Circadian misalignment disrupts biomarkers of cardiovascular disease risk and promotes a hypercoagulable state.

The circadian system regulates 24-h time-of-day patterns of cardiovascular physiology, with circadian misalignment resulting in adverse cardiovascular risk. Although many proteins in the coagulation-fibrinolysis axis show 24-h time-of-day patterns, it is not understood if these temporal patterns are regulated by circadian or behavioral (e.g., sleep and food intake) cycles, or how circadian misalignment influences these patterns. Thus, we utilized a night shiftwork protocol to analyze circadian versus behavioral cycle regulation of 238 plasma proteins linked to cardiovascular physiology. Six healthy men aged 26.2 ± 5.6 years (mean ± SD) completed the protocol involving two baseline days with 8-h nighttime sleep opportunities (circadian alignment), a transition to shiftwork day, followed by 2 days of simulated night shiftwork with 8-h daytime sleep opportunities (circadian misalignment). Plasma was collected for proteomics every 4 h across 24 h during baseline and during daytime sleep and the second night shift. Cosinor analyses identified proteins with circadian or behavioral cycle-regulated 24-h time-of-day patterns. Five proteins were circadian regulated (plasminogen activator inhibitor-1, angiopoietin-2, insulin-like growth factor binding protein-4, follistatin-related protein-3, and endoplasmic reticulum resident protein-29). No cardiovascular-related proteins showed regulation by behavioral cycles. Within the coagulation pathway, circadian misalignment decreased tissue factor pathway inhibitor, increased tissue factor, and induced a 24-h time-of-day pattern in coagulation factor VII (all FDR < 0.10). Such changes in protein abundance are consistent with changes observed in hypercoagulable states. Our analyses identify circadian regulation of proteins involved in cardiovascular physiology and indicate that acute circadian misalignment could promote a hypercoagulable state, possibly contributing to elevated cardiovascular disease risk among shift workers.

Association of intra-shift nap duration with heart rate variability in medical night shift workers.

Napping during night shifts effectively reduces disease risk and improves work performance, but few studies have investigated the association between napping and physiological changes, particularly in off-duty daily lives. Changes in the autonomic nervous system precede diseases like cardiovascular disease, diabetes, and obesity. Heart rate variability is a good indicator of autonomic nervous system. This study aimed to investigate the link between night shift nap durations and heart rate variability indices in the daily lives of medical workers. As indicators of chronic and long-term alterations, the circadian patterns of heart rate variability indices were evaluated. We recruited 146 medical workers with regular night shifts and divided them into four groups based on their self-reported nap durations. Heart rate variability circadian parameters (midline-estimating statistic of rhythm, amplitude, and acrophase) were obtained by obtaining 24-h electrocardiogram on a day without night shifts, plotting the data of the heart rate variability indices as a function of time, and fitting them into periodic cosine curves. Using clinical scales, depression, anxiety, stress, fatigue, and sleepiness were assessed. Linear regression analysis revealed a positive relationship between 61-120-min naps and 24-h, daytime, and night-time heart rate variability indices, and the parasympathetic activity oscillation amplitude (indexed by high-frequency power, the square root of the mean of the sum of squares of differences between adjacent normal intervals, standard deviation of short-term R-R-interval variability) within one circadian cycle. This study indicated that napping for 61-120 min during night shifts could benefit medical workers' health, providing physiological evidence to promote nap management.

Improving sleep health in paramedics through an app-based intervention: a randomised waitlist control pilot trial.

