Diet, Physical Activity, and Daylight Exposure Patterns in Night-Shift Workers and Day Workers

Comparison of the physical activity levels between shift workers and non-shift workers in a large-scale cross-sectional study in Iran

BACKGROUND

Shift work has been related to adverse health outcomes that can partially be attributed to physical inactivity. However, our knowledge of the influence of shift work on physical activity and sedentary behavior is inconclusive. Therefore, this study aimed to assess physical activity levels among shift and non-shift workers among a sample of Iranian adults.

METHODS

Baseline data of the Ravansar Non-Communicable Disease (RaNCD) cohort study were used. All participants of RaNCD except those excluded due to unemployment or considerable disability were included in the study. We evaluated participants' physical activity levels using the PERSIAN cohort questionnaire and examined its associations with being a shift worker.

RESULTS

A total of 4695 participants with a mean age of 46.1 (SD = 7.74) were included in the study. In total, 1108 (23.6%) participants were shift workers, 1420 (30.2%) had insufficient physical activity levels, and 4283 (91.2%) were male. The prevalence of physical inactivity was significantly lower among shift workers compared to non-shift workers (21% vs. 33.1%, p < 0.001). Multiple backward stepwise binary logistic regression tests indicated that being a shift worker was significantly associated with a lower chance of having insufficient physical activity levels (OR = 0.77, 95% CI = 0.65-0.92, p = 0.003).

CONCLUSIONS

The prevalence of insufficient physical activity was higher among non-shift workers than shift workers in our study. By providing the factors associated with insufficient physical activity among the workers in a region of Iran, the current study findings might help policymakers target groups at higher risk of physical activity in Iran and design interventions to improve physical activity, especially among non-shift workers.

Consequences of Shift Work and Night Work: A Literature Review

Nonstandard work schedules such as shift work and night work tend to trigger problems for workers in different areas. To illustrate the diversity of areas affected and the relative interest of the scientific community, we conducted a literature review of the effects of shift work and night work on workers. In particular, we intended to identify the main variables addressed in the field of health, the family sphere, and the organizational context. The literature review was carried out using the Web of Science with the following terms: "shift work", "rotating shifts", and "night work". Inclusion criteria incorporated empirical studies and articles written in Portuguese or English published in 2019. We selected 129 of the 619 articles identified. Regarding the impacts of shift work and night work, there existed a high discrepancy of focus between the three defined areas: health, family life, and organizational context. Specifically, health-related variables were the most studied (83.4%), followed by organizational variables (9.2%), and, lastly, family variables (7.4%). Based on these results, it is essential to extend the study of the two underrepresented impacts to other crucial areas, not only for the worker but also for organizations.

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

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

Improvement in chrono-nutrition is associated with robust weight loss outcomes: An extension of the feasibility study

Previously we had demonstrated the development and feasibility of an integrated chrono-nutrition weight reduction program among non-shift workers with morning and evening chronotypes. In this current paper, we described the association between the changes in chrono-nutrition practice and weight loss outcomes upon completing the weight reduction program. A total of 91 overweight/obese non-shift workers participated in the 12-week integrated chrono-nutrition weight reduction program (Age: 39.6 ± 6.3 y; 74.7% women; BMI: 31.2 ± 4.5 kg/m²). All the assessments including anthropometry, dietary, sleep habits, physical activity, and process of change were measured during pre- and post-intervention. Participants who had lost ≥3% of their body weight were categorized as satisfactory weight loss outcome, and those who did not achieve 3% weight loss were categorized as unsatisfactory weight loss. The satisfactory weight loss had greater daily percent energy intake during earlier in the day from protein (Mean difference (MD): +3.2%, 95% CI: 1.6, 4.9, p < .001) and smaller intake from fat during later in the day (MD: -2.6%, 95% CI: -5.1, -0.1, p = .045), earlier last mealtime (MD: -49.5 min, 95% CI: -86.5, -12.6, p = .009) and midpoint of eating (MD: -27.3 min, 95% CI: -46.3, -8.2, p = .006), shorter eating window (-0.8 h, 95% CI: -1.4, -0.1, p = .031) and greater reduction in night eating syndrome score (MD: -2.4, 95% CI: -4.3, -0.5, p = .015) compared to unsatisfactory weight loss outcome. After accounting for potential confounders, the temporal pattern of energy, protein, and fat intake were associated with greater odds of achieving a satisfactory weight loss. The findings suggest a promising role of chrono-nutrition as one of the strategies in weight reduction intervention.

