A polysomnographic study of morning and afternoon sleep quality during simulated night shift work

Shiftworkers differ as to scheduling their day sleep between night shifts. An experimental study was carried out to compare the effects of morning and afternoon sleep behaviour on sleep quality within and after a period of seven night shifts. Twelve young males participated in a repeated–measures design, six sleeping in the morning and six in the afternoon after night shifts. Sleep quality was evaluated by polysomnographic and subjective measures. Morning and afternoon sleepers showed some differences in the trend of sleep changes over successive sleep periods. However, at the end of the night shift week, there were no marked differences in sleep quality. Both morning and afternoon sleep were characterized by deep sleep, and short sleep onset latencies.     

Performance and alertness on 8 h and 12 h rotating shifts at a natural gas utility

Abstract

An 8 h/5-7 day shift schedule was compared with a newly instituted 12 h/2-4 day schedule in this, our second worksite study of extended workshifts. Workers completed a performance/alertness test battery, and a questionnaire on sleep patterns and other personal habits, 2-4 times a week on all shifts. After 10 months adaptation to the 12 h shift schedule, there were decrements in performance/ alertness attributable to the extra 4 h on the extended shift. There were also reductions in sleep across the workweek which were most apparent on 12 h night shifts. The results are consistent with our first worksite study of 12 h shifts and indicate extra caution should be exercised when scheduling critical activities for extended workshifts, especially extended night shifts.     

Changing the speed of shift rotation: a field study

Abstract

A group of 33 controllers of an emergency service were studied before and after a change in shift roster. The original roster was the traditional weekly rotating type of three shifts, morning, afternoon and night in that direction, in which controllers worked seven consecutive shifts of the same type. This was changed to a rapidly rotating roster of shifts with no more than three consecutive night shifts. The direction of shift change remained the same. Sleep and meal diaries were kept by all controllers for 2 weeks before the roster change. Self-report measures were taken of health, social drug consumption and work variables, an anxiety inventory, the State-Train Anxiety Inventory and the Work Environment Scale were administered both before and 5 months after the roster change. Significant improvements were found after the shift roster change on almost all measures with the exception of self-reported nervousness and loss of appetite and a number of items in the Work Environment Scale. This finding provides some evidence from the field for the argument that rapidly rotating shifts may be the optimal form of shift system.     

Oral temperature and performance in 8 h and 12 h shifts

Abstract

Operators in an 8 h (n = 18) and a 12 h (n = 16) h shift went through an experiment in which oral temperature, disjunctive reaction time(DRT), tapping, logical reasoning, memory and search tasks were measured at 4 h intervals. A performance curve in DRT and in tapping over a 24 h cycle tended to follow the pattern of the body temperature curve. The curves of mental curves were flattened. The values measured in the two groups of Ss revealed differences of statistical significance.     

Work/rest cycles in railroad operations: effects of shorter than 24-h shift work schedules and on-call schedules on sleep

The current study examined the frequency with which shorter than 24-h work/rest cycles occur in locomotive engineer work schedules, and what effects these work/rest cycles had on sleep quantity and sleep quality. The results indicated that shorter than 24-h work/rest cycles occurred in 33.6% of the work days reported by 198 locomotive engineers. In addition, the shorter than 24-h work/rest cycles occurred more frequently in work schedules that created an on-call work system, such as road pool turn and extra board assignments, than in work schedules that used more predictable or regular work times, such as regular road assignments and yard/local work. As would be expected, when engineers worked shorter than 24-h work/rest cycles, they reported less sleep and poorer sleep than under the longer than 24-h work/rest cycles. Similarly, on-call work assignments resulted in less sleep and poorer sleep than regular work assignments. These results indicate that specific aspects of the work schedules used in railroad operations, particularly on-call operations that result in shorter than 24-h work/rest cycles, can lead to increased sleep-related problems. Although the North American railroad industry is making significant changes in on-call operations to minimize sleep-related problems from on-call schedules, better fatigue-related models validated within the railroad industry are needed.     

A shipboard study of a four-crew rotating watchkeeping system

Abstract

Body-temperatures and subjective alertness ratings were obtained at 2-hourly intervals in a shipboard study of six subjects watchkeeping on a rapidly rotating system with a 4-day cycle. The results were compared with those from an earlier study of this system conducted on land in ‘laboratory’ conditions. The similarity of the temperature curves from the two studies indicated that prolonged exposure to shipboard conditions made no difference to the underlying circadian rhythm in this variable, which appeared to be near-normal in form. Subjective alertness showed a clear rhythm of considerable amplitude; the phasing of this rhythm suggested that, under the present system, operational effectiveness is likely to be reduced in watches held in night hours. Further analyses indicated that it was also likely to be reduced in daytime hours following these night watches, because of the disruption of sleep that results from them. An alternative ‘fixed hours’ watchkeeping system is proposed to overcome these unwanted effects.     

