Using pharmacological aids to improve waking function and sleep while working at night

Non-refreshing or insufficient sleep, and impaired alertness on the job, are two nearly universal consequences of night work. The effects of drugs upon the sleep and alertness of night workers has only recently been studied and much work remains to be done. To date, it is clear that sleep during the day can be improved with sedative-hypnotic compounds, particularly the benzodiazepines. Despite improvement in sleep, alertness at night is improved only mildly, if at all, with short-acting sleeping agents and can be further impaired with long-acting drugs. The limited research examining alertness and performance during night shift hours after administration of CNS stimulants suggests significant benefits. The judicious use of CNS stimulants in this way needs further exploration. Precise pharmacological manipulation of the endogenous sleep/wake rhythm is primarily theoretical at this time but should be pursued.     

Psychophysical conditions and hormonal secretion in nurses on a rapidly rotating shift schedule and exposed to bright light during night work

The psychophysical conditions of 15 young female nurses, working in a rapidly-rotating shift system (2-2-2-2), modified according to some psychophysiological criteria, and exposed to short period (4 × 20 min) of bright light (2350 Lux) during their night duty, were studied in order to evaluate their adaptation to night work and to test a possible positive effect on it of bright light. Subjective evaluations of work load and psychophysical conditions, performance measures, hormonal excretion (cortisol, 6-sulphatoxymelatonin and catecholamines), oral temperature and activity-sleep logs were taken during the shiftwork cycle, comprising one morning, one afternoon and two consecutive nights under normal and bright light. The results showed that this rapidly-rotating shift system had little effect upon the normal circadian rhythms of the body. Moreover, the lengthening of the night shift to 10 h can be considered to be acceptable, provided that work load is reduced and there are sufficient rest pauses available. On the other hand, the reduction to 7 h of the length of the day shifts and delayed start of the morning shift to 07:00 h appeared to be convenient both in relation to the work load and sleep duration. Some positive effects of bright light upon psychophysical conditions and performance efficiency were noted, while hormonal excretion and body temperature did not show any effect of bright light; in particular, melatonin excretion was not suppressed appreciably by the bright light used.     

Psychophysical conditions and hormonal secretion in nurses on a rapidly rotating shift schedule and exposed to bright light during night work

Abstract

The psychophysical conditions of 15 young female nurses, working in a rapidly-rotating shift system (2-2-2-2), modified according to some psychophysiological criteria, and exposed to short period (4 × 20 min) of bright light (2350 Lux) during their night duty, were studied in order to evaluate their adaptation to night work and to test a possible positive effect on it of bright light. Subjective evaluations of work load and psychophysical conditions, performance measures, hormonal excretion (cortisol, 6-sulphatoxymelatonin and catecholamines), oral temperature and activity-sleep logs were taken during the shiftwork cycle, comprising one morning, one afternoon and two consecutive nights under normal and bright light. The results showed that this rapidly-rotating shift system had little effect upon the normal circadian rhythms of the body. Moreover, the lengthening of the night shift to 10 h can be considered to be acceptable, provided that work load is reduced and there are sufficient rest pauses available. On the other hand, the reduction to 7 h of the length of the day shifts and delayed start of the morning shift to 07:00 h appeared to be convenient both in relation to the work load and sleep duration. Some positive effects of bright light upon psychophysical conditions and performance efficiency were noted, while hormonal excretion and body temperature did not show any effect of bright light; in particular, melatonin excretion was not suppressed appreciably by the bright light used.     

The impact of rest breaks upon accident risk,fatigue and performance: A review

This review's primary objective is to identify research examining the impact of rest breaks uponaccident risk in industrial settings. In the absence of much directly relevant research, the focus isbroadened to consider the impact of rest breaks upon performance and fatige, as well asepidemioogical evidence, in both transport and non-transport settings. Relevant studies are identifiedfrom a range of electronic sources. In general, regular rest breaks can be an effective means ofmaintaining performance, managing fatigue and controlling the accumulation of risk over prolongedtask perfonmance. While two-hourly breaks are common in many industrial settings, the scheduling ofadditional micro-breaks can be beneficial under at least some circumstances. While some evidencesupports allowing workers to take rest breaks that coincide with periods of heightened fatigue,workers sometims fail to take adequate breaks when they are needed. There is little hard evidenceconcerning the optimun length of rest breaks (other than for heavy physical work), or to support thecontention that increased rest-breaks can off-set the negative inpact of extending shift durations, or tosuggest that rest breaks counteract the neptive impacts of circadian variations in alertness, unless theyinvolve taking a nap or caffeine. The scarcity of epidemiological evidence in this area highlights theneed for more research.     

