Ageing, physical fitness and shiftwork tolerance

Shift work is associated with extensively disordered sleep, especially when working nights

Background

Shift work is generally associated with working and sleeping out of phase with the endogenous, circadian sleep-wake cycle. This exerts detrimental effects on sleep health. The present study aimed at evaluating the presence of short and long sleep as well as sleep disorders within a broad range of shift work schedules and elucidating the role of sociodemographic factors therein.

Methods

A large dataset containing information on sleep was collected through advertisement in a Belgium newspaper (De Standaard). Adult, working individuals were selected (n = 37,662) and categorized based on their work schedule (regular day, early morning, evening, night, and rotating shift). In this cross-sectional study, prevalence rates of short sleep (≤6 h), long sleep (≥9 h) and sleep disorders (screened with Holland Sleep Disorders Questionnaire), and associations between these sleep variables and sociodemographics (age, sex, education, living companion(s)) were analyzed using binominal logistic regression analyses.

Results

In the total sample all sociodemographic factors affected prevalences of short, long and disordered sleep, consistent with previous studies. Compared to day workers, shift workers more frequently reported short sleep, most prominently night workers (26 vs. 50%) (p < 0.001). Furthermore, all sleep disorders as well as sleep disorder comorbidity were more common in shift workers, again most pronounced in night workers (all p < 0.05). In night shift workers the level of education had the strongest associations with disturbed sleep with a two-fold higher prevalence of short and disordered sleep in low relative to academic educated groups (all p < 0.02).

Conclusion

Shift work is related not only to curtailed sleep and shift work disorder, but also to a plethora of sleep disorders, including insomnia, sleep-related breathing disorders and sleep-related movement disorders. Our findings imply that education on coping strategies may be especially important for young and/or lower educated shift workers.

Acute and long-term sleep measurements produce opposing results on sleep quality in 8 and 12 hour shift patterns in law enforcement officers

The occupational demands of law enforcement increase the risk of poor-quality sleep, putting officers at risk of adverse physical and mental health. This cross-sectional study aimed to characterise sleep quality in day workers, 8 and 12 h rotating shift pattern workers. One hundred eighty-six officers volunteered for the study (37 female, age: 41 ± 7). Sleep quality was assessed using the Pittsburgh sleep quality index, actigraphy and the Leeds sleep evaluation questionnaire. The maximal aerobic capacity (VO2max ) was measured on a treadmill via breath-by-breath analysis. There was a 70% overall prevalence of poor sleepers based on Pittsburgh sleep quality index scores, where 8 h shifts exhibited the worst prevalence (92%, p = 0.029), however, there was no difference between age, gender, or role. In contrast, 12 h shifts exhibited the poorest short-term measures, including awakening from sleep (p = 0.039) and behaviour following wakefulness (p = 0.033) from subjective measures, and poorer total sleep time (p = 0.024) and sleep efficiency (p = 0.024) from the actigraphy. High VO2max predicted poorer wake after sleep onset (Rsq = 0.07, p = 0.05) and poorer sleep latency (p = 0.028). There was no relationship between the Pittsburgh sleep quality index scores and any of the short-term measures. The prevalence of poor sleepers in this cohort was substantially higher than in the general population, regardless of shift pattern. The results obtained from the long- and short-term measures of sleep quality yielded opposing results, where long-term perceptions favoured the 12 h pattern, but short-term subjective and objective measures both favoured the 8 h pattern.

A survey of train driver schedules, sleep, wellbeing, and driving performance in Australia and New Zealand

Train drivers work long hours on 24 h schedules and many factors impact their fatigue risk at work, creating a clear imperative for good rostering practice. Adopting a systems approach, this study investigated the relationship between multiple interrelated factors (train drivers’ schedule, sleep, wellbeing, and fatigue) and the perceived influence of these factors on train driving performance and safety using an online survey distributed in Australia and New Zealand. In addition to demographics and work schedule, passenger and freight train drivers (n = 751) answered questions about: (1) Sleep duration; (2) wellbeing, including physical and mental health, the extent to which shiftwork causes sleep, social, domestic, and work problems, and (3) the extent to which ten fatigue, health and wellbeing factors in the work and home environment negatively impact their driving performance. The key factor that emerged from analyses, with the largest and most consistent negative effects (and controlling for other factors) was schedule irregularity. Approved rosters were ranked as having the most important impact on day-to-day driving performance, followed by physical and mental health, and outside work factors. Results also suggested that schedule irregularity may amplify the negative impacts of the roster, impaired physical and mental health, and outside work factors on driving performance. As shift variability and schedule irregularity are often poorly represented in existing industry guidance, these results provide evidence for increased reflection on current fatigue management guidelines for train drivers and suggest a need for greater focus on schedule irregularity through the lens of a systems approach.

Effect of a Recliner Chair with Rocking Motions on Sleep Efficiency

In this study, we analyze the effect of a recliner chair with rocking motions on sleep quality of naps using automated sleep scoring and spindle detection models. The quality of sleep corresponding to the two rocking motions was measured quantitatively and qualitatively. For the quantitative evaluation, we conducted a sleep parameter analysis based on the results of the estimated sleep stages obtained on the brainwave and spindle estimation, and a sleep survey assessment from the participants was analyzed for the qualitative evaluation. The analysis showed that sleep in the recliner chair with rocking motions positively increased the duration of the spindles and deep sleep stage, resulting in improved sleep quality.

Guiding principles for determining work shift duration and addressing the effects of work shift duration on performance, safety, and health: guidance from the American Academy of Sleep Medicine and the Sleep Research Society

CITATION

Risks associated with fatigue that accumulates during work shifts have historically been managed through working time arrangements that specify fixed maximum durations of work shifts and minimum durations of time off. By themselves, such arrangements are not sufficient to curb risks to performance, safety, and health caused by misalignment between work schedules and the biological regulation of waking alertness and sleep. Science-based approaches for determining shift duration and mitigating associated risks, while addressing operational needs, require: (1) a recognition of the factors contributing to fatigue and fatigue-related risks; (2) an understanding of evidence-based countermeasures that may reduce fatigue and/or fatigue-related risks; and (3) an informed approach to selecting workplace-specific strategies for managing work hours. We propose a series of guiding principles to assist stakeholders with designing a shift duration decision-making process that effectively balances the need to meet operational demands with the need to manage fatigue-related risks.

Shift rotation scheme, sleepiness and sleep quality in night-shift workers

BACKGROUND

Shift rotation schemes can influence workers' tolerance of night-shift work and its impact on health.

