Moral decision-making at night and the impact of night work with blue-enriched white light or warm white light: a counterbalanced crossover study

BACKGROUND

Cognitive function, including moral decision-making abilities, can be impaired by sleep loss. Blue-enriched light interventions have been shown to ameliorate cognitive impairment during night work. This study investigated whether the quality of moral decision-making during simulated night work differed for night work in blue-enriched white light, compared to warm white light.

METHODS

Using a counterbalanced crossover design, three consecutive night shifts were performed in blue-enriched white light (7000 K) and warm white light (2500 K) provided by ceiling-mounted LED luminaires (photopic illuminance: ∼200 lx). At 03:30 h on the second shift (i.e. twice) and at daytime (rested), the Defining Issues Test-2, assessing the activation of cognitive schemas depicting different levels of cognitive moral development, was administered. Data from 30 (10 males, average age 23.3 ± 2.9 years) participants were analysed using linear mixed-effects models.

RESULTS

Activation of the post-conventional schema (P-score), that is, the most mature moral level, was significantly lower for night work in warm white light (EMM; estimated marginal mean = 44.3, 95% CI = 38.9-49.6; pholm=.007), but not blue-enriched white light (EMM = 47.5, 95% CI = 42.2-52.8), compared to daytime (EMM = 51.2, 95% CI = 45.9-56.5). Also, the P-score was reduced for night work overall (EMM = 45.9, 95% CI = 41.1-50.8; p=.008), that is, irrespective of light condition, compared to daytime. Neither activation of the maintaining norms schema (MN-score), that is, moderately developed moral level, nor activation of the personal interest schema (i.e. the lowest moral level) differed significantly between light conditions. The MN-score was however increased for night work overall (EMM = 26.8, 95% CI = 23.1-30.5; p=.033) compared to daytime (EMM = 23.1, 95% CI = 18.9-27.2).

CONCLUSION

The results indicate that moral decisions during simulated night work in warm white light, but not blue-enriched white light, become less mature and principle-oriented, and more rule-based compared to daytime, hence blue-enriched white light may function as a moderator. Further studies are needed, and the findings should be tentatively considered.Trial registration: ClinicalTrials.gov (ID: NCT03203538) Registered: 26/06/2017; https://clinicaltrials.gov/study/NCT03203538.

Life onboard a submarine: Sleep, fatigue, and lifestyle behaviors of sailors on a circadian-aligned watchstanding schedule

This study characterizes, for the first time, the lives of U.S. Navy submariners engaged in normal, sea-based operations while following a circadian-aligned 24-h watchstanding schedule. Fifty-eight submarine crewmembers provided objective (actigraphy) and subjective (questionnaires) sleep data, and information about mood and lifestyle behaviors during 30 days underway. Projected performance scores and estimated circadian phase times were also calculated from actigraphy-based sleep/wake data. Submariners' objective (6.62 ± 0.94 h; mean ± SD) and subjective (5.90 ± 1.38 h) daily sleep quantities while underway were largely comparable to the sleep reportedly received by Sailors across other Navy platforms and watchstanding schedules. Additionally, submariners' actigraphy-predicted circadian phases shifted progressively toward better alignment with watchstanding schedules across time. Nevertheless, subjective sleep quality was low, submariners engaged in unfavorable lifestyle behaviors (lack of regular meals and exercise), and participants reported decreased mood at the completion of their underway time. Recommendations for countermeasure development are provided.

Disruption of central and peripheral circadian clocks and circadian controlled estrogen receptor rhythms in night shift nurses in working environments

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.

Sleep quality according to chronotype in nurses working 8-hour shifts

BACKGROUND

To date, studies have been focused on sleep disturbances of nurses working during night shifts. There is a lack of understanding regarding the sleep quality of nurses working in the rapid rotation system for each type of shift work.

AIMS

To determine the relationship between chronotype and sleep quality according to shift type (i.e. day, evening and night shifts) in nurses working 8-hour rotating shifts.

