Rapid adaptation to night work at an oil platform, but slow readaptation after returning home

Validation of the Karolinska Sleepiness Scale in Korean

BACKGROUND AND PURPOSE

The Karolinska Sleepiness Scale (KSS) is widely used for assessing current level of sleepiness, but it has not been validated in South Korea. This study aimed to validate the KSS using the Stanford Sleepiness Scale (SSS), polysomnography (PSG), and electroencephalography (EEG).

METHODS

The sample consisted of 27 adult participants in this study aged 40.5±7.7 years (mean±standard deviation) and included 22 males. They completed questionnaires and underwent EEG recording and overnight PSG. The KSS was completed from 18:00 to 24:00 every 2 hours and following PSG (at 07:00). KSS scores changed over time and in particular increased with the time since waking, with the score peaking at 24:00.

RESULTS

Convergent validity of the KSS was verified by performing a Spearman correlation analysis between the KSS and SSS (r=0.742, p<0.01). Concurrent validity of the KSS was verified by performing a Spearman correlation analysis between the KSS administered before sleep and the sleep onset latency measured using PSG (r=-0.456, p<0.05). Alpha waves were measured 5 minutes before administering the KSS, and the KSS scores were compared with these alpha waves. There were no significant correlations observed between the KSS scores and alpha waves measured in the left occipital area (O1), left frontal area (F3), or left central area (C3). In addition, Spearman correlation analyses of the difference between KSS scores and alpha waves measured at O1, F3, and C3 produced no significant results.

CONCLUSIONS

This study verified the convergent validity and concurrent validity of the KSS, and confirmed the capabilities of this scale in assessing sleepiness changes over time.

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

Object

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

Methods

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

Results

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

Conclusion

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

Application of Ecological Momentary Assessment in Studies with Rotation Workers in the Resources and Related Construction Sectors: A Systematic Review

Whilst Ecological momentary assessment (EMA) can provide important insights over time and across contexts among rotation workers whose work periods alternate with leave at home, it can also be challenging to implement in the resources and construction sectors. This review aimed to provide a summary of the methodological characteristics of EMA studies assessing health outcomes and related behaviors in rotation workers. Systematic searches in PubMed, Medline, EMBASE, CINAHL, PsycINFO, and Scopus were done to include 23 studies using EMA methods in assessing health-related outcomes and behaviors. EMA designs included daily diary: assessments once per day typically fixed at the end of day (47.8%), within day fixed interval time-based design: assessments on multiple times per day at certain times of day (17.4%) and combination of both designs (34.8%). Studies employed paper and pencil diaries (73.9%) and one or more electronic methods (60.9%): wrist-worn actigraphy device (52.2%) and online-based diaries (26.1%) for data collection. Most of the studies (91.3%) did not report prompting -EMAs by schedule alerts or compliance. Daily diary and within day fixed interval dairies designs are common, with the increasing use of electronic EMA delivery techniques. It is unclear how well participants adhere to assessment schedules, as these are inadequately reported. Researchers should report compliance-related information.

Acute and cumulative effects of scheduling on aircrew fatigue in ultra-short-haul operations

Aircrew fatigue constitutes a safety hazard in aviation, which authorities attempt to mitigate through flight time limitations. Some gaps in knowledge exist, however. The purpose of the present study was to investigate the associations of schedule characteristics with fatigue and amount of sleep in the acute 24-h window, and as cumulative effects across the 7-day work period. One hundred and six aircrew (14% cabin crew) participated. They rated fatigue on the Karolinska Sleepiness Scale (KSS) three times per flight day for four 7-day work periods, with up to 7 days off between work periods. Mixed model regression was applied to the data. In the multivariable model, more sleep was associated with lower fatigue (p = .000)), corresponding to 0.26 KSS units less per hour of sleep. Very early, early and late duty types, as well as duty time, were associated with higher fatigue. For the 7-day work period, accumulation of very early duties and longer duty time were associated with increased fatigue, and more accumulated sleep was associated with lower fatigue in the adjusted model (0.08 KSS units per hour of sleep) (p = .000). Accumulated duty time was not significant when analysed as a single variable, but became so after adjustment for sleep. The results suggest that sleep, duty time and early starts are important predictors of fatigue in the 24-h window and that the number of very early starts and short sleep have cumulative effects on fatigue across a 7-day work period.

Good Sleep Quality and Progressive Increments in Vigilance During Extended Night Shifts: A 14-Day Actigraphic Study in Underground Miners

OBJECTIVE

Assess the change in sleep and vigilance of underground miners during long periods of extended shifts.

METHODS

Seventy miners worked 14 consecutive 12-hour day and/or night shifts. Also, they wore an actigraph and completed a visual analog scale for vigilance four times per shift. Linear regression models with mixed effects were used.

