Influence of night shift work on psychologic state and cardiovascular and neuroendocrine responses in healthy nurses

Assessing cardiovascular stress based on heart rate variability in female shift workers: a multiscale-multifractal analysis approach

Introduction

Sleep-wake cycle disruption caused by shift work may lead to cardiovascular stress, which is observed as an alteration in the behavior of heart rate variability (HRV). In particular, HRV exhibits complex patterns over different time scales that help to understand the regulatory mechanisms of the autonomic nervous system, and changes in the fractality of HRV may be associated with pathological conditions, including cardiovascular disease, diabetes, or even psychological stress. The main purpose of this study is to evaluate the multifractal-multiscale structure of HRV during sleep in healthy shift and non-shift workers to identify conditions of cardiovascular stress that may be associated with shift work.

Methods

The whole-sleep HRV signal was analyzed from female participants: eleven healthy shift workers and seven non-shift workers. The HRV signal was decomposed into intrinsic mode functions (IMFs) using the empirical mode decomposition method, and then the IMFs were analyzed using the multiscale-multifractal detrended fluctuation analysis (MMF-DFA) method. The MMF-DFA was applied to estimate the self-similarity coefficients, α(q, τ), considering moment orders (q) between -5 and +5 and scales (τ) between 8 and 2,048 s. Additionally, to describe the multifractality at each τ in a simple way, a multifractal index, MFI(τ), was computed.

Results

Compared to non-shift workers, shift workers presented an increase in the scaling exponent, α(q, τ), at short scales (τ < 64 s) with q < 0 in the high-frequency component (IMF1, 0.15-0.4 Hz) and low-frequency components (IMF2-IMF3, 0.04-0.15 Hz), and with q> 0 in the very low frequencies (IMF4, < 0.04 Hz). In addition, at large scales (τ> 1,024 s), a decrease in α(q, τ) was observed in IMF3, suggesting an alteration in the multifractal dynamic. MFI(τ) showed an increase at small scales and a decrease at large scales in IMFs of shift workers.

Conclusion

This study helps to recognize the multifractality of HRV during sleep, beyond simply looking at indices based on means and variances. This analysis helps to identify that shift workers show alterations in fractal properties, mainly on short scales. These findings suggest a disturbance in the autonomic nervous system induced by the cardiovascular stress of shift work.

Emergency nurses' activity levels across rotating shifts

BACKGROUND

Emergency nurses work consecutive, rotating shift patterns. However, how their occupational physical activity levels are associated between these shifts is unknown. This study aimed to examine the associations between emergency nurses' time spent in different activity levels across one shift and the following day's shift.

METHODS

Fifty emergency nurses (45 female, five male) wore an ActiGraph accelerometer and completed work and sleep diaries across four weeks in 2018. A sub-sample (n = 42) also wore an activPAL inclinometer. Time spent sedentary, physically active, and in postural positions was determined. Multi-level analyses examined associations between one shift and the following day's shift.

RESULTS

Additional time spent sedentary and in light-intensity physical activity during the first shift was associated with more time spent being physically active in the following day's shift for all rotations except back-to-back night shifts. However, additional time spent engaged in moderate- to vigorous-intensity physical activity during the first shift was associated with less time spent physically active in the following day's shift for afternoon-morning and morning-afternoon rotations.

CONCLUSION

These findings demonstrate that shift sequences may impact emergency nurses' physical activity across shifts. Future research should identify the strategies emergency nurses use to maintain activity levels between shifts.

The relation of work-related factors with ambulatory blood pressure and nocturnal blood pressure dipping among aging workers

Objectives

Individuals with reduced nocturnal blood pressure (BP) dipping are at increased risk of cardiovascular disease compared to persons with normal BP dipping. Although the relation of work-related factors and BP has been studied extensively, very little is known of the association between work-related factors and 24-h BP patterns in aging workers. We examined the cross-sectional relation of work-related risk factors, including occupational status, work-time mode, job demands and job control, with ambulatory BP in aging workers, focusing on nocturnal BP dipping.

Methods

208 workers (mean age 62 ± 3 years; 75% women) from two Finnish population-based cohort studies underwent 24-h ambulatory BP monitoring. Work-related factors were inquired using a questionnaire. Nocturnal BP dipping was calculated as [1 − (asleep BP/awake BP)] × 100.

Results

Shift workers demonstrated a higher nocturnal diastolic BP dipping than regular day workers (19% vs. 17%, p = 0.03) and had a significantly higher systolic awake BP than regular day workers (136.5 mmHg vs. 132.5 mmHg, p = 0.03). Participants with high job demands demonstrated a smaller nocturnal systolic BP dipping than participants with low job demands (14% vs. 16%, p = 0.04). We did not observe significant differences in nocturnal systolic or diastolic BP dipping between groups categorized by occupational status or job control.

Conclusions

Although shift workers have a higher daytime BP than regular daytime workers, they exhibit greater nighttime BP dipping. Participants with high job demand had smaller nighttime BP dipping than participants with low job demand. Job control or occupation did not affect the 24-h ambulatory BP profile of aging workers.

Music therapy intervention in cardiac autonomic modulation, anxiety, and depression in mothers of preterms: randomized controlled trial

Background

Mothers of preterm infants often have symptoms of anxiety and depression, recognized as risk factors for the development of cardiovascular diseases and associated with low rates of heart rate variability (HRV). This study aimed to evaluate the influence of music therapy intervention on the autonomic control of heart rate, anxiety, and depression in mothers.

