Effects of shift work on cortisol levels among nurses: a systematic review

Shift work is commonly increasing, and some physiological changes occur as workers sleep less and their circadian rhythms are disrupted. This umbrella review not only summarizes the evidence but also evaluates the validity of the associations of shift work with different health outcomes. We searched the MEDLINE, Web of Science, and Embase databases from their inception to April 25, 2020. For each systematic review and/or meta-analysis, we estimated the summary effect size, the 95% confidence interval, the 95% prediction interval, the between-study heterogeneity, evidence of small-study effects, and evidence of excess-significance bias. Eight eligible systematic reviews and meta-analyses were identified, providing data on 16 associations. We observed highly suggestive evidence for associations between shift work and myocardial infarction (having ever vs having never done shift work) and diabetes mellitus incidence (per 5-year increment in shift work). Furthermore, we observed suggestive evidence for an association between shift work and diabetes mellitus incidence (having ever vs having never done shift work). Two health outcomes, including prostate cancer incidence (having ever vs having never done shift work and rotating night shift work vs daytime work) and colorectal cancer incidence (longest vs shortest shift work time), were only supported by weak evidence. This umbrella review found that shift work was associated with several health outcomes with different levels of evidence. Associations for myocardial infarction and diabetes mellitus incidence were supported by highly suggestive evidence. Registry: PROSPERO; Identifier: CRD42020188537. Wu Q-J, Sun H, Wen Z-Y, etal. Shift work and health outcomes: an umbrella review of systematic reviews and meta-analyses of epidemiological studies. J Clin Sleep Med. 2022;18(2):653-662.

Langmuir probes are used to determine the electron temperature, electron density, and longitudinal heat flux in the immediate vicinity of the limiter in the T-3M tokamak. (AIP)

Introduction: Shift work is associated with increased incidence of obesity and other features of the metabolic syndrome. Health problems in shift workers are caused by several factors, one of these factors is the stress hormone cortisol. Aim of the work: to assess the association between night shift work and the changes in body mass index (BMI), fasting blood glucose, lipid (total cholesterol, HDL, and triglycerides) levels, cortisol hormone secretion, uric acid blood level and salivary cortisol level. Materials & Methods: this study was conducted on 160 male security personnel, their age ranging from 35 to 40 years in Cairo . Regarding the work schedule 80 subjects worked daytime for 8 hours, whereas 80 individuals worked only night shift for 12 hour with one day off, for at least continuous 5 years. Results: the results showed no significant difference between night shift and day workers as regard age and working years. As regard body mass index (BMI) there was highly significant difference (<0.001) between night and day workers. There was no significant difference between night and day shift workers as regard total cholesterol level, triglycerides, and fasting blood glucose (P< 0.05) where as there is a significant difference between night and day shift workers as regard HDL –cholesterol (P<0.05) and a highly significant difference between night and day shift workers as regard uric acid blood level (P<0.001).A significant difference was detected in salivary cortisol levels among night shift workers where the salivary cortisol level is higher in the evening than in the morning, also there is a significant difference in salivary cortisol level among day shift workers where the salivary cortisol level is higher in the morning than in the evening (P<0.05). Conclusion: Our results suggest an association between long-term shift work and increased body mass index, elevation cortisol level, HDL–cholesterol, fasting blood glucose and uric acid level. Further studies are needed to understand the biological mechanisms involved and the complex behavioral and social adaptations experienced by night-shift workers. Regular screening health programs should be done to maintain the health of shift workers.