RESULTS

Sleep efficiency was higher during day shifts than during night shifts (86,5 vs 85.5, P < 0.05) but sleep duration did not differ (6:34 vs 6:44, n.s.). Mean vigilance level at Time 3 (02h00) was significantly lower than that at Time 1 (19h00) during the first 10 night shifts whereas mean vigilance level at Time 4 (05h30) remained significantly lower for the 14 night shifts.

CONCLUSIONS

Underground miners exhibit good sleep quality despite evidence of limited circadian adaptation in terms of nighttime vigilance.

Assessment of work-related stress by using salivary cortisol level examination among early morning shift workers

OBJECTIVE

Early morning shifts have a negative effect on the hypothalamic-pituitary-adrenal axis. The aim of this study was to comprehensively assess the extent of occupational stress in early shift workers of the car industry by using salivary cortisol as an objective marker during a workday and on a day off.

METHODS

For this cross-sectional epidemiological type of study, a survey included 55 suitable volunteers from the car industry. Five saliva samples were collected according to the following schedule: during one work day in the morning, during the morning shift from 6 a.m. - 2 p.m., then after the shift was completed, 3 hours after work and in the evening before going to sleep. Control samples were taken from the same participants on a day off. Radioimmunoanalysis was used as the main analytical method, and the effect of factors and between-factor interactions on the levels of salivary cortisol during the workday were assessed using an ANOVA model.

RESULTS

The cortisol diurnal rhythm was as expected, with the highest values in the morning and declining to the lowest values in the evening hours. Concentrations of salivary cortisol showed higher values during the workday, especially higher concentrations of evening cortisol and attenuated cortisol slope. Based on the results, irregular shift work has a greater increase in cortisol excretion after waking in the morning and a slower progressive recovery of the organism during the workday. In addition, cortisol levels were significantly higher in older women than in older men but did not differ in younger subjects.

CONCLUSIONS

Salivary cortisol levels are a suitable objective marker of stress and can be used as a good predictor of occupational stress by public health services for the purposes of primary prevention.

An active transition from offshore work to family life: Activities that may impact recovery

BACKGROUND

Night shift workers, particularly those working offshore, take a long time to recover from their shifts. The activities that shift workers, such as offshore employees, pursue during their leisure time can influence the process of recovery from work-related fatigue, but little is known about these leisure time activities.

OBJECTIVE

To explore what leisure time activities are pursued that may be relevant to recovery for offshore employees.

METHODS

Sixty-one offshore working family men-20 night shift, 16 swing shift, and 25 day shift workers-reported on six predefined activities for 14 days following their offshore tours. Generalized estimating equations analysis was used to explore trends in the data.

RESULTS

From the start of the free period, almost all participants were involved in household chores and childcare; these activities declined over the 14 days. Throughout the study period, participants actively pursued social, volunteer, and leisure time physical activities. Work-related activities were pursued by half of the participants at some time during the 14 days. Night and swing shift workers were more physically active than day workers throughout the first 14 days of the free period.

CONCLUSIONS

The transition from offshore work to family life can be characterised as active. The activities engaged in by this sample of employees are likely to promote their recovery.

The effects of consecutive night shifts and shift length on cognitive performance and sleepiness: a field study

INTRODUCTION

The aim of this study was to evaluate the effects of consecutive night shifts (CNS) and shift length on cognitive performance and sleepiness.

MATERIALS AND METHODS

This study evaluated the sleepiness and performance of 30 control room operators (CROs) working in 7 nights, 7 days, 7 days off (7N7D7O) and 30 CROs working in 4 nights, 7 days, 3 nights, 7 days off (4N7D3N7O) shift patterns in a petrochemical complex on the last night shift before swinging into the day shift. To assess cognitive performance, the n-back test, continuous performance test and simple reaction time test were employed. To assess sleepiness, the Karolinska sleepiness scale was used.

RESULTS

Both schedules indicated that the correct responses and response times of working memory were reduced (p = 0.001), while intentional errors and sleepiness increased during the shift work (p = 0.001). CNS had a significant impact on reaction time and commission errors (p = 0.001).

CONCLUSION

The main duty of CROs at a petrochemical plant is checking hazardous processes which require appropriate alertness and cognitive performance. As a result, planning for appropriate working hours and suitable number of CNS in a rotating shift system is a contribution to improving CRO performance and enhancing safety.

Trajectories of sleepiness and insomnia symptoms in Norwegian nurses with and without night work and rotational work

Numerous cross-sectional studies report high prevalence rates of sleepiness and insomnia in shift workers, but few longitudinal studies exist. We investigated trajectories of sleepiness and insomnia symptoms in a sample of Norwegian nurses across four measurements, spanning a total of four years (sleepiness) and five years (insomnia). The participants completed the Epworth Sleepiness Scale and the Bergen Insomnia Scale at each measurement instance. Latent growth curve models were used to analyse the data. Separate models examined night work (night work, entering and leaving night work) and rotational work (rotational work, entering and leaving rotational work) as predictors for trajectories of sleepiness and insomnia symptoms, respectively. Baseline values of sleepiness and insomnia were higher among rotational shift workers than among workers with fixed shifts (day or night). The results showed that night work throughout the period and entering night work during the period were not associated with different trajectories of sleepiness or insomnia symptoms, compared to not having night work. The same results were found for rotational work and entering rotational work, compared to not having rotational work. Leaving night work and leaving rotational work were associated with a decrease in sleepiness and insomnia symptoms, compared to staying in such work.

