The acute effects of working time patterns on fatigue and sleep quality using daily measurements of 6195 observations among 223 shift workers

Objectives:This study aimed to estimate acute effects of roster characteristics on fatigue and sleep quality and investigated whether these effects differed by individual characteristics.Methods:Using an ecological measurement assessment survey, fatigue and sleep quality were daily measured among 223 shift workers for up to eight weeks. A questionnaire assessed baseline characteristics, and roster data were retrieved from the company registers to determine roster parameters. The effects between each shift parameter on fatigue and sleep quality were estimated with random- and fixed-effects models.Results:Compared to day shifts, night shifts were related to fatigue [β=0.22; 95% confidence interval (CI) 0.05–0.39] and poorer sleep quality (β =0.64; 95% CI 0.47–0.80), and more successive night shifts with more fatigue (up to β=0.68; 95% CI 0.49–0.87 for ≥2 nights). Fatigue was increased after a quick return (<11 hours) (β=1.94; 95% CI 1.57–2.31) or 11–16 hours (β=0.43; 95% CI 0.26–0.61) compared to >16 hours between shifts. Compared to forward rotation, stable (β=0.22; 95% CI 0.01–0.43) and backward rotation (β=0.49; 95% CI 0.23–0.74) were also associated with more fatigue. Workers with a morning or intermediate chronotype had poorer sleep quality after a night shift, while workers with poor health reported poor sleep quality as well as more fatigue after a night shift.Conclusions:To alleviate acute effects of shift work on fatigue, shift schedules should be optimized by ensuring more time to recover and rotate forwards.     

Distribution of rest days in 12 hour shift systems: impacts on health, wellbeing, and on shift alertness

OBJECTIVES: To investigate of the effects of distribution of rest days in 12 hour shift systems. Although several studies have examined the effects of compressing work schedules by comparing 8 and 12 hour shift systems, there is little published research examining the various forms of 12 hour shift system. METHODS: An abridged version of the standard shiftwork index which included retrospective alertness ratings was completed by a large sample of industrial shiftworkers. The respondents worked 12 hour shift systems that either did or did not incorporate breaks of > 24 hours between the blocks of day and night shifts. For the purposes of the analysis, each of these two groups were further subdivided into those who started their morning shift at 0600 and those who started at 0700. RESULTS: Systems which incorporated rest days between the day and night shifts were associated with slightly higher levels of on shift alertness, slightly lower levels of chronic fatigue, along with longer sleep durations when working night shifts and between rest days. Early changeovers were associated with shorter night sleeps between successive day shifts, but longer and less disturbed day sleeps between night shifts. These effects of changeover time were broadly in agreement with previous research findings. CONCLUSIONS: The distribution of rest days in 12 hour shift systems had only limited effects on the outcome measures, although the few modest differences that were found favoured systems which incorporated rest days between the day and night shifts. It is conceded that the design of the study may have obscured some subtle differences between the shift systems. Nevertheless, it is concluded that the impact of distribution of rest days seems to be minor relative to previously found effects of other features of shift systems--for example, shift duration.

 

     

Randomized placebo-controlled field study of the effects of bright light and melatonin in adaptation to night work

OBJECTIVES: This study evaluated the effects of bright light and melatonin on adaptation to night work on an oil rig in the North Sea. METHODS: Seventeen persons working a schedule of 2 weeks on a 12-hour shift, with the first week on night shift and the second week on day shift (ie, the swing shift schedule) participated. In a randomized controlled crossover design, the shift workers received a placebo, melatonin (3 mg, 1 hour before bedtime), or bright light (30-minute exposure, individually scheduled) during the first 4 days on the night shift and during the first 4 days on the day shift. Subjective and objective measures of sleepiness (Karolinska Sleepiness Scale and a simple serial reaction-time test) and sleep (diary and actigraphy) were recorded. RESULTS: Subjective measures indicated that melatonin modestly reduced sleepiness at work during the day shift and increased sleep by 15-20 minutes per day. Bright light gave values in between those of melatonin and the placebo, but with few significant results. According to the objective measures, bright light improved sleep to a minor degree during the night shift. Hardly any side-effects were reported. CONCLUSIONS: Melatonin and bright light modestly improved sleep and sleepiness in this field study. In well-controlled simulated nightwork studies, both melatonin and bright light are more effective in alleviating sleepiness and sleep problems. The less effect in this field study may be due to competing or conflicting factors present in real life or to an inoptimal timing and duration of the treatments.     