Methods

Prospective randomized clinical trial including 21 mothers of preterms admitted to the Neonatal Intensive Care Unit of a tertiary hospital, recruited from August 2015 to September 2017, and divided into control group (CG; n = 11) and music therapy group (MTG; n = 10). Participants underwent anxiety and depression evaluation, as well as measurements of the intervals between consecutive heartbeats or RR intervals for the analysis of HRV at the first and the last weeks of hospitalization of their preterms. Music therapy sessions lasting 30–45 min were individually delivered weekly using receptive techniques. The mean and standard deviation of variables were obtained and the normality of data was analyzed using the Kolmogorov-Smirnov test. The paired sample t-test or Wilcoxon test were employed to calculate the differences between variables before and after music therapy intervention. The correlations anxiety versus heart variables and depression versus heart variables were established using Spearman correlation test. Fisher’s exact test was used to verify the differences between categorical variables. A significance level of p < 0.05 was established. Statistical analysis were performed using the Statistical Package for the Social Sciences, version 20.

Results

Participants in MTG had an average of seven sessions of music therapy, and showed improvement in anxiety and depression scores and autonomic indexes of the time domain (p < 0.05). Significant correlations were found between depression and parasympathetic modulation using linear (r = − 0.687; p = 0.028) and nonlinear analyses (r = − 0.689; p = 0.027) in MTG.

Conclusion

Music therapy had a significant and positive impact on anxiety and depression, acting on prevention of cardiovascular diseases, major threats to modern society.

Trial registration

Brazilian Registry of Clinical Trials (no. RBR-3x7gz8). Retrospectively registered on November 17, 2017.

Effects of night shift on the cognitive load of physicians and urinary steroid hormone profiles - a randomized crossover trial

Mental and physical stress is common in physicians during night shifts. Neurocognitive effects of sleep deprivation as well as alterations in hormonal and metabolic parameters have previously been described. The aim of this crossover study was to evaluate the effects of night-shift work with partial sleep deprivation on steroid hormone excretion and possible associations with mood, sleep characteristics and cognitive functions in physicians. In total, 34 physicians (mean age 42 ± 8.5 years, 76.5% male) from different departments of the General Hospital of Vienna, Austria, were randomly assigned to two conditions: a regular day shift (8 h on duty, condition 1) and a continuous day-night shift (24 h on duty, condition 2). In both conditions, physicians collected a 24 h urine sample for steroid hormone concentration analysis and further completed psychological tests, including the sleep questionnaire (SF-A), the questionnaire for mental state (MDBF) and the computer-assisted visual memory test (FVW) before and at the end of their shifts, respectively. Although mean sleep deprivation during night shift was relatively small (~1.5 h) the impairment in participants' mental state was high in all three dimensions (mood, vigilance and agitation, p ≤ 0.001). Sleep quality (SQ), feeling of being recovered after sleep and mental balance decreased (p ≤ 0.001), whereas mental exhaustion increased (p < 0.05). Moreover, we could show a nearly linear relationship between most of these self-rating items. Testing visual memory participants made significantly more mistakes after night shift (p = 0.011), however, mostly in incorrectly identified items and not in correctly identified ones (FVW). SQ and false identified items were negatively correlated, whereas SQ and time of reaction were positively associated. It is assumed that after night shift, a tendency exists to make faster wrong decisions. SQ did not influence correctly identified items in FVW. In contrast to previous investigations, we found that only excretion rates for pregnanetriol and androsterone/etiocholanolone ratios (p < 0.05, respectively) were slightly reduced in 24-h urine samples after night shift. A considerable stimulation of the adrenocortical axis could not be affirmed. In general, dehydroepiandrosteron (DHEA) was negatively associated with the sense of recreation after sleep and with the time of reaction and positively correlated with correctly identified items in the FVW test. These results, on the one hand, are in line with previous findings indicating that stress and sleep deprivation suppress gonadal steroids, but, on the other hand, do not imply significant adrenocortical-axis stimulation (e.g. an increase of cortisol) during the day-night shift.

Cortisol Levels and Autonomic Control of Heart Rate in Healthy Subjects

Introduction: There is an increase in level of stress in the general population because of the social, personal and professional demands. Currently, there are only simple tools that can safely measure this stress such as levels of cortisol and heart rate variability (HRV). Objective: To analyze the relationship between salivary cortisol and the cardiac autonomic modulation. Methods: A total of fifty-one male and female subjects between 18 and 40 years old were evaluated. Saliva collection was achieved for the salivary cortisol dosage. The collection was performed through the SalivetteR tube. After this collection, the median cortisol levels (0.24 ug/dl) were analyzed and the volunteers were divided into two groups: i) cortisol below the mediane ii) cortisol above the median. After this division, each group consisted of 25 volunteers and then was verified the following information: age, gender, weight, height, body mass index (BMI), blood pressure. Shortly thereafter was assessment of cardiac autonomic modulation por meio da HRV. The Polar RS800cx heart rate receiver was placed on the chest of the volunteers, in the vicinity of the distal third of the sternum. The volunteers were instructed to remain in rest with spontaneous breathing in dorsal position for 20 minutes. HRV analysis included geometric, time and frequency domain indices. Results: There were no statistical differences for the two groups regarding systolic and diastolic blood pressure, heart rate, RR intervals or linear and frequency indices for the volunteers. In addition, also there was no correlation the cortisol with the analyzed variables (SAP, p=0.460; DAP, p = 0.270; HR, p = 0.360; RR, p = 0.380; SDNN, p = 0.510; rMSSD, p = 0.660; pNN50, p = 0.820; RRtri, p = 0.170; TINN, p = 0.470; SD1, p = 0.650; SD2, p = 0.500; LF [ms2], p = 0.880; LF [nu], p = 0.970; HF [ms2], p = 0.870; HF [nu], p = 0.960; LF/HF, p = 0.380 Conclusion: Heart rate variability autonomic control was unchanged in healthy subjects with physiological distribution of salivary cortisol levels. There was no association between normal salivary cortisol and resting autonomic regulation of heart rate.

