Relationship between night work and health-related quality of life: an analysis based on profiles and cumulative duration of exposure to night work among French workers in the CONSTANCES cohort

OBJECTIVE

The aim of this study is to estimate the association between night work and health-related quality of life (HRQoL) among French workers. The association between cumulative duration of night work and HRQoL was also investigated.

METHODS

Three career-long night work exposure groups were defined at inclusion in the CONSTANCES cohort: permanent night workers, rotating night workers and former night workers. Day workers with no experience of night work were the reference group. HRQoL was assessed using the Short Form Health Survey (SF-12), in particular the physical component summary (PCS) and mental component summary (MCS) scores, with a higher score indicating better HRQoL. Several linear regression models were built to test the association between night work exposure and HRQoL. The relationship between cumulative duration of night work and HRQoL scores was analyzed using generalised additive models.

RESULTS

The sample consisted of 10,372 participants. Former night workers had a significantly lower PCS score than day workers (β [95% CI]: - 1.09 [- 1.73; - 0.45], p = 0.001), whereas permanent night workers had a significantly higher MCS score (β [95% CI]: 1.19 [0.009; 2.36], p = 0.048). A significant decrease in PCS score from 5 to 20 years of cumulative night work was observed among former night workers.

CONCLUSIONS

Former night workers had poorer physical HRQoL in contrast to permanent and rotating night workers who had similar or even better HRQoL than day workers, suggesting the well-known healthy worker survivor effect. Consequently, both current and former night workers require regular and specific follow-up focused on the physical components of their health.

Association of rotating night shift work with tooth loss and severe periodontitis among permanent employees in Japan: a cross-sectional study

Background

The modern 24/7 society demands night shift work, which is a possible risk factor for chronic diseases. This study aimed to examine the associations of rotating night shift work duration with tooth loss and severe periodontitis.

Methods

This cross-sectional study used data from a self-administered questionnaire survey conducted among 3,044 permanent employees aged 20-64 years through a Japanese web research company in 2023. The duration of rotating night shift work was assessed using a question from the Nurses' Health Study. Tooth loss was assessed based on self-reported remaining natural teeth count. Severe periodontitis was assessed using a validated screening questionnaire comprising four questions related to gum disease, loose tooth, bone loss, and bleeding gums. We employed linear regression models for tooth loss and Poisson regression models for severe periodontitis, adjusting for demographic, health and work-related variables and socioeconomic status.

Results

Among participants included, 10.9% worked in rotating night shifts for 1-5 years, while 11.0% worked in such shifts for ≥6 years. In fully adjusted models, rotating night shift work duration of 1-5 years was associated with tooth loss (beta -0.74, 95% confidence interval (CI) [-1.55 to 0.08]) and severe periodontitis (prevalence ratio 1.80, 95% CI [1.33-2.43]); however, the association with tooth loss was not statistically significant.

Conclusions

This study supports that employees who work short-term rotating night shifts may experience poor oral conditions. Further research is needed to determine whether long-term rotating night shift work is associated with deteriorated oral health.

The association between night shift work and osteoporosis risk in adults: A cross-sectional analysis using NHANES

Purpose

Through this study, we assess whether night shift work increases the risk of osteoporosis, and explore the effects of age, gender, or lifestyle differences.

Methods

This cross-sectional study included the collection of data from a sample of the US adults who participated in the National Health and Nutrition Examination Survey (NHANES) over a 7.3-year period (2007-2008, 2009-2010, 2017-March2020), including 4408 participants (2351[52.8%] men and 2057[47.2%] women), with an age range of 20-80 years. The primary variables, health status, nutrition, harmful lifestyle habits, and bone mineral density (BMD), were segregated, and analyzed according to different work schedules. Linear regression models were conducted to evaluate correlations of night shift work and T-scores. Associations between night shift work and osteoporosis were examined using logistic regression analyses. All regression models were stratified by gender and age ≥50 years. Osteoporosis was defined as BMD at the femoral neck or total spine equal to or less than 2.5 standard deviations below the mean for youthful people of the same gender. All data were obtained using questionnaires and examinations collected in mobile examination center (MEC) from NHANES.

Results

After multivariate adjustment, night shift work was related to statistically significant decreases of the total spine in T-scores of females aged ≥50 years. Furthermore, night shift work of the overall population (OR = 2.31 [95% CI, 1.03-5.18]; P = 0.043) and females aged ≥50 years (OR = 4.6 [95% CI, 1.21-17.54]; P = 0.025) was related to an increased prevalence of osteoporosis.

Conclusion

Night shift work correlates with a higher risk of osteoporosis in the population of the US adults, with the combined effect of age, gender, and harmful lifestyle.

Relationship between shift work, night work, and headache and migraine risk: A meta-analysis of observational studies

BACKGROUND

To date, there is insufficient research on whether shift work and night work increase the risk of experiencing headaches and migraines.

OBJECTIVES

This study aimed to evaluate the potential association between shift work, night shift work, and headache/migraine.

METHODS

We conducted a thorough search of the PubMed, Embase, and Web of Science databases up until October 2023 to identify relevant studies. Our inclusion criteria focused on observational studies that investigated the association between shift work exposure and headache/migraine outcomes. We extracted adjusted risk estimates from each study and calculated pooled odds ratios using either fixed or random-effects models. Our methodology followed the Meta-Analysis Group guidelines for observational studies in epidemiology. To ensure accuracy and consistency, two investigators independently reviewed the retrieved records and extracted data based on the predefined inclusion criteria.

RESULTS

This meta-analysis included a total of seven studies involving 422,869 participants. The pooled analysis revealed a significant association between shift work and an increased risk of headaches (HR = 1.32, 95% CI: 1.15-1.52, P < 0.001). Specifically, individuals working night shifts had a 44% higher risk of developing headaches (HR = 1.44, 95% CI: 1.09-1.90, P = 0.011). Furthermore, shift work was also found to be associated with a higher incidence of migraines (HR = 1.63, 95% CI: 1.27-2.08, P < 0.001). Interestingly, night shift work was associated with a decreased incidence of migraines (HR = 0.74, 95% CI: 0.57-0.96, P = 0.024).

CONCLUSION

Our study found a noteworthy association between shift work/night work and the occurrence of headaches and migraines. However, it is important to note that our study does not establish a causal relationship. Future research should investigate potential common vulnerability factors, such as genetics or health behaviors. This knowledge can help inform the implementation of preventive measures and interventions to mitigate the health risks associated with shift work.

A pilot study of light exposure as a countermeasure for menstrual phase-dependent neurobehavioral performance impairment in women

OBJECTIVE

To examine effects of menstrual phase and nighttime light exposure on subjective sleepiness and auditory Psychomotor Vigilance Task performance.

METHODS

Twenty-nine premenopausal women (12 =Follicular; 17 =Luteal) completed a 6.5-hour nighttime monochromatic light exposure with varying wavelengths (420-620 nm) and irradiances (1.03-14.12 µW/cm2). Subjective sleepiness, reaction time, and attentional lapses were compared between menstrual phases in women with minimal (<33%) or substantial (≥33%) light-induced melatonin suppression.

RESULTS

When melatonin was not suppressed, women in the follicular phase had significantly worse reaction time (mean difference=145.1 ms, 95% CI 51.8-238.3, p < .001, Cohen's D=1.9) and lapses (mean difference=12.9 lapses, 95% CI 4.37-21.41, p < .001, Cohen's D=1.7) compared to women in the luteal phase. When melatonin was suppressed, women in the follicular phase had significantly better reaction time (mean difference=152.1 ms, 95% CI 43.88-260.3, p < .001, Cohen's D=1.7) and lapses (mean difference=12.3 lapses, 95% CI 1.14-25.6, p < .01, Cohen's D=1.6) compared to when melatonin was not suppressed, such that their performance was not different (p > .9) from women in the luteal phase. Subjective sleepiness did not differ by menstrual phase (mean difference=0.6, p > .08) or melatonin suppression (mean difference=0.2, p > .4).

CONCLUSIONS

Nighttime light exposure sufficient to suppress melatonin can also mitigate neurobehavioral performance deficits associated with the follicular phase. Despite the relatively small sample size, these data suggest that nighttime light may be a valuable strategy to help reduce errors and accidents in female shift workers.