METHODS

A cross-sectional, descriptive study was conducted from two tertiary hospitals in South Korea from December 2021 to September 2022, including nurses working 8-hour rotating shifts (N = 74). They completed questionnaires to measure general, occupational and sleep-related characteristics, chronotype, insomnia severity and daytime sleepiness. Additionally, sleep parameters were collected from actigraphy and sleep diaries for 7 days.

RESULTS

A total of 64% of nurses had an evening chronotype and 37% of nurses had an intermediate chronotype. Nurses had significantly less total sleep time and worsened sleep latency and efficiency during the day shift compared to other shift types. Compared to nurses with an intermediate chronotype, those with an evening chronotype had poorer sleep quality during day shift work.

CONCLUSIONS

Strategies to enhance nurses' sleep quality during day shifts should consider a two-level approach: individual approaches, such as improving sleep hygiene, and administrative approaches, such as establishing a chronotype-based shift system for scheduling.

Presenteeism and sleep duration on workdays and days off

BACKGROUND

Presenteeism refers to being present at work but experiencing reduced productivity due to health problems, and has been known to be related to sleep loss. Workers commonly sleep longer on days off than on workdays, and presenteeism may be reduced with extended sleep on days off.

AIMS

This study aimed to determine the association between sleep duration both on workdays and days off and presenteeism.

METHODS

The participants were 1967 workers who engaged in work for 5 days and rested for 2 days weekly. Sleep duration was classified into less than 6 hours (short; S), 6-8 hours (medium; M), and 9 hours or longer (long; L), for workdays and days off, respectively. Presenteeism was assessed using the World Health Organization Health and Work Performance Questionnaire.

RESULTS

On both workdays and days off, compared to medium sleep duration, short sleep duration was significantly associated with increased odds of presenteeism. The odds of presenteeism were significantly increased for S-S (odds ratio [OR] 2.17, 95% confidence interval [CI]1.40-3.37), S-M (OR 1.59, 95% CI 1.14-2.22), S-L (OR 2.71, 95% CI 1.05-7.00), and M-S (OR 6.82, 95% CI 2.71-17.17) combined sleep duration for workdays and days off, respectively, compared to an M-M (reference).

CONCLUSIONS

Sleep loss on workdays cannot be compensated for with longer sleep on days off. This study suggests that sufficient sleep duration on both workdays and days off is important for reducing presenteeism.

Feasibility of application-based psychomotor vigilance testing to assess fatigue in doctors working night shifts and correlation with smartwatch assessed shift intensity

OBJECTIVES

To assess: (1) the feasibility of novel data collection methods (wearable technology and an application-based psychomotor vigilance test (PVT)), (2) the impact of night shift working on fatigue, both objective and perceived, for doctors working night shifts in acute hospital specialties and (3) the effects of shift intensity and naps obtained on participant fatigue.

METHODS

We adopted an innovative, multimodal approach to data collection allowing assessment of objective and perceived measures of fatigue, in addition to markers of shift intensity. This comprised 5 min PVT for objective quantification of fatigue (via the validated, smartphone-based NASA PVT+ application), wearable electronic devices (Fitbit Versa2) for assessment of shift intensity (step counts and active minutes) and questionnaires to elicit perceptions of fatigue and shift intensity.

RESULTS

Data was collected from 25 participants for a total of 145 night shifts. Objective fatigue (assessed by PVT performance) was significantly increased post night shift, with a PVT mean reaction time 257 ms pre shift versus 283 ms post shift (p<0.0001). However, differences in PVT pre and post shift were not affected by night shift intensity, nor breaks or naps taken on shift. Differences in psychomotor performance between doctors working in different specialties were also observed.

CONCLUSIONS

The data collection methods used were found to be feasible with good participant engagement. Findings support existing evidence that night shift working in healthcare workers is associated with fatigue, with psychomotor impairment observed post shift. Lower shift intensity and napping did not appear to mitigate this effect.