Night shift and rotating shift in association with sleep problems, burnout and minor mental disorder in male and female employees

OBJECTIVES

Shift work is associated with adverse physical and psychological health outcomes. However, the independent health effects of night work and rotating shift on workers' sleep and mental health risks and the potential gender differences have not been fully evaluated.

METHODS

We used data from a nationwide survey of representative employees of Taiwan in 2013, consisting of 16 440 employees. Participants reported their work shift patterns 1 week prior to the survey, which were classified into the four following shift types: fixed day, rotating day, fixed night and rotating night shifts. Also obtained were self-reported sleep duration, presence of insomnia, burnout and mental disorder assessed by the Brief Symptom Rating Scale.

RESULTS

Among all shift types, workers with fixed night shifts were found to have the shortest duration of sleep, highest level of burnout score, and highest prevalence of insomnia and minor mental disorders. Gender-stratified regression analyses with adjustment of age, education and psychosocial work conditions showed that both in male and female workers, fixed night shifts were associated with greater risks for short sleep duration (<7 hours per day) and insomnia. In female workers, fixed night shifts were also associated with increased risks for burnout and mental disorders, but after adjusting for insomnia, the associations between fixed night shifts and poor mental health were no longer significant.

CONCLUSIONS

The findings of this study suggested that a fixed night shift was associated with greater risks for sleep and mental health problems, and the associations might be mediated by sleep disturbance.

Mothering Experiences: How Single Parenthood and Employment Structure the Emotional Valence of Parenting

Research studies and popular accounts of parenting have documented the joys and strains of raising children. Much of the literature comparing parents with those without children indicates a happiness advantage for those without children, although recent studies have unpacked this general advantage to reveal differences by the dimension of well-being considered and important features in parents' lives and parenting experiences. We use unique data from the 2010, 2012, and 2013 American Time Use Survey to understand emotions in mothering experiences and how these vary by key demographic factors: employment and partnership status. Assessing mothers' emotions in a broad set of parenting activities while controlling for a rich set of person- and activity-level factors, we find that mothering experiences are generally associated with high levels of emotional well-being, although single parenthood is associated with differences in the emotional valence. Single mothers report less happiness and more sadness, stress, and fatigue in parenting than partnered mothers, and these reports are concentrated among those single mothers who are not employed. Employed single mothers are happier and less sad and stressed when parenting than single mothers who are not employed. Contrary to common assumptions about maternal employment, we find overall few negative associations between employment and mothers' feelings regarding time with children, with the exception that employed mothers report more fatigue in parenting than those who are not employed.

Associations of Short Sleep and Shift Work Status with Hypertension among Black and White Americans

Objective. The purpose of this study was to investigate whether short sleepers (<6 hrs) who worked the non-day-shift were at greater likelihood of reporting hypertension and if these associations varied by individuals' ethnicity. Methods. Analysis was based on the 2010 National Health Interview Survey (NHIS). A total of 59,199 American adults provided valid data for the present analyses (mean age = 46.2 ± 17.7 years; 51.5% were female). Respondents provided work schedule and estimated habitual sleep durations as well as self-report of chronic conditions. Results. Of the sample, 30.8% reported a diagnosis of hypertension, 79.1% reported daytime shift work, 11.0% reported rotating shift work, and 4.0% reported night shift work. Logistic regression analysis showed that shift work was significantly associated with hypertension among Blacks [OR = 1.35, CI: 1.06–1.72. P < 0.05], but not among Whites [OR = 1.01, CI: 0.85–1.20, NS]. Black shift workers sleeping less than 6 hours had significantly increased odds of reporting hypertension [OR = 1.81, CI: 1.29–2.54, P < 0.01], while their White counterparts did not [OR = 1.17, CI: 0.90–1.52, NS]. Conclusions. Findings suggest that Black Americans working the non-day-shift especially with short sleep duration have increased odds of reporting hypertension.

Impacts of shift work on sleep and circadian rhythms

Shift work comprises work schedules that extend beyond the typical "nine-to-five" workday, wherein schedules often comprise early work start, compressed work weeks with 12-hour shifts, and night work. According to recent American and European surveys, between 15 and 30% of adult workers are engaged in some type of shift work, with 19% of the European population reportedly working at least 2 hours between 22:00 and 05:00. The 2005 International Classification of Sleep Disorders estimates that a shift work sleep disorder can be found in 2-5% of workers. This disorder is characterized by excessive sleepiness and/or sleep disruption for at least one month in relation with the atypical work schedule. Individual tolerance to shift work remains a complex problem that is affected by the number of consecutive work hours and shifts, the rest periods, and the predictability of work schedules. Sleepiness usually occurs during night shifts and is maximal at the end of the night. Impaired vigilance and performance occur around times of increased sleepiness and can seriously compromise workers' health and safety. Indeed, workers suffering from a shift work sleep-wake disorder can fall asleep involuntarily at work or while driving back home after a night shift. Working on atypical shifts has important socioeconomic impacts as it leads to an increased risk of accidents, workers' impairment and danger to public safety, especially at night. The aim of the present review is to review the circadian and sleep-wake disturbances associated with shift work as well as their medical impacts.

