Shift work and disturbed sleep/wakefulness

Of the many health-related effects of shift work, disturbed sleep is the most common. This review describes the main observed effects of the three principal shifts (night, morning and afternoon) on patterns of sleep and wakefulness. The mechanism of sleep disruption in relation to circadian rhythms and the specific impact of aspects of shift organization (speed and direction of rotation) are discussed. The most troublesome acute symptoms are difficulty getting to sleep, shortened sleep and somnolence during working hours that continues into successive days off. These are only partially amenable to amelioration by manipulating shift patterns. However, there is no clear indication that chronic sleep problems result from long-term shift work.     

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.

 

     

Health disorders of shift workers

The effects of shift work on physiological function through disruption of circadian rhythms are well described. However, shift work can also be associated with specific pathological disorders. This article reviews the evidence for a relationship between specific medical disorders and working at night or on shift systems. The strongest evidence exists for an association with peptic ulcer disease, coronary heart disease and compromised pregnancy outcome.     

Alteration of circadian time structure of blood pressure caused by night shift schedule

The effects of night shift schedules on circadian time structure of blood pressure were studied in seven healthy young subjects by continuous monitoring of blood pressure every 30 min for 72 h. In the control experiment, subjects were instructed to sleep at regular times with the light off at 00.00 h and the light on at 07.00 h. In the shift experiment, they were instructed to go to bed at 06.00 h and wake up at 11.00 h. The circadian rhythm of blood pressure rapidly phase delayed by 3.5 h in the second night shift day as a group phenomenon. Individual differences in changes in power spectral patterns of blood pressure were found in the night shift schedule. Ultradian rhythmicity of blood pressure was more pronounced in three subjects, whereas the circadian rhythmicity was maintained in four subjects. These findings held when the adaptation to shift work was taken into account.     

The impact of shift work on the risk and severity of injuries for hospital employees: an analysis using Oregon workers' compensation data

BACKGROUND: While past research on health care workers has found that shift work can lead to negative physiological and psychological consequences, few studies have assessed the extent to which it increases the risk of specific work-related injuries, nor quantified and compared associated types, severity and costs. AIMS: This study aimed to derive and compare the rates, typologies, costs and disability time of injuries for various hospital worker occupations by day, evening and night shift. METHODS: This study used Oregon workers' compensation claim data from 1990 to 1997 to examine the differences in hospital employee claims (n = 7717) by shift and occupation. Oregon hospital employee claim data, hospital employment data from Oregon's Labor Market Information System and shift proportion estimates derived from the Current Population Survey (CPS) were used to calculate injury rate estimates. RESULTS: The injury rate for day shift per 10,000 employees was estimated to be 176 (95% CI 172-180), as compared with injury rate estimates of 324 (95% CI 311-337) for evening shift and 279 (95% CI 257-302), night shift workers. The average number of days taken off for injury disability was longer for injured night shift workers (46) than for day (38) or evening (39) shift workers. CONCLUSION: Evening and night shift hospital employees were found to be at greater risk of sustaining an occupational injury than day shift workers, with those on the night shift reporting injuries of the greatest severity as measured by disability leave. Staffing levels and task differences between shifts may also affect injury risk.     

Shift work and occupational medicine: an overview

In modern society, more and more people work during 'non-standard' working hours, including shift and night work, which are recognized risk factors for health, safety and social well-being. Suitable preventive and protective measures are required to mitigate the adverse effects and ensure that the worker can cope satisfactorily. These are based mainly on the organization of shift schedules according to ergonomic criteria and on specific medical surveillance. Occupational medicine has to consider very carefully the several factors (psycho-physiological, pathological and social) that can influence tolerance and/or maladaptation.     

Shift work, health, the working time regulations and health assessments.

Shift work and night work in particular have been associated with sleep difficulties, general malaise, fatigue, peptic ulceration, ischaemic heart disease, cigarette smoking and adverse pregnancy outcome. The medical conditions previously regarded as making individuals unsuitable for shift work show wide ranging patho-physiological activity and there is no published evidence for any such condition to be regarded an absolute reason to exclude an individual from shift work. The fulfilment of the legal obligations of the Working Time Regulations 1998 is neither prescribed nor constrained in any way. It is advisable therefore to build on existing health procedures where they are in effect. Periodic health questionnaires can offer health professionals an opportunity to detect any disorder likely to be aggravated by shift work or by a combination of shift work, job demands and workplace conditions. A further purpose of the questionnaire is the assessment of ability to undertake shift work duties. However, health questionnaires are neither sensitive nor specific enough to be used to select applicants or employees for shift work, since they do not consistently predict tolerance of shift work or subsequent health problems. Whether employers should offer anything more than a simple questionnaire will depend on the culture of the company and accessibility of health services. Screening programmes affect many people relative to the few who benefit and with existing knowledge, periodic general health examinations performed in asymptomatic subjects have limited predictive or preventive value.     