AIMS

This study was aimed to assess the influence of shift work rotation schemes on sleepiness and sleep quality.

METHODS

We conducted a cross-sectional study of 145 male workers, 77 from a ceramic tile factory on a fixed, forward-rotating shift work scheme, and 68 from a dockyard company, working on-call night shifts. Participants self-administered the Epworth Sleepiness Scale (ESS) and the Pittsburgh Sleep Quality Index (PSQI) questionnaires and provided data on demographic and lifestyle variables. We set two logistic regression models to predict the risk of daytime sleepiness and poor sleep quality as a function of night-shift work and on-call night shifts, adjusting for personal and lifestyle covariates.

RESULTS

Marital status, body mass index, smoking and alcohol intake did not affect ESS and PSQI scores, nor did they differ between the two cohorts. Night-shift workers from both cohorts were more likely to have a PSQI score ≥6, suggestive of poor sleep quality, with no variation between the two cohorts. ESS scores suggestive of daytime sleepiness were strongly associated with on-call night shifts among dockyard workers for (odds ratio = 13.4; 95% confidence interval 2.9-63.9), in respect the regular, forward-rotating night-shift work among ceramic tile factory workers.

DISCUSSION

Daytime sleepiness occurred more frequently among dockyard workers working on-call night shifts. Poor sleep quality occurred more frequently among night-shift workers, but it did not differ between the two companies.

Observing changes in human functioning during induced sleep deficiency and recovery periods

Prolonged periods of sleep restriction seem to be common in the contemporary world. Sleep loss causes perturbations of circadian rhythmicity and degradation of waking alertness as reflected in attention, cognitive efficiency and memory. Understanding whether and how the human brain recovers from chronic sleep loss is important not only from a scientific but also from a public health perspective. In this work we report on behavioral, motor, and neurophysiological correlates of sleep loss in healthy adults in an unprecedented study conducted in natural conditions and comprising 21 consecutive days divided into periods of 4 days of regular life (a baseline), 10 days of chronic partial sleep restriction (30% reduction relative to individual sleep need) and 7 days of recovery. Throughout the whole experiment we continuously measured the spontaneous locomotor activity by means of actigraphy with 1-minute resolution. On a daily basis the subjects were undergoing EEG measurements (64-electrodes with 500 Hz sampling frequency): resting state with eyes open and closed (8 minutes long each) followed by Stroop task lasting 22 minutes. Altogether we analyzed actigraphy (distributions of rest and activity durations), behavioral measures (reaction times and accuracy from Stroop task) and EEG (amplitudes, latencies and scalp maps of event-related potentials from Stroop task and power spectra from resting states). We observed unanimous deterioration in all the measures during sleep restriction. Further results indicate that a week of recovery subsequent to prolonged periods of sleep restriction is insufficient to recover fully. Only one measure (mean reaction time in Stroop task) reverted to baseline values, while the others did not.

Guiding principles for determining work shift duration and addressing the effects of work shift duration on performance, safety, and health: guidance from the American Academy of Sleep Medicine and the Sleep Research Society

Risks associated with fatigue that accumulates during work shifts have historically been managed through working time arrangements that specify fixed maximum durations of work shifts and minimum durations of time off. By themselves, such arrangements are not sufficient to curb risks to performance, safety, and health caused by misalignment between work schedules and the biological regulation of waking alertness and sleep. Science-based approaches for determining shift duration and mitigating associated risks, while addressing operational needs, require: (1) a recognition of the factors contributing to fatigue and fatigue-related risks; (2) an understanding of evidence-based countermeasures that may reduce fatigue and/or fatigue-related risks; and (3) an informed approach to selecting workplace-specific strategies for managing work hours. We propose a series of guiding principles to assist stakeholders with designing a shift duration decision-making process that effectively balances the need to meet operational demands with the need to manage fatigue-related risks.

Influence of rotating shifts and fixed night shifts on sleep quality of nurses of different ages: a systematic literature review and meta-analysis

The objective of this study was to understand the influence of rotating shifts and fixed night shifts on the sleep quality of nurses using a systematic literature review and meta-analysis and to determine whether the sleep quality of nurses working rotating shifts or fixed night shifts differs from that of nurses working fixed day shifts. We conducted a meta-analysis on literature that had used the Pittsburgh Sleep Quality Index (PSQI) to gauge sleep quality and had been published between 2000 and 2020 in the Cochrane Library, CINAHL, MEDLINE, and PubMed databases. This study was conducted in accordance with PRISMA, and the quality of the literature was assessed using the Joanna Briggs Institute Critical Appraisal Checklist for Analytical Cross Sectional Studies. CMA 3.0 was employed for data analysis, and meta-regression analysis was conducted to examine the differences between the PSQI scores of nurses working fixed day shifts and those working rotating shifts or fixed night shifts. Following assessment, a total of 29 papers (34 items of data) were analyzed. The papers included a total of 3,935 nurses who worked fixed day shifts, 3,777 nurses who worked rotating shifts, and 1,559 nurses who worked fixed night shifts. Our subgroup analysis indicated that the sleep quality of nurses working rotating shifts was poorer than the sleep quality of nurses working fixed day shifts; the standardized mean difference (SMD) was 0.38 (95% CI: 0.24-0.52, p< .001), and the meta-regression analysis found that the difference in sleep quality between nurses over 40 years old working rotating shifts and those working fixed day shifts was significantly smaller than the difference in sleep quality between nurses 40 years old or younger working rotating shifts and those working fixed day shifts (β = -0.368, p= .011). The sleep quality of nurses working fixed night shifts was also poorer than the sleep quality of nurses working fixed day shifts; the SMD was 0.58 (95% CI: 0.38-0.78, p< .001), and the meta-regression analysis revealed that the difference in sleep quality between nurses over 40 years old working fixed night shifts and those working fixed day shifts was not significantly different from the difference in sleep quality between nurses 40 years old or younger working fixed night shifts and those working fixed day shifts (β = -0.118, p= .608). This meta-analysis found that both nurses working rotating shifts and those working fixed night shifts had poorer sleep quality than those working fixed day shifts and that age influenced the difference in sleep quality only between nurses working rotating shifts and those working fixed day shifts; the difference in sleep quality between nurses 40 years old or younger working rotating shifts and those working fixed day shifts was greater than the difference in sleep quality between nurses over 40 years old working rotating shifts and those working fixed day shifts.