The effects of perceived stress on biological parameters in healthcare professionals: A systematic review

We synthesised evidence on biological correlates of psychological stress in hospital-based healthcare professionals, and examined whether there was evidence of consistent biological changes. Electronic databases were searched for empirical studies; 16 articles (0.6%) met the inclusion criteria. Evidence of a relationship between indices of psychological stress and biological parameters was limited and inconsistent. There was some evidence of a consistent relationship between natural killer cells and lymphocyte subpopulations. Considerable heterogeneity in the methods used was seen. Future prospective studies examining the relationship between indices of psychological stress and natural killer cells, including lymphocyte subsets, is required.

Mothers' night work and children's behavior problems

Many mothers work in jobs with nonstandard schedules (i.e., schedules that involve work outside of the traditional 9-5, Monday through Friday schedule); this is particularly true for economically disadvantaged mothers. In the present article, we used longitudinal data from the Fragile Families and Child Wellbeing Survey (n = 2,367 mothers of children ages 3-5 years) to examine the associations between maternal nonstandard work and children's behavior problems, with a particular focus on mothers' night shift work. We employed 3 analytic strategies with various approaches to adjusting for observed and unobserved selection factors; these approaches provided an upper and lower bound on the true relationship between night shift work and children's behavior. Taken together, the results provide suggestive evidence for modest associations between exposure to maternal night shift work and higher levels of aggressive and anxious or depressed behavior in children compared with children whose mothers who are not working, those whose mothers work other types of nonstandard shifts, and, for aggressive behavior, those whose mothers work standard shifts.

Associations of long-term shift work with waking salivary cortisol concentration and patterns among police officers

The objective of this study was to evaluate whether long-term shift work is associated with both the total hormonal secretion after awakening and the pattern of the cortisol levels during the first hour following awakening, among 65 randomly selected police officers who represent a high stress occupation. Dominant shift (Day, Afternoon, or Midnight) was ascertained using daily payroll records of each participant's work activities during the 6-8 yrs prior to saliva sampling. Four salivary samples were collected at 15 min intervals upon first awakening. After accounting for potential confounders, salivary cortisol concentrations averaged across all four time points and total area under the curve differed significantly across shift with midnight shift workers showing suppressed awakening cortisol response relative to the afternoon and day shift. The percent of hours worked on midnight shift was inversely correlated with total awakening cortisol output. In contrast, the pattern of cortisol secretion during the first hour following waking appeared not to be affected as no significant interaction effect was found between time since awakening and shift work. The results show that long-term midnight shift work is associated with decreased absolute mean level and total volume of cortisol released over the waking period.

Shift work disorder in nurses--assessment, prevalence and related health problems

BACKGROUND

This study investigates the prevalence of symptoms of shift work disorder in a sample of nurses, and its association to individual, health and work variables.

METHODOLOGY/PRINCIPAL FINDINGS

We investigated three different shift work disorder assessment procedures all based on current diagnostic criteria and employing symptom based questions. Crude and adjusted logistic regression analyses were performed with symptoms of shift work disorder as the dependent variable. Participants (n = 1968) reported age, gender, work schedule, commuting time, weekly work hours, children in household, number of nights and number of shifts separated by less than 11 hours worked the last year, use of bright light therapy, melatonin and sleep medication, and completed the Bergen Insomnia Scale, Epworth Sleepiness Scale, Global Sleep Assessment Questionnaire, Diurnal Scale, Revised Circadian Type Inventory, Dispositional Resilience (Hardiness) Scale--Revised, Fatigue Questionnaire, questions about alcohol and caffeine consumption, as well as the Hospital Anxiety and Depression Scale.

CONCLUSIONS/SIGNIFICANCE

Prevalence rates of symptoms of shift work disorder varied from 32.4-37.6% depending on the assessment method and from 4.8-44.3% depending on the work schedule. Associations were found between symptoms of shift work disorder and age, gender, circadian type, night work, number of shifts separated by less than 11 hours and number of nights worked the last year, insomnia and anxiety. The different assessment procedures yielded similar results (prevalence and logistic regression analyses). The prevalence of symptoms indicative of shift work disorder was high. We argue that three symptom-based questions used in the present study adequately assess shift work disorder in epidemiological studies.

Patterns of salivary cortisol levels can manifest work stress in emergency care providers

To develop objective assessments of work fatigue, we investigated the patterns of changes in salivary cortisol levels in emergency care providers working extended work shifts. Fourteen subjects, comprising seven physicians and seven physician assistants, provided unstimulated saliva samples at regular intervals over the course of a 24-h work shift and over their subsequent free day. There was a significant time effect, with early morning cortisol levels being significantly attenuated following the work shift. Native diurnal variations varied by gender, with the female subjects manifesting greater cortisol levels. Physicians also had higher cortisol profiles even though their wake-rest cycles were similar to those of the physician assistants. Our results suggest that temporal changes, as well as diurnal similarities, in the salivary cortisol patterns can reflect work-related stress and recovery. In particular, early morning cortisol levels may manifest individual reactivity to work stressors as well as sleep deprivation.

Work-related cardiovascular disease risk factors using a socioecological approach: implications for practice and research

BACKGROUND

Cardiovascular disease (CVD) is a leading cause of mortality. Numerous investigations have linked occupational factors and CVD. Occupational factors such as overtime work have an enormous effect on the CVD risk of industrial workers. However, risk factors for CVD are not systematically reviewed in the workplace. The purpose of the paper is to review work-related risk factors for CVD.

METHODS

A systematic review of work-related CVD risk factors was performed, yielding 180 articles. All articles were assessed in relation to inclusion and exclusion criteria, resulting in 44 articles being reviewed. The sole inclusion criteria was work-related environmental factors and intra/inter-personal factors (psychosocial factors), which is based on the socioecological perspective. The articles were also assessed regarding the quality of each study using the scoring methods developed by Cesario et al. and Brown et al.