Association between nocturnal light exposure and melatonin in humans: a meta-analysis

BACKGROUND

Night shift workers are more susceptible to circadian rhythm disturbances due to their prolonged exposure to nighttime light. This exposure during abnormal periods causes inappropriate suppression of melatonin synthesis and secretion in the pineal gland, thereby disrupting circadian rhythms. While it is believed that nocturnal light exposure is involved in suppressing melatonin secretion, research findings in this area have been inconsistent.

METHODS

Thirteen publications retrieved from PubMed and Web of Science databases were included to compare the differences between night shift workers and controls using aggregated mean differences (MD) and 95% confidence intervals (CI).

RESULTS

After a comprehensive review, 13 publications were included and data on urinary melatonin metabolite 6-sulfameoxymelatonin(aMT6s) were collected for meta-analysis. The results showed that the morning urinary aMT6s levels were significantly lower in the exposed group than in the non-exposed group (MD = -3.69, 95%CI = (-5.41, -1.98), P < 0.0001), with no significant heterogeneity among the original studies (I2 = 42%, P = 0.13). In addition, night shift workers had significantly lower mean levels of 24-h urinary aMT6s than day shift workers (MD = -3.38, 95%CI = (-4.27, -2.49), P < 0.00001, I2 = 0). Nocturnal light was correlated with nocturnal urine aMT6s secretion and inhibited nocturnal aMT6s secretion (MD = -11.68, 95%CI = (-15.70, -7.67), P < 0.00001, I2 = 0). Additionally, nocturnal light inhibited the secretion of melatonin in the blood, with no significant heterogeneity between studies (MD = -11.37, 95%CI = (-15.41, -7.33), P < 0.00001, I2 = 0).

CONCLUSION

The findings of this study indicate that exposure to nocturnal light among night shift workers leads to inhibition of melatonin secretion.

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

OBJECTIVE

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

PARTICIPANTS AND SETTING

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

DESIGN

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

RESULTS

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

CONCLUSIONS

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

Common mental disorders in Brazilian female shift workers: prevalence and associated factors

This study aimed to identify the prevalence of common mental disorders (CMD) and associated factors in female shift workers. A cross-sectional study was conducted with a sample of 450 female workers, aged 18 years or older (± 36.1 years), from an industry located in Southern Brazil. CMD was assessed using the self-reporting questionnaire (SRQ-20 ≥ 8 points), and sociodemographic, occupational, behavioral, morbidity, and self-rated health characteristics were assessed using a questionnaire survey. The prevalence of CMD was 47.3% (95% CI: 42.6-52.1). After adjusting, female workers with black/brown race/skin color had a 22% higher probability of CMD than white workers (prevalence ratio (PR) = 1.22; 95% CI: 1.01-1.49), and workers with sleep disorders or poor sleep quality were 147% more likely to have CMD compared with those with good sleep quality (PR = 2.47; 95% CI: 1.70-3.58), and workers with fair/poor self-rated health were twice as likely to have CMD (PR = 2.00; 95% CI: 1.43-2.80) compared to those with excellent/very good self-rated health. A high prevalence of CMD was observed in female shift workers, especially in workers with a black/brown race/skin color and with poor sleep quality and self-rated health.

Working hours and the regulations for night shift workers

There are several types of shift work in Korea: rotating shift, 24-hour shift, day-night shift, fixed night work, and.so on. As a result of analyzing the 8th Korea National Health and Nutrition Examination Survey and the 6th Korean Working Condition Survey, Korean shift workers accounted for 11.6%-13.9% of wage workers. Weekly working hours of shift workers were 57.69 ± 1.73 (24-hours shift) and 49.97 ± 0.67 (fixed night shift), which were significantly longer than day workers. To prevent health consequences of night work, many countries regulate the working hours of night work not to exceed 7-9 hours a day. However, Korea does not regulate working hours for night work, and some occupations may work more hours than the prescribed overtime hours. To prevent health consequences and reduce working hours for Korean night shift workers, it is necessary to regulate the working hours of night shift workers by law.

The association between night shift work and breast cancer risk in the Finnish twins cohort

Breast cancer is highly prevalent yet a more complete understanding of the interplay between genes and probable environmental risk factors, such as night work, remains lagging. Using a discordant twin pair design, we examined the association between night shift work and breast cancer risk, controlling for familial confounding. Shift work pattern was prospectively assessed by mailed questionnaires among 5,781 female twins from the Older Finnish Twin Cohort. Over the study period (1990-2018), 407 incident breast cancer cases were recorded using the Finnish Cancer Registry. Cox proportional hazards models were used to calculate hazard ratios (HRs) and 95% confidence intervals (CIs) adjusting for potential confounders. Within-pair co-twin analyses were employed in 57 pairs to account for potential familial confounding. Compared to women who worked days only, women with shift work that included night shifts had a 1.58-fold higher risk of breast cancer (HR = 1.58; 95%CI, 1.16-2.15, highest among the youngest women i.e. born 1950-1957, HR = 2.08; 95%CI, 1.32-3.28), whereas 2-shift workers not including night shifts, did not (HR = 0.84; 95%CI, 0.59-1.21). Women with longer sleep (average sleep duration > 8 h/night) appeared at greatest risk of breast cancer if they worked night shifts (HR = 2.91; 95%CI, 1.55-5.46; P_intx=0.32). Results did not vary by chronotype (P_intx=0.74). Co-twin analyses, though with limited power, suggested that night work may be associated with breast cancer risk independent of early environmental and genetic factors. These results confirm a previously described association between night shift work and breast cancer risk. Genetic influences only partially explain these associations.

The development and initial validation of a new working time scale for full-time workers with non-standard schedules

BACKGROUND

Working time characteristics have been used to link work schedule features to health impairment; however, extant working time exposure assessments are narrow in scope. Prominent working time frameworks suggest that a broad range of schedule features should be assessed to best capture non-standard schedules. The purpose of this study was to develop a multi-dimensional scale that assesses working time exposures and test its reliability and validity for full-time workers with non-standard schedules.

METHODS

A cross-sectional study was conducted using full-time, blue-collar worker population samples from three industries - transportation (n = 174), corrections (n = 112), and manufacturing (n = 99). Using a multi-phased approach including the review of scientific literature and input from an advisory panel of experts, the WorkTime Scale (WTS) was created and included multiple domains to characterize working time (length, time of day, intensity, control, predictability, and free time). Self-report surveys were distributed to workers at their workplace during company time. Following a comprehensive scale development procedure (Phase 1), exploratory factor analysis (EFA) (Phase 2) and, confirmatory factor analysis (CFA) (Phase 3; bivariate correlations were used to identify the core components of the WTS and assess the reliability and validity (Phase 4) in three samples.

RESULTS

Phase 1 resulted in a preliminary set of 21 items that served as the basis for the quantitative analysis of the WTS. Phase 2 used EFA to yield a 14-item WTS measure with two subscales ("Extended and Irregular Work Days (EIWD)" and "Lack of Control (LOC)"). Phase 3 used CFA to confirm the factor structure of the WTS, and its subscales demonstrated good internal consistency: alpha coefficients were 0.88 for the EIWD factor and 0.76-0.81 for the LOC factor. Phase 4 used bivariate correlations to substantiate convergent, discriminant, and criterion (predictive) validities.

CONCLUSIONS

The 14-item WTS with good reliability and validity is an effective tool for assessing working time exposures in a variety of full-time jobs with non-standard schedules.

Shiftworkers' attitude to their work hours, positive or negative, and why?

Objective

Shift work is associated with impaired health and safety but there is a lack of systematic knowledge of shift workers attitude to their shift systems. This may be important for the ability to retain valuable personnel in the company/organization, and to attract new employees. The purpose of the present study was to investigate: the prevalence of shift characteristics (nights, long shifts, short rest, etc.) in traditional shift systems, the workers’ attitude to their shift systems, if combinations of problematic shift characteristics are associated with the workers’ attitude, and if work stress and poor sleep, fatigue, or social difficulties are associated with attitudes to shift systems.

Methods

A representative sample of 3,500 individuals with non-day work in the general population of Sweden were asked to participate in the study. A total of 1965 workers remained after drop-outs. The material was analyzed by Chi2 analysis and hierarchical multiple regression.