Sleep in a live-in mining operation: The influence of start times and restricted non-work activities

The amount of sleep obtained between shifts is influenced by numerous factors including the length of work and rest periods, the timing of the rest period relative to the endogenous circadian cycle and personal choices about the use of non-work time. The current study utilised a real-world live-in mining environment to examine the amount of sleep obtained when access to normal domestic, family and social activities was restricted. Participants were 29 mining operators (26 male, average age 37.4 ± 6.8 years) who recorded sleep, work and fatigue information and wore an activity monitor for a cycle of seven day shifts and seven night shifts (both 12 h) followed by either seven or fourteen days off. During the two weeks of work participants lived on-site. Total sleep time was significantly less (p < 0.01) while on-site on both day (6.1 ± 1.0 h) and night shifts (5.7 ± 1.5 h) than days off (7.4 ± 1.4 h). Further, night shift sleep was significantly shorter than day-shift sleep (p < 0.01). Assessment of subjective fatigue ratings showed that the sleep associated with both days off and night shifts had a greater recovery value than sleep associated with day shifts (p < 0.01). While on-site, participants obtained only 6 h of sleep indicating that the absence of competing domestic, family and social activities did not convert to more sleep. Factors including shift start times and circadian influences appear to have been more important.     

The sleep and performance of train drivers during an extended freight-haul operation

The sleep and performance of train drivers was monitored across a 106-h rail operation between the Australian cities of Adelaide and Perth. The drivers worked alternating 8-h shift rotations across the operation and rested in specially equipped, crew-van carriages during non-work periods. The crew-van rest opportunities were associated with shorter bedtime spans, less total sleep time, and poorer sleep efficiency than sleeps initiated at home. The duration of crew-van sleeps was primarily dependent on the time of day at which the rest opportunities occurred. Overall, drivers incurred a significant cumulative sleep loss across the duration of the operation. Despite the deficit, drivers were able to sustain vigilance performance across the operation.     

Operational assessment of the 5-h on/10-h off watchstanding schedule on a US Navy ship: sleep patterns,mood and psychomotor vigilance performance of crewmembers in the nuclear reactor department

We assessed sleep patterns, psychomotor vigilance performance, work demands and mood of 77 crewmembers of USS NIMITZ (CVN-68) on the rotating 5-h on/10-h off (5/10) watchstanding schedule. Within the 3-day cycle of the 5/10, sleep occurred at distinctly different times each day. On two of these days, sailors typically received only brief, 4-h sleep episodes followed by periods of sustained wakefulness (approximately 22 and 20 h). Crewmembers received approximately seven hours of sleep daily, but reported excessive fatigue and dissatisfaction with their schedule. Crewmembers’ mood worsened significantly over the course of the underway phase. Psychomotor vigilance performance (reaction times, lapses) was significantly degraded compared to performance when working circadian-aligned schedules. Overall, standing watch on the 5/10 schedule, combined with other work duties, resulted in poor sleep hygiene. Crewmembers on the 5/10 experienced periodic bouts of sustained wakefulness and accrued a significant sleep debt due to extended workdays and circadian-misaligned sleep.

Practitioner summary: We assessed crewmembers’ sleep patterns, psychomotor vigilance performance and work demands when working a rotating 5-h on/10-h off (5/10) watchstanding schedule. The 5/10, combined with other work duties, resulted in poor sleep hygiene. Crewmembers experienced periodic bouts of sustained wakefulness and accrued a significant sleep debt due to extended workdays and circadian-misaligned sleep.     

A quantitative model of work-related fatigue: background and definition

Fatigue has been identified as a major risk factor for shiftworkers. However, few organizations or governments currently manage work-related fatigue in any systematic or quantitative manner. This paper outlines an approach to managing fatigue that could improve shiftwork management. Using shift start and finish times as an input, the outlined model quantifies work-related fatigue on the basis of its known determinants; that is shift timing and duration, work history and the biological limits on sleep length at specific times of day. Evaluations suggest that work-related fatigue scores correlate very highly with sleep-onset latency, neurobehavioural impairment and subjective sleepiness. The model is useful in that it allows comparisons to be made between rosters independent of shift length and timing or the total number of work hours. Furthermore, unlike many models of sleepiness and fatigue, individual's sleep times are not required as hours of work are used as the input. It is believed the model provides the potential quantitatively to link the effects of shiftwork to specific organizational health and safety outcomes. This simple approach may be especially critical at a time when many organizations view longer and more flexible hours from their employees as an immediate productivity gain.     