Self-Reported Recovery from 2-Week 12-Hour Shift Work Schedules: A 14-Day Follow-Up

Background

Recovery from fatigue is important in maintaining night workers' health. This study compared the course of self-reported recovery after 2-week 12-hour schedules consisting of either night shifts or swing shifts (i.e., 7 night shifts followed by 7 day shifts) to such schedules consisting of only day work.

Methods

Sixty-one male offshore employees—20 night workers, 16 swing shift workers, and 25 day workers—rated six questions on fatigue (sleep quality, feeling rested, physical and mental fatigue, and energy levels; scale 1–11) for 14 days after an offshore tour. After the two night-work schedules, differences on the 1^st day (main effects) and differences during the follow-up (interaction effects) were compared to day work with generalized estimating equations analysis.

Results

After adjustment for confounders, significant main effects were found for sleep quality for night workers (1.41, 95% confidence interval 1.05–1.89) and swing shift workers (1.42, 95% confidence interval 1.03–1.94) when compared to day workers; their interaction terms were not statistically significant. For the remaining fatigue outcomes, no statistically significant main or interaction effects were found.

Conclusion

After 2-week 12-hour night and swing shifts, only the course for sleep quality differed from that of day work. Sleep quality was poorer for night and swing shift workers on the 1^st day off and remained poorer for the 14-day follow-up. This showed that while working at night had no effect on feeling rested, tiredness, and energy levels, it had a relatively long-lasting effect on sleep quality.

Validating and extending the three process model of alertness in airline operations

Sleepiness and fatigue are important risk factors in the transport sector and bio-mathematical sleepiness, sleep and fatigue modeling is increasingly becoming a valuable tool for assessing safety of work schedules and rosters in Fatigue Risk Management Systems (FRMS). The present study sought to validate the inner workings of one such model, Three Process Model (TPM), on aircrews and extend the model with functions to model jetlag and to directly assess the risk of any sleepiness level in any shift schedule or roster with and without knowledge of sleep timings. We collected sleep and sleepiness data from 136 aircrews in a real life situation by means of an application running on a handheld touch screen computer device (iPhone, iPod or iPad) and used the TPM to predict sleepiness with varying level of complexity of model equations and data. The results based on multilevel linear and non-linear mixed effects models showed that the TPM predictions correlated with observed ratings of sleepiness, but explorative analyses suggest that the default model can be improved and reduced to include only two-processes (S+C), with adjusted phases of the circadian process based on a single question of circadian type. We also extended the model with a function to model jetlag acclimatization and with estimates of individual differences including reference limits accounting for 50%, 75% and 90% of the population as well as functions for predicting the probability of any level of sleepiness for ecological assessment of absolute and relative risk of sleepiness in shift systems for safety applications.

The influence of break timing on the sleep quantity and quality of fly-in, fly-out shiftworkers

Although shift and break timing is known to affect the sleep of shiftworkers, this has not been demonstrated in Fly-in, Fly-out (FIFO) settings which, compared to residential based settings, may be favourable for sleep. This study investigated the sleep quantity and quality of shiftworkers working a FIFO operation comprising of shifts, and therefore breaks, across the 24-h day. The sleep of 24 males (50.43 ± 8.57 yr) was measured using actigraphy and sleep diaries. Morning breaks were associated with less sleep (09:00-12:00 h; 4.4 ± 1.3 h) and a poorer sleep quality (06:00-09:00 h; 3.1 ± 1.0, "average") compared to breaks beginning between 00:00 h and 03:00 h (6.8 ± 1.7 h; 2.2 ± 0.9, "good"). Sleep efficiency remained constant regardless of break timing (85.9 ± 5.0% to 89.9 ± 3.5%). Results indicate that even in operations such as FIFO where sleeping conditions are near-optimal and the break duration is held constant, the influence of the endogenous circadian pacemaker on sleep duration is evident.

Insomnia, excessive sleepiness, excessive fatigue, anxiety, depression and shift work disorder in nurses having less than 11 hours in-between shifts

Study objective

To assess if less than 11 hours off work between work shifts (quick returns) was related to insomnia, sleepiness, fatigue, anxiety, depression and shift work disorder among nurses.