Changes in work schedule affect the prevalence of shift work disorder among Norwegian nurses - a two year follow-up study

This study aimed to explore how changes in the work schedule would affect the prevalence of Shift Work Disorder (SWD) over time. Two-year follow-up data from 1076 nurses participating in the longitudinal SUrvey of Shift work, Sleep and Health among Norwegian nurses (SUSSH) were included in the study. The questionnaires included measures of work-related factors, i.e., work schedule and numbers of night shifts and quick returns (QRs) worked the last year, as well as questions related to SWD according to the ICSD-3 diagnostic criteria at both baseline and at 2-year follow-up. Data were analyzed with paired samples t-tests, chi-square tests, and logistic regression analyses adjusting for sex and age. Terminating night work was the strongest predictor for recovering from SWD from baseline to follow-up (OR 10.91, 95% CI 6.11-19.46). Additionally, changing the work schedule from day work to night work from baseline to follow-up was the strongest predictor for developing SWD in the same period (OR 4.75, 95% CI 2.39-9.47). Reductions in number of nights (more than 10) and QRs (more than 10) worked the last year were associated with recovering from SWD between baseline and follow-up. Nurses who recovered from SWD had significantly reduced the mean number of night shifts worked the last year from 32.3 at baseline to 20.4 at follow-up (p = .001). Furthermore, an increase of more than 10 nights or more than 10 QRs worked the last year between baseline and follow-up predicted developing SWD. Nurses developing SWD between baseline and follow-up had significantly increased the mean number of nights worked the last year from 25.8 at baseline to 31.0 at follow-up (p =-.043). Changes in night work exposure were the strongest predictors for both recovering from or developing SWD from baseline to follow-up. Reducing exposure to night work and QRs were associated with recovering from SWD and increasing exposure to night work and QRs were associated with developing SWD. The results imply that unfavorable work schedules play a role in the development of sleep problems among nurses. These results may be useful when designing healthy working schedules.

Circulating Exosomal miRNAs Signal Circadian Misalignment to Peripheral Metabolic Tissues

Night shift work increases risk of metabolic disorders, particularly obesity and insulin resistance. While the underlying mechanisms are unknown, evidence points to misalignment of peripheral oscillators causing metabolic disturbances. A pathway conveying such misalignment may involve exosome-based intercellular communication. Fourteen volunteers were assigned to a simulated day shift (DS) or night shift (NS) condition. After 3 days on the simulated shift schedule, blood samples were collected during a 24-h constant routine protocol. Exosomes were isolated from the plasma samples from each of the blood draws. Exosomes were added to naïve differentiated adipocytes, and insulin-induced pAkt/Akt expression changes were assessed. ChIP-Seq analyses for BMAL1 protein, mRNA microarrays and exosomal miRNA arrays combined with bioinformatics and functional effects of agomirs and antagomirs targeting miRNAs in NS and DS exosomal cargo were examined. Human adipocytes treated with exosomes from the NS condition showed altered Akt phosphorylation responses to insulin in comparison to those treated with exosomes from the DS condition. BMAL1 ChIP-Seq of exosome-treated adipocytes showed 42,037 binding sites in the DS condition and 5538 sites in the NS condition, with a large proportion of BMAL1 targets including genes encoding for metabolic regulators. A significant and restricted miRNA exosomal signature emerged after exposure to the NS condition. Among the exosomal miRNAs regulated differentially after 3 days of simulated NS versus DS, proof-of-concept validation of circadian misalignment signaling was demonstrated with hsa-mir-3614-5p. Exosomes from the NS condition markedly altered expression of key genes related to circadian rhythm in several cultured cell types, including adipocytes, myocytes, and hepatocytes, along with significant changes in 29 genes and downstream gene network interactions. Our results indicate that a simulated NS schedule leads to changes in exosomal cargo in the circulation. These changes promote reduction of insulin sensitivity of adipocytes in vitro and alter the expression of core clock genes in peripheral tissues. Circulating exosomal miRNAs may play an important role in metabolic dysfunction in NS workers by serving as messengers of circadian misalignment to peripheral tissues.

Work and sport: relationships between specific job stressors and sports participation

This study examines the relationships between different job stressors and sports participation. Based on a large-scale representative sample (N = 1935), the paper tested if the number of different job stressors encountered in a job is related to sports participation. Moreover, we examined the relative impact of different stressors on sport participation. As predicted, the number of stressors encountered at work is negatively associated with leisure-time sports participation. When testing the relative effects of different job stressors, intense physical labour, shift and night work, and job insecurity (i.e. having a fixed-term contract or fearing unemployment) are negatively related to sports participation, whereas hazardous exposure (i.e. noise), bad working atmosphere, and long working hours are not related to sports participation. Hence, the total number of job stressors, but also the specificity of job stressors, should be taken into account by professionals in the fields of health research and physical activity promotion. Practioner summary: In a large-scale representative sample, we examined if different adverse job conditions are negatively related to sports participation. We found that the number of different job stressors was negatively related to sports participation. In particular, intense physical labour, shift and night work as well as job insecurity had an impact.

The Influence of 24-hr Sleep Deprivation on Psychomotor Vigilance in Young Women and Men

BACKGROUND

The number of studies on gender differences in psychomotor performance and sleepiness is small and the results are contradictory. The aim of this study was to assess the changes in psychomotor performance, due to 24 h of sleep deprivation in young women and men.

PARTICIPANTS

Eighty-nine students (49 women and 40 men) took part in the study. Participants were randomized into two groups: experimental (sleep deprived) and control (non-sleep deprived).

METHODS

The research was carried out using computer-based tests of the Vienna Test System (COG, DT, WAFF) and pupillography (F²D Fit-For-Duty).

RESULTS

There were no statistically significant effects of the main genders and groups on sleepiness measured by the pupillography. There was no deterioration in the results after deprivation among women and men in the COG test. Changes were noted in the DT and WAFF tests, and their size depended on the test. The number of false responses in psychomotor test was higher in women after sleep deprivation.

CONCLUSION

One night of sleep deprivation may not have been a negative enough stimulus for young, healthy women and men to reveal gender differences in psychomotor tests. Low sleep levels can lead to low productivity at work and accidents due to reduced vigilance. Insufficient sleep in the long term can lead to poor health, resulting in hypertension, obesity and depression.