Sleep, mental health and physical health in new shift workers transitioning to shift work: Systematic review and meta-analysis

This systematic review and meta-analysis (PROSPERO registration CRD42022309827) aimed to describe how shift work impacts new workers' sleep, mental health, and physical health during the transition to shift work and to consolidate information regarding predictors of shift work tolerance (SWT) during this transition period. Inclusion criteria included: new shift workers; sleep, mental health, or physical health outcomes; prospective study design with the first timepoint assessing workers within three months of starting shift work; and written in English. Searches from six databases returned 12,172 articles as of August 2023. The final sample included 48 papers. Publication quality and risk of bias was assessed using the critical appraisal skills program. Forty-five studies investigated longitudinal changes in sleep, mental health, or physical health outcomes and 29 studies investigated predictors of SWT (i.e., better sleep, mental and physical health). Sleep and mental health outcomes worsened following the onset of shift work, while physical health did not significantly change. Pre-shift work mental health, sleep, and work characteristics predicted SWT later in workers' careers. Shift work adversely impacts new workers' sleep and mental health early in their career, and interventions before beginning shift work are needed to promote better SWT.

Assessment and management of sleep disorders in shift workers: Challenges and considerations for general practice

BACKGROUND

Shift work is characterised by displaced sleep opportunities and associated sleep disturbance. Shift workers often report sleepiness and other wake time symptoms associated with poor sleep. However, clinical sleep disorders are also prevalent in shift workers. Although prevalence rates are similar or higher in shift workers compared with the general population, help seeking in shift workers with sleep disorders is low.

OBJECTIVE

This article aims to provide general practitioners with a contemporary overview of the prevalence rates for sleep disorders in shift workers, to clarify the existing evidence relating to mental and physical health consequences of sleep disorders in shift workers and to highlight the need to consider undiagnosed sleep disorders before attributing sleep-related symptoms solely to work schedules.

DISCUSSION

Symptoms of sleep loss associated with shift work overlap with symptoms experienced by individuals living with sleep disorders. Although >40% of middle-aged Australians live with a sleep disorder that requires investigation and management, symptoms in shift workers are often attributed to the work schedule and, as a result, might not be investigated for appropriate diagnosis and treatment. We argue that screening for sleep disorders in shift workers with sleep complaints should be a priority.

The Effect of Night Shift on Blood Pressure in Healthcare Workers

OBJECTIVE

Individuals across all age groups may experience elevated blood pressure due to a combination of internal and environmental factors. Factors influencing arterial pressure include diet, stress, sleep patterns, and lifestyle. This study aims to investigate the susceptibility to high blood pressure among occupational groups working night shifts.

METHOD

The study included healthcare worker participants who had at least six night shifts per month. A control group consisted of participants performing the same roles during daytime. Participants with chronic diseases or those taking blood pressure-affecting medication were excluded. Holter recordings were made over a minimum of 48 hours, including both a free day and a work day.

RESULTS

The study involved 114 participants-55 in the study group and 59 in the control group. Statistically significant differences were noted between the groups in the daylight-night ratios of systolic and diastolic pressures, with P values of 0.006 and 0.005, respectively. The systolic daylight-night difference was -5.7 ± 5.5% in the study group and -9.0 ± 7.0% in the control group. The diastolic daylight-night difference was -7.9 ± 9.6% in the study group and -12.7 ± 8.2% in the control group.

CONCLUSION

Occupations with nighttime work schedules are often associated with non-dipping blood pressure patterns due to sleep disturbances. It is crucial to consider the blunted dipping of blood pressure induced by night shift work when assessing and monitoring hypertension and related medical conditions.

The effect of shift work on body mass index: A systematic review and meta-analysis of observational studies

CONTEXT

Shift work involves working outside the standard working hours of 9 am to 5 pm Monday to Friday and may include working evening, night, weekend, or rotating shift patterns. Since shift workers sleep less and their circadian rhythms are disrupted, they are reported to have higher body weight than day workers.

OBJECTIVE

This meta-analysis aims to determine whether shift workers (SW) are more prone to higher body mass index (BMI) than their day workers (DW) counterparts. It also addresses the question of whether the duration of shift work exposure, sex, or occupational type affect BMI value.