Methods

A questionnaire including established instruments measuring insomnia (Bergen Insomnia Scale), sleepiness (Epworth Sleepiness Scale), fatigue (Fatigue Questionnaire), anxiety/depression (Hospital Anxiety and Depression Scale) and shift work disorder was administered. Among the 1990 Norwegian nurses who participated in the study; 264 nurses had no quick returns, 724 had 1–30 quick returns and 892 had more than 30 quick returns during the past year. 110 nurses did not report the number of quick returns during the past year. The prevalence of insomnia, excessive sleepiness, excessive fatigue, anxiety, depression and shift work disorder was calculated within the three groups of nurses. Crude and adjusted logistic regression analyses were performed to assess the relation between quick returns and such complaints.

Results

We found a significant positive association between quick returns and insomnia, excessive sleepiness, excessive fatigue and shift work disorder. Anxiety and depression were not related to working quick returns.

Conclusions

There is a health hazard associated with quick returns. Further research should aim to investigate if workplace strategies aimed at reducing the number of quick returns may reduce complaints among workers.

Effects of shift and night work in the offshore petroleum industry: a systematic review

Shift and night work are associated with several negative outcomes. The aim of this study was to make a systematic review of all studies which examine effects of shift and night work in the offshore petroleum industry, to synthesize the knowledge of how shift work offshore may affect the workers. Searches for studies concerning effects on health, sleep, adaptation, safety, working conditions, family- and social life and turnover were conducted via the databases Web of Knowledge, PsycINFO and PubMed. Search was also conducted through inspection of reference lists of relevant literature. We identified studies describing effects of shift work in terms of sleep, adaptation and re-adaptation of circadian rhythms, health outcomes, safety and accidents, family and social life, and work perceptions. Twenty-nine studies were included. In conclusion, the longitudinal studies were generally consistent in showing that adaptation to night work was complete within one to two weeks of work, while re-adaptation to a daytime schedule was slower. Shift workers reported more sleep problems than day workers. The data regarding mental and physical health, family and social life, and accidents yielded inconsistent results, and were insufficient as a base for drawing general conclusions. More research in the field is warranted.

The association between shift work and sick leave: a systematic review

Shift work is associated with a number of negative health outcomes, although it is not known whether it is associated with sick leave. This systematic review therefore aimed to determine whether an association exists between shift work and sick leave. A systematic literature search was conducted in six databases on observational studies. Two reviewers independently selected relevant articles and appraised methodological quality. Data extraction was performed independently by review couples. Articles were categorised according to shift work characteristics and summarised using a levels of evidence synthesis. In total, the search strategy yielded 1207 references, of which 24 studies met the inclusion criteria. Nine studies were appraised as high quality and used in the levels of evidence synthesis. Two high quality longitudinal studies found a positive association between fixed evening shifts and longer sick leave for female healthcare workers. The evidence was assessed as strong. Evidence was inconclusive for rotating shifts, shift work including nights, for fixed night work, and for 8-hour and 12-hour shifts. The association found between evening work and sick leave in female healthcare workers implies that the association between shift work and sick leave might be schedule and population specific. To study the association further, more high quality studies are necessary that assess and adjust for detailed shift work exposure.

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.

The efficacy of a restart break for recycling with optimal performance depends critically on circadian timing

OBJECTIVES

Under simulated shift-work conditions, we investigated the efficacy of a restart break for maintaining neurobehavioral functioning across consecutive duty cycles, as a function of the circadian timing of the duty periods.

DESIGN

As part of a 14-day experiment, subjects underwent two cycles of five simulated daytime or nighttime duty days, separated by a 34-hour restart break. Cognitive functioning and high-fidelity driving simulator performance were tested 4 times per day during the two duty cycles. Lapses on a psychomotor vigilance test (PVT) served as the primary outcome variable. Selected sleep periods were recorded polysomnographically.

SETTING

The experiment was conducted under standardized, controlled laboratory conditions with continuous monitoring.

PARTICIPANTS

Twenty-seven healthy adults (13 men, 14 women; aged 22-39 years) participated in the study.

INTERVENTIONS

Subjects were randomly assigned to a nighttime duty (experimental) condition or a daytime duty (control) condition. The efficacy of the 34-hour restart break for maintaining neurobehavioral functioning from the pre-restart duty cycle to the post-restart duty cycle was compared between these two conditions.

RESULTS

Relative to the daytime duty condition, the nighttime duty condition was associated with reduced amounts of sleep, whereas sleep latencies were shortened and slow-wave sleep appeared to be conserved. Neurobehavioral performance measures ranging from lapses of attention on the PVT to calculated fuel consumption on the driving simulators remained optimal across time of day in the daytime duty schedule, but degraded across time of night in the nighttime duty schedule. The 34-hour restart break was efficacious for maintaining PVT performance and other objective neurobehavioral functioning profiles from one duty cycle to the next in the daytime duty condition, but not in the nighttime duty condition. Subjective sleepiness did not reliably track objective neurobehavioral deficits.