CONCLUSION

The literature review demonstrated that work environment factors such as shift work, overtime work, and noise and chemical exposures; and psychosocial factors such as job stress, social support, and socioeconomic status cannot be explained or intervened by one single risk factor. Furthermore, certain occupational factors were shown to aggravate or attenuate other risk factors. The implication of these findings is to incorporate work-related environmental and psychosocial factors into assessment of the patient's CVD risks and intervention plan. Future research should also incorporate a well-defined conceptual framework to address the effects of work-related environmental and psychosocial factors on CVD among CVD patients.

Shift work and cardiovascular risk factors: new knowledge from the past decade

Cardiovascular diseases remain a major public health problem. The involvement of several occupational factors has recently been discussed, notably the organization of work schedules, e.g. shift work. To analyse the progress of knowledge on the relationship between cardiovascular risk factors and shift work. A review of English-language literature dealing with the link between cardiovascular factors and shift workers (published during 2000-2010) was conducted. Studies published in the past 10 years tend to document an impact of shift work on blood pressure, lipid profile (triglyceride levels), metabolic syndrome and, possibly, body mass index. However, the consequences on glucose metabolism are unclear. These results are not yet firmly established, but are supported by strong hypotheses. Some advice could reasonably be proposed to guide the clinical practitioner.

Shiftwork duration and the awakening cortisol response among police officers

Police officers are required to work irregular hours, which induces stress, fatigue, and sleep disruption, and they have higher rates of chronic disease and mortality. Cortisol is a well-known "stress hormone" produced via activation of the hypothalamic-pituitary-adrenal axis. An abnormal secretion pattern has been associated with immune system dysregulation and may serve as an early indicator of disease risk. This study examined the effects of long- and short-term shiftwork on the cortisol awakening response among officers (n = 68) in the Buffalo Cardio-Metabolic Occupational Police Stress (BCOPS) pilot study (2001-2003). The time each officer spent on day (start time: 04:00-11:59 h), afternoon (12:00-19:59 h), or night (20:00-03:59 h) shifts was summarized from 1994 to examination date to characterize long-term (mean: 14 ± 9 yrs) and short-term (3, 5, 7, or 14 days prior to participation) shiftwork exposures. The cortisol awakening response was characterized by summarizing the area under the curve (AUC) for samples collected on first awakening, and at 15-, 30-, and 45-min intervals after waking. Data were collected on a scheduled training or off day. The cortisol AUC with respect to ground (AUC(G)) summarized total cortisol output after waking, and the cortisol AUC with respect to increase (AUC(I)) characterized the waking cortisol response. Officers also completed the Center for Epidemiologic Studies Depression scale. Waking cortisol AUC values were lower among officers working short-term night or afternoon shifts than day shifts, with maximal differences occurring after 5 days of shiftwork. The duration of long-term shiftwork was not associated with the cortisol awakening response, although values were attenuated among officers with more career shift changes.

Influences of shift work on fatigue among nurses

AIM

To compare the symptoms of fatigue and physiological indices in nurses who work during the day with nurses who work in shifts.

METHOD

One-hundred and seven nurses were recruited and asked to assess their symptoms of fatigue before their work commenced and after it finished.

RESULTS

Using logistic regression analysis adjusted for covariates, it was found that nurses who work in shifts were more fatigued than nurses who work during the day (odds ratio = 2.44, P < 0.10). There was a significant difference regarding critical flicker fusion in the two groups of nurses (P = 0.032), and nurses who work in shifts had poorer physiological indices than nurses who work during the day.

CONCLUSION

It is clear that differing work schedules result in differing levels of fatigue, with shift work attributing to higher levels than day work.

IMPLICATIONS FOR NURSING MANAGEMENT

Nurse managers need to take into account the fatiguing effects of different work schedules when designing rostering patterns.

Comparison of sleep-related cardiac autonomic function between rotating-shift and permanent night-shift workers

The purpose of this study was to explore whether sleep-related cardiac sympathetic activity is significantly lower in rotating shift workers than in permanent night shift workers, in order to evaluate whether shift work is preferable to permanent night work. Our sample comprised of twelve permanent night shift nurses and twelve rotating three-shift nurses. All female nurses slept in their dormitories, where they were allowed to sleep and wake spontaneously. All sleep parameters were recorded and analyzed using an ambulatory polysomnographic recorder. No significant differences were identified between permanent night shift (PNS) nurses and rotating three-shift (RTS) nurses in terms of basic demographics and sleep patterns. The low frequency (LF) of PNS nurses was significantly higher than that of RTS nurses during both daytime sleep and wakefulness, as was the low-to-high frequency ratio (LF/HF) during both nighttime sleep and wakefulness. PNS nurses also exhibited significantly higher LF and LF/HF during the first to third episode of non-rapid eye movement (NREM1-3) sleep, and the first episode of rapid-eye movement (REM1) sleep. PNS nurses had higher sympathetic activity during nighttime and daytime sleep than did RTS nurses. These results suggest that a rotating three-shift schedule may be preferable to permanent night work in terms of cardiac autonomic regulation.

Sympathomodulatory effects of Saam acupuncture on heart rate variability in night-shift-working nurses

OBJECTIVE

We assessed the effects of Saam (traditional Korean) acupuncture on the autonomic nervous system in night-shift nurses using power-spectral heart-rate variability (HRV) analysis.

METHODS

This study had a 2 × 4 cross-over design with a series of six (n = 1) controlled trials. Six night-shift nurses were randomly divided into two groups, and each nurse received four acupuncture treatments on the third day of night-shift work. One group started with Saam acupuncture (gallbladder jeonggyeok), while the other started with sham acupuncture. Saam acupuncture and sham acupuncture were applied in turn. HRV was measured before and after treatment. For statistical analysis, the results of the two groups were combined, and a Bayesian model was used to compare the changes in HRV values before and after treatment, between Saam and sham acupuncture.