METHODS

Four databases that is PubMed, EBSCO Host, Scopus, and Web of Science were searched for reports published up to October 2023.

RESULTS

Sixty-three studies involving a total of 693 449 participants met our inclusion criteria. Meta-analyses showed a significant effect of shift work on BMI value (standard mean difference; SMD: 0.10 kg/m2 [95% confidence interval; 95% CI: 0.07; 0.13; p < .001]) as compared with non-shift counterparts. Subgroup analysis revealed that shift work significantly increased BMI for studies where male working on this job schedule (SMD: 0.10 kg/m2 [95% CI: 0.04; 0.17; p = .0018]) for studies where shift workers worked ≥13 years (calculated as the median of shift work experience; SMD: 0.14 kg/m2 [95% CI: 0.10; 0.18; p < .001]) as well as for studies where industrial (SMD: 0.12 kg/m2 [95% CI: 0.05; 0.19; p = .0012]) and other type of occupations were dominated (0.12 kg/m2 [95% CI: 0.07; 0.16; p < .001]).

CONCLUSIONS

We found that in general working on a shift schedule increases BMI as compared with day workers, especially in case of male employed in this job schedule, for shift workers working for long periods of time (≥13 years), and for shift workers employed in industry and other type of occupations(e.g., airline workers, firefighters, police officers, blue collar, security personnel, bus drivers, garbage collectors, railway workers, postal, oil and gas workers).

Systematic review and meta-analysis of the association between long working hours and hypertension risk

BACKGROUND

Hypertension, a major public health problem worldwide, has been linked to lifestyle factors and work conditions, with conflicting evidence on the association between long work hours and risk of hypertension.

METHODS

We conducted a systematic review and meta-analysis of observational studies to investigate the relationship between working hours and hypertension or blood pressure, assessed the risk of bias and performed subgroup analyses. The protocol was registered with the International Prospective Register of Systematic Reviews.

RESULTS

The pooled OR for the association between long working hours and risk of hypertension was 1.09 (95% CI: 0.88 to 1.35) in the 15 studies that used hypertension as the outcome. In the three studies that used blood pressure as the outcome, diastolic blood pressure was higher among those with long working hours compared with those with non-long working hours (1.24 mm Hg, 95% CI: 0.19 to 2.29). In subgroup analysis, the pooled OR for the association between long working hours and risk of hypertension was 1.28 (95% CI: 1.14 to 1.44) and 1.00 (95% CI: 0.64 to 1.56) in women and men, respectively.

CONCLUSIONS

Although this study could not clearly confirm the relationship between long working hours and hypertension, the subgroup analysis suggests that long working hours may be associated with hypertension, particularly among women. More reliable research is needed to establish causality.

PROSPERO REGISTRATION NUMBER

CRD42023406961.

Construct validity and test-retest reliability of a chrononutrition questionnaire for shift work and non-shift work populations

The irregular eating patterns of both shift workers and evening chronotypes adversely affect cardiometabolic health. A tool that conveniently captures temporal patterns of eating alongside an indicator of circadian rhythm such as chronotype will enable researchers to explore relationships with diverse health outcome measures. We aimed to investigate the test-retest reliability and convergent validity of a Chrononutrition Questionnaire (CNQ) that captures temporal patterns of eating and chronotype in the general population (non-shift workers, university students, retirees, unemployed individuals) and shift work population. Participants attended two face-to-face/virtual sessions and completed the CNQ and food/sleep/work diaries. Outcomes included subjective chronotype, wake/sleep/mid-sleep time, sleep duration, meal/snack regularity, meal/snack/total frequency, times of first/last/largest eating occasions (EO), main meal (MM) 1/2/3, and duration of eating window (DEW). 116 participants enrolled (44.5 ± 16.5 years, BMI: 27.3 ± 5.8 kg/m2, 73% female, 52% general population); 105 completed the study. Reliability was acceptable for chronotype, sleep, and all temporal eating patterns except on night shifts. Convergent validity was good for chronotype and sleep except for certain shift/shift-free days. Generally, meal/snack regularity and frequency, and times of first/last EO showed good validity for the general population but not shift workers. Validity was good for DEW (except work-free days and afternoon shifts) and times of MM 1/2/3 (except afternoon and night shifts), while time of largest EO had poor validity. The CNQ has good test-retest reliability and acceptable convergent validity for the general and shift work population, although it will benefit from further validation, especially regarding regularity, frequency, and times of first and last eating occasions across more days amongst a larger sample size of shift workers. Use of the CNQ by researchers will expand our current understanding of chrononutrition as relationships between timing of food intake and the multitude of health outcomes are examined.