CONCLUSIONS

The 34-hour restart break was adequate for maintaining performance in the case of optimal circadian placement of sleep and duty periods (control condition) but was inadequate (and perhaps even detrimental) for maintaining performance in a simulated nighttime duty schedule (experimental condition). Current US transportation hours-of-service regulations mandate time off duty but do not consider the circadian aspects of shift scheduling. Reinforcing a recent trend of applying sleep science to inform policymaking for duty and rest times, our findings indicate that restart provisions in hours-of-service regulations could be improved by taking the circadian timing of the duty schedules into account.

Cortisol, reaction time test and health among offshore shift workers

OBJECTIVE

The stress hormone cortisol shows a pronounced endogenous diurnal rhythm, which is affected by the sleep/wake cycle, meals and activity. Shift work and especially night work disrupts the sleep/wake cycle and causes a desynchronization of the natural biological rhythms. Therefore, different shift schedules may have different impact on performance at work and health.

AIM

The purpose was to study if health, reaction time, and the cortisol rhythm were negatively affected when a group of shift workers changed their work schedule from ordinary day-night shift (fixed shift) to "swing shift".

METHODS AND SETTINGS

19 healthy workers on a Norwegian oil rig participated in the study. They worked 2 weeks offshore followed by 4 weeks off work. The ordinary schedule consisted of 12-h day shift and 12-h night shift every other work period (14 days or nights=fixed shift). "Swing shift" involved 1 week of night shift, followed by 1 week of day shift during the work period. All participants worked ordinary day-night shift when baseline data were collected (questionnaires, saliva cortisol, and reaction time during work). After collection of baseline data the workers changed their work schedule to "swing shift", for every working period, and 9 months later the same data were collected.

RESULTS

"Swing shift" did not give any negative health effects or any negative changes in reaction time during the day they shifted from night work to day work. Personnel adapted to night shift within a week regardless of schedule, but recovery from night shift took longer time. During swing shift the cortisol rhythm went back towards a normal rhythm in the second week, but it was not returned completely to normal values when they returned home for the 4 weeks off period. However, the cortisol rhythms were readapted to normal values after 1 week at home. For personnel returning home directly from 14 consecutive night shifts, cortisol adaptation was not complete after 1 week at home.

CONCLUSION

We found no increase in health complaints from swing shift or reaction time in the shift from night to day work. Recovery from night shift takes longer time.

The effects of different roster schedules on sleep in miners

Shiftwork involving early morning starts and night work can affect both sleep and fatigue. This study aimed to assess the impact of different rostering schedules at an Australian mine site on sleep and subjective sleep quality. Participants worked one of four rosters; 4 x 4 (n = 14) 4D4O4N4O 7 x 4 (n = 10) 7D4O7N40 10 x 5 (n = 17) 5D5N50 14 x 7 (n = 12) 7D7N70. Sleep (wrist actigraphy and sleep diaries) was monitored for a full roster cycle including days off. Total sleep time (TST) was longer on days off (7.0 +/- 1.9) compared to sleep when on day (6.0 +/- 1.0) and nightshifts (6.2 +/- 1.6). Despite an increase in TST on days off, this may be insufficient to recover from the severe sleep restriction occurring during work times. Restricted sleep and quick shift-change periods may lead to long-term sleep loss and associated fatigue.

Adaptation rate of 6-sulfatoxymelatonin and cognitive performance in offshore fleet shift workers: a field study

PURPOSE

To determine the total phase delay and adaptation rate of 6-sulfatoxymelatonin (aMT6s) on subjective and objective sleep quality and cognitive performance after 7 days of working night shifts (1800-0600 hours). The subjects studied were offshore fleet workers (N = 7).

METHODS

Seven days of urine samples were collected to determine the total phase delay and adaptation rate of aMT6s. Subjective and objective sleep quality was registered with sleep diaries and actigraphy on a daily basis. Cognitive performance, as measured by vigilance and reaction time, was measured with the Vienna test system on days 1 and 7. Light exposure was measured in the vessel compartments daily.

RESULTS

The rhythm of aMT6s shifted significantly from 4.78 +/- 0.94 h on day 1 to 8.84 +/- 1.76 h on day 7. Rate of adaptation was 0.84 h per day. Subjective sleep quality showed significant time effects on four variables, but objective sleep quality did not show any significant time effects. Vigilance and reaction time improved significantly from days 1 to 7. Light exposure intensities varied between 3 and 243 lux.

CONCLUSIONS

This field study showed that offshore fleet workers are able to adapt to the imposed regimen of 12-h night shifts. The adaptation is slower compared to other branches of the offshore industry, which most likely is due to lower light exposure. Subjective sleep quality improved to some extent, but the results were not conclusive. No significant effects were observed in the objective measures. Cognitive performance improved significantly, which was likely to be caused by the extended working hours on day 1 and an entrainment of the suprachiasmatic nuclei (SCN).

Subjective and objective sleep and sleepiness among tunnel workers in an extreme and isolated environment: 10-h shifts, 21-day working period, at 78 degrees north

OBJECTIVES

The aim of this study was to examine the effects of extended work hours (10 h on, 14 h off for 21 days) on sleep and sleepiness in an extreme and isolated environment in the far north (Spitsbergen, 78 degrees north). We wanted to examine whether sleep duration, sleepiness and other parameters changed over the 3-week working period and whether the parameters differed between day and night shifts.