Lifestyle and Shiftwork: Designing and Testing a Model for Health Promotion of Iranian Nurses

BACKGROUND: Lifestyle is one factor that forms the nurses' health, particularly those who work in shiftwork schedules. AIMS: The aim of this study was to design and test a model for health promotion of Iranian nurses. In this model, nurses' lifestyle was considered as the precedent, physical and mental health as the outcomes, and sleep disturbance and chronic fatigue as the mediators. METHODS: A cross-sectional study using structural equation modeling was conducted among 240 shiftworker nurses in Iran. The data collection was performed using the Persian versions of the Survey of Shiftworkers Questionnaire and Life Style Questionnaire. Bootstrap in Preacher and Hayes' Macro program was used for testing mediation. RESULTS: Lifestyle had a weak significant direct effect on physical (β = 0.13, p < .04) and mental health (β = 0.12, p < .02), and it had a significant indirect effect on physical health via chronic fatigue (β = -0.11, p < .001) and sleep disturbance (β = -0.05, p < .01). This variable only had a significant indirect effect on mental health via chronic fatigue (β = -0.19, p < .001). The final model proposed a new significant path between sleep disturbances and chronic fatigue (β = 0.22, p < .001). CONCLUSIONS: Therefore, the hospital officials can enhance the nurses' physical and mental well-being by providing interventions and training courses on aspects of healthy lifestyles, such as physical activity, avoidance of smoking, and maintenance of body weight.

[Multimodular Cognitive Training for Nursing Staff Aged 50+: Initial Results of a Pilot Study on Feasibility and Efficacy]

THE AIM OF THE STUDY

was the assessment of the feasibility of a cognitive training program for employees of care 50+.

METHOD

A cognitive training program (13 h, 5 sessions) was conducted with 15 nurses of the University Hospital Munich (KUM). Acceptance of and effects on cognitive and psychological performance were determined.

RESULTS

The measure was well accepted and received positive ratings. In addition, there were significant improvements in cognitive performance and self-efficacy.

CONCLUSION

The training program can be implemented on a regular basis; initial results providing evidence in support of positive training effects must be confirmed in future randomized controlled trials.

Individual vulnerability to insomnia, excessive sleepiness and shift work disorder amongst healthcare shift workers. A systematic review

Shift workers often experience reduced sleep quality, duration and/or excessive sleepiness due to the imposed conflict between work and their circadian system. About 20-30% of shift workers experience prominent insomnia symptoms and excessive daytime sleepiness consistent with the circadian rhythm sleep disorder known as shift work disorder. Individual factors may influence this vulnerability to shift work disorder or sleep-related impairment associated with shift work. This paper was registered with Prospero and was conducted using recommended standards for systematic reviews and meta-analyses. Published literature that measured sleep-related impairment associated with shift work including reduced sleep quality and duration and increased daytime sleepiness amongst healthcare shift workers and explored characteristics associated with individual variability were reviewed. Fifty-eight studies were included. Older age, morning-type, circadian flexibility, being married or having children, increased caffeine intake, higher scores on neuroticism and lower on hardiness were related to a higher risk of sleep-related impairment in response to shift work, whereas physical activity was a protective factor. The review highlights the diverse range of measurement tools used to evaluate the impact of shift work on sleep. Use of standardised and validated tools would enable cross-study comparisons. Longitudinal studies are required to establish causal relationships between individual factors and the development of shift work disorder.

Expert system application for prioritizing preventive actions for shift work: shift expert

INTRODUCTION

Shift patterns, work hours, work arrangements and worker motivations have increasingly become key factors for job performance. The main objective of this article is to design an expert system that identifies the negative effects of shift work and prioritizes mitigation efforts according to their importance in preventing these negative effects. The proposed expert system will be referred to as the shift expert.

METHODS

A thorough literature review is conducted to determine the effects of shift work on workers. Our work indicates that shift work is linked to demographic variables, sleepiness and fatigue, health and well-being, and social and domestic conditions. These parameters constitute the sections of a questionnaire designed to focus on 26 important issues related to shift work. The shift expert is then constructed to provide prevention advice at the individual and organizational levels, and it prioritizes this advice using a fuzzy analytic hierarchy process model, which considers comparison matrices provided by users during the prioritization process. An empirical study of 61 workers working on three rotating shifts is performed. After administering the questionnaires, the collected data are analyzed statistically, and then the shift expert produces individual and organizational recommendations for these workers.

Cumulative exposure to shift work and sickness absence: associations in a five-year historic cohort

BACKGROUND

Exposure to shift work has been associated with negative health consequences, although the association between shift work and sickness absence remains unclear. The aim of this study is to investigate associations between cumulative exposure to shift work and sickness absence among ground staff employees of an airline company.

METHODS

This study used data from the MORE (Monitoring Occupational Health Risks in Employees) cohort, which is a 5-year historic cohort. The population of the present study consisted of 7562 ground staff employees. For each employee, work schedules and sickness absence days between 2005 and 2009 were obtained from company records. For the exposure to different shift schedule types and to the cumulative number of night shifts, the association with long-term sickness absence (>7 consecutive sickness absence days) and the number of sickness absence episodes during 2009, was calculated using logistic and Poisson regression analyses. Socio-demographic variables, work-related variables, job classification variables, and previous sickness absence days were regarded as confounders.

RESULTS

After adjusting for previous sickness absence and job classification variables, only the group of employees that switched into working in a three-shift schedule, showed a significantly increased risk for long-term sickness absence (OR = 1.31, 95%CI 1.02-1.69). Night shift exposure was not significantly associated with long-term sickness absence. Exposure to shift work was negatively associated with more sickness absence episodes. Employees who were exposed to more than 46 night shifts also showed a lower risk for more sickness absence episodes. Subgroup analyses showed that single employees and employees without children had an increased risk for long-term sickness absence when exposed to a three-shift schedule, and when they had changed between shift schedule types.

CONCLUSIONS

Cumulative exposure to shift work proved to be negatively associated with more sickness absence episodes, and was not associated with more long-term sickness absence, although selection bias could not be ruled out. Future research should explore the influence of household composition, and take into account both previous sickness absence and psychosocial and physical work factors to obtain a better estimation of the association between shift work and sickness absence.