BACKGROUND: Due to work commitments, shiftworkers often obtain inadequate sleep, consequently experiencing negative health, wellbeing, and safety outcomes. Given shiftworkers may have limited control over their work commitments, lifestyle and environmental factors within their control may present an intervention opportunity. However, such interventions require tailoring to ensure applicability for this sleep-vulnerable population. METHODS: A randomised waitlist control pilot trial investigated the effectiveness of mobile health application Sleepfit, which delivered a tailored sleep health intervention aimed at improving sleep health and sleep hygiene outcomes amongst paramedic shiftworkers. Outcome measures of self-reported sleep health (sleep need, duration, and quality, fatigue, Insomnia Severity Index, Fatigue Severity Scale, and Epworth Sleepiness Scale scores) and sleep hygiene (Sleep Hygiene Index score) were collected at baseline, post-intervention, and 3-month follow-up. RESULTS: Fifty-eight paramedics (aged 33.4 ± 8.0 years; 50% male) were recruited, and trialed Sleepfit for a 14-day intervention period between August 2021-January 2022. For all participants, there was a significant reduction in Insomnia Severity Index and Sleep Hygiene index scores after intervention engagement. Regression models demonstrated no significant intervention effect on sleep health or sleep hygiene outcomes (intervention versus waitlist control group). A high study drop-out rate (91.4%) prevented assessment of outcomes at 3-month follow-up. CONCLUSIONS: Pilot trial findings demonstrate that Sleepfit may elicit improvements in sleep health and sleep hygiene outcomes amongst paramedic shiftworkers. However, low enrolment and retention means that findings should be interpreted with caution, further highlighting potential engagement challenges, especially among paramedics who are particularly in need of support for improved sleep. TRIAL REGISTRATION: Prospectively registered with the Australian New Zealand Clinical Trial Registry 24/01/2020 (reference no. ACTRN12620000059965).

The relationship between perceived stress and emotional eating in bus drivers: the effect of shift work.

This study discusses the relationship between perceived stress and emotional eating based on shiftwork in city bus drivers. It was conducted with 1403 male city bus drivers working in Istanbul. Questions about the drivers' physical activity and dietary habits, the Healthy Diet Index (HDI), Emotional Appetite Questionnaire and Perceived Stress Scale-10 data were collected and evaluated in two groups: shift and non-shift employees. It was found that the shift workers (SWs) have lower perceived stress, physical activity, HDI and positive emotional appetite averages. In addition, for SWs, a positive correlation was found between negative emotional appetite scores and physical activity and HDI scores. In conclusion, the drivers working in shifts were found to be slightly overweight and had lower physical activity levels, had lower HDI scores, and their nutritional status was more negatively impacted than their counterparts.

Pilot feasibility testing of biomathematical model recommendations for personalising sleep timing in shift workers.

Sleep disturbances and circadian disruption play a central role in adverse health, safety, and performance outcomes in shift workers. While biomathematical models of sleep and alertness can be used to personalise interventions for shift workers, their practical implementation is undertested. This study tested the feasibility of implementing two biomathematical models-the Phillips-Robinson Model and the Model for Arousal Dynamics-in 28 shift-working nurses, 14 in each group. The study examined the overlap and adherence between model recommendations and sleep behaviours, and changes in sleep following the implementation of recommendations. For both groups combined, the mean (SD) percentage overlap between when a model recommended an individual to sleep and when sleep was obtained was 73.62% (10.24%). Adherence between model recommendations and sleep onset and offset times was significantly higher with the Model of Arousal Dynamics compared to the Phillips-Robinson Model. For the Phillips-Robinson model, 27% of sleep onset and 35% of sleep offset times were within ± 30 min of model recommendations. For the Model of Arousal Dynamics, 49% of sleep onset, and 35% of sleep offset times were within ± 30 min of model recommendations. Compared to pre-study, significant improvements were observed post-study for sleep disturbance (Phillips-Robinson Model), and insomnia severity and sleep-related impairments (Model of Arousal Dynamics). Participants reported that using a digital, automated format for the delivery of sleep recommendations would enable greater uptake. These findings provide a positive proof-of-concept for using biomathematical models to recommend sleep in operational contexts.

Daytime, evening, and overnight: the 24-h radiology cycle and impact on interpretative accuracy.

