sickness absence was assessed as first incidence of 30 or more consecutive days off in 2009-2015.

RESULTS

The Danish data showed having evening work or five or more consecutive night shifts were associated with higher risk of long-term sickness absence. When excluding pregnant women, night work was also associated to higher risk of sickness absence. When stratifying on age groups, we observed a lower risk of sickness absence in the youngest age groups and a higher risk among the oldest. The Finnish results showed a higher risk of sickness absence when working nights, longs shifts, quick returns, and long work weeks. When stratifying on age groups, the results showed similar tendencies as the Danish.

CONCLUSIONS

The results show that the scheduling of working hours is likely to affect the risk of long-term sickness absence and that the risk differs in different age groups. No consistent picture was found for the results from Denmark and Finland. Differences may be due to contextual differences thus comparison of risk of sickness absence in relation to working hours between countries should be performed with caution. Tweetable abstract: A recent study from Denmark and Finland shows higher risk for long sickness absence among nurses with five or more consecutive night shifts.

Association between maternal shift work and infant neurodevelopmental outcomes: results from the Taiwan Birth Cohort Study with propensity-score-matching analysis

BACKGROUND

Maternal shift work is associated with preterm delivery, small-for-gestational-age new-borns, childhood obesity and future behavioural problems. However, the adverse effects on and interactions of maternal shift work with infant neurodevelopment remain uncertain. Therefore, we examined the associations between maternal-shift-work status and infant neurodevelopmental parameters.

METHODS

The Taiwan Birth Cohort Study is a nationwide birth cohort study following representatively sampled mother-infant pairs in 2005. The participants' development and exposure conditions were assessed by home interviews with structured questionnaires at 6 and 18 months of age. Propensity scores were calculated with predefined covariates for 1:1 matching. Multivariate conditional logistic regression and the Cox proportional-hazards model were used to examine the association between maternal-shift-work status and infant neurodevelopmental-milestone-achievement status.

RESULTS

In this study, 5637 term singletons were included, with 2098 cases selected in the propensity-score-matched subpopulation. Persistent maternal shift work was associated with increased risks of delays in gross-motor neurodevelopmental milestones [aOR = 1.36, 95% confidence interval (CI) = 1.06-1.76 for walking steadily], fine-motor neurodevelopmental milestones (aOR = 1.39, 95% CI = 1.07-1.80 for scribbling) and social neurodevelopmental milestones (aOR = 1.35, 95% CI = 1.03-1.76 for coming when called upon). Moreover, delayed gross-motor and social development were identified in the propensity-score-matched sub-cohort.

CONCLUSIONS

This study shows negative associations between maternal shift work and delayed neurodevelopmental-milestone achievement in the gross-motor, fine-motor and social domains at 18 months. Future research is necessary to elucidate the possible underlying mechanisms and long-term health effects.

The association of work stress and night work with nutrient intake - a prospective cohort study

Objectives:

In a prospective study among workers in an airline company, we explored whether change in work stress symptoms or night shifts was associated with nutrient intake.

Methods:

Participants in a workplace type 2 diabetes (T2D) prevention study completed a questionnaire on lifestyle, work stress symptoms, work schedule, and food intake at baseline and after 2.4-years follow-up (211 men and 155 women, 93% with increased risk for T2D). Multiple linear regression models with covariates were used to explore the associations between change in work stress symptoms or night shifts and change in nutrient intake during the follow-up.

Results:

Among men, an increase in stress and a decrease in perceived workability was associated with a higher proportion of energy (E%) from fat [β 0.6, 95% confidence interval (CI) 0.07–1.11, β 1.3, 95% CI 0.57–2.05] and saturated fat (β 0.3, 95% CI 0.02–0.58, β 0.5, 95% CI 0.14–0.90), respectively. Furthermore, a decrease in workability was associated with lower vitamin C intake (β -9.2, 95% CI -16.56– -1.84) and an increase in sleepiness with higher E% from saturated fat (β 0.7, 95% CI 0.00–0.15). Among women, an increase in work-related fatigue was associated with higher alcohol intake (β 7.5, 95% CI 1.25–13.74) and an increase of night shifts was associated with higher E% from fat (β 0.24, 95% CI 0.00–0.47) and saturated fat (β 0.17, 95% CI 0.04–0.29).

Conclusions:

Work stress symptoms were associated with a reduction in diet quality especially among men. The possible impact of work stress symptoms on workers’ dietary habits should be acknowledged and the assessment of dietary habits should consequently be incorporated into occupational health examinations.

