Age and adjustment to night work

Working hours and health - key research topics in the past and future

OBJECTIVE

This paper discusses the past and present highlights of working hours and health research and identifies key research needs for the future.

METHOD

We analyzed over 220 original articles and reviews on working hours and health in the Scandinavian Journal of Work, Environment & Health published during the last 50 years. Key publications from other journals were also included.

RESULTS

The majority of identified articles focussed on the effects of shift and night work, with fewer studying long and reduced working hours and work time control. We observed a transition from small-scale experimental and intensive field studies to large-scale epidemiological studies utilizing precise exposure assessment, reflecting the recent emergence of register-based datasets and the development of analytic methods and alternative study designs for randomized controlled designs. The cumulative findings provide convincing evidence that shift work and long working hours, which are often associated with night work and insufficient recovery, increase the risk of poor sleep and fatigue, sickness absence, occupational injuries, and several chronic health conditions such as cardiovascular diseases and cancer. The observed risks are strongly modified by individual and work-related factors.

CONCLUSIONS

Although the observed health risks of shift work and long working hours are mostly low or moderate, the widespread prevalence of exposure and the hazardousness of the many associated potential outcomes makes such working time arrangements major occupational health risks. Further research is needed to identify exposure-response associations, especially in relation to the chronic health effects, and to elucidate underlying pathways and effective personalized intervention strategies.

Sleep quality, sleep duration, and sleep disturbances among hospital night workers: a prospective cohort study

PURPOSE

This study aimed to assess among hospital night workers (i) to what extent sleep quality, sleep duration and sleep disturbances overlap, and (ii) associations between sociodemographic factors, lifestyle factors and work characteristics and sleep components.

METHODS

Data were used from 467 hospital night workers participating in the Klokwerk + study, a prospective cohort study with two measurements. Sleep quality was measured by the Pittsburgh Sleep Quality Index, sleep duration and sleep disturbances were measured by the Medical Outcomes Study Sleep Scale. The overlap between the three sleep measures was visualized with a Venn diagram and the proportions of overlap was calculated. Associations between independent variables (sociodemographic factors, lifestyle factors and work characteristics) and the three sleep outcomes were estimated using between-within Poisson regression models.

RESULTS

About 50% of the hospital night workers had at least one poor sleep outcome. Overlap in poor sleep outcomes was apparent for 36.8% of these workers, while the majority had a poor outcome in one of the sleep components only (63.1%). Former smoking had a significant association with poor sleep quality. For most independent variables no associations with poor sleep outcomes were observed.

CONCLUSION

Our findings suggest that sleep quality, sleep duration and sleep disturbances are separate entities and should be studied separately. Lifestyle factors and work characteristics were generally not associated with poor sleep. Since these factors can have an acute effect on sleep, future research should consider ecological momentary assessment to examine how exposure and outcomes (co)vary within-persons, over time, and across contexts. Trial registration Netherlands Trial Register trial number NL56022.041.16.

A Systematic Review of Workplace-Based Employee Health Interventions and Their Impact on Sleep Duration Among Shift Workers

BACKGROUND

Shift work is associated with long-term health risks. Workplace-based health interventions hold promise for improving or maintaining the health of shift workers; yet, the impact of workplace-based interventions on shift worker sleep duration has not been assessed. We conducted a systematic review of workplace interventions on shift worker sleep.

METHODS

We conducted searches in PubMed, Web of Knowledge, EMBASE, Scopus, and PsycINFO (n = 6,868 records) of all studies published through May 15, 2019. Eligibility criteria included the following: (a) individuals aged ≥18 years; (b) a workplace-based employee intervention; (c) an employee population comprised predominantly of shift workers (>50%); and (d) sleep duration as a study outcome.

FINDINGS

Twenty workplace interventions met eligibility criteria. Mean intervention duration was 125 (SD = 187) days and mean sample size was 116 employees (SD = 256) with a mean age of 36.4 years (SD = 6.5). Interventions most commonly focused on light exposure (25%) or shift timing (25%), followed by sleep hygiene (20%). Most interventions were conducted in the health care and social assistance sector (60%). Study quality on average was 64% (SD = 7%). A majority of the studies found that a workplace-based health intervention was associated with a desirable increase in 24-hour total sleep duration (55%). The overall average increase in daily employee sleep duration achieved by interventions ranged for RCT studies from 0.34 to 0.99 hours and for non-RCT studies from 0.02 to 1.15 hours.