Elevated salivary cortisol levels as a result of sleep deprivation in a shift worker

BACKGROUND: This paper reports a case from a group of 63 shift-workers for whom adaptation to shift-work was evaluated through measurement of salivary cortisol levels. METHODS: Workers' saliva was sampled and cortisol levels measured at intervals of 2 h during morning, evening and night shifts. RESULTS: For one subject among the 63, very high values of cortisol (an approximately 6-fold increase) were observed for the morning (M) shift, but with normal values found for evening (E) and night (N) shifts. Individual mean and peak cortisol values were 48.4 and 67.8 nmol/l against group mean and peak cortisol values of 8.9 and 11.0 nmol/l. Retrospective questioning showed that this subject was healthy and there were no indicators of long-term stress. CONCLUSION: This cortisol rise was deduced to be caused by sleep deprivation as a result of rapidly rotating shift patterns.     

The productivity of female shift workers

The productivity of female shift workers, working on a weekly rotating three-shift system, was examined. The afternoon shift was found to be the most productive and the night shift the least productive one. The greatest difference in productivity between shifts was found in the first two days of the week, when the productivity on night shift was significantly lower than that on the other two shifts. From the third day on there were no longer significant differences in productivity between shifts. The most productive and the least productive workers on night shift did not significantly differ in extraversion or in sleep duration after the night shift. Family responsibility was found to be associated with the duration of sleep after the night shift: married women slept significantly shorter after the night shift than unmarried women. However, this difference in sleep duration was not associated with productivity on night shift. Sleep duration after the afternoon shift (8 hours 40 minutes) was on average two hours longer than after the other two shifts. The difference in sleep duration after different shifts, along with circadian variations in alertness, readiness for work and performance efficiency, could be responsible for differences in productivity between shifts.     

A cross-sectional study of self-reported work conditions and psychiatric health in native Swedes and immigrants

Several studies have demonstrated that immigrants in Scandinaviancountries are more affected by psychosocial disabilities thanthe native-born population. The aim of the study was to evaluatethe possible impact of work-related stressors on psychiatrichealth in immigrants compared to native Swedes. The study includeda cluster selected cohort of 1,040 men born in 1944 (participationratio=79.9%), living in Gothenburg, Sweden. Of these, 182 (18.0%)were immigrants, defined as being born outside Sweden. Informationon work conditions and psychiatric health were obtained by self-administeredquestionnaires. Employment in native Swedes showed inverse associationsto frequent use of anxiolytics [relative risk (RR)=0.2; 95%confidence interval (Cl)=0.067ndash;0.4], frequent use of hypnotics(RR=0.1; Cl=0.02–0.2) and use of antidepressants (RR=0.3;Cl=0.2–0.5). None of the employed immigrants used anxiolyticsor hypnotics frequently. Swedes seemed to display a number ofpsychiatric ill-health factors related to working conditions.These factors included frequent use of hypnotics, frequent insomnia,use of antidepressants, a high degree of melancholy, and wererelated to shift work, dissatisfaction with current work andmanagement and a low degree of influence on work situation,often related to a high degree of stress at work and a frequentdesire to change type of work. These associations were not seenin immigrants, apart from the risk of frequent insomnia (RR=4.7;Cl=1.2–18.3) and dissatisfaction with colleagues (RR=10.4;Cl=2.27ndash;48.8) when working in shift. With a few exceptions,non-optimal working environment was associated with a low degreeof life satisfaction in both groups. It was hypothesized thatoptimal working conditions are important for maintaining psychiatrichealth, and that immigrants, when employed, seem less affectedby impaired working conditions than native Swedes.     

An economic evaluation of occupational health

There is an increasing need to evaluate the costs and benefits of an occupational health service (OHS). However, measuring benefits from an OHS is inherently difficult. Instead, an economic model can be constructed to present the minimum threshold benefits required for OHSs to be cost-effective, given what is known about costs. This model assumes that the benefits of an OHS are to maximize health and morale of employees; maximize performance and increase productivity; minimize medico-legal costs; enhance workplace safety; and reduce sickness absence. A certain distribution across these benefits can be assumed for each OHS. The overall required value of all benefits brought about by use of an OHS is in the range 158-199 Pounds per year. The plausibility of results can be assessed using known data and judgement. Despite many uncertainties it is likely that the minimum benefit thresholds will be achieved overall.     