Motivation states to move, be physically active and sedentary vary like circadian rhythms and are associated with affect and arousal

Introduction

Motivation to be physically active and sedentary is a transient state that varies in response to previous behavior. It is not known: (a) if motivational states vary from morning to evening, (b) if they are related to feeling states (arousal/hedonic tone), and (c) whether they predict current behavior and intentions. The primary purpose of this study was to determine if motivation states vary across the day and in what pattern. Thirty adults from the United States were recruited from Amazon MTurk.

Methods

Participants completed 6 identical online surveys each day for 8 days beginning after waking and every 2-3 h thereafter until bedtime. Participants completed: (a) the CRAVE scale (Right now version) to measure motivation states for Move and Rest, (b) Feeling Scale, (c) Felt Arousal Scale, and (d) surveys about current movement behavior (e.g., currently sitting, standing, laying down) and intentions for exercise and sleep. Of these, 21 participants (mean age 37.7 y; 52.4% female) had complete and valid data.

Results

Visual inspection of data determined that: a) motivation states varied widely across the day, and b) most participants had a single wave cycle each day. Hierarchical linear modelling revealed that there were significant linear and quadratic time trends for both Move and Rest. Move peaked near 1500 h when Rest was at its nadir. Cosinor analysis determined that the functional waveform was circadian for Move for 81% of participants and 62% for Rest. Pleasure/displeasure and arousal independently predicted motivation states (all p's < .001), but arousal had an association twice as large. Eating, exercise and sleep behaviors, especially those over 2 h before assessment, predicted current motivation states. Move-motivation predicted current body position (e.g., laying down, sitting, walking) and intentions for exercise and sleep more consistently than rest, with the strongest prediction of behaviors planned for the next 30 min.

Discussion

While these data must be replicated with a larger sample, results suggest that motivation states to be active or sedentary have a circadian waveform for most people and influence future behavioral intentions. These novel results highlight the need to rethink the traditional approaches typically utilized to increase physical activity levels.

Comparison of adult shift and non-shift workers’ physical activity and sleep behaviours: cross-sectional analysis from the Household Income and Labour Dynamics of Australia (HILDA) cohort

Aim

This study compares the pattern of physical activity and sleep between shift and non-shift workers using a novel physical activity–sleep index. By drawing from a diverse occupational population, this research aims to reduce any occupational specific biases which are prevalent in shift-work research.

Subject and methods

Current data included 7607 workers (shift workers n = 832) from the Household Income and Labour Dynamics of Australia cohort study. The combined physical activity–sleep index comprised three physical activity components and three sleep health components: achieving moderate (1pt) or high (2pts) IPAQ classification; accruing ≥30% of physical activity as vigorous intensity (1pt); meeting sleep duration recommendations on a work night (1pt); and non-work night (1pt); and reporting no insomnia symptoms (1pt) (higher score = healthy behaviour, max. 6). Generalised linear modelling was used to compare behaviours of shift and non-shift workers.

Results

Findings showed shift workers reported significantly lower activity–sleep scores (3.59 vs 3.73, p < 0.001), lower sleep behaviour sub-score (2.01 vs. 2.22, p < 0.001) and were more likely to report insomnia symptoms (p < 0.001) compared to non-shift workers. No difference was reported for overall physical activity (shift = 1.58 vs. non-shift = 1.51, p = 0.383).

Conclusion

When viewed in conjunction using the combined activity–sleep index, shift workers displayed significantly poorer combined behaviours when compared to non-shift workers.

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.