A 14-h night-shift in the control room of a fire brigade

All 29 operators in the control room of a fire brigade performed test sessions during work and leisure time at 2-h intervals on a day with a 14-h night-shift, a day off and a day with a 10-h morning shift. The test sessions consisted of a visual search choice reaction time test and two Sternberg memory search tests (1 or 5 letters had to be memorized). Furthermore, the operators recorded their oral temperature and their subjective alertness before each test session. The subject also kept a diary of work and sleep times for 14 days. The circadian rhythm of body temperature was hardly changed by a single night-shift. Parallel to the body temperature, the subjective alertness fell significantly during the night-shift reaching a minimum value at 06:00 h. The mean reaction times increased non-significantly at the end of the night-shift and the results of the two Sternberg memory search tests showed no significant trends. The sleep of the operators after the night-shift was on average reduced to 5 hs 34 min. The results of subjective rating of alertness and reaction time test are interpreted as effects of the combined influences of circadian rhythmicity, sleep loss and time on professional task. Most results support the conclusion that a 14-h night-shift without extensive breaks is not acceptable.     

A 14-h night-shift in the control room of a fire brigade

All 29 operators in the control room of a fire brigade performed test sessions during work and leisure time at 2-h intervals on a day with a 14-h night-shift, a day off and a day with a 10-h morning shift. The test sessions consisted of a visual search choice reaction time test and two Sternberg memory search tests (1 or 5 letters had to be memorized). Furthermore, the operators recorded their oral temperature and their subjective alertness before each test session. The subject also kept a diary of work and sleep times for 14 days. The circadian rhythm of body temperature was hardly changed by a single night-shift. Parallel to the body temperature, the subjective alertness fell significantly during the night-shift reaching a minimum value at 06:00 h. The mean reaction times increased non-significantly at the end of the night-shift and the results of the two Sternberg memory search tests showed no significant trends. The sleep of the operators after the night-shift was on average reduced to 5 hs 34 min. The results of subjective rating of alertness and reaction time test are interpreted as effects of the combined influences of circadian rhythmicity, sleep loss and time on professional task. Most results support the conclusion that a 14-h night-shift without extensive breaks is not acceptable.     

A 14-h night-shift in the control room of a fire brigade

Abstract

All 29 operators in the control room of a fire brigade performed test sessions during work and leisure time at 2-h intervals on a day with a 14-h night-shift, a day off and a day with a 10-h morning shift. The test sessions consisted of a visual search choice reaction time test and two Sternberg memory search tests (1 or 5 letters had to be memorized). Furthermore, the operators recorded their oral temperature and their subjective alertness before each test session. The subject also kept a diary of work and sleep times for 14 days. The circadian rhythm of body temperature was hardly changed by a single night-shift. Parallel to the body temperature, the subjective alertness fell significantly during the night-shift reaching a minimum value at 06:00 h. The mean reaction times increased non-significantly at the end of the night-shift and the results of the two Sternberg memory search tests showed no significant trends. The sleep of the operators after the night-shift was on average reduced to 5 hs 34 min. The results of subjective rating of alertness and reaction time test are interpreted as effects of the combined influences of circadian rhythmicity, sleep loss and time on professional task. Most results support the conclusion that a 14-h night-shift without extensive breaks is not acceptable.     

On-shift and daily variations in self-report and performance measures in rotating-shift and permanent night nurses

An intensive study was conducted of the influence of type of shift system, type of shift, and time-into-shift on a battery of on-shift and daily measures obtained from 61 female nurses over a 28-day period. Thirty-two rotating-shift nurses and 28 permanent night nurses recorded data on a hand-held computer at the start and end of each day, and every 2-h during their shifts. The measures included a sleep diary, self-ratings of mood, workload, and personal disruption, and two cognitive performance tasks. These results suggest that the permanent night nurses were no worse off and for some measures were actually better off than the rotating-shift nurses after controlling for differences in age and shiftwork experience; the night-shift was problematic for the rotating-shift nurses but so was the early shift; mood deteriorated and reaction time got slower over the course of the night-shift but extra long responses (which may correspond to lapses of attention) and rated workload were lower on the night-shift. The relatively large number of consecutive night-shifts worked by the rotating-shift nurses, the uneven distribution of workload between shifts, and the long night-shift may have contributed to these results.     