Results

The results showed that traditional shift systems included many more shift characteristics than those constituting the core of the systems. All included day work, for example. 90.2% of those with roster work had shifts > 10 h at least once a month. 66.9% of those with roster work without nights had < 11 h rest between shifts at least once a month. Less than 25% of the respondents had a rather or very negative attitude to their shift system, with the lowest level for those who work either fixed days or nights (7.6 and 5.7%, respectively) and highest for three-shift work (21.2%) and roster work without night work (24.4%). Shiftwork or roster work with nights had highest levels (> 50%) of sleep problems and fatigue. The difference across shift systems was significant at p < .001 in all cases. Combinations of the most problematic shift characteristics were associated with some increase in negative attitude to the shift schedule. Among schedule characteristics, only long weeks turned out significant in the multivariable regression. The strongest predictor of negative attitude to work hours were social difficulties due to work schedule [ß = 4.98 (95% Confidence interval (Ci) = 3.41, 7.27; p < .001], fatigue caused by schedule (ß = 3.20 Ci = 2.03, 5.05; p < .001), sleep problems caused by schedule (ß = 2.10 Ci = 1.46, 3.01; p = .01), and stressful work (ß = 1.52 Ci = 1.10, 2.11; p < .05).

Conclusion

It was concluded that shift systems often included many different shift characteristics, that night shift systems had a large proportion of long shifts, and that split shifts mainly occurred in roster day work. Furthermore, it was concluded that the attitude to the worker’s present shift systems seems to be positive for the majority, with the highest level for those who work either fixed days or nights, compared to those who work alternating shifts (including night shifts). Negative attitude to shift systems was more linked to social difficulties, fatigue or sleep problems due to the shift schedule, than to schedule characteristics per se.

Effects of 2-hour nighttime nap on melatonin concentration and alertness during 12-hour simulated night work

A nighttime nap is expected to mitigate melatonin suppression during night work by blocking light input to the retina, but it is unclear. In the present study, we investigated the effects of a nap break on melatonin level, subjective sleepiness, and vigilance performance during simulated night work. Eleven healthy young males (mean ± SD age: 22.2 ± 4.1 years) participated in counterbalanced crossover design experiments with two conditions (nap vs. no nap). The subjects performed 12-hour simulated night work from 21:00 to 09:00 h (illuminance: ~500 lx). Subjects with a nap condition took a nap for 2 hours in a dark room from 03:00, while subjects with a no nap condition continued the simulated night work. The results showed that immediately after the 2-h nap break, the melatonin level at 05:00 h temporarily recovered from light-induced melatonin suppression during the simulated night work but significantly suppressed again at 07:00 and 09:00 h. Subjective alertness and vigilance performance were impaired immediately after the nap break but subsequently enhanced. The results suggest that a single nap break for 2 hours could be a strategy to enhance alertness during the last part of night shift but inadequate for mitigating melatonin suppression.

Comparing risk of depression between day and night/shift workers using the PHQ-9: a study utilizing the 2014, 2016, and 2018 Korea National Health and Nutrition Examination Survey data

Background

In today's work scenario, the number of shift workers, including those in night shifts, is increasing. Shift work can adversely affect workers' health in the long run, but studies on the relationship between shift work and depression have shown inconsistent results. This study aimed to determine whether the number of night/shift workers at risk of depression, as predicted by the Patient Health Questionnaire-9 (PHQ-9), is higher than that of day workers.

Methods

This study was conducted based on data from the 6th and 7th Korea National Health and Nutrition Examination Survey, 2014, 2016, and 2018. Work schedules were classified into 2 types: day work and night/shift work. This study used the PHQ-9, a self-reported depression screening test, to identify workers at risk of depression. Statistical analysis was performed using SPSS 26.0, and descriptive statistics, χ² test, and logistic regression analysis were employed.

Results

After adjusting for age, educational level, working hours per week, and income, men engaging in night/shift work were at a higher risk of depression (odds ratio [OR]: 1.407, 95% confidence interval [CI]: 0.937-2.113). The same was confirmed for women (OR: 1.564, 95% CI: 1.176-2.081).

Conclusions

Our results showed that the OR for those engaged in night/shift work with a PHQ-9 score of 10 or more increased. Considering the large volume of psychiatric history and symptoms in Korea, additional research is needed. Additionally, further discussion on ways to provide realistic help to night/shift workers is warranted.

Length of exposure to long working hours and night work and risk of sickness absence: a register-based cohort study

Background

There is inconsistent evidence that long working hours and night work are risk factors for sickness absence, but few studies have considered variation in the length of exposure time window as a potential source of mixed findings. We examined whether the association of long working hours and night work with sickness absence is dependent on the length of exposure to the working hour characteristics.

Methods

We analysed records of working hours, night work and sickness absence for a cohort of 9226 employees in one hospital district in Finland between 2008 and 2019. The exposure time windows ranged from 10 to 180 days, and we used Cox’s proportional hazards models with time-dependent exposures to analyse the associations between working-hour characteristics and subsequent sickness absence.

Results

Longer working hours for a period of 10 to 30 days was not associated with the risk of sickness absence whereas longer working hours for a period of 40 to 180 days was associated with a lower risk of sickness absence. Irrespective of exposure time window, night work was not associated with sickness absence.

Conclusions

It is important to consider the length of exposure time window when examining associations between long working hours and sickness absence, whereas the association between night work and sickness absence is not similarly sensitive to exposure times.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12913-021-07231-4.

Associations of shift work and night work with risk of all-cause, cardiovascular and cancer mortality: a meta-analysis of cohort studies

BACKGROUND

Epidemiological studies on the relationship of shift work or night work with risk of total and cause-specific mortality have given conflicting results. We aimed at conducting a meta-analysis to summarize the evidence from cohort studies.

METHODS

Embase, PubMed, Web of Science and Scopus databases were searched for eligible studies up to Mar 2021. Cohort studies evaluating the associations of shift work or night work with risk of all-cause, cardiovascular or cancer mortality were reviewed. Study-specific risk estimates were pooled by fixed-effect models when the heterogeneity was not detected; otherwise, random-effect models were employed.

RESULTS

We identified seventeen eligible articles (sixteen cohorts). A total of 958,674 cohort participants were included, with 38,413 total deaths, 24,713 cardiovascular deaths and 10,219 cancer deaths during follow-up. According to the Newcastle-Ottawa Scale, fifteen studies were considered as relatively high quality with low risk of bias. Compared with regular daytime workers, the pooled relative risks for all-cause, cardiovascular and cancer mortality were 1.02 (95% CI: 0.99, 1.06), 1.18 (95% CI: 0.94, 1.47) and 1.05 (95% CI: 0.83, 1.34) for those ever exposing to shift work, respectively. Compared with daytime workers or those never exposing to night work, the pooled relative risks for all-cause, cardiovascular and cancer mortality were 1.06 (95% CI: 1.03, 1.08), 1.15 (95% CI: 1.03, 1.29) and 1.04 (95% CI: 1.00, 1.08) for those ever exposing to night work, respectively. Moderate to high level of heterogeneity across the studies was detected. Publication bias was not detected.

CONCLUSION

Night work may be associated with higher risk of all-cause, cardiovascular and cancer mortality, suggesting that night workers compared with daytime workers may be at higher risk of death, especially due to cardiovascular disease.

[Work, family and nurses perception about their own health: relationship with breast cancer and shift work.]

OBJECTIVE

Breast cancer is a commonly diagnosed disease in nurses that, from recent years, has been linked to shift work and night work. Also, different components of work stress have such an impact on the nurses' health and work, family and social conciliation. The objective of this research was to analyze the family and working characteristics of Spanish nurses who perform shift work (including night shifts) in search of possible associations with manifestations of psychosomatic stress and the risk of breast cancer.

METHODS

A cross-sectional descriptive study was conducted through a virtual questionnaire in a sample of 966 Registered Nurses in Spain between December 2019 and November 2020. A descriptive analysis of sociodemographic and occupational variables was performed, and statistically significant differences and associations were contrasted by estimating risks and confidence intervals.

RESULTS

The number of night shifts throughout life and the number of years worked were statistically significant for the association with breast cancer. In addition, other psychosomatic manifestations such as insomnia, palpitations or extreme tiredness were highlighted. Among the most appreciated aspects to generate job satisfaction, co-worker's relationship was underlined.

CONCLUSIONS

Rotating shift work can cause multiple clinical alterations that could lead to problems related to family conciliation, self-care or employment wellness. It is important to control the physical, psychological and emotional overload of nurses.

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.