Indicators of cardiovascular risk among workers exposed to high intermittent levels of carbon disulphide

The effects of exposure to carbon disulphide have been studied mostly among workers in the viscous rayon industry, where the usual exposure profile has been relatively steady exposure over work shifts. We investigated 13 workers in a small chemical company who were exposed to low levels, peaking intermittently to relatively high levels in the range of 100-200 ppm at the end of the work shift, a pattern that may change the risk profile. Our investigation was part of a compliance order that was fought by the company and our access and follow-up was limited. Two workers had burns on their bodies associated with exposure to caustic. Four had elevations in total serum cholesterol, one had elevated serum triglycerides and three had elevations in fasting blood glucose--two of them were known to be diabetics before employment and one had a history of unexplained peripheral neuropathy. No consistent pattern suggestive of a defined lipoprotein abnormality was obvious but several atherogenic profiles were observed. Five had abnormalities on electrocardiogram, four of whom appeared to be among the most heavily exposed. The presence of these changes taken together in this context may suggest accelerated atherosclerotic changes. Tests of liver and kidney function were within the normal range for all workers, as was a complete blood count. Four of the workers had evidence of a bilateral reduction in hearing threshold at 4,000 Hz. A complete set of recommendations was forwarded to the employer, emphasizing further control of exposure to carbon disulphide, personal protection requirements and a cardiovascular risk reduction programme. Conditions improved in the plant following modifications introduced in response to a stop work order from the provincial government's occupational health and safety agency. However, a fire in 1998 put the company out of business and ended further follow-up or interventions. We conclude that these findings, while difficult to interpret because of the circumstances of the investigation, are compatible with an atherogenic effect of exposure to peaking levels of carbon disulphide. The observation should be tested in a larger population with fewer confounding factors and greater control over the investigation.     

Minor injuries, cognitive failures and accidents at work: incidence and associated features

BACKGROUND: There is a dearth of information examining minor injuries and cognitive failures in the workplace. AIMS: This study aims to describe the incidence of, and characteristics associated with, minor injuries, cognitive failures and accidents in the workplace. METHODS: The study was a community based postal questionnaire survey of people selected at random from the Electoral Registers of Cardiff and Merthyr Tydfil; 7980 questionnaires were returned. RESULTS: Frequent/very frequent minor injuries were reported by 9.8% of the workers and frequent/very frequent cognitive failures (e.g. problems of memory, attention or action) by 10.5%. Work accidents requiring treatment were reported by 5.6% of the workers. Minor injuries, cognitive failures and accidents were associated with a number of demographic and health factors. In addition, minor injuries, cognitive failures and accidents were found to be related to each other. CONCLUSIONS: A large number of workers experience accidents and minor injuries at work. Minor injuries are not recorded by official sources but could have implications in productivity and worker health. Factors identified in this study, as associated with injuries or accidents, could be addressed by specific workplace policies or by raising individual awareness of the risks.     

Changes in psychophysiological functions during night shift in nurses

 The effects of changing from a full-day to a half-day shift work before a night duty shift on physiological and psychological functions during the night shift were investigated in 12 healthy unmarried nurses working on the same ward of a university hospital. Three shift patterns, i.e., a day shift following a day shift, a night shift following a day shift, and a night shift following a half-day shift, were studied in terms of physical activity level, sympathetic and parasympathetic activity levels, cortisol, prolactin, NK cell activity, and changes in mood states. The change to the half-day shift increased the duration of sleep before night duty by about 86 min and brought wake-up times forward by about 1 h, resulting in increases in rest and time before work. In addition, the change was revealed to reduce the influence of reversed-phase circadian rhythms on autonomic nervous activity during the night shift. The score for sleepiness was significantly lower at 0500 hours following a half-day shift. There were some marginal but not significant differences in the scores reflecting the degree of vigor, tiredness and irritation during the night shift. Although the prolactin concentration was significantly decreased at the start of the night shift after the half-day shift, there was no difference in cortisol concentration or NK cell activity between the usual night shift after a day shift and the night shift after the half-day shift. The half-day shift was not observed to cause any marked change in the fixed biorhythms of these nurses. The cortisol and NK cell activity levels were low during the night shift, suggesting that the night shift itself is a high stress level, which is prejudicial to biodefense. Received: 1 August 1995/Accepted: 8 March 1996     

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.     

The impact of the COSHH regulations on workers with occupational asthma

In the UK, the COSHH Regulations give specific guidance thatemployers have duties to inform, instruct and train their employeesabout occupational risks and provide them with suitable healthsurveillance. The aim of the study was to evaluate the impactof the Regulations on employees with occupational asthma. Onehundred consecutive patients attending an occupational lungdisease clinic completed a questionnaire assessing the implementationof the COSHH Regulations in their workplace. Twenty-eight percent had a pre-employment inquiry about asthma, 31% had regularhealth surveillance by questionnaires and 19% had regular lungfunction assessment at work. Pre-employment spirometry was carriedout in 44% of the workers who were exposed to one of the originalseven prescribed agents, significantly more than those who wereexposed to other agents (19%) (p < 0.05). Moreover, figuresfor spirometry during employment were 31% and 8% respectively(p < 0.05). The patients who worked after ‘COSHH’but before ‘MS25’ had a tendency to be providedwith health surveillance more than those who worked after both‘COSHH’ and ‘MS25’. Ninety-one per centof the patients had never been informed about the risks of gettingasthma at work and 73% had never seen the safety data sheets.The workers who (1) worked after ‘COSHH’ introduction;(2) worked in larger firms and (3) were exposed to one of theoriginal seven prescribed agents, had a tendency to be informed,instructed and trained more than the rest. However, there wereonly significant statistical differences (p<0.05) in termsof the safety data sheet provision between the cases who workedbefore the time of the legislation and those employed afterwards.     