CONCLUSIONS/APPLICATIONS TO PRACTICE

More than half of the employee health interventions, especially yoga or mindfulness interventions, resulted in a desirable increase in sleep duration. Workplaces hold promise as an avenue? for delivering programs and policies that aim to improve sleep duration among shift workers.

Association of rotating shift work schedules and the use of prescribed sleep medication: A prospective cohort study

We examined whether working rotating shifts, with or without night work, is associated with the purchase of prescribed sleep medication, and whether the association is dependent on age. Data were obtained from a longitudinal cohort study of Finnish public sector employees who responded to questions on work schedule and background characteristics in 2000, 2004 and 2008. The data were linked to national register data on redeemed prescriptions of hypnotic and sedative medications, with up to 11 years of follow-up. Age stratified Cox proportional hazard regression models were computed to examine incident use of medication comparing two groups of rotating shift workers (those working shifts that included night shifts and those whose schedules did not include night shifts) with day workers who worked in a similar range of occupations. Shift work with night shifts was associated with increased use of sleep medication in all age groups, after adjustments for sex, occupational status, marital status, alcohol consumption, smoking and physical activity levels (hazard ratio [HR], [95% confidence interval, CI] 1.14 [1.01-1.28] for age group ≤39 years; 1.33 [1.19-1.48] for age group 40-49 years; 1.28 [1.13-1.44] for age group ≥50 years). Shift work without nights was associated with medication use in the two older age groups (HR [95% CI] 1.14 [1.01-1.29] and 1.17 [1.05-1.31] for age groups 40-49 years and >50 years, respectively). These findings suggest that circadian disruption and older age puts rotating shift workers, and especially those who work nights, at increased risk of developing clinically significant levels of sleep problems.

Influence of Demographic Characteristics and Muscle Strength on the Occupational Fatigue Exhaustion Recovery Scale in Career Firefighters

OBJECTIVE

Little is known regarding how individual characteristics and changes in muscle strength across a shift cycle are associated with the Occupational Fatigue Exhaustion Recovery scale in career firefighters.

METHODS

Thirty-two career firefighters completed lower body maximal strength testing prior to and following three 24-hour on-off shifts. Demographic data were collected prior to the first shift and the OFER15 questionnaire was completed following the last shift.

RESULTS

Increased age was associated with greater acute and chronic fatigue and poorer recovery. A positive percent change in strength following a shift cycle was related to better recovery. Age was the only significant predictor of acute and chronic fatigue, while age and the change in strength were significant predictors of inter-shift recovery.

CONCLUSIONS

Increased age influences all dimensions of work-related fatigue, with changes in muscle strength influencing inter-shift recovery in career firefighters.

How to schedule night shift work in order to reduce health and safety risks

Objectives This discussion paper aims to provide scientifically based recommendations on night shift schedules, including consecutive shifts, shift intervals and duration of shifts, which may reduce health and safety risks. Short-term physiological effects in terms of circadian disruption, inadequate sleep duration and quality, and fatigue were considered as possible links between night shift work and selected health and safety risks, namely, cancer, cardio-metabolic disease, injuries, and pregnancy-related outcomes. Method In early 2020, 15 experienced shift work researchers participated in a workshop where they identified relevant scientific literature within their main research area. Results Knowledge gaps and possible recommendations were discussed based on the current evidence. The consensus was that schedules which reduce circadian disruption may reduce cancer risk, particularly for breast cancer, and schedules that optimize sleep and reduce fatigue may reduce the occurrence of injuries. This is generally achieved with fewer consecutive night shifts, sufficient shift intervals, and shorter night shift duration. Conclusions Based on the limited, existing literature, we recommend that in order to reduce the risk of injuries and possibly breast cancer, night shift schedules have: (i) ≤3 consecutive night shifts; (ii) shift intervals of ≥11 hours; and (iii) ≤9 hours shift duration. In special cases - eg, oil rigs and other isolated workplaces with better possibilities to adapt to daytime sleep - additional or other recommendations may apply. Finally, to reduce risk of miscarriage, pregnant women should not work more than one night shift in a week.