Workers' Healthcare Assistance Model (WHAM): Development, Validation, and Assessment of Sustainable Return on Investment (S-ROI)

The present study aimed to present and validate the Worker´s Healthcare Assistance Model (WHAM), which includes an interdisciplinary approach to health risk management in search of integral and integrated health, considering economic sustainability. Through the integration of distinct methodological strategies, WHAM was developed in the period from 2011 to 2018, in a workers' occupational health centre in the oil industry in Bahia, Brazil. The study included a sample of 965 workers, 91.7% of which were men, with a mean age of 44.9 years (age ranged from 23 to 73 years). The Kendall rank correlation coefficient and hierarchical multiple regression analysis were used for the validation of WHAM. The assessment of sustainable return on investment (S-ROI) was made using the WELLCAST ROI™ decision support tool, covering workers with heart disease and diabetes. WHAM can be considered an innovative healthcare model, as there is no available comparative model. WHAM is considered robust, with 86% health risk explanatory capacity and with an 85.5% S-ROI. It can be concluded that WHAM is a model capable of enhancing the level of workers' health in companies, reducing costs for employers and improving the quality of life within the organization.

Shift work and sickness absence at a Norwegian hospital: a longitudinal multilevel study

OBJECTIVE

Shift work is known to be related to several negative health consequences and sickness absence. Research results regarding the relationship between types of shift schedules and sickness absence and whether and how individual factors moderate this relationship, are mixed though. The present paper aims to provide more insight in these relationships.

METHODS

We used registry data from a large Norwegian hospital gathered for the years 2012-2016, for >14 000 employees. With random effects at the individual and unit levels, we analysed the relationship between shift schedule worked and sickness absence in the same year.

RESULTS

The results showed increased risk of short-term sickness absence for two-shift and three-shift rotations, as well as fixed night shifts compared with fixed-day shifts. We also found an increased number of absence periods for two-shift rotations without nights and three-shift rotations. Results for long-term sickness absence were mixed, with increased odds for two-shift rotations without nights, but reduced odds for three-shift rotations. We found partial support for a moderating influence of age, gender and parental status.

CONCLUSIONS

There is a clear relationship between working shifts and increased risk of short-term sickness absence. The relationship persists across gender, age group and parental status. The relationship between shift work and long-term sickness absence appears to be schedule and population specific. These findings may have implications for HR policies and the organisation of shift work in healthcare organisations.

Intraindividual variability in sleep and comorbid medical and mental health conditions

STUDY OBJECTIVES

Intraindividual variability (IIV) in sleep may be a risk factor for disease above the influence of mean sleep. Associations between IIV in sleep and risk for a comprehensive set of common medical and mental health conditions have not been assessed in a representative sample.

METHODS

This study examined mean and IIV in total sleep time (TST), sleep quality (SQ), sleep efficiency (SE), and circadian midpoint (CM) in 771 adults recruited for an epidemiological study. Participants completed 14 days of sleep diaries to assess TST, SQ, SE, and CM, after which they reported on medical conditions and mental health symptoms. Data were analyzed using logistic regression, and models controlled for gender, body mass index, age, and race.

RESULTS

Lower mean TST, SQ, and SE were related to increased odds of having gastrointestinal problems, depression, and anxiety. IIV in TST was related to increased odds of having neurological, breathing, and gastrointestinal problems, as well as pain and depression; all results held controlling for mean sleep and adjusting for false discovery rate. IIV in SQ and SE was not associated with odds of having any medical or mental health conditions after adjusting for false discovery rate, nor was IIV in CM or mean CM.

CONCLUSIONS

Confirming previous research, mean TST, SQ, and SE are related to risk for gastrointestinal problems, depression, and anxiety. IIV in TST may be a unique facet of disturbed sleep that is associated with increased risk for a diverse cluster of medical and mental health conditions.

Feeding Rhythms and the Circadian Regulation of Metabolism

The molecular circadian clock regulates metabolic processes within the cell, and the alignment of these clocks between tissues is essential for the maintenance of metabolic homeostasis. The possibility of misalignment arises from the differential responsiveness of tissues to the environmental cues that synchronize the clock (zeitgebers). Although light is the dominant environmental cue for the master clock of the suprachiasmatic nucleus, many other tissues are sensitive to feeding and fasting. When rhythms of feeding behavior are altered, for example by shift work or the constant availability of highly palatable foods, strong feedback is sent to the peripheral molecular clocks. Varying degrees of phase shift can cause the systemic misalignment of metabolic processes. Moreover, when there is a misalignment between the endogenous rhythms in physiology and environmental inputs, such as feeding during the inactive phase, the body's ability to maintain homeostasis is impaired. The loss of phase coordination between the organism and environment, as well as internal misalignment between tissues, can produce cardiometabolic disease as a consequence. The aim of this review is to synthesize the work on the mechanisms and metabolic effects of circadian misalignment. The timing of food intake is highlighted as a powerful environmental cue with the potential to destroy or restore the synchrony of circadian rhythms in metabolism.