On-shift and daily variations in self-report and performance measures in rotating-shift and permanent night nurses

Abstract

An intensive study was conducted of the influence of type of shift system, type of shift, and time-into-shift on a battery of on-shift and daily measures obtained from 61 female nurses over a 28-day period. Thirty-two rotating-shift nurses and 28 permanent night nurses recorded data on a hand-held computer at the start and end of each day, and every 2-h during their shifts. The measures included a sleep diary, self-ratings of mood, workload, and personal disruption, and two cognitive performance tasks. These results suggest that the permanent night nurses were no worse off and for some measures were actually better off than the rotating-shift nurses after controlling for differences in age and shiftwork experience; the night-shift was problematic for the rotating-shift nurses but so was the early shift; mood deteriorated and reaction time got slower over the course of the night-shift but extra long responses (which may correspond to lapses of attention) and rated workload were lower on the night-shift. The relatively large number of consecutive night-shifts worked by the rotating-shift nurses, the uneven distribution of workload between shifts, and the long night-shift may have contributed to these results.     

Ten-hour days and eight-hour nights: Can the Ottawa Shift System reduce the problems of shiftwork?

Most research on condensed working weeks has concentrated either on daywork only or on 12-h shifts. The Police Force in Ottawa, Canada, have been reporting positive experiences with a shift system which retains an 8-h night shift but which extends the day shifts to 10-h, thus enabling a 6-day rest period following night shifts. In the present study, the effects on well-being, personal, social and work disruption, alertness and sleep were evaluated when the same system was adopted by a police force in the UK. A survey was conducted at four police stations prior to the change and again 6 months after the change. Two of the stations did not change to the Ottawa system and hence formed a control group. The stations originally worked 8-h shifts with blocks of seven consecutive shifts. The results suggest that, in contrast to the control group the 'Ottawa' group experienced a significant improvement in well-being, a significant reduction in personal, social and work disruption, and a significant increase in average sleep duration over a shift cycle. Self-rated alertness at the end of shifts was no worse under the Ottawa system. However, the values were still very low at the end of the night shift and, with an average sleep duration between night shifts of only 6-4-h it suggests that the block of seven nights in the Ottawa system may need review.     

Performance, alertness, and sleep after 3·5 years of 12 h shifts: A follow-up study

Control room operators at a continuous processing plant have been working a 12 h/3-4 day rotating shift schedule for over 3 years. After 7 months on this schedule, our initial assessment indicated decrements in performance and alertness, and a mild to moderate sleep debt, when the 12 h shift schedule was compared to the previously-worked 8 h shift schedule. In an effort to track long-term adaptation to the schedule, we conducted a 3 & 5 year follow-up evaluation using the same set of measures. Long-term follow-up testing revealed persistent decrements in performance and alertness attributable to 12 h shifts, and 1-3 h reductions in total sleep time after 12 h night shifts. Little deterioration in performance or alertness was observed across the workweek, which suggested day-to-day recovery from the extended workshift. The popularity of the 12 h shift schedule at this worksite indicates that the workers are willing to tolerate extra fatigue to derive other benefits from this schedule.     

The impact of shiftwork on personnel at a nuclear power plant: An exploratory survey study

Shiftwork may constitute an additional risk factor in high-hazard industries where system failure could exact heavy human, environmental and economic costs. This exploratory survey study examined the impact of shiftwork upon nuclear power plant workers' perceived health, sleep, and social problem, as well as levels of alertness. Overall, the night shik proved to be the most problematic in ternis of decreases in alertness, sleep duration and quality, and disruptions to health, social and family life. The permanent shift preferences of the shiftworkers were also explored to establish the practicability of introducing a theoretically safer permanent mght shdt at such a facility. Importantly, the small proportion of the sample who showed a preference for a pemianent night shift was insufficient to provide operational cover. Although these shtftworkers reported experiencing less disruption on the night shift than those who would choose to work a permanent day shift, their preference appeared to be based upon a greater esprit de corps on this shift rather than on any predisposing individual characteristics. These results have practical implications for work scheduling in high-hazard industries.