The effect of shift rotation on variations of cortisol, fatigue and sleep in sound engineers

The aim was to study the effect of rotation direction on the time-of-day variations of cortisol, fatigue and sleep in sound engineers broadcasting in a life show. The salivary cortisol and ratings of stress, sleepiness and fatigue were followed at three hour intervals in 25 sound engineers: 13 working very fast forward-rotating shifts and 12 working very fast backward-rotating shifts. Cortisol was assessed with radioimmunological kits. The participants reported for stress symptoms and filled sleep diary. Cortisol retained the typical diurnal pattern. The rotation direction interacted with the shift significantly and as a result higher cortisol values during the morning and night shifts in the backward rotating group were found as well as worse quality of sleep. Higher salivary cortisol during morning and night shifts and worse quality of sleep in engineers working very fast backward-rotating shifts may be an indication for insufficient recovery.     

Sleepiness in various shift combinations of irregular shift systems

The present study examined the occurrence of sleepiness in various shift combinations ending with a night or morning shift. Three weeks' sleep/work shift diary data, collected from 126 randomly selected train drivers and 104 traffic controllers, were used in statistical analyses. The occurrence of sleepiness at work (i.e., Karolinska Sleepiness Scale 7 or higher) was tested with a generalised linear model with repeated measurements including explanatory factors related to shifts, sleep, and individual characteristics. The prevalence of severe sleepiness varied between 25% and 62% in the combinations ending with a night shift and between 12% and 27% in the combinations ending with a morning shift. The occurrence of sleepiness did not, however, systematically vary between the shift combinations in either case. An increased risk for sleepiness was associated with high sleep need and long shift duration in the night shift and with high sleep need, short main sleep period, long shift duration and an early shift starting time in the morning shift. Also having a child was associated with an increased risk for sleepiness in the night shift. The results suggest that the shift history of 24-36 h prior to the night and the morning shift is not strongly associated with the occurrence of sleepiness at work, but there are other factors, such as shift length and starting time and sleep need, that affect a risk for sleepiness at work.     

Shift work-related problems in 16-h night shift nurses (2): Effects on subjective symptoms, physical activity, heart rate, and sleep.

We compared the shift work-related problems between 16-h night shift and 8-h evening/night shifts among nurses in a university hospital with respect to subjective symptoms, physical activity, heart rate (HR), and sleep. The nurses of one group (n = 20) worked a 16-h night shift under a rotating two-shift system, while those of the other group (n = 20) worked an 8-h evening or night shift under a rotating three-shift system. The 16-h night shift was staffed by three or four nurses who alternately took a 2-h nap during the shift, and had at least one day off after each shift. Subjective symptoms and daily behavior were measured every 30 min by the nurses before, during, after each shift as well as during days off using a time-budget method. Also, physical activity, heart rate (HR), and posture were recorded during shifts. The results showed similar or lower levels of sleepiness, difficulty in concentration, fatigue, physical activity, and HR during the 16-h shift compared to the 8-h shifts. No differences in subjective symptoms between the two shift schedules were observed before or after the shifts or during days off. The main sleep was longer after the shifts and during days off in the 16-h shift group than in the 8-h shift group. Our results suggest that the work-related problems in 16-h night shift nurses may not be excessively greater than those in 8-h evening/night shift nurses, as long as appropriate countermeasures are taken during and after the extended shift.     