Changes in intestinal parameters and their association with dietary patterns in rotational shift workers

Circadian rhythm disturbances induced by rotating shift work contribute to development of metabolic disorders. However, their effects on intestinal parameters such as epithelial permeability and fecal short chain fatty acid (SCFA) levels have not been established yet. This study was planned to investigate the changes in intestinal integrity, fecal SCFA levels, gut microbiota and nutritional intake of rotational shift workers. The study was conducted on ten male rotational shift workers, 25-40 years old. Circadian rhythm disruption was assumed to have occurred after 14 days in the night shift. Dietary data which was obtained by using 24 h record for 7 days, physical activity data, anthropometric measurements, fecal and blood samples were collected during day and night shift. Changes in dietary consumption, anthropometric measurements, blood chemistry and intestinal epithelial permeability indicator according to day and night shifts were not significant (p > .05). Additionally, acetic, propionic and total SCFA were associated with the intestinal permeability biomarker in night shift, but not in day shift (p < .05). Consumption of dark green vegetables and beans and peas was positively associated with fecal isobutyric acid and fecal total SCFA concentration (r = 0.685, p = .029; r = 0.695, p = .026, respectively). The proportions of the genus including Blautia, Bifidobacterium, Dialister, and Ruminococcus gnavus group increased when individuals shifted to the night shift. Gut microbiota changes responding to circadian rhythm disruption became more prominent when consumed high sugar diet. So, changes have been observed in the gut microbiota of rotational shift workers, especially in individuals with certain dietary pattern. Moreover, in individuals with the circadian rhythm disruption SCFAs levels have been demonstrated to be associated with intestinal barrier integrity. A better understanding of the relation among fecal SCFAs, gut microbiota, intestinal epithelial permeability and circadian rhythm disruption is necessary for the development of new dietary strategies for gut health.

Effect of acceptance and commitment therapy on mood, sleep quality and quality of life in menopausal women: a randomized controlled trial

BACKGROUND

One of the most critical periods in a woman's life is menopause. During menopause, depression and anxiety are among the most common mood changes. Sleep disorders also increase during menopause, which leads to quality of life disorders. Different methods such as medication, psychotherapy, or a combination of them are used to treat these disorders. Acceptance and commitment-based therapy is one of the newest methods in psychotherapy that recently has been used a lot. Therefore, this study was conducted to determine the effect of acceptance and commitment therapy (ACT) on mood (primary outcome), sleep quality, and quality of life (secondary outcomes) of menopausal women.

METHODS

This randomized controlled trial was performed on 86 menopausal women in Tabriz, Iran in 2021. Using the blocking method, participants were randomly assigned into the intervention and control groups. The intervention group received counseling based on ACT approach in 8 sessions of 60 to 90 min. The control group received only routine health care. Depression, Anxiety, Stress Scale-21 (DASS 21), Menopause Quality of Life (MENQOL), and Pittsburgh Sleep Quality Index (PSQI) questionnaires were completed before intervention and immediately after the intervention. Independent t-test and Mann-Whitney U test were used to compare the outcomes between the two groups.

RESULTS

In terms of sociodemographic characteristics and baseline values of the studied variables, there was no statistically significant difference between the study groups before the intervention. At the end of the intervention, the mean (SD: standard deviation) scores of anxiety, stress, and depression in the counseling group were 2.66 (1.28), 2.91 (1.62), and 1.98 (1.59) and in the control group were 4.19 (1.85), 5.61 (1.49) and 3.59 (1.91). In the intervention group, the mean score of all three variables was significantly lower than the control group (P < 0.001). After the intervention, the mean (SD) of the total sleep quality score was 4.04 (2.52) in the counseling group and 4.13 (2.63) in the control group. In addition, the mean (SD) of the total quality of life score was 23.47 (20.13) in the counseling group and 23.14 (17.76) in the control group. Between the study groups, there were no statistically significant differences in the mean of the overall score of sleep quality (P = 0.867) and the overall score of quality of life (P = 0.759).

CONCLUSION

Using ACT-based counseling can improve the mood of menopausal women. However, further randomized clinical trials are needed before making a definitive conclusions.

TRIAL REGISTRATION

Iranian Registry of Clinical Trials (IRCT): IRCT20120718010324N65. Date of registration: 2/19/2021. Date of first registration: 2/19/2021. URL: https://en.irct.ir/user/trial/53544/view; Date of recruitment start date: 2/22/2021.