Complexities in cardiovascular rhythmicity: perspectives on circadian normality, ageing and disease

Biological rhythms exist in organisms at all levels of complexity, in most organs and at myriad time scales. Our own biological rhythms are driven by energy emitted by the sun, interacting via our retinas with brain stem centres, which then send out complex messages designed to synchronize the behaviour of peripheral non-light sensing organs, to ensure optimal physiological responsiveness and performance of the organism based on the time of day. Peripheral organs themselves have autonomous rhythmic behaviours that can act independently from central nervous system control but is entrainable. Dysregulation of biological rhythms either through environment or disease has far-reaching consequences on health that we are only now beginning to appreciate. In this review, we focus on cardiovascular rhythms in health, with ageing and under disease conditions.

Aging Affects the Capacity of Photoperiodic Adaptation Downstream from the Central Molecular Clock

Aging impairs circadian clock function, leading to disrupted sleep-wake patterns and a reduced capability to adapt to changes in environmental light conditions. This makes shift work or the changing of time zones challenging for the elderly and, importantly, is associated with the development of age-related diseases. However, it is unclear what levels of the clock machinery are affected by aging, which is relevant for the development of targeted interventions. We found that naturally aged mice of >24 months had a reduced rhythm amplitude in behavior compared with young controls (3-6 months). Moreover, the old animals had a strongly reduced ability to adapt to short photoperiods. Recording PER2::LUC protein expression in the suprachiasmatic nucleus revealed no impairment of the rhythms in PER2 protein under the 3 different photoperiods tested (LD: 8:16, 12:12, and 16:8). Thus, we observed a discrepancy between the behavioral phenotype and the molecular clock, and we conclude that the aging-related deficits emerge downstream of the core molecular clock. Since it is known that aging affects several intracellular and membrane components of the central clock cells, it is likely that an impairment of the interaction between the molecular clock and these components is contributing to the deficits in photoperiod adaptation.

Drowsiness measures for commercial motor vehicle operations

Timely detection of drowsiness in Commercial Motor Vehicle (C MV) operations is necessary to reduce drowsiness-related CMV crashes. This is relevant for manual driving and, paradoxically, even more so with increasing levels of driving automation. Measures available for drowsiness detection vary in reliability, validity, usability, and effectiveness. Passively recorded physiologic measures such as electroencephalography (EEG) and a variety of ocular parameters tend to accurately identify states of considerable drowsiness, but are limited in their potential to detect lower levels of drowsiness. They also do not correlate well with measures of driver performance. Objective measures of vigilant attention performance capture drowsiness reliably, but they require active driver involvement in a performance task and are prone to confounds from distraction and (lack of) motivation. Embedded performance measures of actual driving, such as lane deviation, have been found to correlate with physiologic and vigilance performance measures, yet to what extent drowsiness levels can be derived from them reliably remains a topic of investigation. Transient effects from external circumstances and behaviors - such as task load, light exposure, physical activity, and caffeine intake - may mask a driver's underlying state of drowsiness. Also, drivers differ in the degree to which drowsiness affects their driving performance, based on trait vulnerability as well as age. This paper provides a broad overview of the current science pertinent to a range of drowsiness measures, with an emphasis on those that may be most relevant for CMV operations. There is a need for smart technologies that in a transparent manner combine different measurement modalities with mathematical representations of the neurobiological processes driving drowsiness, that account for various mediators and confounds, and that are appropriately adapted to the individual driver. The research for and development of such technologies requires a multi-disciplinary approach and significant resources, but is technically within reach.

Shift-specific associations between age, chronotype and sleep duration

The objective of this study was to examine the association of age with chronotype and sleep duration in day workers and rotating shift workers, including night shift work. Between October 2012 and February 2015, a cross-sectional study was conducted in a German chemical company. Using the "Munich ChronoType Questionnaire" (MCTQ), data about sleep onset and sleep offset during workdays and work-free days were retrieved and the chronotype was computed during regular voluntary occupational health check-ups. Associations between age and chronotype, as well as sleep duration, were assessed using linear regression analyses. Potential effect modification by the working time system was examined. Within the study period, 4,040 employees (82.3% and 17.7% were engaged in day work and rotating shift work, respectively) completed the questionnaire. Study participants were on average 41.8 years old (Min = 18.0, Max = 65.0, SD = 10.2) and predominantly male (75.4%). Mean chronotype and overall sleep duration was 03:22 (SD = 54 min) and 7.2 h (SD = 1.0 h) respectively. Older age was associated with earlier chronotype and reduced overall sleep duration in both day workers and rotating shift workers (p < 0.001 for all models). Compared to day workers, employees whom engaged in rotating shift work were later chronotypes and had overall a longer sleep duration. With older age, the difference between day and rotating shift workers regarding chronotype increased, while the difference regarding overall sleep duration decreased (p_interaction<0.005 for both models). This finding could indicate that both changes in circadian physiology and exposure to certain work schedules contribute to the age-related changes. Older rotating shift workers, with early chronotypes may have issues with night shifts, while day work and morning shifts may be best compatible to earlier chronotypes. Differences in sleep timing across age groups, might indicate that the same work hours will affect shift workers differently, dependent on their age, suggesting that more flexible and chronotype-adapted work hours could provide useful; especially for older employees. Sleep education in the form of courses and health campaigns could be a way to raise awareness of the importance of a healthy sleep pattern. This could be achieved by learning strategies to better adjust individual sleep patterns to work hours.