Night shift schedule alters endogenous regulation of circulating cytokines

Night shift work is a risk factor for viral infection, suggesting that night shift schedules compromise host defense mechanisms. Prior studies have investigated changes in the temporal profiles of circulating cytokines important for priming and restraining the immune response to infectious challenges from night shift work, but not by way of a 24-h constant routine of continuous wakefulness devoid of behavioral or environmental influences. Hence the true endogenous pattern of cytokines, and the combined effect of sleep loss and circadian misalignment on these cytokines remains unknown. Here, 14 healthy young men and women underwent three days of either a simulated night shift or a simulated day shift schedule under dim light in a controlled in-laboratory environment. This was followed by a 24-h constant routine protocol during which venous blood was collected at 3-h intervals. Those who had been in the night shift schedule showed lower mean circulating TNF-α (t₁₃ = -6.03, p < 0.001), without any significant differences in IL-1β, IL-8 and IL-10, compared with those who had been in the day shift (i.e., control) schedule. Furthermore, circulating IL-6 increased with time awake in both shift work conditions (t₁₃ = 6.03, p < 0.001), such that temporal changes in IL-6 were markedly shifted relative to circadian clock time in the night shift condition. These results indicate that night shift work compromises host defense by creating cytokine conditions that initially impede anti-viral immunity (lower TNF-α) and may eventually promote autoimmunity (mistimed rise in IL-6).

•

Night shift schedules compromise host defense mechanisms to infection.

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This could be from dysregulated cytokine responses.

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We show by a novel constant routine paradigm, that cytokine dysregulation occurs.

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Cytokine dysregulation exposes night shift workers to increased risk for SARS-CoV-2.

Relationship Between Shift Intensity and Insomnia Among Hospital Nurses in Korea: A Cross-sectional Study

Objectives

This study explored the relationship between shift intensity and insomnia among hospital nurses.

Methods

The participants were 386 female hospital nurses who underwent a special health examination for night workers in 2015. The Korean Insomnia Severity Index (ISI), indices of shift work intensity, and other covariates such as amount of exercise, level of alcohol consumption, employment duration, and hours worked were extracted from the health examination data. The indices for shift intensity were (1) number of 3 consecutive night shifts and (2) number of short recovery periods after a previous shift, both assessed over the prior 3 months. Multiple logistic regression analysis adjusted for the aforementioned covariates was performed to evaluate the association of shift intensity with insomnia, defined as an ISI score of ≥8.

Results

The nurses with insomnia tended to be younger (p=0.029), to have worked 3 consecutive night shifts more frequently (p<0.001), to have experienced a greater number of short recovery periods after the previous shift (p=0.021), and to have worked for more hours (p=0.006) than the nurses without insomnia. Among the other variables, no statistically significant differences between groups were observed. Experiences of 3 or more consecutive night shifts (odds ratio [OR], 2.33; 95% confidence interval [CI], 1.29 to 4.20) and 3 or more short recovery periods (OR, 2.01; 95% CI, 1.08 to 3.73) were associated with increased odds of insomnia.

Conclusions

The results suggest that decreasing the shift intensity may reduce insomnia among hospital nurses working rotating shifts.

Cardiovascular mortality in a Swedish cohort of female industrial workers exposed to noise and shift work

PURPOSE

The aim was to study mortality due to cardiovascular disease as well as total mortality, among female industrial workers, and the association to occupational noise and shift work.

METHODS

Women from cohorts of soft tissue paper mills (N = 3013) and pulp and paper mills (N = 1483) were merged into one cohort. Job exposure matrices were developed and used for classification of shift work and noise exposure. Every year was classified as shift work excluding nights or shift work including nights. Noise was classified into seven 5 dB(A) bins from < 75 to ≥ 100 dB(A). Mortality from cardiovascular diseases and total mortality during 1956-2013 was calculated as a standardized mortality ratio (SMR) with 95% confidence interval (CI) using the female general population as a reference.

RESULTS

Fatal myocardial infarctions (N = 144) were increased in the total cohort, SMR 1.20 (95% CI 1.01-1.41) but not total mortality. The SMR for myocardial infarction for women exposed to noise ≥ 90 dB(A) for > 10 years was 1.41 (95% CI 1.02-1.89) and for those exposed to night shifts > 10 years, 1.33 (95% CI 0.91-1.89). Shift workers without nights ≤ 65 years, with noise exposure ≥ 90 dB(A), had SMR 2.41 (95% CI 1.20-4.31) from myocardial infarction. There was no increased mortality from cerebrovascular disease.

CONCLUSIONS

Female paper mill workers had an increased mortality from acute myocardial infarction, especially before retirement age, when exposed to noise ≥ 90 dB(A) and with long-time employment. Exposure to shift work and noise usually occurred concurrently.

Eating habits, sleep, and a proxy for circadian disruption are correlated with dyslipidemia in overweight night workers

OBJECTIVE

The aim of this study was to evaluate the relationship between proxy for circadian disruption, eating habits, sleep characteristics, and dyslipidemic parameters.

METHODS

This was a randomized, double-blind, crossover controlled clinical trial, and for this study, only baseline data were used. The sample was composed of 36 overweight female nurses who worked on a fixed night shift (12 × 36 h). Linear regression models were used to assess the relationship between the mentioned variables.

RESULTS

The participants' average age was 39.4 y (Standard error (SE) 1 y) and the average nighttime sleep duration was 5.76 h (SE 0.16 h). The average chronotype indicated a moderate early type (03:03 h; SE 20 min) and the average social jetlag was 03:42 h (SE 10 min). It was found that 1 h less of nighttime sleep increased very-low-density lipoprotein cholesterol levels by 2.75 mg/dL and triacylglyceride levels by 3.62 mg/dL. Additionally, higher social jetlag was associated with higher low-density lipoprotein cholesterol levels. On the other hand, each additional hour in the chronotype increased high-density lipoprotein cholesterol levels by 3.06 mg/dL and a time interval >2 h between the last meal and sleep onset was associated with higher high-density lipoprotein cholesterol levels.

CONCLUSION

Short duration of nighttime sleep and high social jetlag are risk factors for dyslipidemia, whereas the late type and the longer time interval between the last meal and sleep onset appear to be protective factors for dyslipidemia.

Effects and mechanisms of action of light-emitting diodes on the human retina and internal clock

White light-emitting diodes (LEDs) will likely become the most used lighting devices worldwide in the future because of their very low prices over the course of their long lifespans which can be up to several tens of thousands of hours. The expansion of LED use in both urban and domestic lighting has prompted questions regarding their possible health effects, because the light that they provide is potentially high in the harmful blue band (400-500 nm) of the visible light spectrum. Research on the potential effects of LEDs and their blue band on human health has followed three main directions: 1) examining their retinal phototoxicity; 2) examining disruption of the internal clock, i.e., an out-of-sync clock, in shift workers and night workers, including the accompanying health issues, most concerningly an increased relative risk of cancer; and 3) examining risky, inappropriate late-night use of smartphones and consoles among children and adolescents. Here, we document the recognized or potential health issues associated with LED lighting together with their underlying mechanisms of action. There is so far no evidence that LED lighting is deleterious to human retina under normal use. However, exposure to artificial light at night is a new source of pollution because it affects the circadian clock. Blue-rich light, including cold white LEDs, should be considered a new endocrine disruptor, because it affects estrogen secretion and has unhealthful consequences in women, as demonstrated to occur via a complex mechanism.

Relationship of work-related stress with obesity among Brazilian female shift workers

OBJECTIVES

To explore the relationship between work-related stress and obesity among female shift workers. Additionally, we also aimed to test the interaction between shift work and work-related stress in this association.

DESIGN

A cross-sectional study was conducted among Brazilian female shift workers. Work-related stress was assessed through a demand-control questionnaire (Job Stress Scale). Work-related stress was defined by the presence of high psychological demands and low control at work. The obesity cases were defined as those with a BMI of 30 kg/m2 or more. Multivariate Poisson regression with robust variance was used to obtain the prevalence ratios (PR) and their respective 95 % CI.

SETTING

A group of industries located in southern Brazil in 2017.

PARTICIPANTS

Four hundred and twenty female workers aged 18-59 years.

RESULTS

The overall prevalence of obesity was 30 % (95 % CI: 25·6, 34·4), and the presence of work-related stress was identified in 24 % (95 % CI: 19·9, 28·1) of the sample. We found an indication of interaction between work-related stress and night shift work on obesity (P = 0·026). After adjusting for confounding factors, work-related stress was associated with a 71 % greater probability of obesity (PR = 1·71; 95 % CI: 1·02, 2·87; P = 0·042) among female night shift workers.