Effectiveness of a Mobile Wellness Program for Nurses with Rotating Shifts during COVID-19 Pandemic: A Pilot Cluster-Randomized Trial

Nurses with rotating shifts, including night shifts, have suffered from low physical activity during the COVID-19 pandemic and lower sleep quality due to the disruption of their circadian rhythm. This study aimed to develop and examine the effectiveness of a mobile wellness program on daily steps, sleep quality, exercise self-efficacy, intrinsic motivation for exercise, self-rated fatigue, and wellness. A cluster randomized controlled trial design was used to examine the effectiveness of the mobile wellness program for nurses with rotating shifts. Sixty nurses from one university hospital participated and were allocated to an intervention group and a control group. The intervention group received a 12-week mobile wellness program to improve their physical activity and sleep quality, and the control group was only given a Fitbit to self-monitor their health behaviors. There were significant differences between the two groups in daily steps (p = 0.000), three components (subjective sleep quality, sleep disturbance, daytime dysfunction) of the PSQI, exercise self-efficacy, intrinsic motivation for exercise, and wellness. In conclusion, this study provides meaningful information that the mobile wellness program using Fitbit, online exercise using Zoom, online health coaching on a Korean mobile platform, and motivational text messages effectively promoted physical activity and sleep quality for nurses with rotating shifts during the COVID-19 pandemic.

Physical activity and sedentary behaviour in shift and non-shift workers: A systematic review and meta-analysis

Research examining the prevalence, physical activity (PA) and sedentary behaviour (SB) in shift workers show mixed results. This systematic review and meta-analysis aimed to compare PA and SB in shift workers with non-shift workers following the PRISMA guidelines. Ebscohost megafile ultimate (CINHAL, E-journals, Academic search ultimate, health source consumer edition, SPORT Discus), PubMed, Scopus, Web of Science, and Science Direct databases were searched up to April 2021. Cross-sectional and baseline data from longitudinal studies reporting PA and SB in full time workers were eligible. Data on participants characteristics and time spent in PA and SB and/or prevalence of workers meeting PA guidelines were extracted and pooled with random effects model. The Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) 10-item checklist was adapted and used. A total of 49 studies met inclusion criteria and 21 studies included for meta-analysis. The prevalence of meeting physical activity guidelines (OR 0.84, 95% CI: 0.68, 1.03) and standardized mean difference (SMD) of time spent in moderate-to-vigorous physical activity (SMD -0.1, 95% CI: -0.4, 0.20) were similar in shift and non-shift workers. Time spent in sedentary behaviour was lower in shift workers than non-shift workers (SMD -0.2, 95% CI: 0.50, -0.001). While the differences in PA are not so evident between shift and non-shift workers, the prevalence of sufficient PA was low in both groups. These preliminary findings provide support for inclusion of physical activity and sedentary behaviour in health promotion interventions targeted at shift workers.

Healthy Habits in Firefighters: Assessment in Shift Days Versus Days Off

OBJECTIVE

The aim of this study was to compare dietary habits, sleep habits, and injury incidence between shift days and days off among Spanish firefighters.

METHODS

24-Hour dietary recalls, and sleep and injury questionnaires on both days were collected from 28 Sevillian professional firefighter, as well as anthropometric measurements and a physical activity questionnaire.

RESULTS

Firefighters consumed 433 more kilocalories (P < 0.001), 2.4% and 3.1% more kilocalories from fat and monounsaturated fatty acids, respectively (P < 0.05), had 3.7 times greater chance of being injured and slept 2 hours and 18 minutes less (P < 0.001) in their shift days. Higher body fat percentages were found in older and less active firefighters.

CONCLUSIONS

Shift work appears to influence their dietary habits, injury incidence, and sleep habits, so measures to alleviate the consequences of shift work in firefighters should be taken.

Work Shift, Lifestyle Factors, and Subclinical Atherosclerosis in Spanish Male Workers: A Mediation Analysis