Introduction Shift work, particularly night shift, has been linked to poor sleep, which could increase the risks of various chronic diseases and mental health issues through potential disruptions in the rest-activity circadian rhythm (RAR) caused by the changing shift schedules. While recent studies have shown that day and afternoon shift nurses had better RAR than night shift nurses, the extent to which night shifts affect nurses’ RAR is underexplored. Therefore, our study aimed to investigate the association between different shift work schedules and RAR parameters among Hong Kong nurses using actigraphy accelerometers. Methods This was a 7-day device-monitored study that recruited 201 nurses and 100 daytime office workers. Actigraphy accelerometers were applied to collect RAR, sleep and activity metrics over a consecutive 168 hours. Of the 301 participants, 277 participants had at least 96 hours of valid data. A self-reported questionnaire including sociodemographic characteristics, lifelong occupational history, and lifestyle information was completed by the participants. Multivariate logistic regression models were used to calculate the odds ratios (ORs) and 95% confidence intervals (CIs) for the relationships between RAR parameters and different shift work profiles. Results Nurses in our study tended to be younger, had higher monthly earnings, and possessed shorter work durations compared to the daytime counterparts. Furthermore, a higher prevalence of poor mental health and sleep disturbances was observed among the nurses than daytime workers. There were 182 nurses, and 95 daytime workers had valid actigraphy data. Involving in night shift schedule (aOR=3.12, 95%CI: 1.78-5.49) and working frequent night shifts (≥ 2 nights) in the past 7 days (aOR=10.94, 95%CI: 3.67-32.64, ptrend =0.011) were significantly associated with reduced amplitude, indicating dampened RAR among nurses. Additionally, male sex and low levels of physical activity modified the association between work schedules and reduced RAR amplitude. Conclusion In conclusion, reduced RAR amplitude was significantly associated with shift work schedules and frequent night shift work, and the effect was particularly high among male shift workers. While frequent night shift work is not recommended for male shift nurses, high levels of physical activity might help shift nurses better adapt to night shift work. Support (if any) Health and Medical Research Fund (No.18190471)

<h3>Objective</h3> Most literature examining the health effects of shift work prioritize night work as the exposure of interest. However, little attention has been paid to the co-occurrence of working time characteristics beyond shift type (e.g. night vs day) that may lead to circadian rhythm disruption; characteristics such as shift intensity, shift duration, rotation pattern, and weekend work. We hypothesize that the co-occurrence of these characteristics with and without night work could explain why shift work without night work is sometimes associated with adverse health effects. <h3>Methods</h3> Time-registry data on 14,430 full-time (&gt;150 shifts/year) healthcare workers from 2012–2016 were sourced from the Working Hours in the Finnish Public Sector (WHFPS) study to describe the prevalence and co-occurrence of working time characteristics that may lead to circadian rhythm disruption. First, each characteristic (type, intensity, duration, rotational pattern, and weekend work) was cross-classified in a matrix to examine its co-occurrence with all other characteristics (e.g. how many night shifts were also long shifts). Second, the prevalence of each working hour characteristic by annual shift schedules (permanent or rotating day/evening/night) were examined. <h3>Results</h3> Our results provide evidence that working hour characteristics hypothesized to cause circadian rhythm disruption have a varying distribution with each other and across shift schedules- even schedules that don’t include nights. While day shifts are thought to not cause circadian rhythm disruption, 32% of day shifts versus 34% of night shifts co-occurred with long work hours, quick returns, and rotations. Furthermore, despite not including nights, the Day/Evening schedule had more quick returns than the Day/Evening/Night schedule and still contained rotations, long hours, and weekend work. <h3>Conclusion</h3> Thus, a cautious interpretation of the association between night work and human health may be warranted, as circadian rhythm disruption may be caused by long hours, rotations, or quick returns which may or may not accompany night work.

Does shift work cause cancer?