CONCLUSIONS

In this study, we revealed that exposure to work-related stress and night shift work were associated with obesity among female shift workers. Furthermore, the prevalence of obesity was high among female shift workers.

Effect of consuming a late-night high-protein/moderate-carbohydrate vs. low-protein/high-carbohydrate meal by night workers on their food perceptions later during the day: a randomized crossover study

It is typical of night workers to consume a large dinner meal before their work shift, even though this practice may increase the risk for metabolic disorders. Night workers usually eat at night to socialize with colleagues as well as to stay alert and to avoid upset stomach during the night shift. However, little is known if and how the composition of the nighttime meal by night shift workers influences their food perceptions and eating behavior later during the day. The aim of this study was to analyze the effect of a high-protein/moderate-carbohydrate (HP/MCHO) meal vs. low-protein/high-carbohydrate (LP/HCHO) meal eaten at night by night-shift workers on their food consumption and perceptions later during the day. Fourteen male night shift workers were followed-up for 7 days for their eating and sleep habits. Then, participants underwent two isocaloric dietary events - one event a HP/MCHO meal containing 45% carbohydrate, 35% protein, and 20% fat and the other event a LP/HCHO meal containing 65% carbohydrate, 15% protein, and 20% fat, with a 6-day washout period between them - at 01:00 h during their night shift. Thereafter throughout the day, participants filled a food register of all the food consumed and perceptions, including hunger before meals, enjoyment of meals, and satiety. Generalized estimating equation analyses were used to examine the effect of both conditions on food consumption and food perceptions. Appetite for salty food snacks was greater after the HP/MCHO condition than after the LP/HCHO condition (p = .041). During the day following consumption of the nighttime HP/MCHO vs. LP/HCHO meal, there was higher percentage of carbohydrate consumption during lunch and a lower percentage of fat consumption during dinner (48.14% vs. 36.98% and 27.34% vs. 40.39%, respectively). These findings suggest the composition in terms of carbohydrates, protein, and fats of the meal consumed for the night shift by night workers may affect later during the day both food consumption and perceptions.

Night Work, Rotating Shift Work and the Risk of Cancer in Japanese Men and Women: the JACC Study

Background

Limited epidemiological evidence has suggested a positive relationship between night shift work and the risk of cancer. Herein, we investigated the prospective association between different forms of work schedule and the risk of numerous cancers and all-cause cancer among Japanese men and women.

Methods

This cohort study included 45,390 working men and women aged 40–79 years and registered in the Japan Collaborative Cohort Study (JACC Study). The Cox proportional hazards models were used to calculate the hazard ratios (HRs) and their 95% confidence intervals (CIs) for incident cancer among those who reported engagement in night work and rotating shift work for their longest occupations compared with day work.

Results

Within a median follow-up duration of 14.2 years, 2,283 (9.4%) men and 1,309 (4.5%) women developed cancer. Among men, rotating shift work was significantly associated with increased risk of esophageal cancer (HR 2.47; 95% CI, 1.42–4.31) and decreased risk of liver cancer (HR 0.54; 95% CI, 0.30–0.98). Also, rotating shift work tended to be associated with the increased risk of prostate cancer (HR 1.42; 95% CI, 0.95–2.12). Night work and rotating shift work were not related to the risk of all-cause cancer in either sex.

Conclusion

Rotating shift work might contribute to the increased risk of esophageal cancer and prostate cancer and the decreased risk of liver cancer among Japanese men.

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.

The riddle of shiftwork and disturbed chronobiology: a case study of landmark smoking data demonstrates fallacies of not considering the ubiquity of an exposure

BACKGROUND

Failing to integrate all sources of a ubiquitous hazard candidate may explain inconsistent and/or null, and overall misleading, results in epidemiological studies such as those related to shift-work.

METHODS

We explore this rationale on the assumption that Doll and Hill had confined their 1950 landmark study to smoking at workplaces alone. We assess how non-differential, or how differential, underestimation of exposure could have biased computed risks.

RESULTS

Systematically unappreciated exposures at play could have led to substantial information bias. Beyond affecting the magnitude of risks, not even the direction of risk distortion would have been predictable.

CONCLUSIONS

Disturbed chronobiology research should consider cumulative doses from all walks of life. This is a conditio sine qua non to avoid potentially biased and uninterpretable risk estimates when assessing effects of a ubiquitous hazard candidate.

Shift work, and burnout and distress among 7798 blue-collar workers

Objective

This study aimed to investigate the association between shift work, and burnout and distress, and differences by degree of satisfaction with shift schedule and its impact on private life.

Methods

Population 4275 non-shift factory workers and 3523 rotating 5-shift workers. Workers participated between 2009 and 2016 one to three times in the companies’ periodical occupational health checks. Burnout was measured using the distance, exhaustion and competence subscales of the Dutch Maslach Burnout Inventory and distress by the subscale of the Four-Dimensional Symptom Questionnaire (scale: 0–100). Multiple-adjusted linear mixed models were used to assess between- and within-subject associations between shift work and outcomes, and differences by age, years of shift work, and satisfaction with and impact of shift schedule.

Results

Shift work was significantly associated with lower scores on burnout distance (B − 1.0, 95% − 1.8 to 0.3), and among those aged < 48 years with burnout exhaustion (range B − 1.3 to − 1.6). However, the effect sizes were small. Compared to non-shift workers, shift workers dissatisfied with their schedule and those experiencing a high impact on private life had significantly higher burnout (range B 1.7–6.3) and distress levels (range B 4.9–6.1). In contrast, satisfied shift workers and those experiencing a low impact of shift schedule had lower burnout (range B − 0.2 to − 2.2) and no difference in distress levels (P ≥ 0.05). No clear pattern by years of shift work was observed.

Conclusions

Shift work was associated with burnout and distress in those who were dissatisfied with or who had perceived high impact on the private life of their shift schedule.

Electronic supplementary material

The online version of this article (10.1007/s00420-020-01536-3) contains supplementary material, which is available to authorized users.

Preventing Shift Work Disorder in Shift Health-care Workers

The occurrence of the shift work disorder (SWD) in health-care workers (HCWs) employed in 24/7 hospital wards is a major concern through the world. In accordance with literature, SWD is the most frequent work-related disturb in HCWs working on shift schedules including night shift. In agreement with the Luxembourg Declaration on workplace health promotion (WHP) in the European Union, a WHP program has been developed in a large Hospital, involving both individual-oriented and organizational-oriented measures, with the aim to prevent the occurrence of SWD in nurses working on shifts including night shift. The objective assessment of rotating shift work risk and the excessive sleepiness were detected before and after the implementation of the WHP program, by using the Rotating Shiftwork-questionnaire and the Epworth Sleepiness Scale. The findings of this study showed the effectiveness of the implemented WHP program in minimizing the impact of shift work on workers' health and in preventing the misalignment between sleep-wake rhythm and shift working.

The longitudinal association between shift work and headache: results from the Danish PRISME cohort

PURPOSE

We investigated the effect of shift work on headache. Furthermore, we investigated whether the association between shift work and headache was explained by potential mediators in terms of perceived stress, poor sleep and health behaviors.

METHODS

In this longitudinal study, we used questionnaire data (collected in 2007 and 2009) from civil servants and hospital employees from the PRISME study. 2952 individuals were available for the analyses of shift work and headache and 2272 individuals were available for the analyses of shift work and migraine. Headache was operationalized as the participants' experience of "being bothered by headache during the past 4 weeks". Migraine was operationalized as "ever being diagnosed with migraine by a medical doctor". We used binary logistic regression to compare shift workers with permanent day workers and adjusted for socio-demographic factors. In a subsequent step, we adjusted for potential mediators.

RESULTS

We found higher odds of unspecific headache (OR = 1.25; 95% CI 1.02-1.54) and migraine (OR = 1.72; 95% CI 1.04-2.86) among shift workers compared with day workers. Our results suggest that the effect of shift work on headache and migraine differ between men and women. Inclusion of potential mediators in the analyses did not attenuate the associations.

CONCLUSION

Shift workers have higher risk of reporting being bothered by headache as well as reporting being diagnosed with migraine. Future research is needed to disentangle the underlying mechanisms with the aim of reducing headache related to occupational exposures.

Night shift work, short sleep and obesity

BACKGROUND

Obesity is associated with increased general mortality and comorbidities, it is multifactorial and some evidence has shown that sleep duration and shift work may be implicated in its pathogenesis.