Who is sleepier on the night shift? The influence of bio-psycho-social factors on subjective sleepiness of female nurses during the night shift

Sleepiness is a common complaint during the night shift and may impair performance. The current study aims to identify bio-psycho-social factors associated with subjective sleepiness during the night shift. Ninety-two female nurses working rotating shifts completed a sociodemographic questionnaire, the Munich ChronoType Questionaire for shift workers, the Pittsburg Sleep Quality Index, and the Pre-sleep Arousal Scale. Subjective sleepiness was measured hourly during two night shifts using the Karolinska Sleepiness Scale, and activity monitors assessed sleep duration 24-h before each shift. Findings showed that increased sleepiness was associated with increased age in nurses with early chronotypes and with more children. High cognitive pre-sleep arousal, but not sleep, was associated with increased sleepiness, especially in late chronotypes. The impact of bio-psycho-social factors on night shift sleepiness is complex, and depends on mutual interactions between these factors. Nurses most prone to increased sleepiness must develop personal strategies for maintaining vigilance on the night shift. Practitioner Summary: This study aims to identify bio-psycho-social factors associated with subjective sleepiness of female nurses during the night shift. Increasing sleepiness was associated with increased age in nurses with early chronotypes and with more children. Increased cognitive pre-sleep arousal, but not sleep, was associated with increased sleepiness, especially in late chronotypes.

Study of insomnia in rotating shift-workers

BACKGROUND

Shift-workers commonly suffer from insomnia. This study evaluates different domains of insomnia.

AIM

This study was aimed to study sleep and insomnia in rotating shift-workers and compare with day-workers.

MATERIALS AND METHODS

This was case-control study. The sleep of rotating shift-workers is compared with day workers using Athens Insomnia Scale.

RESULTS

Rotating shift-workers had significantly higher scores on Athens insomnia scale on domains of initial, intermediate and terminal insomnia than day workers. Duration and quality of sleep and sense of well-being are lower in rotating shift-workers. Rotating shift-workers also experienced more day-time sleepiness than day workers. However, there was no difference in perceived physical and mental functioning between the two groups.

CONCLUSION

Individuals working in rotating shifts for more than 15 days have significantly higher prevalence of insomnia than day-workers.

Shift Work and Shift Work Sleep Disorder: Clinical and Organizational Perspectives

Throughout the industrialized world, nearly one in five employees works some form of nontraditional shift. Such shift work is associated with numerous negative health consequences, ranging from cognitive complaints to cancer, as well as diminished quality of life. Furthermore, a substantial percentage of shift workers develop shift work disorder, a circadian rhythm sleep disorder characterized by excessive sleepiness, insomnia, or both as a result of shift work. In addition to adverse health consequences and diminished quality of life at the individual level, shift work disorder incurs significant costs to employers through diminished workplace performance and increased accidents and errors. Nonetheless, shift work will remain a vital component of the modern economy. This article reviews seminal and recent literature regarding shift work, with an eye toward real-world application in clinical and organizational settings.

What is the preferred number of consecutive night shifts? results from a crossover intervention study among police officers in Denmark

Among police officers in Denmark, we studied (i) how many consecutive night shifts participants preferred at baseline; (ii) preferences regarding three intervention conditions (two, four, and seven consecutive night shifts followed by the same number of days off/day shifts: '2 + 2', '4 + 4', '7 + 7') at follow-up; (iii) characteristics of participants preferring each of these intervention conditions. Questionnaire data from a crossover intervention study were used (baseline: n = 73; follow-up: n = 68). At baseline, 49% preferred four consecutive night shifts. At follow-up, 57% preferred '4 + 4', 26% preferred '2 + 2' and 26% preferred '7 + 7'. Participants, who preferred longer spells of night work experienced that night work was less demanding, found it easier to sleep at different times of the day, and were more frequently evening types compared with participants who preferred shorter spells of night work. The participants' preferences are likely to be influenced by their previous shift work experience. Practitioner Summary: We investigated police officers' preferences regarding the number of consecutive night shifts. The majority preferred four consecutive night shifts. Those who preferred the longer spells of night work found night work less demanding, found it easier to sleep at different times of the day, and were more frequently evening types.