PURPOSE: To assess the influence of time of day when a study is interpreted on discrepancy rates for common and advanced studies performed in the acute community setting. METHODS: This retrospective study used the databank of a U.S. teleradiology company to retrieve studies between 2012 and 2016 with a preliminary report followed by a final report by the on-site client hospital. Neuroradiology, abdominal radiology, and musculoskeletal radiology studies were included. Teleradiologists were fellowship trained in one of these subspecialty areas. Daytime, evening, and overnight times were defined. Associations between major and minor discrepancies, time of day, and whether the study was common or advanced were tested with significance set at p = .05. RESULTS: A total of 5,883,980 studies were analyzed. There were 8444 major discrepancies (0.14%) and 17,208 minor discrepancies (0.29%). For common studies, daytime (0.13%) and evening (0.13%) had lower major discrepancy rates compared to overnight (0.14%) (daytime to overnight, RR = 0.57, 95%CI: 0.45, 0.72, p < 0.01 and evening to overnight, RR = 0.57, 95%CI: 0.49,0.67, p < 0.01). Minor discrepancy rates for common studies were decreased for evening (0.29%) compared to overnight (0.30%) (RR = 0.89, 95%CI: 0.80,0.99, p = 0.029). For advanced studies, daytime (.15%) had lower major discrepancy rates compared to evening (0.20%) and overnight (.23%) (daytime to evening, RR = 0.77, 95%CI: 0.61, 0.97, p = 0.028 and daytime to overnight, RR = 0.66, 95%CI: 0.50, 0.87, p ≤ 0.01). CONCLUSION: Significantly higher major discrepancy rates for studies interpreted overnight suggest the need for radiologists to exercise greater caution when interpreting studies overnight and may require practice management strategies to help optimize overnight work conditions. The lower major discrepancy rates on advanced studies interpreted during the daytime suggest the need for reserving advanced studies for interpretation during the day when possible.

Shiftwork sleep disorder and associated factors among nurses working at public hospitals in Harari Regional state and Dire Dawa Administration, Eastern Ethiopia: a cross-sectional study.

BACKGROUND: Shiftwork sleep disorder is one of the most common health-related effects of Shiftwork, particularly among healthcare workers. It is a chronic condition that is directly related to a person's work schedule. In Ethiopia, although a mental health strategy is in place, little attention is given to studies that focus on shiftwork sleep disorders among nurses. This study aimed to determine the magnitude of shiftwork sleep disorder and associated factors among nurses working at public hospitals in Harari Regional State and the Dire Dawa Administration. METHODS: Institutional based cross-sectional study was conducted from June 1-30, 2021 among 392 nurses selected by a simple random sampling technique. A structured interviewer-guided self-administered questionnaire was used for data collection. The International Classification of Sleep Disorders 3rd edition (ICSD-3), Bargen Insomnia Scale (BIS) and Epworth Sleepiness Scale were used to assess shift-work sleep disorder. The data were entered into EpiData and exported to SPSS for analysis. Bivariable logistic regression was used to see the association between the outcome and the explanatory variables. Bivariate and Multivariate analyses were performed, and AOR with 95% CI was used to measure the strength of the association. Those variables with a p-values of < 0.05 were considered as statistically significant. RESULTS: In this study, the magnitude of shiftwork sleep disorder among nurses was 30.4% (95% CI: 25.4-34.5). Being female (AOR = 2.4, 95% CI: 1.3, 4.2), working an average number of nights > 11 per month in the last 12 months (AOR = 2.5, 95% CI: 1.3, 3.8), and khat use in the last 12 months (AOR = 4.9, 95% CI: 2.9, 8.7) were significantly associated with the shiftwork sleep disorder. CONCLUSIONS: The study revealed that about one-third of the nurses had a shiftwork sleep disorder implying a high burden of the problem among nurses in the study setting, which endangers nurses, patients, and the healthcare system. Being female, working an average number of nights > 11 per month in the last 12 months, and khat use showed statistically significantly associated with the shiftwork sleep disorder. Early detection of shiftwork sleep disorder, having a policy on khat use and considering rest/recovery while scheduling work time should be addressed to prevent shiftwork sleep disorder.

