Personality differences in the phase of circadian rhythms: a comparison of morningness and extraversion

Abstract

Individual differences in the phase of circadian (around 24 h) rhythms are thought to be important in determining adjustment to shift work and rapid time-zone transitions. Attempts to predict such phase differences on the basis of paper and pencil ‘personality’ tests have concentrated on extraversion and morningness, of which Kerkhof (1985), in a recent review of this literature, concluded morningness was the more important. However, the literature on which this conclusion was based suffers from a number of problems. The present study attempted to overcome these problems by examining the trends over a complete 24 h cycle for a range of performance and psychophysiological measures in students with extreme scores for both extraversion and morningness. In general, the results support KerkhoFs conclusion. However, reliable phase differences associated with morningness were confined to subjective ratings of alertness, oral temperature, and, in combination with extraversion, choice reaction time. Two alternative interpretations of this pattern of results are considered, and their practical implications discussed.     

A comparison of circadian rhythms in work performance between physically active and inactive subjects

This study compared circadian rhythms in physiological, subjective, and performance measures between groups exhibiting different levels of habitual physical activity. Fourteen male subjects, aged 19–29 years, were assigned to a physically active (group I, n=7) or a physically inactive (group II,n= 7) group on the basis of leisure–time physical activity. Rectal temperature, oral temperature, resting pulse rate, subjective arousal and sleepiness were measured at 02:00,06:00, 10:00, 14:00, 18:00 and 22:00 in a counter–balanced sequence for each subject. Whole–body flexibility, back and leg strength, grip strength (right and left), flight time in a vertical jump, PWC₁₅₀ and self–chosen work–rate were also recorded at each time point. At least 8h separated each test session. Subjects avoided exercise 48h prior to, and during the experiment. Data were subjected to the group cosinor method. Group I evidenced 1·5–2·5 times greater rhythm amplitudes than Group II for oral temperature, subjective arousal, sleepiness, flexibility, left and right grip strength, submaximal heart rate, and self–chosen work–rate (p<0·05). Oral temperature and arousal for Group I were lower than Group II only at 06:00. Early morning troughs in most of the performance measures were significantly greater for Group I (p<005). The groups did not differ with respect to phasing of the rhythms (p<005). These results confirm with physical performance measures that rhythm amplitudes are higher for physically fit subjects. This could be attributed to greater early–morning troughs in the measures for active individuals. Since the subjects were sedentary immediately prior to testing, it is plausible that these findings are training effects of physical activity.     

Hours of work at sea: watchkeeping schedules,circadian rhythms and efficiency

Abstract

This review is concerned with the hours of work of personnel engaged in watchkeeping duties on board ocean-going vessels plying between distant ports. After an introduction to the general problem, existing research findings are considered in the context of the degree of adjustment shown by physiological and performance rhythms to the various watchkeeping systems in use on different types of ship. The findings are discussed in relation to a proposed programme of research aimed at determining the optimal system for maintaining efficiency in crews operating the modern, fully automated vessels now coming into service.     

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.     

Axillary temperature: a circadian marker rhythm for shift workers

Abstract

This study was designed to test the usefulness of the axillary temperature as a circadian marker rhythm, e.g. for shift workers in field experiments, where recordings may be required over extended periods. Axillary and rectal temperatures were recorded automatically at 5 or 15min intervals (Δt) using a ‘Chronotherm’ ambulatory system. Conventional (t-test, analysis of variance (ANOVA), correlation) and curve-fitting (cosinor) methods as well as power spectra were used for statistical analyses, (a) Rectal and axillary temperature rhythms were compared in five subjects over a 36 h span in laboratory conditions. Apart from rather small but constant differences in respective mesors (24 h mean) and acrophases (peak time location on the 24 h scale), rectal and axillary temperature recordings gave similar results in each individual. (b) In analyses of axillary temperatures recorded over periods of up to 15 days in a further five subjects (a field study with usual activities), only minor changes in circadian rhythm parameters were found to result from manipulation of the sampling interval over the range Δt= 15 min to Δt= 240 min, with or without data during sleep, (c) The axillary temperature recorded at Δt= 15 min over a 13 day span in a 32 year old worker on a 3-4 day rotating shift schedule had a prominent period (τ) of 22.3 h, although the prominent period of the rhythms of both wrist activity and the sleep-wake cycle remained unaltered at 24 h. Thus internal desynchronization was shown to have occurred in this subject.     