RESULTS

As the ratio of low- to high-frequency power (LF/HF) for HRV increased on the third day of night-shift work in the pilot study, HRV measurements were made on the third day. Compared with sham acupuncture, Saam acupuncture reduced sympathetic activity; the overall median treatment effect estimate in LF normalised units decreased by -17.4 (confidence interval (CI): -26.67, -8.725) and that for LF/HF decreased by -1.691 (CI: -3.222, -0.3789). The overall median treatment effect estimate in HF normalised units increased by 17.41 (CI: 6.393, 27.13) with Saam acupuncture, suggesting an increase in parasympathetic activity.

CONCLUSION

Saam acupuncture may attenuate the imbalance between sympathetic and parasympathetic activities induced by night-shift work in nurses.

Arrhythmias and increased neuro-endocrine stress response during physicians' night shifts: a randomized cross-over trial

AIMS

To evaluate the effects of a 24 h (h) physicians on-call duty (OCD) ('night shift') on 24 h electrocardiogram (ECG), heart rate variability, blood pressure (BP), and various biochemical serum and urine 'stress markers' compared with a 'regular' day at work.

METHODS AND RESULTS

The study was designed as a prospective randomized cross-over trial with each physician completing a 24 h (h) OCD and a 24 h control period including a regular 8 h non-OCD. Thirty healthy physicians with a median age of 33.5 years (range 29.0-45.0) were analysed. Twenty-four hours ECG and BP monitoring were performed and participants were instructed to fill out an event diary and perform a 24 h urine collection. Furthermore, blood was drawn before and after OCD and control day. Twenty-four hours ECG showed a higher rate of ventricular premature beats (VPB) during early morning hours (VPB 0-6 h, 0.5 vs. 0.0, P = 0.047) and increased low-frequency normalized units (29.3 vs. 25.5, P = 0.050) during night shift when compared with respective control night at home. During OCD, BP monitoring revealed a greater diastolic BP throughout 24 h (83.5 vs. 80.2 mmHg, P = 0.025) as well as during night-time (75.4 vs. 73.0, P = 0.028) associated with a higher rate of systolic BP more than 125 mmHg during sleep time. Tumour necrosis factor alpha concentrations increased significantly during night shift (0.76 vs. 0.05 pg/mL, P = 0.045). Urinary noradrenaline excretion was greater during OCD when compared with control day (46.0 vs. 36.0 microg/24 h, P = 0.007).

CONCLUSION

Our results highlight the association of OCD with an increased risk profile for cardiovascular disease. In addition to the acute effects observed, frequent night-calls over a longer period possibly elicit sustained alterations in cardiovascular homeostasis.

Japanese study to organize proper lifestyle modifications for metabolic syndrome (J-STOP-MetS): design and method

Prevalence of the metabolic syndrome is now a very serious health problem in Japan and a public preventive strategy is essential to reduce morbidity. A systematic interventional strategy for the metabolic syndrome remains to be established. In order to address this issue, a multi-center study; Japanese Study to Organize Proper lifestyle modification for the metabolic syndrome (J-STOP-MetS), has been established by nine preventive medical centers among Rosai hospital groups. This study comprises a cross-sectional study (J-STOP-MetS 1) and a prospective randomized control study (J-STOP-MetS 2). J-STOP-MetS 1 examines the causes of the metabolic syndrome by means of a questionnaire in a large cohort of patients with the metabolic syndrome and control subjects matched for age and sex. J-STOP-MetS 2 examines the hypothesis that guidance on lifestyle modifications will help at risk patients to reduce abdominal fat and cardiovascular risk factors. The metabolic syndrome patients are randomly assigned either to a single visit to a guidance group or multiple visits every two months. The individualized guidance is provided by the coordination of physician, trained nurse, dietician and exercise trainer. Several parameters are measured before and six months after the first guidance session, including, body weight, waist circumference, blood pressure, several blood markers and arterial stiffness. The J-STOP-MetS is the first large-scale clinical study of the metabolic syndrome in Japan and should provide important evidence for the practical management of the metabolic syndrome.

Dynamic blood pressure changes and recovery under different work shifts in young women

BACKGROUND

Some studies have reported that shift work can affect blood pressure (BP), but few have studied recovery from BP changes occurring during different shifts.

METHODS

We recruited 16 young female nurses working rotating shifts and six working the regular day shift. All received repeated ambulatory BP monitoring (ABPM) during their workdays and following day off.

RESULTS

Our linear mixed-effect model showed that both systolic and diastolic BPs were significantly decreased during sleeping period and significantly increased while on working period, on a work day, but increased during sleeping period after a night shift or evening shift. BP measurements that changed after evening shift usually returned to baseline on consecutive off-duty day after day shift, but they did not completely return to baseline after a night shift (P < 0.05). We also found 69% of those working rotating shifts had at least changed once in dipper/nondipper status. The rates of change in dipper/nondipper status between work day and off-duty day were 33, 44, 50, and 38% for nurses worked in outpatient clinic, night shift, evening shift, and day shift, respectively.

CONCLUSION

Shift work is significantly associated with BP and possibly dipper/nondipper status in young female nurses. Except for those working night shifts, BP levels returned to baseline the off-duty day after day shift. We recommend that potential influence of shift work be considered when evaluating a person's BP.