OBJECTIVES

The aim of this study was to evaluate the association between shift work, quality of life and obesity among healthcare workers of a Brazilian University Hospital.

METHODS

A cross-sectional study was performed from April 2013 to December 2014 with 200 workers of a University Hospital. Sociodemographic data were evaluated and BREF WHOQOL was used for quality of life. The physical activity was evaluated using the International Physical Activity Questionnaire (IPAQ), Chronotypes and daily sleep preference were investigated using Munich Chronotype Questionnaire (MCTQ). Venous blood was collected after 12-h of fasting for laboratory tests.

RESULTS

In this sample, the night shift workers had higher income and were older compared to day shift workers. Night shift workers sleep less hours, had higher weight, body mass index and abdominal circumference when compared to the day shift workers. Night shift workers had almost 3 times higher association with abdominal obesity independent of age and gender, than day shift workers. MCTQ parameters showed that night shift workers had lower sleep duration during working days and also during free days, associated with a higher level of social jetlag. Social jetlag had an association with obesity. We found no difference for quality of life between shifts.

CONCLUSIONS

Night work was a risk factor for abdominal obesity, social jetlag was higher in night shift workers and it was associated with presence of obesity.

IARC 2019: "Night shift work" is probably carcinogenic: What about disturbed chronobiology in all walks of life?

In June of 2019, a working group convened by the International Agency for Research on Cancer [IARC] concluded that “night shift work” is probably carcinogenic to humans (a Group 2A carcinogen). This was based on sufficient evidence of cancer and strong mechanistic evidence in experimental animals and limited evidence from human epidemiological studies. The biological basis from experimental work is clear and compelling: Disturbed chronobiology such as due to alterations in the light-dark schedule which shift-workers experience is associated with carcinogenicity. But is it correct to assume in epidemiological studies that “night shift work” provides the same dose of disturbed chronobiology to all night workers and that disturbed chronobiology from activities outside of work does not count? Both chronobiological theory and supporting evidence suggest that much-needed future epidemiology should address these questions and should consider disturbed chronobiology in all walks of life.

The Effects of Workplace Rest Breaks on Health Problems Related to Long Working Hours and Shift Work among Male Apartment Janitors in Korea

Background

Rest breaks at work are reported to reduce fatigue and job stress. Apartment janitors in Korea who perform night shift work and work long hours can be exposed to various health problems (HPs). However, few studies have evaluated relationships between their rest breaks and HPs. This study was conducted to examine the relationships between long working hours, shift work, and insufficient rest breaks and HPs among Korean apartment janitors.

Methods

Data on 1,212 selected male apartment janitors were obtained from the 3rd and 4th Korean Working Conditions Surveys. Demographic and occupational characteristics were collected using self-reported questionnaires. Rest breaks at work were classified as "sufficient" or "insufficient." Long working hours were considered as working more than 60 hours per week. Zero-inflated negative binomial (ZINB) regression was performed to investigate the effects of shift work and long working hours on HPs and the effects of rest breaks on relationships between HPs and long working hours and shift work.

Results

Among those with insufficient rest breaks at work, significant associations were found between long working hours and the risk of HPs [odds ratio (OR) = 1.489; 95% confidence interval (CI) = 1.038-2.136] and work-related HPs (WRHPs) [OR 1.621; 95% CI = 1.156-2.272], and between shift work and HPs [OR = 1.603; 95% CI = 1.084-2.372]. These relationships became nonsignificant when sufficient rest breaks were provided.

Conclusion

It is important to provide breaks at work to reduce HPs because of long working hours and shift work among aged workers such as apartment janitors.

Pain complaints are associated with quick returns and insomnia among Norwegian nurses, but do not differ between shift workers and day only workers

PURPOSE

To determine whether common work schedule characteristics among Norwegian nurses were associated with subjective pain complaints.

METHODS

A cross-sectional study in a sample of 1585 nurses, part of the longitudinal questionnaire-based cohort project 'Survey of Shift work, Sleep and Health' (SUSSH). Pain from six regions were assessed: 'headache', 'neck/shoulder/upper back', 'upper extremities', 'lower back', 'lower extremities', and 'abdomen'. Logistic and negative binomial regression (adjusted for age, sex, percentage of full-time equivalent, marital status and children living at home) were conducted where work schedule, number of night shifts last year, number of quick returns (QR) last year (< 11 h between shifts) and insomnia were predictors of localized pain, widespread pain and number of pain sites.

RESULTS

Localized pain, widespread pain and number of pain sites were associated with insomnia (OR 2.06, 95% CI 1.66-2.55, OR 2.14, 95% CI 1.47-3.09, IRR 1.70, 95% CI 1.51-1.91, respectively). Work schedule and number of night shifts worked last year were not associated with any of the three pain measures. Number of QRs worked last year tended to be associated with number of pain sites.

CONCLUSION

The study did not support the hypothesis that non-daytime work schedules are associated with pain complaints. Neither was there support for the hypothesis linking number of night shifts, or the number of QRs, to pain complaints. Future studies should aim to determine the association between QRs and pain in more detail. Pain complaints were associated with insomnia.

Working hour characteristics and schedules among nurses in three Nordic countries - a comparative study using payroll data

Background

Organisation of working hour schedules in the Northern European countries are rather similar. EU countries are obliged to adopt national legislation regarding duration of weekly working hours and rest periods. Yet, working hour characteristics and schedules are likely to differ with respect to starting times and duration depending e.g. on culture and tradition. Yet, very little is known about potential differences between shifts and schedules across countries among nursing personel. This knowledge is relevant, since the potential differences in working hour characteristics may influence and possibly explain some of the differences observed in studies of health and safety.The aim of the study was to compare characteristics of working hours and work schedules among nursing personel in three Nordic countries: Denmark, Finland and Norway.

Methods

The study populations included nursing personnel holding a ≥ 50% position at public hospitals in Denmark (n = 63,678), Finland (n = 18,257) or Norway (n = 1538) in 2013. Objective payroll based registry data with information on daily starting and ending times were used to compare working hour characteristics e.g. starting time, duration of shift, and quick returns (< 11 h between two shifts), as well as work schedules e.g. permanent or 3-shift work between the three countries.

Results

Night shifts generally started earlier and lasted longer in Finland (10-11 h starting at 20:00-22:59) than in Norway (10 h starting at 21:00-21:59) and in Denmark (8 h starting at 23:00-23:59). Very long shifts (≥12 h) were more common in Denmark (12%) compared to Finland (8%) and Norway (3%). More employees had many (> 13/year) quick returns in Norway (64%) and Finland (47%) compared to Denmark (16%). The frequency of 3-shift rotation workers was highest in Norway (41%) and lower in Denmark (22%) and Finland (22%). There were few differences across the countries in terms of early morning shifts and (very) long weekly working hours.

Conclusion

Despite similar distribution of operational hours among nurses in the three countries, there were differences in working hour characteristics and the use of different types of work schedules. The observed differences may affect health and safety.

Association between night work and dyslipidemia in South Korean men and women: a cross-sectional study

BACKGROUND

Previous studies have reported that an irregular work schedule, particularly nighttime work, is associated with an altered lipid profile. Additionally, a mismatch in circadian rhythm can affect sleeping and eating habits, leading to poor health. This study aimed to examine the association between night work and dyslipidemia among South Korean adults aged ≥30 years.

METHODS

For this study, the data of 5813 participants in the 2013-2016 Korea National Health and Nutrition Examination Survey were analyzed. Diagnoses of dyslipidemia were based on blood sampling tests of total cholesterol, high-density lipoprotein (HDL), low-density lipoprotein (LDL) cholesterol, and triglyceride levels. Night work was defined as that conducted during evening (6 P.M.-12 A.M.) and overnight hours (12 A.M.-8 A.M.). The association between night work hours and dyslipidemia in South Korean men and women was investigated using a logistic regression analysis.

RESULTS

After adjusting for sociodemographic, economic, health-related, and nutritional factors, an association of night work with dyslipidemia was observed in male participants (odds ratio = 1.53, 95% confidence interval: 1.05-2.24). In subset analyses of male participants, night workers who skipped meals were more likely to have dyslipidemia than their day-working counterparts. Among men who slept < 7 h, night workers had a higher probability of dyslipidemia than day workers. In contrast, no statistically significant association between night work and dyslipidemia was observed in female participants, although the probability of dyslipidemia appeared to increase with advancing age. Furthermore, when women with dyslipidemia were subdivided by occupational categories, night workers in white collar positions were more likely to have dyslipidemia than their day-working counterparts.