Scheduled evening sleep and enhanced lighting improve adaptation to night shift work in older adults

OBJECTIVES

We tested whether a sleep and circadian-based treatment shown to improve circadian adaptation to night shifts and attenuate negative effects on alertness, performance and sleep in young adults would also be effective in older adults.

METHODS

We assessed subjective alertness, sustained attention (psychomotor vigilance task, PVT), sleep duration (actigraphy) and circadian timing (salivary dim-light melatonin onset, DLMO) in 18 older adults (57.2±3.8 years; mean±SD) in a simulated shift work protocol. 4 day shifts were followed by 3 night shifts in the laboratory. Participants slept at home and were randomised to either the treatment group (scheduled evening sleep and enhanced lighting during the latter half of night shifts) or control group (ad-lib sleep and typical lighting during night shifts).

RESULTS

Compared with day shifts, alertness and sustained attention declined on the first night shift in both groups, and was worse in the latter half of the night shifts. Alertness and attention improved on nights 2 and 3 for the treatment group but remained lower for the control group. Sleep duration in the treatment group remained similar to baseline (6-7 hours) following night shifts, but was shorter (3-5 hours) following night shifts in the control group. Treatment group circadian timing advanced by 169.3±16.1 min (mean±SEM) but did not shift (-9.7±9.9 min) in the control group.

CONCLUSIONS

The combined treatment of scheduled evening sleep and enhanced lighting increased sleep duration and partially aligned circadian phase with sleep and work timing, resulting in improved night shift alertness and performance.

Circadian Rhythm Sleep-Wake Disorders

The circadian system regulates the timing and expression of nearly all biological processes, most notably, the sleep-wake cycle, and disruption of this system can result in adverse effects on both physical and mental health. The circadian rhythm sleep-wake disorders (CRSWDs) consist of 5 disorders that are due primarily to pathology of the circadian clock or to a misalignment of the timing of the endogenous circadian rhythm with the environment. This article outlines the nature of these disorders, the association of many of these disorders with psychiatric illness, and available treatment options.

Aging and Circadian Rhythms

Aging is associated with numerous changes, including changes in sleep timing, duration, and quality. The circadian timing system interacts with a sleep-wake homeostatic system to regulate human sleep, including sleep timing and structure. This article reviews key features of the human circadian timing system, age-related changes in the circadian timing system, and how those changes may contribute to the observed alterations in sleep.

Circadian Insights into Motivated Behavior

For an organism to be successful in an evolutionary sense, it and its offspring must survive. Such survival depends on satisfying a number of needs that are driven by motivated behaviors, such as eating, sleeping, and mating. An individual can usually only pursue one motivated behavior at a time. The circadian system provides temporal structure to the organism's 24 hour day, partitioning specific behaviors to particular times of the day. The circadian system also allows anticipation of opportunities to engage in motivated behaviors that occur at predictable times of the day. Such anticipation enhances fitness by ensuring that the organism is physiologically ready to make use of a time-limited resource as soon as it becomes available. This could include activation of the sympathetic nervous system to transition from sleep to wake, or to engage in mating, or to activate of the parasympathetic nervous system to facilitate transitions to sleep, or to prepare the body to digest a meal. In addition to enabling temporal partitioning of motivated behaviors, the circadian system may also regulate the amplitude of the drive state motivating the behavior. For example, the circadian clock modulates not only when it is time to eat, but also how hungry we are. In this chapter we explore the physiology of our circadian clock and its involvement in a number of motivated behaviors such as sleeping, eating, exercise, sexual behavior, and maternal behavior. We also examine ways in which dysfunction of circadian timing can contribute to disease states, particularly in psychiatric conditions that include adherent motivational states.