Behavioral-Social Rhythms and Cardiovascular Disease Risk in Retired Night Shift Workers and Retired Day Workers

OBJECTIVE

Stability in the timing of key daily routine behaviors such as working/doing housework, sleeping, eating, and engaging in social interactions (i.e., behavioral-social rhythms) contributes to health. This study examined whether behavioral-social rhythms were associated with cardiovascular disease (CVD) risk factors in retired night shift workers and retired day workers and explored whether past night shift work exposure moderated this association.

METHODS

A total of 154 retired older adults participated in this study. Multiple logistic regression models were used to examine associations between behavioral-social rhythms and CVD risk factors. Independent variables included Social Rhythm Metric (SRM)-5 score and actigraphy rest-activity rhythm intradaily variability (IV) and interdaily stability (IS). Dependent variables were metabolic syndrome prevalence and its five individual components.

RESULTS

More regular behavioral-social rhythms were associated with lower odds of prevalent metabolic syndrome (SRM: odds ratio [OR] = 0.57, 95% confidence interval [CI] = 0.35-0.88; IV: OR = 4.00, 95% CI = 1.86-8.58; IS: OR = 0.42, 95% CI = 0.24-0.73) and two of its individual components: body mass index (SRM: OR = 0.56, 95% CI = 0.37-0.85; IV: OR = 2.84, 95% CI = 1.59-5.07; IS: OR = 0.42, 95% CI = 0.26-0.68) and high-density lipoprotein cholesterol (SRM: OR = 0.49, 95% CI = 0.30-0.80; IV: OR = 2.49, 95% CI = 1.25-4.96; IS: OR = 0.35, 95% CI = 0.19-0.66). Past shift work history did not moderate the association between behavioral-social rhythms and metabolic syndrome.

CONCLUSIONS

Behavioral-social rhythms were related to CVD risk factors in retired adults regardless of prior night shift work exposure. Older retired workers may benefit from education and interventions aiming to increase behavioral-social rhythm regularity.

Effects of chronotype on sleep, mood and cardiovascular circadian rhythms in rotating night shift medical workers

PURPOSE

Whether chronotype affects the health outcomes of night shift work populations is unknown. This study aimed to assess the influence of different chronotypes in the rotating night shift population on sleep status, mood, blood pressure (BP), and heart rate variability (HRV), as well as the circadian rhythm of BP and HRV.

METHODS

A total of 208 rotating night shift workers were included. All participants completed structured questionnaires to assess chronotype, mood and sleep status. During their daily lives outside of the night shift, they underwent 24-hour Holter electrocardiogram monitoring and 24-hour ambulatory blood pressure monitoring. Day-time and night-time BP and BP dipping were obtained. Day-time and night-time HRV values (SDNN, RMSSD, LF, HF, LF nu, SD1, SD2 and SD2/SD1) were calculated and fitted to the cosine period curve. Three circandian parameters (mesor, amplitude and acrophase) were extracted to quantify the circadian rhythm of the HRV indices.

RESULTS

Among all three groups, E-type showed more fatigue and sleepiness. In addition, E-type showed blunted diastolic BP dipping. Notably, E-type showed association with higher RMSSD, LF, HF and SD1 in the night time, and higher mesors of RMSSD and LF and amplitude of SD2/SD1 in circadian analysis.