Psychological, lifestyle and coping contributors to chronic fatigue in shift-worker nurses

AIM

This paper is a report of a study to assess the following in shift-worker nurses: (1) the relationships amongst chronic fatigue and psychological variables including anxiety, mood and locus of control; (2) the relationships amongst chronic fatigue and a number of lifestyle factors such as shiftwork, sleep and exercise; and (3) various coping behaviours that best predict chronic fatigue.

BACKGROUND

In the shift-working population, individual psychological, lifestyle and coping differences influence fatigue levels. However, some of these factors are somewhat unexplored and their relative contribution to fatigue remains poorly understood. Methods. An exploratory design was adopted with 111 eldercare shift-worker nurses. Data were collected during 2006. Nurses completed self-administered questionnaires examining fatigue, anxiety, mood disturbance, locus of control, sleep, work, lifestyle and coping characteristics.

FINDINGS

Multiple regressions showed that mood disturbance, locus of control and trait anxiety are statistically significant predictors of chronic fatigue. Poor sleep quality was the lifestyle factor which most strongly contributed to fatigue. Other lifestyle predictors included higher workload perception, lack of exercise and the non-availability of support. Whilst problem-focused coping behaviours were not associated with fatigue, coping by using alcohol, letting emotions out and avoiding the situation significantly predicted chronic fatigue.

CONCLUSION

The challenge for improving the fatigue outcomes requires further investigation of the profile of a nurse who is at a high risk of fatigue, and then integrating this profile into a fatigue management programme which considers relative contributions of the psychological, lifestyle and coping factors.

Circadian cortisol profiles and psychological self-reports in shift workers with and without recent change in the shift rotation system

Cortisol profiles including the cortisol rise in the first hour after awakening (CAR) were assessed during shift work and days off (eight saliva samples per shift). Participants were 102 healthy permanent day and night shift workers (comparison groups) and former permanent day and night shift workers after implementation of a new fast-forward rota including morning, evening, and night shifts. Results show that the CAR is detectable in day as well as night shifts. In permanent night workers cortisol profiles appear to be blunted during night work and days off. However, circadian cortisol profiles are not disturbed in former night workers who recently switched to the fast rotating shift schedule. In contrast, implementation of night work in former day workers seems to lead to initially blunted cortisol profiles that normalize after a short adjustment period. Results of a psychological assessment including exhaustion, chronic stress, effort-reward imbalance, and ratings of sleep quality and sleep length are also presented.

Modafinil for excessive sleepiness associated with chronic shift work sleep disorder: effects on patient functioning and health-related quality of life

OBJECTIVE

We evaluated the effects of modafinil, a wake-promoting agent, on patient functioning, health-related quality of life, and nighttime and daytime sleep in patients with excessive sleepiness associated with shift work sleep disorder (SWSD).

METHOD

A 12-week, randomized, double-blind, placebo-controlled study was performed at 31 centers in the United States between February 2001 and March 2002. Adults (N = 278) with excessive sleepiness associated with chronic SWSD (International Classification of Sleep Disorders criteria) were randomly assigned to receive modafinil 200 or 300 mg or placebo, 30 to 60 minutes before each night shift. Effects on patient functioning and quality of life were assessed using the Functional Outcomes of Sleep Questionnaire (FOSQ) and the 36-item Short Form Health Survey (SF-36), respectively. Daily patient diaries were used as a sleep log.

RESULTS

Modafinil 300 mg significantly improved mean FOSQ total score relative to placebo (2.3-point increase from baseline vs. 1.6 for placebo; p < .05). Both doses of modafinil significantly improved mean SF-36 mental component scores relative to placebo (mean changes from baseline of 3.2, 3.7, and 0.7 points in the modafinil 300-mg, modafinil 200-mg, and placebo groups, respectively; p < .05 for each comparison vs. placebo). Modafinil did not adversely affect sleep when sleep was desired or caffeine use. Modafinil was well tolerated. Headache (21.5%) and nausea (12.4%) were the most common adverse events in modafinil-treated patients. Differences between modafinil and placebo for vital sign measurements, physical examination findings, or electrocardiography results were not clinically meaningful.

CONCLUSIONS

Modafinil significantly improves functioning and quality of life in patients with SWSD. Modafinil is an effective treatment for excessive sleepiness associated with SWSD.

Cardiac autonomic imbalance in female nurses with shift work

The pathophysiology underlying the shift work-related cardiovascular disease is still poorly understood. The chronic effects of shift work on cardiac autonomic functions were assessed in 47 hospital nurses working under a rotating three-shift system (shift nurses) and 36 public health nurses without shift work (non-shift nurses). The heart rate variability, %LF and %HF (i.e., proportions of sympathetic and vagal activities, respectively), and LF/HF ratio were calculated from the electrocardiographic RR intervals by using autoregressive spectral analysis, and heart rate-corrected QT interval (QTc and QT index) was also measured. The LF/HF ratio, %LF, and QT index were significantly larger in the shift nurses than in the non-shift nurses; also, the power spectral density of HF (PSD(HF)) was significantly decreased in the shift nurses. There was a significant, inverse correlation between the corrected QT interval and PSD(HF) in the non-shift nurses, but not in the shift nurses. It is suggested that shift work in female nurses may cause a sympathodominant state due to depressed vagal tones. Also, a pathophysiology of shift work-related cardiovascular disease, derived from the present and previous findings, may be characterized by the attenuation of the inverse association between the corrected QT interval and vagal activity observed in non-shift workers.