Shift rotation and age - interactions with sleep-wakefulness and inflammation

The interaction of age with shift rotation in relation to sleep-wakefulness and inflammation were studied among male employees (n = 772). Cross-sectional analyses in day, two-shift and three-shift work with different shift rotations, as well as changes in leukocytes and hsCRP among three shift workers who changed their shift system during the 2.5- yr follow-up were completed. Shift work was associated with problems to fall asleep (p < 0.001) and feeling of the current working time being harmful to sleep and wakefulness (p < 0.001). Quickly forward-rotation shift workers considered their working time less harmful compared with slower backward-rotation shift workers. Age did not influence sleep in general, but older workers in the quickly forward-rotating three-shift system had less sleep complaints than their younger colleagues. The age differences in the inflammatory markers partly depended on the shift system. The results give some support that rapidly forward-rotating shift systems are more 'age-friendly' than backward-rotating shift systems.

Personality factors predict sleep-related shift work tolerance in different shifts at 2-year follow-up: a prospective study

OBJECTIVES

The aim of the present study was to investigate whether the personality variables morningness, flexibility, languidity and hardiness could predict sleep-related shift work tolerance for the day, evening and night shifts, respectively.

DESIGN

Prospective study design with questionnaires administered in winter 2008/2009 (wave 1) and 2 years later in spring 2011 (wave 3).

SETTING

Different healthcare institutions in Norway.

PARTICIPANTS

The sample comprised in all 700 nurses working a three-shift rotating schedule.

PRIMARY AND SECONDARY OUTCOME MEASURES

The personality variables were assessed at wave 1, as were the demographic, lifestyle and work-related variables. Sleep-related shift work tolerance, assessed at wave 3, was measured separately for the day, evening and night shifts with the Bergen Shift Work Sleep Questionnaire.

RESULTS

Morningness was positively associated with sleep-related day shift tolerance (p<0.001). Flexibility was positively associated with sleep-related tolerance for the evening as well as night shift (p<0.001). Furthermore, languidity was negatively associated with sleep-related shift tolerance for the day, evening and night shifts (p<0.001, <0.01, <0.05, respectively). Hardiness was positively associated with sleep-related tolerance for the day, evening and night shifts (p<0.001, <0.01, <0.05, respectively). Age was negatively associated with sleep-related shift tolerance for the day, night (p<0.01) and evening shifts (p<0.001).

CONCLUSIONS

The findings indicate that hardiness and languidity predict sleep-related shift work tolerance across all shift types among shift working nurses. The effects of flexibility and morningness seem to depend on the shift schedule. By and large, our results are in accordance with previous studies; however, we have now demonstrated the prospective importance of personality in relation to sleep-related shift work tolerance across different shifts.

Circadian rhythm sleep disorders

There have been remarkable advances in our understanding of the molecular, cellular, and physiologic mechanisms underlying the regulation of circadian rhythms, and of the impact of circadian dysfunction on health and disease. This information has transformed our understanding of the effect of circadian rhythm sleep disorders (CRSD) on health, performance, and safety. CRSDs are caused by alterations of the central circadian timekeeping system, or a misalignment of the endogenous circadian rhythm and the external environment. This article reviews circadian biology and discusses the pathophysiology, clinical features, diagnosis, and treatment of the most commonly encountered CRSDs in clinical practice.

Survey and comparison of sleep quality among fixed and changing shift staff in a steel factory in Tehran, Iran

BACKGROUND

Given the hazardous nature of the work in steel factories and that the staff has to deal with hazardous equipment and machines, improper sleep quality and drowsiness among the works tackles performance and boosts rate of job accidents. This study is aimed to survey the quality of sleep and sleepiness status and the pertinent factors among the workers in a rolling mill and a steel production company in Tehran, Iran.

METHODS

In a Cross-Sectional study 2011, 180 workers were selected randomly from a rolling mill and a steel production company in Tehran. A questionnaire was designed to collect demographic data and variables of work condition. Pitersborg's sleep quality questionnaire was used to survey quality and problems of Participants' sleep. Epworth Sleepiness questionnaire was used to deals with sleepiness during work, studying, watching TV, or during time spent in public.

RESULTS

Average score of sleep quality for the fixed shift staff and changing shift staff were 7.5±2.82 and 8.49±2.95 respectively. Surveys of sleep quality for the two groups of the participants based on T-test showed a significant difference between the two groups so that the changing shift staff group suffered poorer sleep quality (p=0.03). Comparison of average drowsiness scores between the two groups of participants based on Mann-Whitney test showed no significant difference (p>0.005). Chi square test showed a significant difference between severity of drowsiness and type of working shift (p =0.028 and 0.009).