Night shift paralysis in air traffic control officers

Abstract

In an earlier paper (Folkard et al. 1984) we reported on the incidence of a temporary but incapacitating paralysis known as ‘night shift paralysis’. This appeared to be a special form of sleep paralysis that occurs when night workers manage to maintain a state of wakefulness despite considerable pressures to sleep. The incidence of this paralysis might thus be assumed to reflect the level of sleep deprivation associated with different shift systems or individuals. The present survey was designed to examine this possibility in a sample of 435 Air Traffic Control Officers (ATCOs) from 17 different countries who were on a variety of different work schedules. The incidence of this paralysis was found to be affected by four main factors, all of which might reasonably be assumed to influence the night-worker's level of sleep deprivation or sleepiness. These were the time of night, the number of consecutive night shifts, the requirement to work both a morning and a night shift starting on the same day and individual differences in the flexibility of sleeping habits. These results suggest that the incidence of this paralysis may indeed prove to be a useful ‘critical incident’ for comparing the level of sleep deprivation associated with different shift systems or individuals.     

The effects of VDT work on urinary excretion of catecholamines

The mental components of 2 hours of VDT work for three age groups of volunteers were investigated using urinary excretions of noradrenaline and adrenaline. After the work of searching for target words, the noradrenaline excretion showed a tendency to decrease in the young group, a significant increase in the middle-aged and a tendency to increase in the elderly. There was no change in adrenaline excretion in any age group. The elderly had a slower work speed than the young or middle-aged.

Noradrenaline excretion showed a significant increase after VDT work using small letters, no significant change with large letters and a tendency to decrease after hard-copy work. The adrenaline excretion, did not change. The work speed was slower during the VDT work with small letters than during the hard-copy work

These data suggest that the elevated level of sympathetic nervous activity resulting from VDT work is not caused by the VDT itself but by the intensity of the VDT work, and suggest that the effect of the VDT work may be exacerbated by aging.     

Physical workload,trapezius muscle activity,and neck pain in nurses' night and day shifts: A physiological evaluation

The purpose of this study was to compare physical workload, electromyography (EMG) of the trapezius muscle, neck pain and mental well-being at work between night and day shifts in twenty Swiss nurses. Work pulse (average increase of heart rate over resting heart rate) was lower during night (27 bpm) compared to day shifts (34 bpm; p < 0.01). Relative arm acceleration also indicated less physical activity during night (82% of average) compared to day shifts (110%; p < 0.01). Rest periods were significantly longer during night shifts. Trapezius muscle rest time was longer during night (13% of shift duration) than day shifts (7%; p < 0.01) and the 50th percentile of EMG activity was smaller (p = 0.02), indicating more opportunities for muscle relaxation during night shifts. Neck pain and mental well-being at work were similar between shifts. Subjective perception of burden was similar between shifts despite less physical burden at night, suggesting there are other contributing factors.     

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.     