Variations of cortisol, fatigue and sleep disturbances in sound engineers: effect of job task and fast backward-rotating shifts

The aim was to study the effect of job task and fast backward-rotating shifts on the time-of-day variations of cortisol, fatigue, and sleep disturbances in broadcasting sound engineers. The concentration of saliva cortisol and ratings of stress, sleepiness, and fatigue were followed at 3-hour intervals during the fast backward-rotating shifts in 26 sound engineers: 14 subjects from control rooms, aged 45.1 +/- 7.3 years, and 12 subjects working in direct transmissions, aged 51.7 +/- 6.0 years. Saliva cortisol was assessed using an radioimmunology kit. The participants reported for stress symptoms after the shifts and filled a sleep diary. The effects of job task, shift, and time-of-day were analyzed by tests of between-subjects effects (SPSS). Cortisol retained the typical diurnal pattern with a highly significant effect of the shift. The job task and the shift interacted significantly. Higher cortisol values during the morning and night shifts in engineers working in direct transmissions were found. Their stress ratings were also higher, as well as the ratings of sleepiness and fatigue. The quality of sleep was worse in engineers working in direct transmissions. In conclusion, our data indicate that stress and fast backward-rotating shifts in sound engineers working in direct transmissions affect physiological stress markers such as cortisol and increase sleepiness, fatigue, and sleep problems.     

A study of weekly and rapidly rotating shiftworkers

Summary Diary sleep and oral body temperature data are presented for two groups of experienced rotating shiftworkers (2 or 3, and 5 successive night shifts).The data analysis shows for both rotas: a flattened temperature curve on night shift; sleep loss on both morning and night shift; few breaks in sleep for either day or night sleeps, with no significant increase for day sleeps; a marked tendency for no-day sleep to be taken prior to the first night shift; and a shorter latency to sleep onset for day sleep.The night shift body temperature curves and diary sleep data are related to earlier studies. They are interpreted as reflecting partial—not chronic—sleep loss, and an ongoing normal circadian rhythmicity.No particular number of consecutive night shifts is recommended. Rather it is suggested that shift rota selection should be based on an assessment of how the rota will facilitate an acceptable balance between useful free time and sleep duration for individual work groups.     

Duration of sleep depending on the type of shift work

Summary Time budget studies were performed in eight groups of shift workers. The 9,480 diary records of altogether 1,230 shift workers were analyzed and related to corresponding shift types. The shortest night sleep was found before the morning shift (mean 7.0 h). There were large differences in the duration of day sleep when classifying this sleep into specific types, as day sleep before 1st night shift (mean 2.1 h), between two night shifts (mean 6.1 h), or after last night shift (mean 4.2 h). Average sleep durations of five kinds of day sleep and 12 kinds of night sleep are presented together with 14 frequency distributions of durations of sleep.It is concluded that there should not be many night shifts in succession and that morning shifts should not begin too early to avoid an accumulation of sleep deficits.Dedicated to Dr. H. Loskant on the occasion of his 65th birthday     

The fitness for shift work of operators working according to schedules with a rapid shift rotation]

Integral parameter of professional capacity for work in day and night shifts were studied in 52 operators of heat electric power stations and compared with the results of sociopsychologic questioning. 19% of the operators having higher work capacity in the night shift than in the day one (according to integral parameter) were characterized by lower anxiety, better mood and sleep, and lesser fatigue during the night shift than 19% of examinees, whose night working capacity was lower in comparison with the day shift. The rest 62% of the operators showed a stable level of capacity for work during day and night shifts, their position according to the sociopsychologic parameters is intermediate.     