CONCLUSION

Staff in revolving shifts suffers poor sleep quality comparing with staff with fixed working shift. Moreover, type of working shift greatly affects severity of drowsiness as staff at different work shift experienced different level of sleepiness. It is essential to survey sleep disorder of the staff in the industry and pay more emphasis on sleep disorder epidemic in other fields of industry.

Self-reported sleep and health among Norwegian hospital nurses in intensive care units

AIM AND BACKGROUND

Shift work, and especially night work, is associated with poor health. Nurses, work a variety of work schedules including night work. So far, few studies have specifically investigated sleep and health among intensive care nurses.

DESIGN AND METHODS

We investigated sleep, sleepiness, fatigue, subjective health complaints, anxiety and depression in 150 intensive care nurses (convenience sample representing a response rate of 56·2%). The nurses worked at two major University hospitals in Norway and answered a questionnaire survey.

RESULTS

The intensive care nurses reported poorer sleep, more sleepiness, more fatigue, more anxiety and more depression compared to normative data. Poor sleep was reported by 70% and excessive sleepiness by 25% of the nurses; however, the design of the study did not allow us to determine the causes underlying these findings. Multiple linear regression analyses showed that age was positively associated with sleep problems, fatigue, subjective health complaints and anxiety and depression. In contrast, shift work experience was negatively associated with sleep problems, suggesting better coping with shift work over time.

CONCLUSIONS

Nurses working in intensive care units reported poorer sleep, more sleepiness, more fatigue, more anxiety and more depression compared to Norwegian norm groups. Age was positively related to these complaints, whereas shift work experience was negatively related to poor sleep. More studies are needed on strategies to improve sleep and health in nurses.

Subjective and objective sleepiness among oil rig workers during three different shift schedules

OBJECTIVES

Examine sleepiness in three different shift work schedules (within-subject design) in the offshore oil industry.

METHODS

Sleepiness was measured in 19 oil rig workers, using subjective (Karolinska Sleepiness Scale; Accumulated Time with Sleepiness) and objective measures (reaction time). The work schedule consisted of two weeks of 12 h day work (day shifts), two weeks of 12 h night work (night shifts), and two weeks of swing shift work (one week of night work followed by one week of day work).

RESULTS

Sleepiness was highest during the first days of night and swing shifts, and also in the middle of the swing shift work period, but gradually decreased as the days on the night shift progressed. While at home following the two-week work period, the workers reported more subjective sleepiness after night shift than after day or swing shifts. Reaction time tests during the work period showed no significant differences between the shift schedules. There was a significant shorter reaction time the last day compared to the beginning or middle of the work period.

CONCLUSIONS

Subjective sleepiness was higher during the first days of night work compared to day work, and also when the swing shift workers changed from night work to day work in the middle of the two-week work period. Subjective sleepiness was increased at home following night shifts compared to after day and swing shifts, suggesting that swing shift workers adapted their circadian rhythm during their second period of work, during the day shift week, offshore.

What is the evidence for less shift work tolerance in older workers?

This paper explores the suggestion that older people would be less tolerant to shift work. Field studies on age-shift work interaction effects on sleep, fatigue, performance, accidents and health were reviewed. Studies on age-shift (morning, afternoon, night) and age-shift system (roster) interactions were also reviewed. In nine studies, shift and day workers were compared and interactions with age were addressed. Two studies reported more problems in older people, four studies reported opposite results, while in five studies no significant age-shift work interaction was observed. From across-shift comparisons (six studies), it was deduced that older compared with younger workers have more sleep problems with night shifts, while the opposite is true for morning shifts. This review did find some differences between older and younger workers, but did not find evidence for the suggestion of more shift work problems in older workers. STATEMENT OF RELEVANCE: This systematic review reveals the limited evidence that exists concerning shift work tolerance in older workers, highlighting an area for future research. Some interactions between age and shift type and shift system have been found, however. In view of these, it is argued that age-specific aspects should be considered in shift work planning.

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.

Recovery of cognitive performance and fatigue after one night of sleep deprivation

OBJECTIVES

The aim of this study was to investigate how subjective sleepiness, mood states, simple and high-order cognitive performance change after one night of sleep deprivation (SD) and recover to after 7 h normal recovery sleep opportunity during three recovery days.

METHODS

Ten healthy subjects participated in this study. We measured their subjective sleepiness, mood states and their performances of 2 simple tasks and 4 high-order cognitive tasks twice a day for 5 days, on the baseline day, post-vigil day and 3 recovery days after SD. This study was conducted considering each participant's motivation for task, learning effect and diurnal variation of performance.