CONCLUSION

Chronotype is a factor affecting fatigue, sleepiness and cardiovascular circadian rhythms of rotating night shift workers. Chronotype should be taken into consideration for managing night-shift rotation to promote occupational health.

Shift schedules and circadian preferences: the association with sleep and mood

Object

We explored the circadian preferences of non-shift workers (non-SWs) and various types of shift workers (SWs), and the associations of these preferences with sleep and mood.

Methods

In total, 4,561 SWs (2,419 women and 2,142 men aged 37.00 ± 9.80 years) and 2,093 non-SWs (1,094 women and 999 men aged 37.80 ± 9.73 years) completed an online survey. Of all SWs, 2,415 (1,079 women and 1,336 men aged 37.77 ± 9.96 years) reported regularly rotating or fixed schedules ("regular SWs"), and 2,146 (1,340 women and 806 men aged 36.12 ± 9.64 years) had irregular schedules ("irregular SWs"). Of the regular SWs, 2,040 had regularly rotating schedules, 212 had fixed evening schedules, and 163 had fixed night schedules. All participants completed the Morningness-Eveningness Questionnaire (MEQ) exploring circadian preferences, the short form of the Center for Epidemiological Studies-Depression Scale (CES-D) evaluating depression, the Insomnia Severity Index (ISI), and the Epworth Sleepiness Scale (ESS).

Results

Compared to non-SWs, SWs had lower MEQ scores, i.e., more eveningness, after controlling for age, gender, income, occupation, and weekly work hours (F = 87.97, p < 0.001). Irregular SWs had lower MEQ scores than regular SWs (F = 50.89, p < 0.001). Among regular SWs, the MEQ scores of fixed evening and fixed night SWs were lower than those of regularly rotating SWs (F = 22.42, p < 0.001). An association between the MEQ and ESS scores was apparent in non-SWs (r = -0.85, p < 0.001) but not in SWs (r = 0.001, p = 0.92).

Conclusion

SWs exhibited more eveningness than non-SWs; eveningness was particularly prominent in SWs with irregular or fixed evening/night shifts. Eveningness was associated with sleepiness only in non-SWs, but not in SWs.

The influence of shift work: A bibliometric analysis of research progress and frontiers on health effects

Shift work has been found to disrupt the circadian system, leading to negative health effects. The objective of this study was to assess the progress and frontiers in research on the health-related influence of shift work. The study analyzed 3,696 data points from Web of Science, using the bibliometric software CiteSpace to visualize and analyze the field. The results showed a steady increase in annual publications, particularly in the last 5 years, with a rapid increase in publications from China. The United States contributed the most to the number of publications and worldwide collaborations. The most prolific institution and author were the Brigham and Women's Hospital and Professor Bjorn Bjorvatn, respectively. The Journal of Chronobiology International ranked at the top and focused primarily on shift worker research. In the first decade of study, the primary focus was on the associations between shift work and cardiovascular disease and metabolic disorders. Over time, research on the health effects of shift work has expanded to include cancer and mental health, with subsequent studies investigating molecular mechanisms. This study provides a comprehensive and intuitive analysis of the negative health impacts of shift work. It highlights existing research hotspots and provides a roadmap for future studies. Further research is needed to explore the adverse health consequences and related mechanisms of shift work exposure, as well as interventions to mitigate its health effects.

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.

Effects of shift work on sleep quality and cardiovascular function in Taiwanese police officers