The present study investigates the dimensional structure of the psychosocial work environment as assessed by Karasek's job characteristics scales and a set of factorial scales derived from the Dictionary of Occupational Titles (DOT) observers' ratings of occupational characteristics for census occupations. Scale scores on the Karasek and DOT were linked to information on occupation from the Epidemiologc Catchment Area (ECA) study sample. Scale intercorreladons and factor analysis were performed on those ECA subjects who reported ever having a full-time job (n=11,789). DOT'sS Substantive Complexity scale was positively correlated with Karasek's Skill Discretion and Decision Authority scales, and DOT's Physical Demands and Hazards scale was positively correlated with Karasek's Physical Demands scale. In addition, the DOT system compared to the Karasek system seems to assess psychosocial work domains less characteristic of traditional industrial jobs (interpersonal stress, expressive work). The content validity of the Karasek scales might be increased with the assessment of these domains. Giving support to Karasek's Demand/Control Model, the factor structure of the psychosocial work enviromnent in the probability sample of five US metropolitan populations yielded two major dimensions: Control, and Physical Demands.     

Shiftwork effects in nuclear power workers: A field study using portable computers

This field study of nuclear power shiftworkers reports the use of hand-held computers to record alertness levels, cognitive task performance and workload ratings. Subjective ratings and performance tasks (Search and Memory-5 (SAM-5); Choice Reaction Time (CRT) were completed on the computers at 2-h intervals during selected shifts in the work schedule by maintenance crews and reactor operators. Sleep duration and quality data were also obtained during the 35-day shift cycle. Workload remained relatively stable across shifts. The night-shift was associated with shorter sleep durations and poorer sleep quality. Significantly lower levels of alertness and poorer perforniance for components of the performance tasks were also observed on the night-shift. Tinic-on-shift effects on alertness were evident, where by for the night-shift, especially, alertness dropped dramatically during the early hours. Components of SAM-5 performance showed differential time-on-shift patterning relative to each shift whereas CRT was unresponsive to time-on-shift effects. Significant variations were observed in alertness and performance components during the 12-h night-shift. Perhaps paradoxically, performance on the 12-h night-shift appeared to improve rather than deteriorate during the early-hour period that was associated with the greatest drop in alertness. This was suggestive of extra effort expenditure during this critical period.     

Is there an optimum number of night shifts? Relationship between sleep, health and well-being

By concentrating on the impact of a specific shift-system feature on the well-being of those concerned, rather than on the impact of the shift system as a whole, one might be able to offer more meaningful suggestions as to what constitutes a better form of shift system. The present study focused on the impact of the number of consecutive night shifts worked on the health and well-being of two groups of nurses (permanent night and rotating shift). All nurses completed a copy of the Standard Shiftwork Index, which is a set of questionnaires designed for comparing the effects of different types of shift system on large groups of workers. It includes measurements of psychological ill-health, physical ill-health, chronic fatigue, social and domestic disruption, attitudes towards shiftwork, sleep quality and sleep habits. Results showed clearly the impact of the number of consecutive nights worked on health and well-being, not directly, but indirectly through the impact on sleep duration and sleep quality. Sleep duration was shown to increase with more consecutive nights worked. This in turn was found to predict sleep quality, which in turn was found to be the stronger direct predictor of psychological and physical ill-health: i.e. better health was associated with longer and better quality sleeps. Explanations in terms of circadian adaptation are discussed.     

Shiftwork effects in nuclear power workers: A field study using portable computers

Abstract

This field study of nuclear power shiftworkers reports the use of hand-held computers to record alertness levels, cognitive task performance and workload ratings. Subjective ratings and performance tasks (Search and Memory-5 (SAM-5); Choice Reaction Time (CRT) were completed on the computers at 2-h intervals during selected shifts in the work schedule by maintenance crews and reactor operators. Sleep duration and quality data were also obtained during the 35-day shift cycle. Workload remained relatively stable across shifts. The night-shift was associated with shorter sleep durations and poorer sleep quality. Significantly lower levels of alertness and poorer perforniance for components of the performance tasks were also observed on the night-shift. Tinic-on-shift effects on alertness were evident, where by for the night-shift, especially, alertness dropped dramatically during the early hours. Components of SAM-5 performance showed differential time-on-shift patterning relative to each shift whereas CRT was unresponsive to time-on-shift effects. Significant variations were observed in alertness and performance components during the 12-h night-shift. Perhaps paradoxically, performance on the 12-h night-shift appeared to improve rather than deteriorate during the early-hour period that was associated with the greatest drop in alertness. This was suggestive of extra effort expenditure during this critical period.     