METHODS

The work consisted of tunnel construction in Svea, Spitsbergen. The participants worked alternate fixed day shift (06:00-16:00) or fixed night shift (18:00-04:00) for a 21-day work period in a counterbalanced, crossover design. The participants were 25 male workers (age 24-60 years). We used subjective and objective measures of sleep (diary and actigraphy) and a subjective daytime sleepiness and function questionnaire.

RESULTS

The workers had a high sleep efficiency measured both subjectively and objectively. This did not change across days or between day and night shifts. Total sleep time was significantly shorter (about (1/2) to 1h) during the day shift period than during the night shift period, as measured both subjectively and objectively, but did not differ across days. Subjective ratings of sleepiness did not differ between shifts.

CONCLUSIONS

There were few differences between the day and night shift periods and across the 21-day working period, as measured both subjectively and objectively. The subjects experienced few problems and seemed to adapt easily to their work schedule. This contrasts with what is usually the case in more conventional shift work situations, where workers do not adapt well, as measured by sleepiness and various sleep parameters.

Sleep Parameters among Offshore Workers: An Initial Assessment in the Campos Basin, Rio De Janeiro, Brazil

Shift work has potentially adverse effects on health, particularly on sleep. The purpose of the present study was to assess sleep parameters among personnel working in oil and gas offshore installations in the Campos Basin, Rio de Janeiro, Brazil. One hundred and seventy-nine subjects were asked to complete a sleep questionnaire with multiple-choice answers. Offshore workers were divided into two groups according to their work schedule: (1) fixed daytime workers (n = 86; age: 35.8+/-9.6 yrs) and (2) shift (n = 87) or night (n = 6) workers (total n = 93; age: 37.7+/-9.7 yrs). Shift/night workers reported poor sleep more frequently than the daytime workers (20.4% vs. 1.2%, p < 0.01), as well as habitual difficulty in falling asleep (15.1% vs. 4.7%, p<0.01), long latency of sleep onset (28% vs. 7%, p<0.01), fragmented sleep (45.2% vs. 16.3%, p<0.01), short sleep episodes (44.1% vs. 16.3%, p < 0.01), irregular bedtimes (29.0% vs. 12.8%, p < 0.01), and feeling tired upon awakening (15.1% vs. 3.5%, p < 0.01). Habitual napping and loud snoring were reported twice as often in shift/night than in day workers (p < 0.01). Nightmares, somnambulism, and unpleasant feeling in the legs were equality reported by both groups (p > 0.05). Few offshore workers had sought medical help for their sleep problems. A higher number of shift/night workers reported feelings of sadness compared with day workers (26.9% vs. 9.3%, p < 0.01). The findings of this study show that subjective reports of sleep-related problems are quite common among Brazilian offshore shift workers. Reliance on self-reported sleep problems and a cross-sectional design are the main limitations of our study.

Sleep Loss and Fatigue in Shift Work and Shift Work Disorder

Shift work is highly prevalent in industrialized societies (>20%) but, when it includes night work, it has pronounced negative effects on sleep, subjective and physiological sleepiness, performance, accident risk, as well as on health outcomes such as cardiovascular disease and certain forms of cancer. The reason is the conflict between the day oriented circadian physiology and the requirement for work and sleep at the "wrong" biological time of day. Other factors that negatively impact work shift sleepiness and accident risk include long duration shifts greater than 12 hours and individual vulnerability for phase intolerance that may lead to a diagnosis of shift work disorder; i.e., those shift workers with the greatest sleepiness and performance impairment during the biological night and insomnia during the biological day. Whereas some countermeasures may be used to ameliorate the negative impact of shift work on nighttime sleepiness and daytime insomnia (combined countermeasures may be the best available), there seems at present to be no way to eliminate most of the negative effects of shift work on human physiology and cognition.

Direct and interactive effects of occupational stress and coping on ulcer-like symptoms among Chinese male off-shore oil workers

BACKGROUND

Off-shore oil production is widely regarded as a stressful occupation and digestive system problems were commonly observed in off-shore oil workers. Is occupational stress from off-shore oil work associated with the occurrence of digestive problems among off-shore oil workers? And are coping styles also related to their occurrence? The aim of this study was to explore the direct and interactive association of occupational stress and coping styles with ulcer-like symptoms in Chinese male off-shore oil workers.

METHODS

A cross-sectional survey was conducted among 561 Chinese male off-shore oil workers. They were invited to fill in a self-administered questionnaire exploring their socio-demographic characteristics, occupational stress, coping style, and ulcer-like symptoms. A stepwise multiple regression procedure was used to assess the direct and interactive effects of occupational stress and coping behaviors on ulcer-like symptoms.