Personality factors related to shift work tolerance in two- and three-shift workers

This study aimed to investigate whether different personality variables were associated with shift work tolerance, and whether these potential associations were moderated by various types of shift work. The sample comprised 1505 nurses who worked either two or three rotating shifts. Personality traits were measured in terms of morningness, flexibility, languidity and hardiness. Morningness reflects the tendency to be alert relatively early in the morning and sleepy relatively early in the evening. Flexibility denotes the ability to both work and sleep at odd times of the day, while languidity concerns the tendency to become tired/sleepy when cutting down on sleep. Hardiness relates to resilience to stressful life events. The dependent variables in this study comprised of measures of insomnia, sleepiness, depression and anxiety. Hierarchical regression analyses, which controlled for demographic variables and work load, revealed that Morningness was significantly and negatively related to insomnia. The Morningness by Shift type interaction was overall significant for depressive symptoms. Morningness was near significantly associated with lower levels of depressive symptoms in three-shift workers, but unrelated to depressive symptoms in two-shift workers. Flexibility was associated with higher levels of depressive symptoms. Flexibility by Shift type interaction was significant for insomnia, indicating that flexibility was negatively associated with insomnia for three-shift workers and unrelated with insomnia for two-shift workers. Languidity was associated with higher levels of sleepiness, depressive and anxiety symptoms. Hardiness was associated with lower levels of all four dependent variables.     

Gender and ergonomics: a case study on the 'non-formal' work of women nurses

Women's work activities are often characterised by 'non-formal actions' (such as giving support). Gender differences in ergonomics may be due to this peculiarity. We applied the method of organisational congruencies (MOC) to ascertain the 'non-formal' work portion of nurses employed in three hospital units (haematology, emergency room and general medicine) during the three work shifts in a major University Hospital in Rome, Italy. We recorded a total of 802 technical actions performed by nine nurses in 72 h of work. Twenty-six percent of the actions in direct patient's care were communicative actions (mainly giving psychological support) while providing physical care. These 'double actions' are often not considered to be a formal part of the job by hospital management. In our case study, the 'non-formal' work of nurses (psychological support) is mainly represented by double actions while taking physical care of the patients. The dual task paradigm in gender oriented research is discussed in terms of its implications in prevention in occupational health. PRACTITIONER SUMMARY: The main purpose of the study was to assess all the formal and non-formal activities of women in the nursing work setting. Offering psychological support to patients is often not considered to be a formal part of the job. Our case study found that nurses receive no explicit guidelines on this activity and no time is assigned to perform it. In measuring the burden of providing psychological support to patients, we found that this is often done while nurses are performing tasks of physical care for the patients (double actions). The article discusses the significance of non-formal psychological work load of women nurses through double actions from the ergonomic point view.     

The impact of work configuration,target angle and hand force direction on upper extremity muscle activity during sub-maximal overhead work

Overhead work has established links to upper extremity discomfort and disorders. As many jobs incorporate working overhead, this study aimed to identify working conditions requiring relatively lower muscular shoulder load. Eleven upper extremity muscles were monitored with electromyography during laboratory simulations of overhead work tasks. Tasks were defined with three criteria: work configuration (fixed, stature-specific); target angle (?15°, 0°, 15°, 30° from vertical); direction of applied hand force (pulling backwards, pushing forwards, downwards, sideways, upwards). Normalised electromyographic activity was greater for fixed configurations, particularly when pulling in a backward direction (total activity = 108.3% maximum voluntary exertion (MVE)) compared to pushing down or forward (total activity ranging from 10.5 to 17.3%MVE). Further, pulling backwards at angles of –15° and 0° showed the highest muscular demand (p < 0.05). These results suggest that, if possible, positioning overhead work in front of the body with exertions directed forwards will result in the lowest upper extremity muscle demand.

Statement of Relevance: Overhead work pervades occupational settings and is associated with risk of upper extremity musculoskeletal disorders. The muscular intensity associated with performing overhead work was assessed in several combinations of work placement and hand force direction. These findings should have utility for designing overhead work tasks that reduce muscular exposure.     

物联网技术在学生体温监测定位系统中的应用研究

当大规模的传染病爆发时,患者体温指标的测量尤为重要,本系统通过采用物联网技术来获得体温数据,可以更加有效和安全地降低医护人员及其他病人被感染的几率,基于物联网的温度采集是一种安全解决方案.     