Rise and shine: The use of polychromatic short-wavelength-enriched light to mitigate sleep inertia at night following awakening from slow-wave sleep.

Sleep inertia is the brief period of performance impairment and reduced alertness experienced after waking, especially from slow-wave sleep. We assessed the efficacy of polychromatic short-wavelength-enriched light to improve vigilant attention, alertness and mood immediately after waking from slow-wave sleep at night. Twelve participants (six female, 23.3 ± 4.2 years) maintained an actigraphy-confirmed sleep schedule of 8.5 hr for 5 nights, and 5 hr for 1 night prior to an overnight laboratory visit. In the laboratory, participants were awakened from slow-wave sleep, and immediately exposed to either dim, red ambient light (control) or polychromatic short-wavelength-enriched light (light) for 1 hr in a randomized crossover design. They completed a 5-min Psychomotor Vigilance Task, the Karolinska Sleepiness Scale, and Visual Analogue Scales of mood at 2, 17, 32 and 47 min after waking. Following this testing period, lights were turned off and participants returned to sleep. They were awakened from their subsequent slow-wave sleep period and received the opposite condition. Compared with the control condition, participants exposed to light had fewer Psychomotor Vigilance Task lapses (χ2 [1] = 5.285, p = 0.022), reported feeling more alert (Karolinska Sleepiness Scale: F1,77  = 4.955, p = 0.029; Visual Analogue Scalealert : F1,77  = 8.226, p = 0.005), and reported improved mood (Visual Analogue Scalecheerful : F1,77  = 8.615, p = 0.004). There was no significant difference in sleep-onset latency between conditions following the testing period (t10  = 1.024, p = 0.330). Our results suggest that exposure to polychromatic short-wavelength-enriched light immediately after waking from slow-wave sleep at night may help improve vigilant attention, subjective alertness, and mood. Future studies should explore the potential mechanisms of this countermeasure and its efficacy in real-world environments.

Longitudinal and cross-sectional associations between the dietary inflammatory index and objectively and subjectively measured sleep among police officers.

Police officers experience exposures associated with increased inflammation, such as the stress associated with shiftwork and poor-quality diet, both of which have been shown to affect sleep duration and quality. This study examined the longitudinal and cross-sectional effects of the Energy-density Dietary Inflammatory Index (E-DII™) on objectively and subjectively measured sleep among police officers. Data were derived from the Buffalo Cardio-Metabolic Occupational Police Stress Cohort (n = 464 at baseline), with longitudinal data collected from 2004 to 2019. A food frequency questionnaire obtained estimated dietary intake from which E-DII scores were calculated. Dependent variables were objectively (Micro Motion Logger Sleep Watch™) and subjectively (Pittsburgh Sleep Quality Index) measured sleep quality and quantity. The analyses included a series of linear mixed-effects models used to examine cross-sectional and longitudinal associations between the E-DII and sleep quantity and quality. Cross-sectionally, more pro-inflammatory diets were associated with higher wake-after-sleep-onset but improved subjective sleep quality. In models accounting for both longitudinal and cross-sectional effects, for every 1-unit increase in the E-DII scores over time (representing a pro-inflammatory change), wake-after-sleep-onset increased by nearly 1.4 min (p = 0.07). This result was driven by officers who primarily worked day shifts (ß = 3.33, p = 0.01). Conversely, for every 1-unit increase in E-DII score, the Pittsburgh Sleep Quality Index global score improved. More pro-inflammatory diets were associated with increased wake-after-sleep-onset, an objective measure of sleep quality. Intervention studies to reduce dietary inflammatory potential may provide greater magnitude of effect for changes in sleep quality.

Insomnia and circadian sleep disorders in ovarian cancer: Evaluation and management of underestimated modifiable factors potentially contributing to morbidity.