RESULTS

After controlling for age, educational level, marital status and years of off-shore working, the ulcer-like symptoms were significantly positively associated with occupational stress and "internal behavior" coping methods, negatively associated with external/social behavior coping methods, and positively associated with the interaction between occupational stress and internal behavior coping.

CONCLUSION

The results of the present study suggest that occupational stress was associated with gastric health problems and that this association might be moderated by certain coping behaviors.

A systematic review of patient-reported outcome instruments measuring sleep dysfunction in adults

Sleep dysfunction can manifest in several ways, ranging from insomnia to somnolence, and from disrupted sleep to lack of restful sleep. Measuring sleep dysfunction is an area of active research and there exist a number of patient-reported outcome instruments that measure various aspects of sleep dysfunction. However, these instruments have not been evaluated systematically. We used a conceptual model of sleep that included four physical domains of general interest to patients and investigators, and cover the breadth of this disorder: sleep initiation; sleep maintenance; sleep adequacy; and somnolence. We next considered the additional health-related quality-of-life (HR-QOL) domains of psychological and social functioning, progressing along the continuum to include health perceptions and opportunity. We then conducted a literature review to identify instruments and, using criteria developed by the Medical Outcomes Trust Scientific Advisory Committee, evaluated these instruments for their potential use in measuring sleep dysfunction. Twenty-two instruments were identified. Six instruments were found to include the four physical domains defined a priori (Basic Nordic Sleep Questionnaire, Leeds Sleep Evaluation Questionnaire, Medical Outcomes Study - Sleep Problems Measures, Pittsburgh Sleep Diary, Pittsburgh Sleep Quality Index, Self-Rated Sleep Questionnaire and the Sleep Dissatisfaction Questionnaire). Several additional instruments addressed at least some of the domains and thus may be useful for specific purposes. A few instruments addressed overall HR-QOL, but did not include all four domains of interest (Functional Outcomes of Sleep Questionnaire, Quality of Life in Insomniacs and the Sleep-Wake Activity Inventory). Two instruments had undergone extensive psychometric evaluation (Medical Outcomes Study - Sleep Problems Measures and Pittsburgh Sleep Quality Index), with only the latter reporting information about interpretability. Our review indicates that measuring sleep dysfunction in adults is an area of active research and that much work still needs to be completed, specifically the study of interpretability and the application of patient preferences or item response theory. The specific research focus should dictate instrument selection.

Light treatment and circadian adaptation to shift work

Work at unconventional hours can have both long and short term consequences. Shift workers are often required to perform their duties at times that are not favoured by the body's endogenous clock, or circadian pacemaker. A typical night shift worker, for example, may report reductions in alertness and performance during shifts, or significant difficulty attaining sleep of recuperative value in the day, all the while being more likely to develop health complications. The study of circadian physiology has significantly contributed to our current ability to aid the shift worker deal with atypical schedules. We discuss the usefulness of light treatment as a countermeasure for maladaptation to atypical work schedules.

Shiftwork and environment as interactive predictors of work perceptions

Evidence suggests that the work environment may play a role in the elevated risk of adverse health outcomes among shiftworkers compared with dayworkers. Perceived work environment measures (physical stressors, job demand, job control, skill discretion, supervisor support, and safety perceptions) from UK oil industry personnel (N=1,867) were analyzed in relation to shiftwork (day/night rotation vs daywork) and objective work environment (onshore vs offshore). Age, education, job type, and negative affectivity were also included. The Environment * Shiftwork interaction was significant in multivariate tests and in 5 of the 6 univariate analyses. Onshore, shiftworkers perceived their environment significantly less favorably than dayworkers, but differences were less marked offshore. Results are discussed in relation to the demand-control-support model of work stress.

Methamphetamine attenuates disruptions in performance and mood during simulated night-shift work

RATIONALE

Increased sleepiness while working and sleep disruptions are common complaints among shift workers. Consequently, shift workers may be more susceptible to diminished performance and work-related accidents.

OBJECTIVE

To examine the effects of the central nervous system stimulant methamphetamine on psychomotor task performance, subjective effects, and food intake during shift work under laboratory conditions.

METHODS

Seven participants completed this 23-day, within-participant design, residential laboratory study. They received a single oral methamphetamine dose (0, 5, 10 mg) 1 h after waking for three consecutive days under two shift conditions: (1) during the day shift, participants performed computerized psychomotor tasks from 0830 hours to 1730 hours and went to bed at 2400 hours and (2) during the night shift, participants performed tasks from 0030 hours to 0930 hours and went to bed at 1600 hours. Shifts alternated three times during the study; shift conditions were separated by an "off" day during which participants were not on a schedule and data were not collected.

RESULTS

When participants received placebo, psychomotor task performance and subjective effects were disrupted during the night shift, relative to the day shift. Changing shift conditions did not alter food intake significantly. Methamphetamine reversed performance and subjective-effects disruptions, and decreased food intake during the night shift.