The purpose of our study was mainly to explore the effect of different shift work on cognitive and executive performance in a real clinical environment among nurses from China. Working in shifts can disrupt circadian rhythm, resulting in reduced sleep duration, which can have a detrimental effect on cognitive function. To provide continuous service for patient care, shift work is often a special requirement for nurses. The Stroop test can be used to measure selective attention and reaction time during executive function. However, there have been limited studies about the effect of shift work on the cognitive performance of nurses by Stroop tests. Additionally, no study has been conducted in nurses working in shifts from China. Registered nurses in general ward, Department of Neurology, from West China Hospital of Sichuan University, were eligible and consecutively included if they were simultaneously responsible for the day, evening and night shifts on the shift work schedule. A fatigue questionnaire and Stroop tests were performed for each subject separately before and after three working shifts (morning, evening and night shift) to measure changes in fatigue, reaction time and accuracy. Eighteen registered nurses (4 males and 14 females) were included in our study, with a median age of 25 years old. The fatigue degree was significantly increased after day and evening shifts (p = .015 and <.001, respectively). Compared with those in the preshifts, the reaction time in the neutral task and incongruent task was significantly quicker after the day shift (p = .001, p < .001) and night shift (p = .008, .019). In contrast, the reaction time after the evening shift was mildly increased, although without significance. There was no significant difference in accuracy among the three different working shifts. In addition, there was a negative correlation between the fatigue score and reaction time on the incongruent task in the Stroop test before the day shift (r = -.542, p = .020). The fatigue score in the postday shift was found to be inversely related to working hours in the daytime (r = -.500, p = .034). Our study showed that increased fatigue was found in nurses after day and evening shifts, and shift work can affect the reaction time after the evening shift. However, there was no significant difference in accuracy and a high level of attention could be maintained among the three working shifts, suggesting a highly developed sense of responsibility in our nurses. In addition to focusing on the common adverse effects of evening or night shifts on nurses, fatigue in the day shift should be paid special attention to by the leadership in the nursing management. Also, nurse managers can implement specific strategies to reduce fatigue after the day shift by shortening the working hours in the daytime appropriately, setting rest periods in the day shift or dividing nurses into morning and afternoon shifts.

Rotating shifts (mostly 8- or 12-h) are common among nurses to ensure continuity of care. This scheduling system encompasses several adverse health and performance consequences. One of the most injurious effects of night-time shift work is the deterioration of sleep patterns due to both circadian rhythm disruption and increased sleep homeostatic pressure. Sleep problems lead to secondary effects on other aspects of wellbeing and cognitive functioning, increasing the risk of errors and workplace accidents. A wide range of interventions has been proposed to improve the sleep quality of nurses and promote an increase in attention levels. In recent years, particular attention has been paid to individual and environmental factors mediating the subjective ability to cope with sleep deprivation during the night shift. Given the predictive role of these factors on the negative impact of a night shift, an individualized intervention could represent an effective countermeasure by ensuring suitable management of shift schedules. Therefore, the aims of this mini-review are to: (a) provide an updated overview of the literature on sleep problems in night shift nurses and their adverse consequences; and (b) critically analyze the psychosocial factors that mediate the negative impact of shift work with the ultimate goal of defining an effective countermeasure based on an individualized approach.

Chronic disruption of circadian rhythms by night shift work is associated with an increased breast cancer risk. However, little is known about the impact of night shift on peripheral circadian genes (CGs) and circadian-controlled genes (CCGs) associated with breast cancer. Hence, we assessed central clock markers (melatonin and cortisol) in plasma, and peripheral CGs (PER1, PER2, PER3, and BMAL1) and CCGs (ESR1 and ESR2) in peripheral blood mononuclear cells (PBMCs). In day shift nurses (n = 12), 24-h rhythms of cortisol and melatonin were aligned with day shift-oriented light/dark schedules. The mRNA expression of PER2, PER3, BMAL1, and ESR2 showed 24-h rhythms with peak values in the morning. In contrast, night shift nurses (n = 10) lost 24-h rhythmicity of cortisol with a suppressed morning surge but retained normal rhythmic patterns of melatonin, leading to misalignment between cortisol and melatonin. Moreover, night shift nurses showed disruption of rhythmic expressions of PER2, PER3, BMAL1, and ESR2 genes, resulting in an impaired inverse correlation between PER2 and BMAL1 compared to day shift nurses. The observed trends of disrupted circadian markers were recapitulated in additional day (n = 20) and night (n = 19) shift nurses by measurement at early night and midnight time points. Taken together, this study demonstrated the misalignment of cortisol and melatonin, associated disruption of PER2 and ESR2 circadian expressions, and internal misalignment in peripheral circadian network in night shift nurses. Morning plasma cortisol and PER2, BMAL1, and ESR2 expressions in PBMCs may therefore be useful biomarkers of circadian disruption in shift workers.