Effects of shift work on autonomic and neuromotor functions in female nurses

Thirty-seven nurses with shift work, working under a rotating three-shift system, and 37 nurses without shift work, having worked during the daytime for one or more years prior to this study, were examined to assess the effects of shift work on cardiac autonomic and neuromotor functions. Their ages ranged from 25 to 58 yr. The electrocardiographic (ECG) R-R interval variability, %LF and %HF (i.e., proportions of sympathetic and parasympathetic activities, respectively), and LF/HF ratio were computed by means of autoregressive spectral and component analyses. The %LF and LF/HF ratio were significantly larger in the nurses with shift work than in those without shift work, although there was no significant difference in the heart rate-corrected QT interval on ECG between them. And, hand-ear coordination differed significantly between the nurses with shift work and those without. Despite the presence of potential selection bias, it is suggested that shift work in nurses may cause not only a long-term sympathodominant state but also some neuromotor impairment.

Reduced sympathetic outflow and adrenal secretory activity during a 40-day stay in the Antarctic

Human adaptation to unknown and extreme environments requires changes in the psychological and physical homeostasis. We previously reported a significant decrease of anterior pituitary and adrenal hormonal levels and a significant modification of psychophysiological correlates of stress, such as galvanic skin response, after exposure to Antarctica, suggesting a possible decrease of individual arousal. The latter was hypothesized to be correlated with a modification of autonomic balance, mainly represented by a possible reduction of adrenergic output. The aim of the present study was to assess the patterns of hormonal circadian rhythms and the autonomic nervous system balance by means of spectral analysis of heart rate variability (HRV). These parameters were evaluated during 3 sessions (baseline, session 1 and session 2), before, at the beginning and after a 40-day stay in Antarctica (Station of Terra Nova Bay; average temperature in the study period: -11 degrees C, 24 h of light, sea level). In each of the sessions, 6 healthy male subjects underwent a 24-h electrocardiogram and blood sampling (08.00, 12.00, 16.00, 20.00, 24.00 and 08.00 h) for hormonal determinations. The data showed a remarkable decrease of hormonal levels without significant changes in circadian rhythms. Spectral analysis of HRV showed an imbalance of the autonomic nervous system with a relative significant decrease of the low frequency band (0.1 Hz) in session 1 and 2 compared to baseline, which can be functionally interpreted as a relative decrement of the sympathetic component. In conclusion, the exposure to a cold and extreme environment seems to affect autonomic balance over a 40-day period. This is followed by a significant reduction of the anterior pituitary and adrenal hormonal secretory patterns with preserved hormonal circadian rhythms (within the same time period of 40 days). This pattern is suggestive of a trophotropic neurovegetative adaptive process.

Psychological and physical stress-induced cardiovascular reactivity and diurnal blood pressure variation in women with different work shifts

There is increasing evidence that diurnal blood pressure (BP) variation, in addition to high BP per se, is related to target organ damage and the incidence of cardiovascular events. However, the determinants of diurnal BP variation are not adequately understood. This paper tests the hypothesis that cardiovascular reactivity to acute stress and/or delayed recovery predicts greater diurnal BP variation (i.e., a lower sleep/awake BP ratio). We studied the relationship of diurnal BP variation (assessed by ambulatory BP monitoring) to mental stress (mental arithmetic and anger recall tasks) and physical stress (treadmill)-induced cardiovascular reactivity and recovery in 87 female nurses who worked different shifts. The sleep/awake systolic BP (SBP) ratio was negatively correlated with relative SBP reactivity (maximum SBP increase/baseline SBP: r = -0.21, p = 0.06) and relative stress response (average of SBP during stress/baseline SBP:r = -0.23, p = 0.04) induced by anger recall, while the correlations of the sleep/awake SBP ratio with other parameters of reactivity or recovery in the anger recall or mental arithmetic task were not significant. When subjects were divided into day-shift workers (n=54) and night-shift workers (n = 33), the sleep/awake SBP ratio was negatively correlated with relative SBP reactivity (r = -0.41, p = 0.02) and relative stress response of SBP (r = -0.48, p = 0.006) induced by anger recall, and positively correlated with recovery rate (r = 0.34, p = 0.06) in the latter group, while these correlations were not significant in the former group. The sleep/awake SBP ratio was inversely correlated with the exercise-induced SBP increase in the day-shift workers (r = -0.30, p = 0.03), while this association was not found in the night-shift workers. In conclusion, cardiovascular reactivity triggered by psychological and physical stress in the laboratory may be a weak, but significant, determinant of diurnal BP variation; in addition, work shift (day or night) appears to moderate the relationship between these two pressor mechanisms.

Brain function and effects of shift work: implications for clinical neuropharmacology

Night or shift work is to a relevant extent unavoidable, suits a growing preference for flexibility and is predicted to spread. However, a significant percentage of shift workers report discomfort or health problems and they often (15-20% of cases) move to different occupations. Apart from social implications, the issue has medical and scientific relevance, with evidence suggesting that the circadian rhythm phases are neither equivalent nor interchangeable with respect to function and performance. Shift work may affect the gastrointestinal and cardiovascular functions, alter the hormonal and sleepiness cycles, favor sleep disturbances of medical relevance, interfere with behavior and social life and increase the risk of accidents (e.g. road accidents). The implications for clinical (neuro)pharmacology are relevant and, in several instances, critical. Shift work can interfere with mechanisms regulating drug kinetics in peripheral compartments and action at selective brain sites, either directly or through effects on the gastrointestinal/hormonal cycles. In this paper, the relevant literature is reviewed and original data on the effects of shift work are reported. Basic and clinical research should take into account the possible effects on drug action of an active life and working schedule in inappropriate phases of the circadian cycles and the risk of inadequate drug dosing or unexpected abnormal action in subjects under long-term or chronic treatment. A scientific approach, action by the scientific community involved in pharmacological research and monitoring by the regulating agencies are advisable. Regulation may help reduce the medical and social impact and improve quality of life.