基于web的学生顶岗实习系统的设计与实现

顶岗实习是高职院校遗行人才培养的一个重要形式,一般是在完成教学及大部分基础知识后,到专业对口的公司或企业进行顶岗锻炼,通过完成一定的生产任务,提高自己的操作能力。但是学生进行顶岗实习的过程中,大部分院校都存在着学生放出去没人管、联系不上学生、实习生放任自流等问题,导致顶岗实习达不到预期效果,研究和开发一个运行在网络上的顶岗实习管理系统,已势在必行。针对以上问题,对学生顶岗实习系统的必要性、系统的需求分析、系统设计等方面进行了详细论述,力求为学校顸岗实习管理者提供更加便捷的平台。     

Sensemaking,safety, and cooperative work in the intensive care unit

Making sense of circumstances and situations is critical to coordinate cooperative work. Especially in process control domains, we may expect that effective and reliable organizations will possess processes that develop, maintain, distribute, and, when necessary, repair this social understanding (sensemaking). Our research has focused on collective sensemaking process in an intensive care unit (ICU). Thus, sensemaking is most likely to be visible to researchers in high tempo, high uncertainty work settings such as hospital ICU, where complexity, criticality, and uncertainty are the main characteristics of the working activities and making sense of what is happening is one of the most important challenge of the team of physicians working in this context. The research demonstrates how workers create and distribute sense within small work groups and also how they use the results of these efforts to coordinate ongoing work activities. Practitioners tradeoff the opportunity costs of formal, collective sensemaking (sensemaking at intervals) against the value that this preparation provides to sensemaking during high tempo work (sensemaking on-the-fly). Further study of this dynamic balance will provide insight about how practitioners construct platforms for action during future, uncertain, high stakes work.     

The evaluation of smaller plasterboards on productivity, work demands and workload in construction workers

Manual handling of plasterboards in order to construct interior building walls is a risk factor for musculoskeletal complaints. Unfortunately, mechanical lifting aids to reduce the physical workload are impractical for this task. Therefore, the effect of smaller plasterboards on productivity, work demands and workload was evaluated in an exploratory study among experienced construction workers (n=4-8) at the worksite. The dimensions and weight of the conventional and smaller plasterboards (PB) were: PB120 (2440 x 1200 x 15 mm; 33 kg) and PB90 (2440 x 900 x 12.5 mm; 20 kg), respectively. Productivity was defined as meters of plasterboard mounted. Work demands were assessed by means of real time observations of tasks and activities. Workload was determined using continuous heart rate monitoring and subjective judgments of perceived workload. Productivity and total work time per working day did not differ between PB120 and PB90. Duration of mounting (29% increase) and anchoring (26% increase) were longer for PB90 than PB120. Duration of lifting, carrying and turning over plasterboards, and percentage of heart rate reserve showed no difference between PB120 and PB90. A majority of the workers preferred PB90. For the last two reasons and because PB90 weighs approximately 40% less than PB120, PB90 seems preferable. The workload in both conditions, however, was considered high.     

Study of the relationship between lacrimation and blink in VDT work

VDT (Visual Display Terminal) work generates various symptoms in operators’ eyes such as strain, a sensation of dryness, the presence of a foreign body, and so on. Research suggests that lacrimal abnormality may be related causally to such symptoms. In this paper, the relationship between lacrimation (the secretion of tears) and the frequency of blink due to VDT work in health subjects and VDT workers with such symptoms, and consequent therapeutic methods, were studied. When lacrimation, BUT (Break-UP Time), and the frequency of blink before and after VDT work compared in the control subjects and VDT-operators, an essential difference was noted in experiment 1 the frequency of blink decreased only during VDT operation, and a decreasing tendency of lacrimation was also noted while lacrimation before operation was already less in the VDT group; no large variation was noted before or after VDT operation. The frequency of blink was relatively high during operation, and a decreasing tendency of BUT was noted, compared with that for control subjects. In experiment 2, lacrimation increased remarkably in four eyes (of two operators), and relief from the subjective symptoms was noted. However, BUT intactly reduced similarly before the use of a gelatin rod during the whole process. The insertion of a gelatin rod was consecutively carried out every two weeks for approximately eight months; the development of complications such as dacryosolenitis, etc., was not noted. From these results, it is considered that the insertion of a gelatin rod is clinically useful for VDT operators with decreasing lacrimation.     