Disturbed sleep is the most common problem among the many health-related effects of shift work, with shift workers clearly having higher rates of cardiac disorders. However, the possible mechanism underlying the related health effects of shift work has yet to be examined. Consequently, this study aimed to explore the influence of long-term night shift work on the sleep patterns of nurses and their cardiac autonomic nervous system during sleep. Our sample comprised ten permanent night shift and ten regular morning shift nurses. Nurses slept in their dormitory where they were allowed to sleep and wake spontaneously. All sleep parameters were digitized using an ambulatory polysomnographic recorder. Using sleep patterns and heart rate variability, the day- and nighttime sleep of permanent night shift nurses were compared with the nighttime sleep of regular morning shift nurses. Compared with the nighttime sleep of regular morning shift nurses, the pattern of daytime sleep of permanent night shift nurses showed significantly lower sleep onset latency. Permanent night shift nurses' daytime sleep also had greater proportions of Stage 3 and 4 (deep sleep), and arousal index than recorded during their nighttime sleep. Both the low frequency and low to high frequency ratio of the nighttime sleep of night shift nurses were significantly higher during periods of non-rapid eye movement (NREM) sleep than the nighttime sleep of morning shift workers. In addition, the electroencephalography delta-power of the nighttime sleep of night shift nurses was significantly lower during the first NREM episode sleep than those of both the daytime sleep of night shift workers and the nighttime sleep of morning shift nurses. Permanent night shift nurses have higher sympathetic activity during nighttime sleep than regular morning shift nurses. Night shift working may have effects on the sleeping patterns of nurses in the long run, inducing higher cardiac sympathetic regulation.

Aims: This study aims to determine the sleep quality of night-shift workers, determine the prevalence and characteristics of sleep disorders related to shift work, and compare sleep characteristics between shift workers and day workers. Subjects and Methods: The study included 1473 individuals employed in three different areas (health, security, and labor) as shift (78.5%) or day (21.5%) workers in the city of Adana, Turkey. Data were collected using a structured questionnaire consisting of 132 questions. The questionnaire included demographic data, education level, socioeconomic status, shift schedule, accompanying health problems, sleep disorders and sleeping habits, the Epworth Sleepiness Scale, the Pittsburgh Sleep Quality Index, the Berlin Questionnaire, and the Restless Legs Syndrome (RLS) scale. Statistical Analysis Used: The SPSS for Windows 20.00 software package was used for statistical analyses. Results: Day workers and shift workers exhibited excessive daytime sleepiness in 17.1% and 24.9% (P = 0.004), poor sleep quality in 41.5% and 44.3% (P = 0.374), chronic insomnia in 8% and 16.2% (P &lt; 0.001), RLS in 4.7% and 5.3% (P = 0.818), and sleep-disordered breathing in 7.3% and 7% (P = 0.864), respectively. Conclusions: Shift work significantly compromises sleep quality. In particular, fixed night shifts or rotating shift workers experience relatively higher rates of decline in subjective sleep quality, excessive daytime sleepiness, and chronic insomnia compared with day workers.