CONCLUSION

These data indicate that shift changes produce performance impairments and mood alterations, and that a single low to moderate dose of methamphetamine attenuates many shift change-related disruptions in performance and mood.

Circadian adaptation to night-shift work by judicious light and darkness exposure

In this combined field and laboratory investigation, the authors tested the efficacy of an intervention designed to promote circadian adaptation to night-shift work. Fifteen nurses working permanent night schedules (> or = 8 shifts/ 15 days) were recruited from area hospitals. Following avacation period of > or = 10 days on a regular daytime schedule, workers were admitted to the laboratory for the assessment of circadian phase via a 36-h constant routine. They returned to work approximately 12 night shifts on their regular schedules under one of two conditions. Treatment group workers (n = 10, mean age +/- SD = 41.7 +/- 8.8 years) received an intervention including 6 h of intermittent bright-light exposure in the workplace (approximately 3,243 lux) and shielding from bright morning outdoor light with tinted goggles (15% visual light transmission). Control group workers (n = 9, mean age +/- SD = 42.0 +/- 7.2 years) were observed in their habitual work environments. On work days, participants maintained regular sleep/wake schedules including a single 8-h sleep/darkness episode beginning 2 h after the end of the night shift. A second 36-h constant routine was performed following the series of night shifts. In the presence of the intervention, circadian rhythms of core body temperature and salivary melatonin cycles were delayed by an average (+/- SEM) of -9.32 +/- 1.06 h and -11.31 +/- 1.13 h, respectively. These were significantly greater than the phase delays of -4.09 +/- 1.94 h and -5.08 +/- 2.32 h displayed by the control group (p = 0.03 and p = 0.02, respectively). The phase angle between circadian markers and the shifted schedule was reestablished to its baseline position only in the treatment group of workers. These results support the efficacy of a practical intervention for promoting circadian adaptation to night-shift work under field conditions. They also underline the importance of controlling the overall pattern of exposure to light and darkness in circadian adaptation to shifted sleep/wake schedules.

Age, smoking, and negative affectivity as predictors of sleep patterns among shiftworkers in two environments

Although adaptation to shiftwork has been widely studied, little is known about how individual and environmental factors combine to influence sleep among shiftworkers. This study examined age, smoking, and negative affectivity (NA) as predictors of sleep duration and quality for 3 work phases (day shifts, DS; night shifts, NS; and leave periods, LP). Data were collected from personnel working 12-hr shifts, onshore (n = 330) or offshore (n = 456). Individual factors predicted patterns of sleep measures across the DS, NS, and LP phases onshore, but not offshore; onshore, work phase interacted with smoking and with age to predict sleep duration and with NA to predict sleep quality. The role of the offshore environment in shiftwork adaptation is discussed.

Adaptation to night shifts and synchronisation processes of night workers

Human beings are accustomed to being active and awake during the day, and asleep and rest at night. Since we live in a society which is organised predominantly along daytime activity, therefore working in the night shift may deeply disrupt our social and family life. It is also a well-known fact that night shift causes fatigue and circadian disruption. The basic manifestation of fatigue and circadian rhythm has been linked to health and safety problems, involving decrements in psychophysical and physiological functions, plus subjective complaints. In this context quantitative relationships between shift work and circadian rhythm need to be assessed to explore suitable time schedule, and to minimise sleep depth and fatigue. There is also a great need to discuss circadian disruption, sleepiness and the increasing cost of work related illness among night workers. In this regard, some aspects of fatigue and circadian disruption caused from night shift work are revealed in this paper aiming to increase workers' health, safety and well being as well as productivity. Light/dark cycle and social stimuli issues acting on the circadian timing systems are also explored to solicit opinions and discussion on the controversy of night work. Suggestions are therefore likewise given to enhance workers' adaptation to night shift and synchronization process.

Bright light treatment used for adaptation to night work and re-adaptation back to day life. A field study at an oil platform in the North Sea

Night workers complain of sleepiness, reduced performance and disturbed sleep due to lack of adjustment of the circadian rhythm. In simulated night-work experiments scheduled exposure to bright light has been shown to reduce these complaints. Here we studied the effects of bright light treatment on the adaptation to 14 days of consecutive night work at an oil platform in the North Sea, and the subsequent readaptation to day life at home, using the Karolinska sleep/wake diary. Bright light treatment of 30 min per exposure was applied during the first 4 nights of the night-shift period and the first 4 days at home following the shift period. The bright light exposure was scheduled individually to phase delay the circadian rhythm. Bright light treatment modestly facilitated the subjective adaptation to night work, but the positive effect of bright light was especially pronounced during the re-adaptation back to day life following the return home. Sleepiness was reduced and the quality of day was rated better after exposure to bright light. The modest effect of bright light at the platform was, possibly, related to the finding that the workers seemed to adapt to night work within a few days even without bright light. These results suggest that short-term bright light treatment may help the adaptation to an extended night-work period, and especially the subsequent re-adaptation to day life.