The effects of the number of consecutive night shifts on sleep duration and quality

Objectives:The organization of night shift work affects sleep duration and quality. The aim of this study was to investigate the effects of the number of consecutive night shifts on sleep duration and quality among police officers with night shift work as part of their normal schedule.Methods:This quasi-experimental, within-subject crossover study included 73 police officers. All participants performed three work schedules: two, four and seven consecutive night shifts followed by the same number of recovery days, ie, day work or days off (2+2, 4+4, and 7+7). Sleep assessed through sleep diaries and actigraphy after all night shifts and recovery days (totaling 26 days) was compared by use of repeated measures analysis.Results:Participants experienced shorter sleep duration (with and without naps), more premature awakening, less difficulty falling asleep, and more non-refreshing sleep after night shifts compared with recovery days. Sleep duration and quality did not change with increasing number of consecutive night shifts. Sleep was shorter and of poorer quality after the last night shift in the 2+2 and 4+4 work schedule compared with the second and fourth night shift, respectively, in the 7+7 schedule.Conclusion:Sleep duration was reduced after night shift work and did not increase with more consecutive night shifts, which leads to accumulated sleep debt. Sleep duration was shortest and sleep quality was poorest after the last night shift in a series of night shifts.     

An occupational health physician's report on the improvement in the sleeping conditions of night shift workers

This paper reviews briefly our research findings on sleep and health for shift workers at a bakery and a dish factory and aims to give some information on health protection with improved sleep. Our medical examinations revealed that rises in blood pressure (BP) were frequently observed in male bakery workers on the fixed night shift. They took a two-hour nap from 1:00 to 3:00 during the night shifts according to our advice. As a result, their diastolic BP significantly decreased in subsequent years. Women working shifts before 3:00 at a dish factory seemed to show more sleep disturbance, higher daytime sleepiness, and more fatigue than those working shits from 3:00. Total sleep hours taken during the daytime was similar between two groups. Among the dish, factory workers who switched to midnight or night shifts, 70% reported slow recovery from fatigue and 30% felt deteriorated health. These women also reported increased efforts to obtain a deep sleep, probably making up for shortened sleep. Occupational physicians can act to improve shift work conditions through monitoring the health of workers, applying naps, and designing possible schedules to secure deep, sufficient sleep.     

Twenty-four-hour light exposure and melatonin levels among shift workers

OBJECTIVES: We sought to measure melatonin levels and 24-hour light intensity exposure in health care workers over a 7-day period in natural occupational and residential settings. METHODS: Five office workers and 17 nurses working either days or rotating night and day shifts wore a device to record light intensity exposure for one or two 7-day periods, completed a questionnaire, and provided three saliva samples for melatonin. RESULTS: Rotating shift workers had irregular light exposure patterns and abnormal melatonin levels compared with those working days. In addition to lower-than-normal melatonin levels during sleep periods, rotating shift workers exhibited higher-than-normal melatonin levels on arising and during work. Self-reported years of shift work were correlated with measured melatonin and light. CONCLUSIONS: Rotating shift work is supported as a surrogate for exposure to light-at-night and circadian disruption.     

Modifying effects of perceived adaptation to shift work on health, wellbeing, and alertness on the job among nuclear power plant operators

This study examined the relationship between perceived adaptation to shift work and shift-related problems. A total of 608 male operators at nuclear power plants completed a set of validated questionnaires including a modified version of the Standard Shiftwork Index, which covered adaptation to shift work, fit to job content, chronotypes, chronic fatigue, sleep, naps, shift work locus of control (SHLOC), psychological health, social/family life, daytime sleepiness, workload, alertness on the job, and lifestyle factors. Participants were divided into two groups according to their perceived level of adaptation to shift work. The good adaptation group showed better outcomes than the poor adaptation group in terms of fit to job content, chronic fatigue, daytime sleep before night shifts, social and family disruption, SHLOC, psychological health, and alertness during night shifts (ps<0.001). Operators who reported good adaptation also took a more frequent, longer nap and more cigarettes during night shifts (ps<0.05). The cross-sectional study design cannot determine a causal relationship between perceived adaptation and shift work problems, yet the present results suggest that the effects of working shifts may be modified by perceptions of shift work adaptation.     