&lt;sec&gt;&lt;st&gt;Introduction&lt;/st&gt; Usually night and shift work have been associated with insomnia and fatigue. The current industry model implies the existence of many groups of night workers. For this reason we consider of interest to conduct a systematic review to evaluate the relationship between shift or night work as risk factors for health. &lt;/sec&gt; &lt;sec&gt;&lt;st&gt;Objectives&lt;/st&gt; Evaluate the relationship between shift or night work as a risk factor for health and performance for working. &lt;/sec&gt; &lt;sec&gt;&lt;st&gt;Methodology&lt;/st&gt; Literature review from Pubmed database (01/10/2015) with keywords (“sleep disorder or insomnia”) and (occupational or workplace) and active filters: last 5 years, human, Spanish, English or French. 571 publications were found, of which 141 were selected from title critical lecture (3 independent reviewers, and articles were selected if 2 or 3 of the 3 reviewers agree). Critical lecture of abstracts for 5 reviewers was performed and 35 of the 141 were selected. 6 of 141 papers were not found. &lt;/sec&gt; &lt;sec&gt;&lt;st&gt;Results&lt;/st&gt; In this review, a relationship between shift and night work with loss of sleep (OR 1.17-4.1) and increased accidents (OR 1.62) is observed. Time control, sleep 2–3 hours during the night shift, and working maximum 3 consecutive night days, are also seen as protective factors. &lt;/sec&gt; &lt;sec&gt;&lt;st&gt;Conclusions&lt;/st&gt; Night and shift work is related to insomnia and fatigue, which leads to a reduced work capacity and increased accidents; although it seems that it does not lead to premature ageing. It would be desirable to identify profiles of night workers (owls) and evaluate the effects of the double presence with these types of work, especially in women. There is controversy as to whether these jobs can cause anxiety disorder and/or depression. &lt;/sec&gt;

The effect of sleep–wake rhythm disruption on neuromuscular control and muscle fatigue has received little attention. Because nurse shift work is so varied, including overnight duty, rotating shift schedules, early awakening, and interrupted nocturnal sleep, it offers an interesting model to study this paradigm. It has been investigated so far using only subjective markers. A combined approach based on the simultaneous analysis of surface electromyographic (sEMG) and force signals can objectively detect possible deficits in neuromuscular control and muscle fatigue. With this study we investigated neuromuscular activation and muscle contraction capacity at submaximum and maximum level in nurses working two night-shift schedules and compared them to levels in nurses working entirely in day shifts. Sleep quality and activity levels were also assessed. The study sample was 71 nurses grouped by their shift work schedule: night shift for 5 days (NS5, n = 46), night shift for 10 days (NS10, n = 9), and only day/swing shift (DS, n = 16). Before and after the shift-work cycle, maximum voluntary contraction (MVC) force and muscle activation, neuromuscular control, and muscle fatigability were measured in the finger flexor muscles. Activity level and sleep quality during the shift-work cycle were recorded with a wrist actigraph. After the shift-work cycles, MVC force and muscle activation were decreased (−11 ± 3% and −33 ± 3%, p < 0.001) as was neuromuscular control (−36 ± 8%, p = 0.007), whereas muscle fatigability was increased (+ 19 ± 9%, p = 0.006) in the NS5 and the NS10 group. Sleep quality was lower in the NS5 and the NS10 group (−8 ± 1.8% and −15%3, respectively, p < 0.001), while the activity level for the three groups was similar. There was a clear reduction in neuromuscular control and an increase in muscle fatigue in the nurses working the night shift. These findings may inform of work schedule planning or recommendations for devising new recovery strategies to counteract neuromuscular alterations in night shift nurses.