This study aimed to investigate the effects of shift work on sleep quality, cardiovascular function, and physical activity (PA) levels in Taiwanese police officers. Twenty-one male police officers aged 26.9 ± 4.1 years old located in Taipei voluntarily participated in this study. The participants completed the resting heart rate (HR) and hemodynamic variables (e.g. blood pressure, BP) before and after day-time (DTW) and night-time (NTW) shift work phases (5 working days and 2 resting days for each phase). Additionally, an actigraphy was administered to measure PA and sleep patterns in the last 3 working days. The average total sleep time and sleep efficiency were 278.5 ± 79. 6 min and 72.9 ± 10%, respectively, in the NTW phases, which were significantly lower than that in the DTW phases. A comparison of the PA characteristics between the two phases revealed that a lower proportion of moderate-vigorous PA (1.2 ± 0.8%) and a greater proportion of sedentary behaviour PA (74.8 ± 6.4%) was found in the NTW phases. The results of hemodynamic measures demonstrated that the police officers have significantly elevated systolic BP by 3.3% and diastolic BP by 3.9% after the NTW phases. Furthermore, the NTW phases exhibited a significantly higher percentage change ratio of systolic BP and diastolic BP compared to the DTW phases. Compared with the DTW phases, the NTW phase was significantly more likely to report higher decreasing parasympathetic-related HR variability with a range of -5.9% to -7.8%. In conclusion, night-time shift work resulted in negative physiological changes leading to adverse effects on the health and well-being of Taiwanese police officers.

Sleep quality and the intention to modify sleep behaviors among night-shift nurses

PURPOSE

To explore the relationship between sleep quality and intent to change sleep behaviors among night-shift nurses.

METHODS

Full-time night-shift nurses in a hospital setting completed a cross-sectional online survey including demographics, Snoring, Tiredness during daytime, Observed apnea, and High Blood Pressure (STOP) Questionnaire, the Pittsburgh Sleep Quality Index (PSQI), and the Intention to Change Behavior Scale (ICBS). The relationship between PSQI and ICBS scores was tested using Spearman's rho correlation coefficient.

RESULTS

Most participants reported poor sleep and did not engage in health behaviors that promote good sleep. There was a weak, positive relationship between PSQI and ICBS scores. Those who reported poor sleep quality indicated a high intent to improve sleep.

CONCLUSION

These findings support the need for night-shift nurses to prioritize enhancing their sleep quality by advocating for policy and practice improvements. The findings also highlight the importance of support from nurse leaders, educators, and researchers to raise awareness and implement holistic strategies for better sleep health.

Field-based longitudinal evaluation of multimodal worker fatigue assessments in offshore shiftwork

Fatigue in offshore environments is a critical safety hazard, yet the utility of daily fatigue assessments has not been longitudinally examined in these environments. The aim of this exploratory longitudinal field study across two drillships in the Gulf of Mexico was to determine the changes in subjective, performance-based, and physiological fatigue measures over time across different shift types (day, night, and swing) and to identify correlations between these multimodal fatigue assessments. Repeated measures correlation analyses of daily fatigue data from seventy offshore workers revealed that while total sleep time remained unaffected by time on rig, workers' performances on the psychomotor vigilance test (PVT) deteriorated over time across all shift types. Several correlations between the various multimodal measures were consistent with the extant literature on worker fatigue symptoms and perceptual and physiological manifestations. These findings emphasize the utility of PVT and single item self-reports to capture worker fatigue in offshore shiftwork.

Administration of blue light in the morning and no blue-ray light in the evening improves the circadian functions of non-24-hour shift workers

In modern 24-hour society, various round-the-clock services have entailed shift work, resulting in non-24-hour schedules. However, the extent of behavioral and physiological alterations by non-24-hour schedules remains unclear, and particularly, effective interventions to restore the circadian functions of non-24-hour shift workers are rarely explored. In this study, we investigate the effects of a simulated non-24-hour military shift work schedule on daily rhythms and sleep, and establish an intervention measure to restore the circadian functions of non-24-hour shift workers. The three stages of experiments were conducted. The stage-one experiment was to establish a comprehensive evaluation index of the circadian rhythms and sleep for all 60 participants by analyzing wristwatch-recorded physiological parameters and sleep. The stage-two experiment evaluated the effects of an intervention strategy on physiological rhythms and sleep. The stage-three experiment was to examine the participants' physiological and behavioral disturbances under the simulated non-24-hour military shift work schedule and their improvements by the optimal lighting apparatus. We found that wristwatch-recorded physiological parameters display robust rhythmicity, and the phases of systolic blood pressures and heart rates can be used as reliable estimators for the human body time. The simulated non-24-hour military shift work schedule significantly disrupts the daily rhythms of oxygen saturation levels, blood pressures, heart rates, and reduces sleep quality. Administration of blue light in the morning and no blue-ray light in the evening improves the amplitude and synchronization of daily rhythms of the non-24-hour participants. These findings demonstrate the harmful consequences of the non-24-hour shift work schedule and provide a non-invasive strategy to improve the well-being and work efficiency of the non-24-hour shift population.