(1) Background: Working night shifts has been associated with altered circadian rhythms, lifestyle habits, and cardiometabolic risks. No information on the potential association of working shift and the presence of atherosclerosis is available. The aim of this study was to quantify the association between different work shifts and the presence of subclinical atherosclerosis objectively measured by imaging. (2) Methods: Analyses were conducted on the baseline data of the Aragon Workers Health Study (AWHS) cohort, including information on 2459 middle-aged men. Categories of shift work included central day shift, rotating morning-evening or morning-evening-night shift, and night shift. The presence of atherosclerotic plaques was assessed by 2D ultrasound in the carotid and femoral vascular territories. Multivariable logistic models and mediation analysis were conducted to characterize and quantify the association between study variables. (3) Results: Participants working night or rotating shifts presented an overall worse cardiometabolic risk profile, as well as more detrimental lifestyle habits. Workers in the most intense (morning-evening-night) rotating shift presented higher odds of subclinical atherosclerosis (odds ratio: 1.6; 95% confidence interval: 1.12 to 2.27) compared to workers in the central shift, independently of the presence of lifestyle and metabolic risk factors. A considerable (21%) proportion of this association was found to be mediated by smoking, indicating that altered sleep-wake cycles have a direct relationship with the early presence of atherosclerotic lesions. (4) Conclusions: Work shifts should be factored in during workers health examinations, and when developing effective workplace wellness programs.

A field investigation of the relationship between rotating shifts, sleep, mental health and physical activity of Australian paramedics

Paramedics working on a rotating shift are at an increased risk of developing chronic health issues due to continuous circadian rhythm disruption. The acute effects of shift rotation and objectively measured sleep have rarely been reported in paramedics. This study investigated the relationships between a rotating shift schedule and sleep (using actigraphy), subjective reports of sleepiness, mood, stress and fatigue. Galvanic Skin Response, energy expenditure and physical activity (BodyMedia SenseWear Armband) were also recorded across the shift schedule. Paramedics were monitored for a period of eight consecutive days across pre-shift, day shift, night shift, and 2 days off. Fifteen paramedics (M age = 39.5 and SD = 10.7 years) who worked rotational shifts experienced sleep restriction during night shift compared to pre-shift, day shift and days off (p < 0.001). Night shift was also associated with higher levels of stress (p < 0.05), fatigue (p < 0.05), and sleepiness (p < 0.05). One day off was related to a return to pre-shift functioning. Such shift-related issues have a compounding negative impact on an already stressful occupation with high rates of physical and mental health issues. Therefore, there is an urgent need to investigate methods to reduce rotating shift burden on the health of paramedics. This could be through further research aimed at providing recommendations for shift work schedules with sufficient periods for sleep and recovery from stress.

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.

Decrease in sleep quality during COVID-19 outbreak

PURPOSE

The COVID-19 outbreak witnessed in the first months of 2020 has led to unprecedented changes in society's lifestyles. In the current study, we aimed to investigate the effect of this unexpected context on sleep.

METHODS

During the COVID-19 outbreak, we performed an online survey with individuals formerly recruited for validation of the Spanish version of the sleep questionnaire Satisfaction, Alertness, Timing, Efficiency, and Duration (SATED). In the current survey, we asked the participants to complete the previously answered questionnaires including the Pittsburgh Sleep Quality Index (PSQI), a modified version of the Epworth Sleepiness Scale (ESS), and the SATED questionnaire. We also assessed the mood by the Profile of Mood States (POMS) questionnaire.

RESULTS

The 71 participants were mostly women (75%) with a mean (± SD) age of 40.7 ± 11.9 years. Comparing the previous PSQI score to that during the COVID-19 outbreak, we observed worsening sleep quality (5.45 ± 3.14 to 6.18 ± 3.03 points, p = 0.035). In parallel, there was an increase in the negative mood (p = 0.002). Accordingly, the decrease in sleep quality was substantially correlated with negative mood (p < 0.001). There were no differences in the ESS or SATED.

CONCLUSIONS

The COVID-19 outbreak-associated events correlate with decreased sleep quality in association with an increase in negative mood. Considering the importance of sleep for a healthy life, and in particular for immune function, efforts should be made to improve awareness on this matter and to offer psychological assistance to affected individuals.

Free-Living Sleep, Food Intake, and Physical Activity in Night and Morning Shift Workers