Health-Related Quality of Life and Associated Factors of Frontline Railway Workers: A Cross-Sectional Survey in the Ankang Area, Shaanxi Province, China

After validation of the widely used health-related quality of life (HRQOL) generic measure, the Short Form 36 version 2 (SF-36v2), we investigated the HRQOL and associated factors of frontline railway workers in China. Ground workers, conductors, and train drivers were selected from Ankang Precinct by using a stratified cluster sampling technique. A total of 784 frontline railway workers participated in the survey. The reliability and validity of SF-36v2 was satisfactory. The physical component summary (PCS) scores of three subgroups attained the average range for the USA general population, whereas the mental component summary (MCS) scores were well below the range. Most domains scored below the norm, except for the physical functioning (PF) domain. Among three subgroups, train drivers reported significantly lower scores on MCS and six health domains (excluding PF and bodily pain (BP)). After controlled confounders, conductors had significantly higher PCS and MCS scores than ground workers. There is heterogeneity on risk factors among three subgroups, but having long or irregular working schedules was negatively associated with HRQOL in all subgroups. SF-36v2 is a reliable and valid HRQOL measurement in railway workers in China. The frontline railway workers’ physical health was comparative to American norms, whilst mental health was relatively worse. Long or irregular working schedules were the most important factors.

The relationship between quality of sleep and night shift rotation interval

BACKGROUND

Shift work is closely related with workers' health. In particular, sleep is thought to be affected by shift work. In addition, shift work has been reported to be associated with the type or direction of shift rotation, number of consecutive night shifts, and number of off-duty days. We aimed to analyze the association between the night shift rotation interval and the quality of sleep reported by Korean female shift workers.

METHODS

In total, 2,818 female shift workers from the manufacturing industry who received an employee physical examination at a single university hospital from January to August in 2014 were included. Subjects were classified into three groups (A, B, and C) by their night shift rotation interval. The quality of sleep was measured using the Korean version of the Pittsburgh Sleep Quality Index (PSQI). Descriptive analysis, univariate logistic regression, and multivariate logistic regression were performed.

RESULTS

With group A as the reference, the odds ratio (OR) for having a seriously low quality of sleep was 1.456 (95% CI 1.171-1.811) and 2.348 (95% CI 1.852-2.977) for groups B and C, respectively. Thus, group C with the shortest night shift rotation interval was most likely to have a low quality of sleep. After adjustment for age, obesity, smoking status, alcohol consumption, exercise, being allowed to sleep during night shifts, work experience, and shift work experience, groups B and C had ORs of 1.419 (95% CI 1.134-1.777) and 2.238 (95% CI 1.737-2.882), respectively, compared to group A.

CONCLUSION

Our data suggest that a shorter night shift rotation interval does not provide enough recovery time to adjust the circadian rhythm, resulting in a low quality of sleep. Because shift work is influenced by many different factors, future studies should aim to determine the most optimal shift work model and collect accurate, prospective data.

Sleep deprivation due to shift work

Sleep deprivation due to shift work is related to perturbation of the sleep/wake cycle, associated with the modified activity/rest pattern. This may cause a significant disruption of circadian rhythms of biologic functions, driven by the body clock located in the suprachiasmatic nuclei of the hypothalamus. Shift and night workers have to change sleep times and strategies according to their duty periods; consequently, both sleep length and quality can be considerably affected depending on the variable start and finish times on different shifts. About 10% of night and rotating shift workers, aged between 18 and 65 years, have been estimated to have a diagnosable "shift-work sleep disorder," according to the International Classification of Sleep Disorders, version 2 (ICSD-2). In the long run, this may lead to persistent and severe disturbances of sleep, chronic fatigue and psychoneurotic syndromes, besides being a risk or aggravating factor for accidents, gastrointestinal, cardiovascular, and reproductive disorders, as well as, probably, for cancer. Preventive and corrective actions deal with the organization of shift schedules according to ergonomic criteria, careful health surveillance, appropriate education and training on effective countermeasures, in particular, sleep hygiene and napping.

Predictors of shift work disorder among nurses: a longitudinal study

BACKGROUND

Shift work is associated with sleep problems and impaired health. The main aim of the present study was to explore predictors of developing shift work disorder (SWD) among Norwegian nurses using a longitudinal design.

METHODS

A total of 1533 nurses participating in a survey on shift work, sleep and health responded to questionnaires at baseline and at follow-up about two years later. SWD was defined as problems of excessive sleepiness and/or complaints of insomnia related to the work schedule.

RESULTS AND CONCLUSIONS

There was a significant reduction (p < 0.001) in the prevalence of SWD from baseline to follow-up, from 35.7% to 28.6%. Logistic regression analyses showed significant risks of having SWD at follow-up and the following variables measured at baseline: number of nights worked the last year (OR = 1.01, 95% CI = 1.01-1.02), having SWD (OR = 5.19, 95% CI = 3.74-7.20), composite score on the Epworth Sleepiness Scale (OR = 1.08, 95% CI = 1.04-1.13), use of melatonin (OR = 4.20, 95% CI = 1.33-13.33), use of bright light therapy (OR = 3.10, 95% CI 1.14-8.39), and symptoms of depression measured by the Hospital Anxiety and Depression Scale (OR = 1.07, 95% CI = 1.00-1.14). In addition, leaving night work between baseline and follow-up was associated with a significantly reduced risk of SWD at follow-up (OR = 0.12, 95% CI = 0.07-0.22).

Prevalence of anxiety and depressive symptoms and related risk factors among physicians in China: a cross-sectional study

BACKGROUND

Physicians' poor mental health not only hinders their professional performance and affects the quality of healthcare provided but also adversely affects patients' health outcomes. Few studies in China have evaluated the mental health of physicians. The purposes of this study are to quantify Chinese physicians' anxiety and depressive symptoms as well as evaluate associated risk factors.

METHODS

In our study, 2641 physicians working in public hospitals in Shenzhen in southern China were recruited and interviewed by using a structured questionnaire along with validated scales testing anxiety and depressive symptoms. Multivariable logistic regression models were used to identify risk factors for anxiety and depressive symptoms.

RESULTS

An estimated 25.67% of physicians had anxiety symptoms, 28.13% had depressive symptoms, and 19.01% had both anxiety and depressive symptoms. More than 10% of the participants often experienced workplace violence and 63.17% sometimes encountered it. Among our study population, anxiety and depressive symptoms were associated with poor self-reported physical health, frequent workplace violence, lengthy working hours (more than 60 hours a week), frequent night shifts (twice or more per week), and lack of regular physical exercise.

CONCLUSIONS

Our study demonstrates that anxiety and depressive symptoms are common among physicians in China, and the doctor-patient relationship issue is particularly stressful. Interventions implemented to minimize workload, improve doctor-patient relationships, and assist physicians in developing healthier lifestyles are essential to combat anxiety and depressive symptoms among physicians, which may improve their professional performance.

Strain and health implications of nurses' shift work

OBJECTIVES

The study investigated whether nurses' different working schedules are associated with different levels of job-related strain, health symptoms and behavior. No reports have been accessible in the relevant literature on the possible association between shift work and job-related strain in nurses.