ABSTRACTThis epidemiological cohort study, based on Finnish public sector data, investigated the associations between objective working hour characteristics and work–life conflict in day and shift work. The comprehensive data of hospital workers (n = 8 931, 92% women, average age 45 years), consisted of survey responses from 2012, linked with the payroll data of working hour characteristics from 91 days preceding the survey. Logistic regression analysis was used to investigate the associations between working hour characteristics and experiencing work–life conflict often/very often. The analyses were adjusted for age (< 39, 40–49 and >50 years), sex, level of education, marital status, number of small (0–6 years) and school-aged (7–18 years) children, and the overall stressfulness of the life situation. We also conducted stratified analyses of age and sex on the basis of significant interactions. Difficulties in combining work and life were more often associated with shift work without night shifts and shift work with night shifts than with day work (41% and 34 versus 27%; OR for shift work with night shifts 1.78, 95% CI 1.59–2.00, OR for shift work without night shifts 1.42, 95% CI 1.26–1.60). A high proportion (> 25%) of long (> 40h, (OR 1.26, 95% 1.14–1.39) and very long (> 48h, OR 1.31, 95% CI 1.15–1.49) weekly working hours were associated with work–life conflict, and in the stratified analysis, the latter was also true among women (OR 1.54, 95% CI 1.25–1.89). Of the unsocial working hour characteristics, a relatively large amount (> 10% of all shifts) of evening (OR 1.56, 95% CI 1.41–1.72) and night shifts (OR 1.46, 95%CI 1.32–1.61), a high proportion (> 25% of all shifts) of quick returns (< 11h) (OR 1.46, 95% CI 1.31–1.63), and weekend work (OR 1.44, 95% CI 1.31–1.58) were associated with work–life conflict. A large amount of single days off (> 25% of all days off) was associated with work–life conflict among men (OR 1.90, 95% CI 1.11–3.25), but not in the whole sample. When the two types of shift work were analyzed separately, shift work without night shifts and very long work weeks had higher odds (OR 1.47, 95% CI 1.20–1.80) of work–life conflict than shift work with night shifts. Conversely, weekend work and evening shifts had higher odds of work–life conflict among shift workers with night shifts (OR 1.74, 95% 1.55–1.96; (OR 1.57, 95% CI 1.40–1.77) than among those without night shifts. To conclude, this study shows that shift workers with and without night shifts more often have difficulties combining work and life than day workers. Several unsocial working hour characteristics, including long work weeks, evening and night shifts, weekend work, and quick returns, are associated with work–life conflict.

Introduction Sleep deficiencies are common in nurses, with up to 89% of nurses working some form of shiftwork (i.e., working before 6am and/or after 9pm). It is estimated that approximately 34% of nurses report insomnia disorder and 14% report shift work sleep disorder. Nurses face unique physical, psychological, and occupational demands that disrupt their sleep quality and duration and may conflict with their natural circadian rhythm. Methods Nurses (N = 26, 88% female, 80% white, mean age = 36.16 years, SD = 8.56) were asked to wear an Actiwatch to measure objective sleep parameters, a daily adhesive sweat collection patch, provide two blood samples (at Day 1 and Day 7), and report daily subjective sleep parameters (total sleep time, sleep onset latency, wake after sleep onset, and sleep efficiency) via the Consensus Sleep Diary for 7 days. The sample was further divided into day shift (n = 14) and night shift (n = 12) nurses. Data collection and cleaning are ongoing and preliminary results of complete sleep diary data are presented. Results Results of the independent sample t tests suggest that total sleep time was significantly different on days on shift versus off shift (t(86) = 2.94, p = .002) for day shift nurses but not for night shift nurses (t(76) = .48, p = .317). There was no difference in total sleep time between day and night shift workers. Additional exploratory analyses will be completed by the conference, comparing additional parameters (e.g., timing) in individual sleep periods (i.e., 1st work day, 2nd work day; 1st off day, 2nd off day) both within (night &amp; day shift), as well as between (night vs day shift) groups on the final sample (N=40; 20 day and 20 night shift). Conclusion The results may indicate that day shift nurses have more variable sleep than night shift nurses. Further analyses will help fill gaps in our understanding of the deficient (i.e., inadequate, interrupted, mistimed) sleep in nurses (i.e., within and between day and night working), as well as inform potential interventions (i.e., CBTI for shift workers) to improve the sleep of critical nursing staff. Support (if any)