Objective: Shift work is associated with risk for adverse health outcomes including cardiovascular disease, type 2 diabetes, cancer, and obesity. Short sleep duration combined with disruptions to the circadian system may alter factors involved with the behavioral regulation of energy intake and expenditure. We aimed to determine how shift work affects sleep, food intake, and physical activity.Methods: This was a field-based observational study using objective assessments of sleep and physical activity and a 24-hour dietary recall in shift workers. Day (n = 12) and night (n = 12) hospital shift workers (nurses and technicians) who were women had their free-living sleep and physical activity tracked via accelerometry, and completed a computer-assisted 24-hour food recall, during a series of work shifts.Results: Compared to day workers, night workers had significantly shorter sleep duration and reported more premature awakenings and feeling less refreshed upon awakening. Daily self-reported energy and macronutrient intakes were not different between groups, although the night shift workers reported a significantly longer total daily eating duration window than day workers. Objectively recorded physical activity levels were not different between groups.Conclusions: The present findings confirm that sleep is disturbed in women night workers, while there are relatively less effects on objectively recorded physical activity and self-reported food intake. We also observed a prolonged daily eating duration in night vs. day workers. These observations can help inform the design of novel behavioral interventions, including, potentially, time restricted feeding approaches (e.g., by limiting daily eating episodes to within a 10-12 h window), to optimize weight management in shift workers.

Plasma sCD36 as non-circadian marker of chronic circadian disturbance in shift workers

Shift work induces chronic circadian disturbance, which might result in increased health risks, including cardio-metabolic diseases. Previously, we identified sCD36 as a potential non-circadian biomarker of chronic circadian disturbance in mice. The aim of the current study (n = 232 individuals) was to identify whether sCD36 measured in plasma can be used as a non-circadian marker of chronic circadian disturbance in humans, which would allow its use to measure the effects of interventions and monitoring in large-scale studies. We compared levels of plasma sCD36 of day workers with recent (< 2 years) and experienced (> 5 years) night-shift workers within the Klokwerk study. We detected no differences in sCD36 levels between day workers and recent or experienced night-shift workers, measured during a day or afternoon shift. In addition, sCD36 levels measured directly after a night shift were not different from sCD36 levels measured during day or afternoon shifts, indicating no acute effect of night shifts on sCD36 levels in our study. In summary, our study does not show a relation between night-shift work experience (recent or long-term) and plasma levels of sCD36. Since we do not know if and for which time span night-shift work is associated with changes in sCD36 levels, and our study was relatively small and cross-sectional, further evidence for an association between chronic circadian disruption and this candidate biomarker sCD36 should be gathered from large cohort studies.

Feasibility and Preliminary Efficacy of an m-Health Intervention Targeting Physical Activity, Diet, and Sleep Quality in Shift-Workers

Poor health behaviors are prevalent in shift-workers, but few multiple health-behavior interventions consider their unique needs. This study aimed to (1) evaluate the feasibility and acceptability of an existing app-based intervention to improve physical activity, diet, and sleep quality in a shift-worker population, (2) estimate intervention effect in a four-week pilot randomized controlled trial (RCT) (ACTRN12618001785291). Shift-workers (18–65 years old) were randomized to intervention (n = 20) or wait-list (n = 20) groups. Outcomes included recruitment, engagement, attrition, usefulness ratings, System Usability Scale (SUS), qualitative interviews, and estimation of treatment effect (minutes of physical activity, diet quality, and sleep quality) using mixed model analysis. Recruitment took one week. App-use at week four was 55% (11/20), 85% (34/40) completed the four-week follow-up questionnaire, and 20% (4/20) of the intervention group completed the qualitative interview. The intervention was rated as slightly to moderately useful by 76.9% (10/13) of participants on a five-point scale. The SUS score was 62.7 (12.7) out of 100. Diet quality improved for the intervention (4.5 points; 95% confidence interval (CI) = 0.1, 8.9; p = 0.047) vs. the wait-list group, but not physical activity or sleep quality. Qualitative interviews found that a more tailored intervention, more accessible information, and interactive features were desired. The intervention was feasible in terms of recruitment, but modifications to increase engagement are needed.

Shedding Light on the Association between Night Work and Breast Cancer

Shift work that involves circadian disruption has been classified as probably carcinogenic to humans by the International Agency for Research on Cancer, although more recent epidemiological evidence is not consistent. Several mechanisms have been postulated to explain an association between night work and female breast cancer, but the most likely is suppression of the hormone melatonin by light exposure at night. Three articles recently published in this journal describe aspects of exposure to light during night work. These articles and other evidence suggest that nighttime light levels may not always be sufficient to affect melatonin production, which could in part explain the inconsistencies in the epidemiological data. There is need to improve the specificity and reliability of exposure assessments in future epidemiological studies of night shift workers.