Is there an optimum number of night shifts? Relationship between sleep,health and well-being

Abstract

By concentrating on the impact of a specific shift-system feature on the well-being of those concerned, rather than on the impact of the shift system as a whole, one might be able to offer more meaningful suggestions as to what constitutes a better form of shift system. The present study focused on the impact of the number of consecutive night shifts worked on the health and well-being of two groups of nurses (permanent night and rotating shift). All nurses completed a copy of the Standard Shiftwork Index, which is a set of questionnaires designed for comparing the effects of different types of shift system on large groups of workers. It includes measurements of psychological ill-health, physical ill-health, chronic fatigue, social and domestic disruption, attitudes towards shiftwork, sleep quality and sleep habits. Results showed clearly the impact of the number of consecutive nights worked on health and well-being, not directly, but indirectly through the impact on sleep duration and sleep quality. Sleep duration was shown to increase with more consecutive nights worked. This in turn was found to predict sleep quality, which in turn was found to be the stronger direct predictor of psychological and physical ill-health: i.e. better health was associated with longer and better quality sleeps. Explanations in terms of circadian adaptation are discussed.     

Behavioural techniques for enhancing alertness and performance in shift work

This paper reviews behavioural and cognitive methods for increasing alertness, enhancing performance, and decreasing long-term negative consequences due to shift work. Methods having the most potential for effective intervention include the short-term alerting effects of the optimal timing of work breaks, social activity during breaks, and sensory stimulation. Stress coping techniques and sleep hygiene information for workers and their families have the most potential for addressing long-tcrm effects of shift work. Recommendations for areas requiring further investigation include the altering effects of bright light, fresh air, and cold water; performance enhanccmcnt through psychophysiological self-regulation and imagery; and the impact on performance of second jobs and family responsibilities.     

Pilot Study Sleepiness in physicians on night call duty

Little is known about how physicians' feelings of sleepiness and sleep patterns are affected by night call duties. In the present pilot study, the authors followed a group of staff (hospital) physicians during and following night call duties. They recorded feelings of sleepiness and sleep patterns every third hour. Results show measurable effects on the sleepiness scale with residual effects lasting up to two days after the actual night call duty. The authors suggest that increased attention should now be given to studies of the psychophysiological effects of both present and alternative work schedules for physicians.     

Uncovering the factors behind new ventures’ international performance: Capabilities,alertness and technological turbulence

This research is based on the perception that the explanation of International New Ventures' (INVs) performance demands a process view, going deeper than the standard approach, in empirical papers, of testing a direct relationship between company-level antecedents and performance. A three-tier model was developed to investigate the process leading to INVs international performance, emphasizing the role of entrepreneurial alertness. Based on the dynamic capabilities framework, entrepreneurial alertness was envisaged as the mediating element between firms' capabilities and their international performance. Empirical research confirmed the hypothesized model. Firms' capabilities (entrepreneurial orientation, foreign market knowledge, and absorptive capacity) significantly influence the level of entrepreneurial alertness, which impacts on the levels of self-reported satisfaction with the company's international performance. The paper makes four contributions to International Entrepreneurship literature. First, it highlights the key role played by entrepreneurial alertness in explaining INVs' international performance. This is convergent with the dynamic capabilities view on firms' ability to sense and seize specific international business opportunities. Second, this study considers entrepreneurial alertness as a capability that is not limited to the entrepreneur, but it is an organizational capability. Third, it shows that entrepreneurial alertness does not exist in the vacuum, is based on a set of base capabilities, namely entrepreneurial orientation, foreign market knowledge, and absorptive capacity, that simultaneously leverage the INVs to sense possible opportunities and constrain the focus of opportunities to international markets, as a key element to foster INVs' higher performance. Fourth, it underlines the role of technological turbulence as a moderator of the relationship between entrepreneurial alertness and INVs' international performance.     

Effects of sleep inertia on cognitive performance following a 1-hour nap

Abstract

This study investigated the effects of a 1-h nap on subsequent performance in spatial memory (SM) and logical reasoning (LR) tasks. The objective was to evaluate the duration of the effects of sleep inertia (SI). The performance was measured in two independent groups of subjects. The 1-h nap took place at 00:00 h in group 1 and at 03:00 h in group 2. In each task, the experimental design comprised one no-nap condition in which subjects had no sleep before the night tests, and a nap condition that comprised the 1-h nap followed by the test sessions. To measure the duration of SI effects, the subjects were tested in two 30-min sessions and the data in each session were analysed in sub-units of time of 3 min each. In each task the results showed no effects on accuracy, and no circadian effects of napping were found. In each task, analyses of pooled data of the two groups showed that the performance in the 1-h nap condition exhibited significant reductions of speed immediately following awakening, when compared with no-nap, reflecting SI effects. In SM, the slowing lasted 24 min, and 27 min in LR. Practical implications of the results are discussed.