CONCLUSION

Our study observed an association of night work with dyslipidemia, particularly in men. Although these findings may support interventions for South Korean night workers, further studies are needed for validation.

Association of musculoskeletal disorders and workload with work schedule and job satisfaction among emergency nurses

BACKGROUND

The emergency department is a highly demanding work environment, considered by high workload and stress. The impact of work-related factors on musculoskeletal disorders (MSDs) in emergency nurses (ENs) are not yet well understood. We investigated the association of MSDs and workload with work schedule (permanent day and night work) and job satisfaction in ENs.

METHOD

Data were collected through a questionnaire including individual and work-related factors, workload (National Aeronautics and Space Administration-Task Load Index [NASA-TLX]) and MSDs (Standardized Nordic Questionnaire) from 380 ENs in five hospitals.

RESULTS

The findings revealed that work schedule and job satisfaction levels were significantly associated with the MSDs in different body regions. Work schedule was significantly related to physical demand, performance, frustration, and overall workload, whereas it was not to the mental and temporal demands and effort. Job satisfaction level was negatively associated with mental demand and frustration. A high prevalence of musculoskeletal problems, particularly in knees, upper back, lower back, neck and shoulders were found.

CONCLUSION

MSDs are highly prevalent among ENs involved in night work and with low job satisfaction levels. The results are discussed in terms of their implications for emergency hospital nurses. The findings can help to better understand the working conditions and emphasize the need for ergonomic interventions in order to reduce MSDs and workload. Also, the study findings highlight the importance of mental aspects of workload in this occupational group.

Exposure to working-hour characteristics and short sickness absence in hospital workers: A case-crossover study using objective data

INTRODUCTION

Shift work characteristics, such as the number of night shifts or quick returns, are linked to disturbed sleep and greater work-life conflict, but little is known about their association with short sickness absences. Studies utilizing objective working-hour characteristic data can provide knowledge on specific shift work characteristics that may associate with sick leave. We investigated the association between working-hour characteristics in shift work and the incidence of short (1-3 days) sickness absences.

PARTICIPANTS AND METHODS

The individual-level data were collected from the employers' electronic working time records of the Finnish Public Sector study. The final analytical sample was restricted to the first incidence of short sickness absence (1-3 days) from January 1, 2008 to the end of 2015. We studied employees with shift work contracts (n = 12 156) and day work contracts (n = 6225). Of these, 89% were female workers, with a mean age of 37.1 years, and 12% worked part-time. We calculated type of shift (morning, day, evening, and night), quick returns (< 11 h between two work shifts), length of work shift and weekly working time. We utilized case-crossover study design to compare the working-hour characteristics of the 28 days preceding sickness absence (exposure window) and those of the 28 days before the exposure window (control window), using conditional logistic regression models for odds ratios with 95% Confidence Intervals (95%CI).

RESULTS

Exposure to ≥ 2, and especially ≥ 4 consecutive night shifts associated with an increased likelihood of short sickness absence (OR 1.24, 95%CI 1.12-1.38 and OR 1.54, 95%CI 1.10-2.15, respectively) among shift workers, whereas a high number (> 25%) of evening shifts and having ≥ 2 consecutive evening shifts associated with lower odds of sickness absence. Over 40-hour weeks (OR 1.29, 95%CI 1.20-1.39), over 48-hour weeks (OR 1.24, 95%CI 1.01-1.54) and quick returns (OR 1.02, 95%CI 1.01-1.02) increased the likelihood of sickness absence. Having only a few (0-1 or 2-3) quick returns over 28 days decreased the likelihood of sickness absence (ORs 0.46 and 0.67), whereas having ≥ 5 quick returns over 28 days increased it (OR 1.88, 95%CI 1.76-1.99). These associations were similar among both shift and day workers.

CONCLUSIONS

Long working hours, several consecutive night shifts and quick returns increase the risk of short sickness absence. These working-hour characteristics should be avoided in shift scheduling to minimize sickness absence and increased costs for the employer.

Sleep duration mediates abdominal and lower-extremity pain after night work in nurses

OBJECTIVES

The aim of this study was to investigate the association between different working shifts (i.e. morning, evening, night shifts) and headache, musculoskeletal and abdominal pain, and the extent to which reduced sleep duration could account for these associations.

METHODS

Nurses (N = 679, 649 female, aged 22-53 years) were followed up for a period of 28 consecutive days, responding to a diary about sleep, shift type and pain complaints (measured on a Likert-type scale ranging from 0 to 3). Generalised structural equation modelling mediation analysis (GSEM) was performed to test whether shift type was associated with higher incidence or higher intensity of pain (headache, pain in neck/shoulders/upper back, upper extremity, low back, lower extremity and abdominal pain), and if this effect was mediated by sleep duration (continuous variable), after controlling for age, work and lifestyle factors.

RESULTS

Pain scores in lower extremities were decreased following night shifts in general. However, when night shifts were followed by short sleep duration, the risk of pain in the lower extremities and abdominal pain were increased. Headache and pain in the upper extremity were increased after night shifts, but were not associated with sleep duration. Pain in the neck/shoulder/upper back and lower back was not related to shift work.

CONCLUSIONS

Among nurses in a three-shift rotating schedule, night shifts increased the risk of pain in several regions, but only pain in the lower extremities and abdomen was related to reduced sleep duration.

A Review of Data of Findings on Night Shift Work and the Development of DM and CVD Events: a Synthesis of the Proposed Molecular Mechanisms

PURPOSE OF REVIEW

Night shift work has become highly prevalent in our 24/7 societies, with up to 18% of the US work force working alternate shift schedules. However, studies indicate that there may be adverse health effects of chronic night work across diverse populations. These effects are likely due to misalignment of the circadian system with work schedules, mediated by the system's primary marker melatonin as well as other downstream molecules.

RECENT FINDINGS

Melatonin has multiple biologic actions that are relevant to cardiometabolic disease, including modulation of oxidative stress, inflammation, and (via the melatonin receptor) vasoconstriction. Behavioral traits, such as chronotype and meal timing, have recently been shown to interact with the effects of night work on cardiometabolic health. Together with recent findings suggesting a role for circadian genes in cardiometabolic risk, the interactions of night shift work and behavioral traits are likely to facilitate novel treatment and prevention approaches for cardiovascular disease and type 2 diabetes, incorporating aspects of clock and timing.

Night work effects on salivary cytokines TNF, IL-1β and IL-6

Shift work is unavoidable in modern societies, but at the same time disrupts biological rhythms and contributes to social distress and disturbance of sleep, health and well-being of shift workers. Shift work has been associated with some chronic diseases in which a chronic inflammatory condition may play a role. However, few studies investigating the association of cytokine and other inflammation markers with shift workers have been published in recent years. In this study we evaluated the effects of permanent night work on the production of tumor necrosis factor (TNF), interleukin-1β (IL-1β), IL-6 and melatonin in saliva. Another aim was to demonstrate the benefit of the use of salivary cytokines for studies in chronobiology, since it is an easy and non-invasive method that allows for sampling at several times. Thirty-eight healthy male workers, being 21 day workers and 17 night workers, agreed to participate in this study. Sleep was evaluated by actigraphy and activity protocols. Saliva was collected during three workdays approximately at the middle of the work shift and at bed and wake times of the main sleep episode. Saliva samples were then analyzed by enzyme-linked immunosorbent assay to measure TNF, IL-1β, IL-6 and melatonin levels, and the results were submitted to non-parametric statistical analysis. The use of saliva instead of blood allowed for a greater number of samples from the same subjects, allowing identifying alterations in the daily production patterns of salivary cytokines TNF, IL-1β and IL-6 that probably are linked to night work. Salivary TNF and IL-1β levels were similar for day and night workers, with higher daily production after awakening, in the morning hours for day workers and in the afternoon for night workers. Both groups presented a significant daily variation pattern of these two cytokines. Day and night workers produced similar amounts of salivary IL-6. Nevertheless, the daily variation pattern observed among day workers, with a peak after awakening, was absent among night workers. Thus, in our study, night workers showed partially adjusted daily variation patterns for salivary TNF and IL-1β, not seen for salivary IL-6. Results for salivary IL-6 could be better explained as a consequence of circadian disruption due to permanent night work. Our results suggest that the whole circadian system, including clocks and pineal gland, is involved in regulating cytokine profile in shift workers and that a coordinated production of these cytokines, important for an adequate inflammatory response, could be disturbed by shift work. The distinct effects that shift work may have on different cytokines could give some cues about the mechanisms involved in this association.