Influence on working hours among shift workers and effects on sleep quality – An intervention study

The aim of the present intervention study was to examine if increased influence on working hours among shift workers led to better sleep quality.391 employees were categorized into groups based on the performed activities: High (self-rostering), moderate (education and/or policy for working hours), and low intensity intervention (meetings and discussions) and reference. Sleep quality was assessed by Karolinska Sleep Questionnaire (KSQ) at baseline and follow-up (12 months). To elucidate the process of the intervention interviews were conducted.Influence on one’s own working hours increased only in the high intensity group (p < 0.001). No effects of interventions on sleep quality were observed. Thus, sleep quality was not improved by increasing work time influence in the present group of Danish elder care workers. This was partly due to program failure (failed intervention), but may also be due to other factors such as few participants working night and few working full time.     

Locomotive engineers and their spouses: coffee consumption,mood, and sleep reports

Locomotive engineers (train drivers) on irregular work schedules reported a general coffee consumption rate higher than that reported by a comparison sample of permanent shift factory workers. The present study examines the impact of this consumption on workday and non-workday sleep behaviour and mood ratings. Twenty-seven engineers and their spouses each completed daily logs for 30 consecutive days. Daily logs were then sorted into workday and non-workday categories. Workday sleep length was significantly shorter than non-workday sleep length for both engineers and spouses. For the engineers only, coffee consumption on workdays was higher than on non-workdays. This increased coffee consumption was correlated with longer sleep latency, increased negative mood, and decreased positive mood on both work and non-workdays. This was not true for spouses. These results may be related to a days-off carry-over effect of caffeine or a general consumption behaviour characteristic.     

Worktime control-dependent reductions in fatigue, sleep problems, and depression

We investigated the association between worktime control and fatigue, sleep problems, and depressive symptoms in a sample of daytime and shift workers. A total of 3681 permanent daytime workers and 599 shift workers completed a questionnaire designed to assess the above variables. Worktime control was evaluated in terms of both “control over daily working hours” and “control over days off”. Worktime control × work schedule × gender analysis of covariance, adjusted for age and employment status, showed overall reductions in incomplete recovery, insomnia symptoms, daytime sleepiness, and depressive symptoms with increasing levels of worktime control. However, no associations between control over daily working hours and insomnia symptoms were observed in women. The reductions appeared to be more evident for control over days off. These results remained consistent after adjustments for other potential covariates. The present findings indicate that increased worktime control and enhanced control over days off in particular, may be associated with favorable health outcomes.     

Sleep and circadian rhythms in mining operators: limited evidence of adaptation to night shifts

Cumulative sleep deprivation is often associated with work patterns involving night shift or early morning shifts. Adaptation of the circadian system to the shift pattern is reported to promote improved duration and quality of sleep and a concurrent improvement in performance. The current study followed twenty-nine operators at a live-in mining operation working to a seven-day, seven-night shift pattern who collected saliva samples for melatonin measurement, recorded sleep using activity monitors and diaries, and underwent performance testing (psychomotor vigilance task) for one complete roster cycle. The time of onset of melatonin secretion changed significantly (P=0.022) across the week of both Day and Night shifts (2104 h ± 16 min versus 2130 h ± 16 min, respectively), but the small magnitude of the change indicates a lack of true circadian rhythm adaptation to the lifestyle. Total sleep time was longer following the seventh Day shift (associated with a period of 24 h off prior to the commencement of Night shifts). There were no other changes in total sleep time. Further, there were no improvements in sleep onset latency or sleep efficiency on Day or Night shifts. However, reaction times recorded at the end of the shifts slowed across the seven Day and seven Night shifts indicative of impairments in psychomotor performance (F(6,168)=6.087, P<0.001). The results suggest that previous reports of adaptation to consecutive night shifts cannot necessarily be applied to onshore or Australian environments. Adaptation is dependent on factors such as light exposure, environmental conditions, shift parameters such as wake-up, work start and work end times and individual characteristics.     

An experimental change of the speed of rotation of the morning and evening shift

Eighty-five Dutch railway traffic controllers were studied before and after a change in their continuous shift schedule. The original schedule was slowly rotating, while the experimental schedule had a moderately rapid rotating morning and evening shift, but a slowly rotating night shift. Before and 6 months after the change, questionnaires and a diary were filled in. A decrease in sleep complaints and weekly workload was found. No reduction in the amount of complaints regarding leisure time in the evening was registered; only an increase in satisfaction with leisure time in the evening.     