MATERIALS AND METHODS

This was a cross-sectional study conducted at a large university hospital in North-East Italy, involving 806 nurses working in selected departments. A multilevel logistic regression was applied to assess the association between work shift conditions and selected outcomes.

RESULTS

Night shifts were associated not only with higher odds of having a high Job Demand, but also with lower odds of having a high Decision Authority and consequently with a stronger likelihood of having higher levels of Job Strain (high Job Demand score ≥ 38 and Low Decision Authority). The night shift was associated with various symptoms, particularly exhaustion (p = 0.039) and gastric pain (p = 0.020). Nurses' working schedules did not affect their job satisfaction scores.

CONCLUSIONS

It has been confirmed that night shifts are a risk factor for nurses' health perception and working night shifts carries a considerable degree of strain. This is a condition that hospital nursing managements need to consider carefully to avoid burnout in nursing personnel and prevent an excessive turnover in this profession, which is a recurring problem for health care organizations.

Caring for the country: fatigue, sleep and mental health in Australian rural paramedic shiftworkers

This study investigated sleep quality, fatigue, mental health and physical activity in rural paramedic shiftworkers. Although limited, previous studies have associated high fatigue levels and poorer health in this sector with shiftwork rostering and occupational demands. A modified version of the Standard Shiftwork Index was completed by 150 paramedics (117 male and 31 females) from rural Victoria. Single sample t tests found significantly higher levels of fatigue, depression, anxiety, and stress, and significantly poorer sleep quality than reference samples. Paramedics also reported less physical activity than community samples. By regression analysis, sleep quality explained the greatest amount of variance in fatigue scores, followed by depression and age. No gender differences in levels of depression or fatigue were found. Consistent with an earlier study of metropolitan paramedics based on the same methodology, findings suggest rural ambulance paramedic shiftworkers are at particular risk for increased levels of fatigue and depression (regardless of age or gender) and poor quality sleep. Organisational intervention was suggested.

Shiftwork and emergency medical practice

Shiftwork has numerous negative effects on workers, but it is an essential component of the demanding 24/7 practice of emergency medicine. We conducted a systematic literature review to characterize the effects of shiftwork on physician health, well-being and practice, and to describe rational strategies to mitigate its impact on Canadian emergency physicians.

Beyond working time: factors affecting sleep behaviour in rail safety workers

There are many factors that may affect the sleep behaviour and subsequent fatigue risk of shift workers. In the Australian rail industry the emphasis is primarily on the impact of working time on sleep. The extent to which factors other than working time might affect the sleep behaviour of employees in the large and diverse Australian rail industry is largely unknown. The present study used sleep, work and fatigue diaries completed for two weeks, in conjunction with actigraphy, to understand the contribution of demographic and health factors to sleep behaviour in 40 rail safety workers. Both shift type and having dependents were significant predictors of sleep duration (P<.05). Sleep duration was greatest prior to night shifts, followed by afternoon shifts and morning shifts. Participants with dependents got significantly less sleep than participants without dependents. Both timing of sleep and smoking were significant predictors of sleep quality (P<.05). Day sleeps were associated with lower subjective sleep quality than night sleeps and smokers reported poorer sleep quality than non-smokers. These findings indicate that factors other than working time have the potential to influence both the sleep duration and subjective sleep quality of rail safety workers.

Main effects of sleep disorders related to shift work-opportunities for preventive programs

The sleep-related problems of shift workers usually occur as transient phenomena related to the timing of work. Sleep disorders, related to sleep deprivation, have a major impact on the quality of life and health status of healthcare workers. Reduced quantity and quality of sleep negatively affects the activities of shift workers, particularly in terms of their social functioning, quality of life and health. However, it seems that health authorities and the medical staff are negligent when it comes to the negative effects on health caused by work in night shifts. Recently published studies in this field suggest that appropriate public health preventive programs dealing with sleep disorders successfully contribute towards the quality of life of workers.

Demographic factors, fatigue, and driving accidents: An examination of the published literature

This article reviews the literature pertaining to the association between demographic variables (e.g., age, sex, race, socio-economic status) with fatigue, and when feasible, accident risk. It also explores their potential influence and interaction with some working arrangements, commute time, personality characteristics, and circadian chronotype. Fatigue has been implicated in a range of impairments that can have detrimental effects on individuals, and it is differentially associated with conventional demographic variables. However, several major methodological limitations prevent clear conclusions. First, there is absence of a shared definition both within and across disciplines. Second, although fatigue has been investigated using a variety of diverse designs, they have either been too weak to substantiate causality or lacked ecological validity. Third, while both subjective and objective measures have been used as dependent variables, fatigue has been more often found to be more strongly linked with the former. Fourth, with the exception of age and sex, the influence of other demographic variables is unknown, since they have not yet been concomitantly assessed. In instances when they have been assessed and included in statistical analyses, they are considered as covariates or confounders; thus, their contribution to the outcome variable is controlled for, rather than being a planned aspect of investigation. Because the interaction of demographic factors with fatigue is largely a neglected area of study, we recommend greater interdisciplinary collaborations, incorporation of multiple demographic variables as independent factors, and use of within-participant analyses. These recommendations would provide meaningful results that may be used to inform public policy and preventive strategies.

Shift work and health: current problems and preventive actions

The paper gives an overview of the problems to be tackled nowadays by occupational health with regards to shift work as well as the main guidelines at organizational and medical levels on how to protect workers' health and well-being. Working time organization is becoming a key factor on account of new technologies, market globalization, economic competition, and extension of social services to general populations, all of which involve more and more people in continuous assistance and control of work processes over the 24 hours in a day. The large increase of epidemiological and clinical studies on this issue document the severity of this risk factor on human health and well being, at both social and psychophysical levels, starting from a disruption of biological circadian rhythms and sleep/wake cycle and ending in several psychosomatic troubles and disorders, likely also including cancer, and extending to impairment of performance efficiency as well as family and social life. Appropriate interventions on the organization of shift schedules according to ergonomic criteria and careful health surveillance and social support for shift workers are important preventive and corrective measures that allow people to keep working without significant health impairment.