Efficacy of adjusting working height and mechanizing of transport on physical work demands and local discomfort in construction work

The efficacy of ergonomics measures to reduce physical work demands in a real working situation is often assumed, but seldom studied. In this study, the effect of adjusting working height and mechanization of transport on physical work demands and local discomfort of bricklayers' work was evaluated during a field experiment in the construction industry. In a within-subjects controlled experiment, 10 bricklayers and 10 bricklayers' assistants worked in two different conditions. Working height of bricks and mortar, and transport of materials were manipulated. The physical work demands were assessed through real time observations at the work site. Local discomfort of the lower back and of the shoulder region was measured by means of a visual analogue scale. Working with a scaffolding console to adjust the working height of the storage of materials resulted in a significant reduction of the frequency and duration of trunk flexion (?>?60°) by 79% and 52% respectively, compared with bricks set out on the ground floor. Mechanization of transport of materials resulted in a significant reduction of the frequency and duration of trunk flexion (?>?60°) by 94% and 92% respectively, compared with the condition of manual handling. The frequency of handling objects (?>?4?kg) reduced significantly by 86%. Local discomfort of the lower back was significantly less in the ergonomic conditions, while no significant difference was found for local discomfort of the shoulder between both conditions in bricklayers' assistants.     

The effects of a self-selected nap opportunity on the psychophysiological,performance and subjective measures during a simulated industrial night shift regimen

This study compared the effects of a 1 h self-selected recovery period to those of a standard night shift arrangement (with a total break time of 1-h) over a simulated three-day night shift schedule in a laboratory setting. Results showed that the inclusion of the flexible nap scheme resulted in higher performance output, improvements in physiological strain responses and reduced sleepiness during each night shift and generally over the three-night cycle. Certain variables also revealed the impact of napping compared with the standard rest break condition on the circadian rhythm. The sleep diary records show that the inclusion of the current intervention did not significantly reduce daytime recovery sleep. The results suggest that the potential benefits of flexible napping may outweigh the logistical effort it requires in a workplace environment.

Practitioner summary: Consensus on appropriate napping strategies for shift work remains a challenge. This simulated night shift laboratory study sought to determine the effects of a 1-h self-selected nap opportunity relative to a normal shift set-up. The nap improved performance and decreased sleepiness, without affecting daytime sleep.     

Musculoskeletal outcomes in multiple body regions and work effects among nurses: the effects of stressful and stimulating working conditions

This study investigated the various stressors encountered by the nursing profession. In particular, the following hypotheses were tested: (1) working conditions of nurses significantly affect perceived risk of injury and illness, work dissatisfaction, work satisfaction, energy state at the end of workday, the effort exerted by the registered nurse (RN), psychosomatic outcomes, and musculoskeletal symptoms (in multiple body regions); (2) both intermediate work effects (i.e., effort, perceived risk of injury/illness, work satisfaction/dissatisfaction, energy state at end of workday) and psychosomatic outcomes significantly affect musculoskeletal outcomes (in multiple body regions); (3) both working conditions and effects significantly affect musculoskeletal outcomes. In a preliminary study conducted on 34 registered nurses, results show that: (1) stressful working conditions affect musculoskeletal outcomes in multiple body regions, and (2) physical maladies such as lower back problems are not only associated with physical factors but also with a complex interaction of working conditions. Further research is warranted to obtain a better understanding of the complex interaction and the synergistic effects of the various nursing working conditions.