Ovarian cancer is the leading cause of gynaecological cancer deaths and the seventh most commonly diagnosed cancer among women worldwide, so that, as it is related to substantial and increasing disease burden, the management of ovarian cancer survivors should be a priority. Such issues involve prevention and management of emotional distress, anxiety/depressive symptoms, and maintenance of quality of life from initial diagnosis to post-treatment. Within this framework, sleep disturbances, in particular insomnia, are emerging as modifiable determinants of mental health, also contributing to substantial morbidity among cancer, including ovarian cancer. To this aim we conducted a systematic review according to PRISMA guidelines on prevalence and management of insomnia and circadian sleep disorders in ovarian cancer, while selecting 22 papers. Insomnia was evaluated in ovarian cancer and, while circadian sleep disturbances were poorly assessed in ovarian cancer, insomnia increased from 14% to 60% of patients. Insomnia was associated with cancer-related comorbid conditions such as emotional distress, anxiety/depressive symptoms and low quality of life. Despite this evidence, no studies have been conducted about insomnia treatment in ovarian cancer. The burden of insomnia and circadian sleep disorders in patients with ovarian cancer still needs to be addressed, and requires a call to action for the evaluation and management of these potential modifiable factors that might contribute to ovarian cancer morbidity.

Because they're worth it? A discussion paper on the value of 12-h shifts for hospital nursing.

The organisation of the 24-h day for hospital nurses in two 12-h shifts has been introduced with value propositions of reduced staffing costs, better quality of care, more efficient work organisation, and increased nurse recruitment and retention. While existing reviews consider the impact of 12-h shifts on nurses' wellbeing and performance, this discussion paper aims to specifically shed light on whether the current evidence supports the value propositions around 12-h shifts. We found little evidence of the value propositions being realised. Staffing costs are not reduced with 12-h shifts, and outcomes related to productivity and efficiency, including sickness absence and missed nursing care are negatively affected. Nurses working 12-h shifts do not perform more safely than their counterparts working shorter shifts, with evidence pointing to a likely negative effect on safe care due to increased fatigue and sleepiness. In addition, nurses working 12-h shifts may have access to fewer educational opportunities than nurses working shorter shifts. Despite some nurses preferring 12-h shifts, the literature does not indicate that this shift pattern leads to increased recruitment, with studies reporting that nurses working long shifts are more likely to express intention to leave their job. In conclusion, there is little if any support for the value propositions that were advanced when 12-h shifts were introduced. While 12-h shifts might be here to stay, it is important that the limitations, including reduced productivity and efficiency, are recognised and accepted by those in charge of implementing schedules for hospital nurses.

Evolution of work ability, quality of life and self-rated health in a police department after remodelling shift schedule.

BACKGROUND: There exists a great diversity of schedules concerning the way shift work is organized and implemented with ample agreement regarding recommendable features of a shift system. In order to adapt the shift schedule of a metropolitan police department to current recommendations, a remodelled shift schedule was introduced in 2015. The aim of this study was to evaluate the potential associations between the remodelled shift schedule and work ability, quality of life and self-rated health after one and five years. METHODS: A controlled before-and- after study was conducted during the piloting phase (2015-2016) as well as a 5-year follow-up using paper questionnaires. Outcome parameters included work ability, quality of life and self-rated health. RESULTS: Work ability, quality of life and self-rated health improved after the first year of the newly implemented shift schedule among police officers working in the piloting police stations compared to those working according to the former schedule. In 5-year follow-up differences between indicators diminished. CONCLUSIONS: The implementation of a remodelled shift schedule including more 12-h shifts accompanied by more days off and a coherent weekend off duty was not associated with detrimental effects to work ability, quality of life or self-reported health among police officers.

Perceived stigma, substance use and self-medication in night-shift healthcare workers: a qualitative study.