RESULTS

The performances of simple tasks such as addition or short-term memory were not reduced after SD and were the poorest on the baseline day, and improved gradually; however the high-order cognitive performances were at their lowest on the post-vigil day and needed 2 recovery sleep opportunities to return to the baseline level. Fatigue and confusion in mood states and subjective sleepiness were also at their lowest after SD. Subjective sleepiness nearly recovered to the baseline level on the 1st recovery day, but fatigue and confusion reached the baseline levels on the 2nd recovery day.

CONCLUSION

These results suggest that cognitive deterioration and the recovery process may differ between simple task performance and high-order cognitive task performance, which needed 2 ordinary sleep opportunities to recover to the baseline level, and the change of subjective mood states were also different for each mood.

Expression profiles of PERIOD1, 2, and 3 in peripheral blood mononuclear cells from older subjects

AIMS

Circadian clocks regulate daily rhythms of behavior and physiology such as the sleep-wake cycle and hormonal secretion. Numerous characteristics of the behavioral and physiological processes change with age. In this study, we evaluated the circadian clockwork in older people by measuring daily profiles of PERIOD (PER) gene expression in peripheral blood mononuclear cells (PBMCs).

MAIN METHODS

Blood samples were collected from 6 healthy older subjects (mean age 62 years) at 2-h intervals over a 24-h period under a semi-constant routine condition where masking effects are minimized. PBMCs were isolated from whole blood and temporal mRNA expression profiles of PER1, PER2, and PER3 were determined by RT-PCR. Phases of the PER rhythms, and times of sleep onset and offset were determined using data from those subjects who showed significant 24-h rhythms. The values for the parameters were compared between the older subjects and 8 young control subjects (mean age 21 years).

KEY FINDINGS

Prominent daily rhythms of PER1, PER2, and PER3 mRNA levels, advanced sleep-wake timing and advanced phases of PER rhythms were observed in the older subjects compared to the young controls. There was no significant age-related phase difference in PER1 or PER2 rhythm with respect to sleep timing; however, PER3 expression pattern was altered in the older subjects.

SIGNIFICANCE

This preliminary study shows that human circadian clockwork in PBMCs remains intact at least until the presenile stage and suggests that the altered PER3 expression pattern may reflect decreased homeostatic sleep drive in older people.

Differences in sleep, light, and circadian phase in offshore 18:00-06:00 h and 19:00-07:00 h shift workers

Complaints concerning sleep are high among those who work night shifts; this is in part due to the disturbed relationship between circadian phase and the timing of the sleep-wake cycle. Shift schedule, light exposure, and age are all known to affect adaptation to the night shift. This study investigated circadian phase, sleep, and light exposure in subjects working 18:00-06:00 h and 19:00-07:00 h schedules during summer (May-August). Ten men, aged 46+/-10 yrs (mean+/-SD), worked the 19:00-07:00 h shift schedule for two or three weeks offshore (58 degrees N). Seven men, mean age 41+/-12 yrs, worked the 18:00-06:00 h shift schedule for two weeks offshore (61 degrees N). Circadian phase was assessed by calculating the peak (acrophase) of the 6-sulphatoxymelatonin rhythm measured by radioimmunoassay of sequential urine samples collected for 72 h at the end of the night shift. Objective sleep and light exposure were assessed by actigraphy and subjective sleep diaries. Subjects working 18:00-06:00 h had a 6-sulphatoxymelatonin acrophase of 11.7+/-0.77 h (mean+/-SEM, decimal hours), whereas it was significantly later, 14.6+/-0.55 h (p=0.01), for adapted subjects working 19:00-07:00 h. Two subjects did not adapt to the 19:00-07:00 h night shift (6-sulphatoxymelatonin acrophases being 4.3+/-0.22 and 5.3+/-0.29 h). Actigraphy analysis of sleep duration showed significant differences (p=0.03), with a mean sleep duration for those working 19:00-07:00 h of 5.71+/-0.31 h compared to those working 18:00-06:00 h whose mean sleep duration was 6.64+/-0.33 h. There was a trend to higher morning light exposure (p=0.07) in the 19:00-07:00 h group. Circadian phase was later (delayed on average by 3 h) and objective sleep was shorter with the 19:00-07:00 h than the 18:00-06:00 h shift schedule. In these offshore conditions in summer, the earlier shift start and end time appears to favor daytime sleep.