Optimization of night and shiftwork plans among policemen in Kuwait: A field experiment

Summary A pilot survey was designed to define incidence, rotation period, rotation direction and cycle of shiftwork plans in the production and service units in Kuwait. Preliminary results from the Ministry of Interior showed that four different shift plans are widely used. Forty policemen, ten from each shift plan, volunteered to fill in a diary for a period of two or more cycles. The diary was comprised of a set of questions planned to reveal disturbances in sleep duration, sleep quality, food intake and appetite. The daily questionnaire also covered psychosomatic complaints and subjective judgement of recovery. A control group, on permanent day work, volunteered to fill in the diary for the same period. The results indicated that one of the four shift plans was quite satisfactory and least harmful to the policemen. Two plans were associated with excessive strain during working days, but the number of free days was sufficient to achieve complete recovery. The fourth plan was associated with excessive strain during working days and recovery was not achieved after 24h of rest at the end of the shift cycle.Supported by the Research Council, Kuwait University, Project No. MDC 046     

Rescheduling a three shift system at a steel rolling mill: effects of a one hour delay of shift starting times on sleep and alertness in younger and older workers.

OBJECTIVE: To evaluate a new work schedule at a Finnish steel mill with special attention to effects on older workers. The schedule was designed to improve sleep before the morning shift, and alertness during the morning shift, by delaying shift start and end times. METHODS: Evaluation was by a shiftwork health and safety questionnaire, recordings of work-rest-sleep cycles with activity monitors worn on the wrist, daily diaries, and on site computerised testing of fatigue and alertness by the NIOSH fatigue test battery. RESULTS: The one hour delay in shift starting times improved sleep before the morning shift, and improved waking fatigue, sleepiness, and performance during the morning shift. Evening and night shift sleep and fatigue or sleepiness, however, were affected negatively by the new work schedule, but the results for those shifts were less consistent across the various measures. Despite the improvements, most workers were not satisfied with the new schedule because of social concerns. Few interactions of age with the new work schedule were found, suggesting that the effects of the work schedule were uniform across age groups. CONCLUSION: A change of as little as one hour in shift starting times can improve morning shift sleep and alertness, but there are trade offs from these improvements in terms of night shift effects and social considerations. It seems, then, that optimal shift start and end times for an entire organisation are difficult to institute on a wide scale. Tailoring shift schedules to subgroups within an organisation is suggested.     

Disturbed sleep and fatigue in occupational burnout

OBJECTIVES: The purpose of this study was to investigate sleep with polysomnography and self-ratings and the diurnal pattern of sleepiness and fatigue in a group suffering from severe occupational burnout. METHOD: Twelve white-collar workers on long-term sick leave (>3 months) and 12 healthy controls with high and low scores on the Shirom Melamed Burnout Questionnaire (SMBQ) were included. A 1-night polysomnographic recording (after habituation) was carried out at home, and sleepiness and mental fatigue were rated at different times of the day for weekdays and the weekend. Precipitating factors at the time of the illness at work and real life were considered, and different dimensions of occupational fatigue were described. A repeated-measures analysis of variance using two or three within group factors was used to analyze the data. RESULTS: The main polysomnographic findings were more arousals and sleep fragmentation, more wake time and stage-1 sleep, lower sleep efficiency, less slow wave sleep and rapid eye movement sleep, and a lower delta power density in non-rapid eye movement sleep in the burnout group. The burnout patients showed pronounced sleepiness and mental fatigue at most times of the day for weekdays without reduction during weekends. The precipitating factor was occupational stress (psychiatric interview), and work stress indicators were increased. CONCLUSIONS: Occupational burnout is characterized by impaired sleep. It is suggested that impaired sleep may play a role in the development of fatigue or exhaustion in burnout.     