BACKGROUND: Many risk factors related to altered circadian rhythms impact the health of night-shift hospital workers (NSHW), resulting in mental and somatic disorders. Easy access to psychoactive substances (PS) may facilitate addictive behaviors in NSHW. They are also exposed to a stressful work environment, which may further affect sleep quality. This study aimed to explore the link between sleep deprivation, work-related psychosocial stress and psychoactive substance use as a self-medication response in NSHW. METHODS: Qualitative study to verify the plausibility of the self-medication theory applied to addictive behaviors. Semi-structured interviews (N = 18 NSHW) and thematic analysis, following consolidated criteria for reporting qualitative research recommendations. RESULTS: Stigma against NSHW was a primary element of a stressful work environment. The stressful and stigmatizing environment, together with night-shift work, further affected NSHW sleep and their mental and physical health. The use of PS appeared to be for self-medication, encouraged by social and professional environments, source(s) of stress, discrimination, and isolation. The work environment, through aggravated sleep disorders, led NSHW to use non-prescribed sleeping pills. Alcohol after work and smoking were used as a social break but also as a means to reduce stress. CONCLUSION: Anti-stigma interventions in the healthcare setting and screening of mental/somatic disorders in NSHW can help reduce harmful self-medication behaviors and improve hospital care in the COVID-19 era.

Findings from a systematic review of fatigue interventions: What's (not) being tested in mining and other industrial environments.

BACKGROUND: Fatigue negatively impacts mineworker health and safety. In this paper, we identify fatigue interventions tested on industrial shiftworkers and explore their effects and the factors that may influence application in an industrial setting such as a mine site. METHODS: This review adhered to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) checklist. A structured, systematic search of the literature was conducted to identify relevant studies published between 1980 and 2020. Researchers independently conducted article screening and study quality appraisals against pre-established criteria, and then extracted data and conducted a narrative synthesis of the included studies. RESULTS: Seven intervention studies, out of 1651 articles initially screened, were retained for narrative synthesis. Four studies tested the alerting effects of bright-light treatment, one evaluated the effectiveness of blue-light blocking glasses at improving daytime sleep quality and nighttime vigilance, and two examined whether sleep hygiene and alertness management trainings improved sleep quality or alertness. There was substantial evidence for the use of bright-light treatments to improve night shiftworker alertness, but insufficient evidence to draw conclusions about the effectiveness of blue-light blocking glasses and sleep hygiene and alertness management trainings due to the small number of studies included. Shiftworkers were mostly male and employed in industrial subsectors such as production and manufacturing, oil and gas, and transportation. No mining-specific intervention studies were identified. CONCLUSIONS: Future research is needed to identify effective fatigue risk management interventions for the mining industry as well as best practices for implementing these interventions with mineworkers.

US research needs related to fatigue, sleep, and working hours among oil and gas extraction workers.

BACKGROUND: During 2003-2013, 1189 US oil and gas extraction (OGE) workers died while working, resulting in an average annual workplace fatality rate seven times that for all US workers. OGE work commonly involves long hours, shiftwork, irregular schedules, and long commutes, but effects of these factors on fatigue, occupational injury, and illness in OGE are largely unknown. METHODS: A scoping review of relevant OGE research during 2000-2019 was completed and supplemented by input from a NIOSH-sponsored Forum. RESULTS: Seventy-eight papers were identified; 76% reported only offshore research. Five themes for research needs emerged: build knowledge about the impacts of fatigue; explore interactions between on- and off-the-job risk factors; identify and evaluate interventions; assess effectiveness of technology; and increase the diffusion of fatigue risk management information. CONCLUSIONS: Further collaboration between researchers and OGE operators and contractors can lead to action-oriented recommendations to mitigate the effects of fatigue, inadequate sleep, and shiftwork.

Alertness during working hours among eight-hour rotating-shift nurses: An observational study.