Sleepiness,alertness and performance during a laboratory simulation of an acute shift of the wake-sleep cycle

Monitoring the presence of sleepiness on the job and its effects on performance is of primary importance for improving schedule systems of shiftworkers. Shiftworkers, often involved in night-time operations and irregular work schedules, frequently complain of nocturnal sleepiness especially in conditions of abrupt shift of the wakesleep cycle. In this study, the authors evaluated the effects of a laboratory simulation of acute night-shift changes on sleepiness, vigilance and performance, using Maintenance of Wakefulness Test,Multiple Sleep Latency Test and three pencil and paper tests: Digit Symbol Substitition Test, ‘Deux Barrages’ Test and a 3-Letter Cancellation Task. All of the tests were administered four times at 2-hourly intervals during the night after daytime sleep. Results showed that the ability to maintain wakefulness and to perform simple visuo-attentive tasks is substantially spared during the night. On the other hand, sleep tendency and performance on a more complex and monotonous task (Letter Cancellation Task) reveal, respectively, increasing sleepiness and degrading performance.     

A fuzzy expert system for noise-induced sleep disturbance

In this paper, an attempt has been made to develop a fuzzy expert system for predicting the effects of sleep disturbance by noise on humans as a function of noise level, age, and duration of its occurrence. The modelling technique is based on the concept of fuzzy logic, which offers a convenient way of representing the relationships between the inputs and outputs of a system in the form of IF-THEN rules. It has been established on the basis of findings of various researchers that the effect of noise on sleep disturbance depends to a large extent on age. The middle-aged people have more probability of sleep disruption than the young people at the same noise levels. However, very little difference is found in sleep disturbance due to noise between young and old people. In addition, the duration of occurrence of noise is an important factor in determining the sleep disturbance over the limited range from few seconds to few minutes. Finally, we have compared our model results with some of the findings of researchers reported in International Journals.     

Work hours, workload, sleep and fatigue in Australian Rail Industry employees

Research suggests that less than 5 h sleep in the 24 h prior to work and/or more than 16 h of wakefulness can significantly increase the likelihood of fatigue-related impairment and error at work. Studies have also shown exponential safety declines with time on shift, with roughly double the likelihood of accident or injury after 10 h relative to the first 8 h. While it is acknowledged that reduced sleep, increased wakefulness and longer work hours produce work-related fatigue, few studies have examined the impact of workload on this relationship. Studies in the rail industry have focused on drivers. This study investigated fatigue in a large sample of Australian Rail Industry Employees. Participants were from four companies (n = 90: 85m, 5f; mean age 40.2 ± 8.6 y). Data was analysed for a total of 713 shifts. Subjects wore wrist actigraphs and completed sleep and work diaries for 14-days. They also completed the Samn–Perelli Fatigue Scale at the beginning and end of shifts, and the NASA-TLX workload scale at least twice during each shift. Average (±SD) sleep length (7.2 ± 2.6 h), prior wake at shift end (12.0 ± 4.7 h), shift duration (8.0 ± 1.3) and fatigue (4.1 ± 1.3, “a little tired, less than fresh”) were within limits generally considered acceptable from a fatigue perspective. However, participants received 5 h or less sleep in the prior 24 h on 13%, were awake for at least 16 h at the end of 16% and worked at least 10 h on 7% of shifts. Subjects reported that they felt “extremely tired, very difficult to concentrate,” or “completely exhausted, unable to function effectively” on 13% of shifts. Sleep length (OR = 0.88, p < 0.01), shift duration (OR = 1.18, p < 0.05), night shift (REF = morning shift, OR = 2.12, p < 0.05) and workload ratings (OR = 1.2, p < 0.05) were significant predictors of ratings of extreme tiredness/exhaustion (yes/no). While on average, sleep loss, extended wakefulness, longer work hours and work-related fatigue do not appear problematic in this sample, there is still a notable percentage of shifts that are likely to be associated with high levels of work-related fatigue. Given the size of the Australian Rail Industry, with thousands of shifts occurring each day, this is potentially of operational concern. Further, results indicate that, in addition to sleep length, wakefulness and work hours, workload significantly influences fatigue. This has possible implications for bio-mathematical predictions of fatigue and for fatigue management more generally.     

Sleep patterns,shiftwork, and individual differences: a comparison of onshore and offshore control-room operators

Abstract

The sleep patterns of offshore control-room operators were compared with those of personnel carrying out similar work onshore, taking into account individual differences in age, number of years of shiftwork, and neuroticism. The dependent variables were self-reported sleep quality and duration for day-shift (D-S) and night-shift (N-S) work, and during leave periods (L-P) Offshore workers reported longer N-S sleep duration, and lower D-S sleep quality than those onshore, but the two groups did not differ in L-P measures. The effects of environmental differences (onshore versus offshore) on sleep patterns were more marked than those of the two different shift systems (weekly rotation and fast rotation) in operation onshore. Age was negatively related to both duration and quality of sleep; over and above age, number of years of shiftwork was negatively related to sleep duration. Neuroticism was also negatively related to sleep duration and, more strongly, to sleep quality. These findings are discussed in relation to the literature on shiftwork and sleep in general, and the characteristics of the offshore environment in particular