Melatonin, sleep, and shift work adaptation

BACKGROUND: Night work is associated with disrupted circadian rhythms, fatigue, accidents, and chronic disease. Melatonin secretion helps regulate sleep and circadian rhythms. OBJECTIVE: Melatonin, sleep disturbances, and symptoms (sleep, fatigue, mental) were compared among workers on permanent day, swing, and night shifts. METHODS: Urinary 6-hydroxymelatonin sulfate (6-OHMS) was measured in postwork and postsleep samples. Disrupted circadian melatonin production was evaluated using the sleep:work 6-OHMS ratio. Wrist actigraphy characterized light exposures and sleep characteristics. RESULTS: Night workers had altered melatonin, disrupted sleep, and elevated symptom prevalence. Subjects grouped by their sleep:work 6-OHMS ratio rather than shift had even greater symptom prevalence. Risks for two or more symptoms were 3.5 to 8 times greater among workers with sleep:work ratios < or =1 compared to those with ratios >1. CONCLUSIONS: This ratio may help identify workers at increased risk for accidents or injuries.     

某铁路局机车司机职业倦怠影响因素分析

目的了解某铁路局机车司机职业紧张与倦怠的现状,探讨两者间的关系。方法采用国内已有应用并具较高信度和效度的心身健康测量量表结合我局实际情况编写调查问卷,对某铁路局2258名机车司机进行问卷调查。采用Epidata软件建立数据库进行数据交叉双录入并进行一致性检验,数据导出后用SPSS统计软件进行多元线性回归方法统计分析不同职业紧张因子与职业倦怠的关系。结果某铁路局机车司机存在一定的心理、生理健康方面的问题,影响机车司机职业倦怠的主要因素按照标准化偏回归系数贡献大小依次为:心理健康、生理健康、睡眠障碍、付出-回报、工作-家庭冲突、内在投入等。其中诸如付出-回报失衡、睡眠障碍、生活压力、工作-家庭冲突等加重了机车司机工作倦怠的程度。睡眠障碍、付出-回报、工作-家庭冲突、内在投入、年龄、周工作时间、吸烟、生活压力、体育锻炼、轮班情况、饮酒等职业紧张因素与工作倦怠有密切关系(P<0.05)。结论预防机车司机群体的职业倦怠需降低职业紧张程度,增加社会支持,同时开展心理健康咨询及宣传教育。     

倒班和睡眠时间对钢铁工人肝功能异常的影响

  目的  探讨倒班、平均睡眠时间及其联合作用对钢铁工人肝功能异常的影响,为保护钢铁工人肝脏提供理论依据。  方法  采用横断面研究,以某钢铁公司6 907名工人作为研究对象, 并收集信息。采用非条件Logistic回归分析模型和限制性立方样条函数进行分析。  结果  肝功能异常的检出率为18.0%,且男性高于女性(19.2% vs. 5.1%)。调整混杂因素后,倒班年限和肝功能异常之间存在非线性剂量反应关系。倒班和平均倒班频率＞7夜/月患肝功能异常的风险分别增加1.24倍(OR=1.24, 95% CI: 1.04~1.49)和1.29倍(OR=1.29, 95% CI: 1.07~1.56)。以倒班状态分层,在倒班工人中平均睡眠时间较短(≤5 h/d)和较长(＞7 h/d)患肝功能异常的风险分别增加1.19倍(OR=1.19, 95% CI: 1.01~1.43)和1.22倍(OR=1.22, 95% CI: 1.02~1.44)。且平均睡眠时间较长或较短均与倒班存在正向相乘的交互作用。根据平均睡眠时间分层后,平均睡眠时间＞5~7 h/d的各倒班指标与肝功能异常的联系无统计学意义。  结论  倒班工作和睡眠时间较长或较短联合作用会增加钢铁工人肝功能异常的风险,倒班工作对肝功能异常的独立作用也不容忽视。