Home Care Workers' Objective and Subjective Recovery From Work

OBJECTIVE

The aim of this cross-sectional study was to examine the recovery from work in Finnish home care nurses with objective and subjective recovery measures.

METHODS

Heart rate and heart rate variability recordings were performed in home care nurses over a period of one work shift and the following night. Following the measurements, the participants ( N = 91) answered a questionnaire including questions about their self-rated recovery from work and sleep disturbances.

RESULTS

The objectively measured recovery was within the recommended heart rate variability range, yet the self-rated recovery from work was only mediocre. Subjective recovery was not associated with objectively measured recovery.

CONCLUSIONS

There is a discrepancy between objectively and subjectively measured recovery from work. Therefore, an additional objective method in occupational field studies, along with questionnaires, is recommended to measure physiological recovery.

The effect of a night shift nap on post-night shift performance, sleepiness, mood, and first recovery sleep: A randomized crossover trial

OBJECTIVES

This study aimed to test the effect of a 30-minute nap versus a 2-hour nap opportunity taken during a simulated night shift on performance, fatigue, sleepiness, mood, and sleep at the end of shift and during post-night shift recovery.

METHODS

We conducted a randomized crossover trial of three nap conditions (30-minute, 2-hour, and no-nap) during 12-hour simulated night shifts. We tested for differences in performance, fatigue, sleepiness, mood, and sleep during in-lab and at-home recovery. Performance was measured with the Brief Psychomotor Vigilance Test (PVT-B). Subjective ratings were assessed with single-item surveys.

RESULTS

Twenty-eight individuals consented to participate [mean age 24.4 (standard deviation 7.2) years; 53.6% female; 85.7% Emergency Medical Services clinicians]. PVT-B false starts at the end of the 12-hour night shift (at 07:00 hours) and at the start of in-lab recovery (08:00 hours) were lower following the 2-hour nap versus other conditions (P<0.05). PVT-B response time at +0 minutes post-recovery nap was poorer compared to pre-recovery nap for the no-nap condition (P=0.003), yet not detected for other nap conditions (P>0.05). Sleepiness, fatigue, and some mood states were lower at most hourly assessments during the in-lab recovery period following the 2-hour nap condition compared to the other conditions. Sleep during recovery did not differ by duration of night shift nap.

CONCLUSIONS

A 2-hour nap opportunity versus a 30-minute or no-nap opportunity is beneficial for performance, alertness, and mood post-night shift. No differences were detected in sleep during recovery.

Time-of-day effects on speed and accuracy performance during simulated shiftwork

Performance on tasks involving speed and accuracy fluctuate throughout the 24-h day negatively affecting shift workers and organizations. Two simulated work shifts common in occupational settings were used to assess performance on a vigilance and math task. In study 1, 33 sleep-deprived participants completed a nightshift. In study 2, 32 partially sleep-deprived participants completed a dayshift. These studies found that performance differed between the type of task and the type of simulated shift where performance during the nightshift was worse than during the dayshift. In addition, collapsing speed and accuracy on the math task into inverse efficiency scores provided a unique measure that captured the impact of circadian rhythms during shiftwork. The current study also indicated that participants adopted cognitive strategies including speed-accuracy tradeoff and regulatory foci regarding work motivation (prevention focus and promotion focus) when completing the tasks depending on time-of-day, type of shift, circadian rhythms, and amount of sleep deprivation. This suggests that researchers and organizations should consider cognitive strategies in addition to the physiological components of sleep deprivation and circadian rhythms when investigating and documenting the impact of time-of-day due to different types of shiftwork conditions on performance and safety.