PURPOSE: The aim of this study was to identify the patterns of the decline in the alertness of rotating-shift nurses during working hours across different shift types (day, evening, and night) using an objective measure. DESIGN: An observational study using ReadiBand wrist actigraphs was conducted. METHODS: Data were collected from June 2019 to February 2020. Participants were rotating-shift nurses (N = 82) who provided direct nursing care for patients in acute care hospitals in South Korea. Nurses wore actigraphs continuously for 14 days on their non-dominant hand to identify sleep-wake cycles and predict their alertness scores hourly. All participants completed a sleep diary. FINDINGS: Nurses working during night shifts had lower average alertness scores (mean = 77.12) than nurses working during day (mean = 79.05) and evening (mean = 91.21). Overall, alertness showed a declining trend and the specific patterns of decline differed across shifts. Participants with alertness scores less than 70 or 80 demonstrated a significant decline in alertness across all shifts. CONCLUSIONS: Distinct patterns of decline in alertness per nursing shift were revealed. Each shift feature should be considered when developing interventions to increase nurses' alertness, promote high-quality care provision, and ensure patient safety. CLINICAL RELEVANCE: The implementation of interventions to increase alertness among shift nurses is needed at the organizational level, and the cooperation of nursing managers and administrators is required.

Work schedule characteristics and occupational fatigue/recovery among rotating-shift nurses: A cross-sectional study.

AIMS: To determine the effects of work schedule characteristics on occupational fatigue and recovery among rotating-shift nurses in South Korea. BACKGROUND: Understanding the effects of work schedule characteristics on occupational fatigue is important to prevent adverse nurse outcomes and to ensure patient safety. METHODS: This study used secondary data analysis with a cross-sectional design. Data were collected on 436 rotating-shift nurses in 2018. Nurses' occupational fatigue and recovery were measured using the Occupational Fatigue Exhaustion/Recovery Scale. We used quantile regression models. RESULTS: The scores for acute and chronic fatigue and intershift recovery were 70.40, 73.39, and 29.82, respectively. Overtime hours, number of night shifts, number of consecutive days off, and breaks were significant influential factors in some quantiles of acute fatigue, chronic fatigue, and intershift recovery, while total working hours was only associated with chronic fatigue in the 25th quantile. CONCLUSIONS: The quantile and linear regression models revealed different results for work schedule factors that affect occupational fatigue and intershift recovery among rotating-shift nurses. IMPLICATION FOR NURSING MANAGEMENT: These findings have important implications for developing targeted strategies and policies to reduce occupational fatigue and improve intershift recovery for rotating-shift nurses with different levels of occupational fatigue and recovery.

Social jetlag, a novel predictor for high cardiovascular risk in blue-collar workers following permanent atypical work schedules.

Cardiovascular diseases cause >4 million deaths each year in Europe alone. Preventive approaches that do not only consider individual risk factors but their interaction, such as the Systematic COronary Risk Evaluation (SCORE), are recommended by European guidelines. Increased cardiovascular risk is associated with shift-work, surely interacting with the concurrent conditions: disruption of sleep, unhealthy behaviours, and circadian misalignment. Social jetlag (SJL) has been proposed as a way to quantify circadian misalignment. We therefore investigated the association between SJL and cardiovascular health in a cross-sectional observational study involving blue-collar workers, who either worked permanent morning, evening, or night shifts. Sociodemographic, health and productivity data were collected through questionnaires. Blood pressure and cholesterol were measured and the cardiovascular risk was estimated according to the relative risk SCORE chart. Bivariate analysis was performed according to the cardiovascular risk and the relationship between SJL and high cardiovascular risk was analysed through logistic regression. Cumulative models were performed, adjusted for various confounding factors. After 49 exclusions, the final sample comprised 301 workers (56% males; aged <40 years, 73%). Mean standard deviation (SD) SJL was 1:57 (1:38) hr (59.4% ≤2 hr). Cardiovascular risk was high in 20% of the sample. Multivariate analysis revealed SJL to be an independent risk factor for high cardiovascular risk. Each additional hour of SJL increased this risk by >30% (odds ratio 1.31, 95% confidence interval 1.02-1.68). This is the first study indicating that SJL potentially increases cardiovascular risk, and suggests that sleep and individual circadian qualities are critical in preventing negative health impacts of shift-work.