Aromatherapy alleviates endothelial dysfunction of medical staff after night-shift work: preliminary observations

Night-shift work causes mental stress and lifestyle changes, and is recognized as a risk of cardiovascular diseases associated with impaired endothelial function. Aromatherapy is becoming popular as a complementary therapy that is beneficial for mental relaxation. The purpose of this study was to investigate the effect of aromatherapy on the endothelial function of medical staff after night-shift work. This study consisted of 19 healthy medical personnel (19 men, mean age 32 ± 7 years), including 11 physicians and 8 technicians. Aromatherapy was performed for 30 min by inhalation of the essential oil of lavender. Flow-mediated dilation (FMD) of the brachial artery was measured three times in each subject: on a regular workday, and after night-shift work before and immediately after aromatherapy. A control study was performed to assess the effect of a 30-min rest without aromatherapy. The mean value of sleep time during night-shift work was 3.3 ± 1.3 h. FMD after night-shift work was lower than on a regular workday (10.4 ± 1.8 vs. 12.5 ± 1.7%, P<0.001), which improved after aromatherapy (11.8 ± 2.5%, P=0.02 vs. before aromatherapy). FMD was stable in the control study (10.1 ± 1.9 vs. 10.1 ± 2.2%, P=0.9). This study demonstrated that night-shift work impaired endothelial function in medical staff, an effect that was alleviated by short-term aromatherapy.

Right prefrontal activity reflects the ability to overcome sleepiness during working memory tasks: a functional near-infrared spectroscopy study

It has been speculated that humans have an inherent ability to overcome sleepiness that counteracts homeostatic sleep pressure. However, it remains unclear which cortical substrate activities are involved in the ability to overcome sleepiness during the execution of cognitive tasks. Here we sought to confirm that this ability to overcome sleepiness in task execution improves performance on cognitive tasks, showing activation of neural substrates in the frontal cortex, by using a modified n-back (2- and 0-back) working memory task and functional near-infrared spectroscopy. The change in alertness was just correlated with performances on the 2-back task. Activity in the right prefrontal cortex changed depending on alertness changes on the 2- and 0-back tasks independently, which indicates that activity in this region clearly reflects the ability to overcome sleepiness; it may contribute to the function of providing sufficient activity to meet the task load demands. This study reveals characteristics of the ability to overcome sleepiness during the n-back working memory task which goes beyond the attention-control function traditionally proposed.

Relationships between leisure-time energy expenditure and individual coping strategies for shift-work

A total of 13 to 14% of European and North American workers are involved in shift work. The present aim is to explore the relationships between coping strategies adopted by shift workers and their leisure-time energy expenditure. Twenty-four female and 71 male shift workers (mean +/- SD age: 37 +/- 9 years) completed an adapted version of the Standard Shift-work Index (SSI), together with a leisure-time physical activity questionnaire. Predictors of age, time spent in shift work, gender, marital status and the various shift-work coping indices were explored with step-wise multiple regression. Leisure-time energy expenditure over a 14-d period was entered as the outcome variable. Gender (beta = 7168.9 kJ/week, p = 0.023) and time spent in shift work (beta = 26.36 kJ/week, p = 0.051) were found to be predictors of energy expenditure, with the most experienced, male shift workers expending the most energy during leisure-time. Overall 'disengagement' coping scores from the SSI were positively related to leisure-time energy expenditure (beta = 956.27 kJ/week, p = 0.054). In males, disengagement of sleep problems (beta = -1078.1 kJ/week, p = 0.086) was found to be negatively correlated to energy expenditure, whereas disengagement of domestic-related problems was found to be positively related to energy expenditure (beta = 1961.92 kJ/week, p = 0.001). These relations were not found in female shift workers (p = 0.762). These data suggest that experienced male shift workers participate in the most leisure-time physical activity. These people 'disengage' more from their domestic-related problems, but less from their sleep-related problems. It is recommended that physical activity interventions for shift workers should be designed with careful consideration of individual domestic responsibilities and perceived disruption to sleep.

Comparação da percepção de fadiga e de capacidade para o trabalho entre trabalhadores têxteis de empresas que se encontram em diferentes estágios de responsabilidade social empresarial no estado de São Paulo, Brasil

OBJETIVOS: Comparar as características demográficas e as percepções da capacidade para o trabalho, fadiga e condições de trabalho entre trabalhadores de indústrias têxteis que estejam em diferentes estágios de responsabilidade social empresarial (RSE). MÉTODOS: Em estudo transversal, 126 trabalhadores de três empresas e cinco fábricas responderam a questionário de caracterização demográfica, condições e estilos de vida, a autoavaliações sobre fadiga, condições de trabalho e capacidade para o trabalho. As empresas foram classificadas em dois grupos de pontuação de indicadores de RSE (o grupo um de menor pontuação e o grupo dois de maior pontuação), com base nas respostas dadas em questionário específico. RESULTADOS: Não foram encontradas diferenças (p > 0,05) nos resultados de capacidade para o trabalho, fadiga e na maior parte dos dados demográficos obtidos entre os trabalhadores dos dois grupos. As melhores condições de trabalho, no grupo de maior pontuação (p = 0,008), deveram-se principalmente ao fornecimento de refeições nas fábricas. CONCLUSÕES: O desenvolvimento e a implementação de projetos de RSE não implicam, necessariamente, em melhores condições de trabalho ou em percepções dos trabalhadores de menor fadiga ou maior capacidade para o trabalho, em relação a empresas que não dispõem desses projetos. Por tratar-se de estudo transversal com população reduzida e como a capacidade para o trabalho pode diminuir com o envelhecimento do trabalhador novos estudos, preferencialmente longitudinais, deverão ser realizados, com populações maiores.

Rail signallers' assessments of their satisfaction with different shift work systems

This paper describes rail employee views on shift-work systems obtained from administration of the Rail Ergonomics Questionnaire (REQUEST) to a large sample of rail professionals in Great Britain, achieving a response rate of 83%. Results from signallers, the largest occupational grouping in the survey (n = 3230), are presented. ANOVA has been used to investigate the effects of different aspects of the shift patterns (the length of shift and the speed and direction of rotation of shifts) and the effects of age on the ratings of satisfaction with the shift system. The findings from the analyses indicate preferences for the 12-h shift system over the 7-9-h rotating shift system. There were no main effects of the direction of rotation of shifts, though there were significant interactions between the direction of rotation of shifts, the numbers of consecutive shifts and the age of respondents. There is a need for clear data addressing the impact on workers of key shift-related parameters such as shift length, direction of rotation of shifts, numbers of consecutive shifts and personal factors such as age. This paper presents findings of the effects of these key shift and personal parameters and their interactions on respondents' ratings of satisfaction with the shift system, using data collected with REQUEST in a national survey of rail signallers.