Nanotechnology and the occupational physician

Nanoparticles differ from the same material at larger scale in chemical and physical properties. Evidence from studies of fibres leads to the conclusion that inhalation of nanotubes could be dangerous and should be regulated. Air pollution research has suggested that particles may be more toxic to cells at the nanoscale. At present the marketing of nanoparticles is advancing more rapidly than research into their safety and toxicology, and one serious inhalation episode has been reported in Germany from apparent use of a nanoproduct. This rapidly developing industry will make an impact on the work of occupational physicians, first in universities and small concerns but later more widely. The future safety of workers and consumers is dependent on research into hazard and risk, an area in which the UK and most other countries are dragging their feet. However, a resource, the Safety of Nanomaterials Interdisciplinary Research Consortium, has been established in the UK to assist those active in this field.     

Relationship between self-reported low productivity and overtime working

OBJECTIVE: To investigate the relationship between overtime working and self-reported low productivity due to poor health over the course of 1 year. METHODS: The subjects were 94 random-sampled workers at a Japanese manufacturing company. The data on sickness absence and low productivity due to poor health were collected by self-report questionnaires every month from October 1999 to September 2000. Seventy-four workers returned complete answers. The complete data on overtime hours of forty-nine of these employees were obtained from company records. RESULTS: In those reporting low productivity, cold-like symptoms and sleep loss were given as the causes. Low productivity was closely linked to overtime worked, whereas sick leave tended to increase during periods of change in overtime working. CONCLUSION: Our results suggest the possibility of a relationship between overtime working and self-reported low productivity.     

Ergonomics in mining

Like other areas of occupational health and safety (OHS) ergonomics is evolving and becoming more integrated into overall work management systems. As we learn more about the complex interaction between psychosocial and physical factors in the aetiology of work-related illness and injury the more we rely on managers to 'get it right' if we are to prevent these conditions. Risks to health and safety in the mining industry posed by longer shift lengths, higher work loads, less task variation and decision latitude have not really been well researched. Heavy physical workloads and stresses are still areas of concern, but are likely to be intermittent rather than constant. Recent research confirms current thinking rather than shedding new light on the subject. The contribution of slips, trips and falls and increasing age of miners to manual handling injuries is still not clear. In some cases sedentary work and the operation of machinery has completely replaced heavy physical work. The issues of machinery design for operations and maintenance and whole-body vibration exposures when operating machines and vehicles are becoming more critical. The link between prolonged sitting, poor cab design and vibration with back and neck pain is being recognized but has yet to be addressed in any systematic way by the mining industry. On the plus side some mining companies have well-developed participative approaches to problem solving and these need to be extended to areas such as ergonomics.     

Cyanide poisoning: pathophysiology and treatment recommendations

This paper aims to assess and compare currently available antidotes for cyanide poisoning. Such evaluation, however, is difficult. Thus, extrapolation from the results of animal studies has potential pitfalls, as significant inter-species differences in response may exist, and these experiments often involve administration of toxin and antidote almost simultaneously, rather than incorporating a more realistic time delay before initiation of treatment. Direct inference from human case reports is also problematic; either because of uncertainties over the exposure levels involved (and hence the likely outcome without treatment), or because of difficulties in identifying the specific contribution of a particular antidote within the overall treatment regimen. Certainly an effort to compare the relative efficacy of cyanide antidotes produces equivocal findings, with no single regimen clearly standing out. Indeed, factors such as the risks of antidote toxicity to various individuals and other practical issues, may be more important considerations. There is therefore no single treatment regimen which is best for all situations. Besides individual risk factors for antidote toxicity, the nature of the exposure and hence its likely severity, the evolving clinical features and the number of persons involved and their proximity to hospital facilities, all need to be considered. Clinically mild poisoning may be treated by rest, oxygen and amyl nitrite. Intravenous antidotes are indicated for moderate poisoning. Where the diagnosis is uncertain, sodium thiosulphate may be the first choice. With severe poisoning, an additional agent is required. Given the various risks with methaemoglobin formers or with unselective use of kelocyanor, hydroxocobalamin may be preferred from a purely risk-benefit perspective. However the former alternatives will likely remain important.