Endogenous circadian regulation and phase resetting of clinical metabolic biomarkers.

Shiftwork and circadian disruption are associated with adverse metabolic effects. Therefore, we examined whether clinical biomarkers of metabolic health are under endogenous circadian regulation using a 40 hours constant routine protocol (CR; constant environmental and behavioral conditions) and evaluated the impact of typical daily conditions with periodic sleep and meals (baseline; 8 hours sleep at night, four meals during a 16 hour wake episode) on the phase and amplitude of these rhythms. Additionally, we tested whether these circadian rhythms are reset during simulated shiftwork. Under CR (n = 16 males, mean age ± SD = 23.4 ± 2.3 years), we found endogenous circadian rhythms in cholesterol, HDL and LDL, albumin and total protein, and VLDL and triglyceride. The rhythms were masked under baseline conditions except for cholesterol, which had near-identical phases under both conditions. Resetting of the cholesterol rhythm and Dim Light Melatonin Onset (DLMO) was then tested in a study of simulated shiftwork (n = 25, 14 females, 36.3 ± 8.9 years) across four protocols; two with abrupt 8 hour delay shifts and exposure to either blue-enriched or standard white light; and either an abrupt or gradual 8 hour advance (1.6 hours/day over 5 days) both with exposure to blue-enriched white light. In the delay protocols, the cholesterol rhythm shifted later by -3.7 hours and -4.2 hours, respectively, compared to -6.6 hours and -4.7 hours, for DLMO. There was a significant advance in cholesterol in the abrupt (+5.1 hours) but not the gradual (+2.1 hours) protocol, compared to +3.1 hours and +2.8 hours in DLMO, respectively. Exploratory group analysis comparing the phases of all metabolic biomarkers under both studies showed evidence of phase shifts due to simulated shiftwork. These results show that clinical biomarkers of metabolic health are under endogenous circadian regulation but that the expression of these rhythms is substantially influenced by environmental factors. These rhythms can also be reset, which has implications for understanding how both behavioral changes and circadian shifts due to shiftwork may disrupt metabolic function.

A classification approach to estimating human circadian phase under circadian alignment from actigraphy and photometry data.

The time of dim light melatonin onset (DLMO) is the gold standard for circadian phase assessment in humans, but collection of samples for DLMO is time and resource-intensive. Numerous studies have attempted to estimate circadian phase from actigraphy data, but most of these studies have involved individuals on controlled and stable sleep-wake schedules, with mean errors reported between 0.5 and 1 hour. We found that such algorithms are less successful in estimating DLMO in a population of college students with more irregular schedules: Mean errors in estimating the time of DLMO are approximately 1.5-1.6 hours. We reframed the problem as a classification problem and estimated whether an individual's current phase was before or after DLMO. Using a neural network, we found high classification accuracy of about 90%, which decreased the mean error in DLMO estimation-identifying the time at which the switch in classification occurs-to approximately 1.3 hours. To test whether this classification approach was valid when activity and circadian rhythms are decoupled, we applied the same neural network to data from inpatient forced desynchrony studies in which participants are scheduled to sleep and wake at all circadian phases (rather than their habitual schedules). In participants on forced desynchrony protocols, overall classification accuracy dropped to 55%-65% with a range of 20%-80% for a given day; this accuracy was highly dependent upon the phase angle (ie, time) between DLMO and sleep onset, with the highest accuracy at phase angles associated with nighttime sleep. Circadian patterns in activity, therefore, should be included when developing and testing actigraphy-based approaches to circadian phase estimation. Our novel algorithm may be a promising approach for estimating the onset of melatonin in some conditions and could be generalized to other hormones.