Vitamin D supply in shift working nurses

We studied determinants of Vitamin D in serum of 67 female health care workers (aged 25-60 years), including age, body mass index, physical activity, and shift work. Overall, vitamin D levels were low, ranging from 6 to 51 ng/mL (median: 20 ng/mL). Lower serum levels were found in samples drawn in winter and spring and in obese subjects. Shift work had only small effects on vitamin D levels. The high prevalence of vitamin D undersupply is in line with observations from the German general population. Vitamin D supply particularly in winter and spring should be ensured to avoid health problems.

Interleukin-6 Level among Shift and Night Workers in Japan: Cross-Sectional Analysis of the J-HOPE Study

Aim: Shift workers have a high risk of cardiovascular disease (CVD). Systemic inflammation measured has been associated with the risk of CVD onset, in addition to classical risk factors. However, the association between work schedule and inflammatory cytokine levels remains unclear. The purpose of this study was to examine the association between work schedule and interleukin-6 (IL-6)/high-sensitivity C-reactive protein (hs-CRP) levels among Japanese workers.

Methods: The present cross-sectional study was a part of the Japanese Study of Health, Occupation and Psychosocial Factors Related Equity (J-HOPE). A total of 5259 persons who measured inflammatory cytokine were analyzed in this study. One-way analysis of variance was used to test log-transformed IL-6/hs-CRP differences by work schedule. Multiple regression analysis was used to examine the difference adjusted for other possible CVD risk factors.

Results: There were 3660 participants who had a regular work schedule; the remaining schedules were shift work without night work for 181 participants, shift work with night work for 1276 participants, and only night work for 142 participants. The unadjusted model showed that only night workers were significantly related to high levels of IL-6 compared with regular workers. Even in the multiple regression analysis, the higher level of IL-6 among only night workers remained significant (β = 0.058, P = 0.01). On the contrary, hs-CRP was not.

Conclusion: The present study revealed that only night shift work is significantly associated with high levels of IL-6 in Japanese workers. These observations help us understand the mechanism for the association between work schedule and CVD onset.

Comparison of Melatonin Profile and Alertness of Firefighters with Different Work Schedules

Introduction:

A two-shift work schedule with different rotations is common among firefighters in Iranian petrochemical companies. This study compared salivary melatonin and sleepiness on the last night before turning to day shift at 19:00, 23:00, 3:00, and 7:00 among petrochemical firefighters (PFFs) working seven and four consecutive night shifts.

Methods:

Sixty four PFFs working in the petrochemical industry were selected. To measure melatonin, saliva samples were taken, whereas the KSS index was used to assess sleepiness. Chi-square and independent samples t-test were carried out to analyze the data, and generalized linear model (GLM) was employed to determine the effect of confounding factors such as lighting and caffeine.

Results:

The levels of melatonin at 3:00 and 7:00, and the overall changes during the shift in the two shift patterns under the study were different (P < 0.05). Sleepiness was significantly different only at 3:00 in the two studied shift patterns, while the effects of lighting and caffeine on melatonin changes were not significant (P > 0.05).

Conclusion:

It seems that a slow shift rotation is better because it reduces the secretion of melatonin (hence reducing sleepiness during the night) and changes the peak of melatonin secretion to the daytime, which is a sign of adaptation.

The relationship between night work and breast cancer

Background

Since the International Agency for Research on Cancer classified shift work that involves circadian disruption as “probably carcinogenic to humans,” there has been growing concern on the relationship between night work and breast cancer. In Korea, about 10–15% of workers are engaged in night-shift work, and breast cancer is one of the most common cancers in women. The purpose of this study was to review epidemiologic evidence on the relationship between night work and breast cancer.

Methods

We reviewed 21 original articles and 5 meta analyses on relationship between nightwork and breast cancer, and investigated the compensation criteria of Denmark.

Results

The association between breast cancer and night work has been reported by numerous epidemiologic studies, including cohort studies, case-control studies, and meta-analysis. However, a dose-response relationship has not clearly emerged among workers exposed to less than 20 years of night work.

Conclusion

Although there are some limitations to the epidemiological studies so far, further consideration of breast cancer cases in patients with high exposure to night work is needed to assess breast cancer as a work-related disease.

Sleep-related problems and minor psychiatric disorders among Brazilian shift workers

The aim of this study was to explore the association between sleep-related problems with the occurrence of minor psychiatric disorders in shift workers of southern Brazil. A cross-sectional study with 1202 workers (785 females) aged 18-50 years was carried out. Minor psychiatric disorders were assessed using the Self-Reporting Questionnaire (SRQ-20), and four sleep problems were collected and analyzed: sleep deprivation (≤ 5h), difficulty falling asleep, waking up during sleep, and sleep medication use. Results show that the overall prevalence of minor psychiatric disorders was 26.8%, but it was more prevalent among females than males (30.2% vs. 20.4%). Nightshift work was significantly associated with the occurrence of sleep-related problems. After adjusting for confounding factors, the number of sleep-related problems showed a positive linear trend with psychiatric disorders in both sexes. Having two or more sleep-related problems was associated with increased probability of psychiatric disorders approximately three-fold among males and two-fold among females, when compared with those without sleep problems. In conclusion, this study demonstrated that sleep-related problems have a strong and independent association with psychiatric disorders among shift workers. Furthermore, the prevalence of both conditions was higher among females than males; however, the strength of these associations was higher in males.

Can yesterday's smoking research inform today's shiftwork research? Epistemological consequences for exposures and doses due to circadian disruption at and off work

In 1950, landmark epidemiology studies by Wynder & Graham and Doll & Hill contributed to identifying smoking as a potent carcinogen. In 2007, IARC classified shiftwork involving circadian disruption (CD) as probably carcinogenic; however, epidemiological evidence in regards to the carcinogenicity of shiftwork that involves nightwork is conflicting. We hypothesize that shiftwork research is lacking chronobiological and methodological rigor and that lessons can be learned from comparison with smoking research. Herein, we provide a factual view at, and a fictional case study of, 1940s smoking research which serves as an analogy for current shiftwork research dilemmas. This analogy takes the form of limiting counting cigarettes to a particular time window (i.e. at work) rather than assessing exposures to, and doses of, accumulated smoking over 24 h, highlighting the importance of exposure and dose. Simply put, smoking insights could have been delayed or even disallowed. In conclusion, CD may be similar to smoking insofar as for quantitative measures of cumulative doses, exposures both at and off work may have to be considered. Future work must explore whether such similarity factually exists and whether CD is a cancer hazard in IARC terms.

The effect of blue-enriched white light on cognitive performances and sleepiness of night-shift workers: A field study

INTRODUCTION

Night-shift works are basically accompanied by reduced cognitive performance, sleepiness, and higher possibility for human error and related incidents. It is therefore crucial to improve individuals' performance and alertness in sensitive places like industries' control room with the ultimate goal of increasing efficiency and reducing the number of possible incidents. Previous research has indicated that blue light is a critical cue for entraining circadian rhythm. As a result, the present study was an attempt to investigate whether blue-enriched white light illumination was a practical strategy to decrease sleepiness and improve cognitive performance during night shifts.

MARTIAL AND METHODS

The study, which adopted a before-after interventional design, was conducted among 30 control room staff members of petrochemical industry. After baseline assessments under existing lighting conditions, every participant was exposed to two new lighting conditions (namely, 17,000K and 6500K blue-enriched white light), each lasting for a week. Assessments were conducted again at the end of these treatments. In order to measure the subjective sleepiness, Karolinska Sleepiness Scale (KSS) was utilized. Subjects also performed the Conners' Continuous Performance Test II (CPT-II) and 1-back test in order to gauge their cognitive performance, and melatonin assessment was carried out using salivary and Eliza technique. The data was analyzed using two-way repeated measure ANOVA.

RESULTS

The results indicated that, compared to normal lighting conditions, participants' sleepiness and melatonin rhythm significantly declined when they were exposed to blue-enriched white light. Furthermore, the experimental condition had a significant effect on the reduction of working memory errors. It also decreased omission errors and the reaction time during the sustained attention task.

CONCLUSIONS

Thus, using blue-enriched white light may be a proper ergonomic strategy for improving performance and alertness, especially during night, in sensitive environments like control rooms.