Exercise, energy balance and the shift worker

Shift work is now common in society and is not restricted to heavy industry or emergency services, but is increasingly found amongst 'white collar' occupations and the growing number of service industries. Participation in shift work is associated with increased body mass index, prevalence of obesity and other health problems. We review the behavioural and biological disturbances that occur during shift work and discuss their impact on leisure-time physical activity and energy balance. Shift work generally decreases opportunities for physical activity and participation in sports. For those shift workers who are able to exercise, subjective and biological responses can be altered if the exercise is taken at unusual times of day and/or if the shift worker is sleep deprived. These altered responses may in turn impact on the longer-term adherence to an exercise programme. The favourable effects of exercise on body mass control and sleep quality in shift workers have not been confirmed. Similarly, recent reports of relationships between sleep duration and obesity have not been examined in a shift work context. There is no evidence that exercise can mediate certain circadian rhythm characteristics (e.g. amplitude or timing) for improved tolerance to shift work. Total energy intake and meal composition do not seem to be affected by participation in shift work. Meal frequency is generally reduced but snacking is increased on the night shift. Unavailability of preferred foods in the workplace, a lack of time, and a reduced desire to eat at night explain these findings. 'Normal' eating habits with the family are also disrupted. The metabolic responses to food are also altered by shift work-mediated disruptions to sleep and circadian rhythms. Whether any interactions on human metabolism exist between timing or content of food intake and physical activity during shift work is not known at present. There are very few randomized controlled studies on the efficacy of physical activity or dietary interventions during shift work. Some favourable effects of such interventions on fatigue levels at work have been reported, but biological and behavioural outcomes relevant to long-term health and energy balance have not been studied adequately. In addition, recruitment and retention of research participants for randomized controlled trials of physical activity or dietary interventions have been very difficult. We present a model of the various behavioural and biological factors relevant to exercise and energy balance during shift work as a framework for future research.

Ageing, working hours and work ability

The current paper reports the main results of several studies carried out on Italian workers using the work ability index as a complementary tool for workers' periodical health surveillance. The work ability index shows a general decreasing trend over the years, but it changes differently according to working conditions and personal health status. In jobs with higher mental involvement and autonomy, but lower physical constraint, it remains quite constant and high over the years, while it significantly decreases with a steeper trend the higher the physical work load and the lower the job control are. Sex and working hours appear to act concurrently in influencing work ability, particularly in association with more physically demanding jobs. It is therefore necessary to adopt flexible interventions, able to give ageing shift workers a proper support for maintaining a satisfactory work ability, by means of actions addressed both to work organization and psycho-physical conditions.

Ontogênese do sistema de temporização: a construção e as reformas dos ritmos biológicos ao longo da vida humana

Nesta revisão apresentamos fatos e comentários sobre a evolução dos sistemas de temporização ("relógios biológicos") na espécie humana. Na Introdução definimos alguns conceitos básicos da Cronobiologia que serão utilizados ao longo do artigo. Nas quatro seções subseqüentes, discutimos fatos marcantes que caracterizam a ritmicidade biológica em distintas etapas da ontogênese: bebês, adolescentes, adultos e idosos. Concluímos o artigo com um convite à reflexão sobre as perspectivas que se abrem com esse novo campo do conhecimento.

Implications of shift work for junior doctors

Yasmin Ahmed-Little provides evidence that junior doctors' dislike of shift working is more than a stubborn reaction and discusses how to make shifts more tolerable

Sincronização não-fótica: o efeito do exercício físico aeróbio

As principais alterações, agudas e crônicas, provocadas pelo exercício físico aeróbio (EF) sobre o organismo são, de maneira geral, bem conhecidas. No entanto, existe um efeito em particular do EF que começou a ser elucidado no começo da década de 90, em humanos, que tem a capacidade de alterar a relação temporal do organismo com o meio. A modificação da expressão dos ritmos circadianos, causada pelo EF, qualifica-o como sincronizador dos osciladores biológicos. O principal sincronizador da ritmicidade biológica é o ciclo geofísico claro/escuro. A alternância do dia e da noite, através de diferenças nos níveis de luminosidade, é percebida por meio de vias fóticas pelo sistema de temporização circadiana (STC). Esses estímulos, chamados fóticos, fornecem informações temporais para o STC sincronizando os osciladores biológicos com esse ciclo ambiental. Outros estímulos também são capazes de sincronizá-los e são chamados de sincronizadores não-fóticos. Esta revisão aborda o efeito do EF sobre o sistema de temporização e, ao mesmo tempo, discute as possíveis e prováveis aplicações cronobiológicas dos conhecimentos abordados. O EF pode afetar o STC através de vias não-fóticas, podendo beneficiar a saúde de indivíduos em diversas situações, tais como vôos transmeridianos, trabalhos noturnos e distúrbios do sono. Ressalta-se, também, que devem ser realizados mais estudos no cotidiano das pessoas para compreender melhor a relação entre, e a contribuição dos, diferentes sincronizadores em um contexto real.

The effect of scheduled forced wheel activity on body weight in male F344 rats undergoing chronic circadian desynchronization

OBJECTIVE

To examine whether scheduled forced wheel activity counteracts the increased body weight gain in rats undergoing chronic circadian desynchronization induced by repeated 12-h shifts in the light-dark cycle.

DESIGN

Four age- and body weight-matched groups of adult male F344 rats were subjected to 12-h intermittent forced wheel activity daily (2.2 km/day). Each group had the following schedule for 13 weeks: a fixed schedule of a daily 12:12-h light-dark cycle and activity training (WF); a fixed light-dark cycle and 12-h shifts twice a week in activity training (WS); 12-h shifts twice a week in the light-dark cycle and a fixed schedule of activity training (LSWF); and 12-h shifts twice a week in both the light-dark cycle and activity training (LSWS). Two additional age- and body weight-matched sedentary rat groups were selected from our database: one was maintained on a fixed light-dark cycle (LC) and the other was subjected to 12-h shifts twice a week in the light-dark cycle (LS).

RESULTS

The four rat groups that were exercised showed different response patterns of the daily body temperature rhythm to different combinations of forced activity and lighting schedules. Their food intake was more than that of the two sedentary rat groups, but their body weight was comparable with that of the LC rats and less than that of the LS rats during the forced activity period. The LSWS rats were heavier than the WF and WS rats in the first and second months of the experimental treatment, but their body weight was comparable with that of the WS and WF rats in the third month.

CONCLUSION

Forced activity was effective in reducing the body weight gain in chronic circadian desynchronization that was induced by repeated shifts in the light-dark cycle, although such an effect might become significant only after some time.