shift work in nursing

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Shift Work in Nursing: Is it Really a Risk Factor for Nurses' Health: Policy

Implications

Hanna Admi, PhD, RN, is Director of Nursing, Rambam Health Care Campus, Haifa, Israel.

Orna Tzischinsky, DsC, is a Member of The Sleep Laboratory and Faculty of Medicine,

Technion-Israel Institute of Technology, Emek Yezreel Academic College, Emek Yezreel, Israel.

Rachel Epstein, MA, is a Researcher, Sleep Laboratory, Faculty of Medicine, Technion-Israel

Institute of Technology, Haifa, Israel.

Paula Herer, MS, is Statistical Consultant, Sleep Laboratory, Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israel.

Peretz Lavie, PhD, is Vice President for Resource Development and Public Affairs, SleepLaboratory, Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israel.

Introduction

Shift work is now a major feature of work life across a broad range of industries. Over 20% of

workers in industrialized nations are shift workers, and about 10% of them are diagnosed as

having sleep disorders. However, the health and safety issues associated with shift work in

general (Basent, 2005; Drake, Roehers, Richardson, Walsh, & Roth, 2004) and with nurses'health and patient safety in particular have been poorly explored (Muecke, 2005). Moreover,

most of the research in the field of shift work and sleep disorders does not take into account the

roles of ethnicity, age, and gender. The present study attempts to fill this gap by examining theimpact of shift work on the quality of performance (e.g., work absenteeism, errors, and adverse

clinical incidents) among nurses and by comparing males and females in the same profession.

Effects of Shift Work

Shift work can have an impact on sleep, well-being, performance, and organizational outcomes.

The existing scientific studies indicate that shift work affects both sleep and waking bydisrupting circadian regulation, familial and social life (Gordon, Cleary, Parker, & Czeisler,

1986; Labyak, 2002; Lee, 1992). Sleep obtained during the day or at irregular times is of poorer

quality than that obtained during normal nighttime sleep. Chronically restricted sleep patterns

and the subsequent sleep debt that accumulates over time may be most pervasive in suchprofessions as health care delivery that function 24 hours a day, 7 days a week.


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Evidence of high risk for significant behavioral and health-related morbidity is associated with

sleep disorders among shift workers. Shift workers with sleep disorders have higher rates ofcardiovascular diseases and digestive tract problems. Research into the impact on professionals

has consistently identified a range of negative outcomes in physical, psychological, and social

domains (Akerstedt, 1988; Costa, Lievore, Casaletti, Gaffuri, & Folkard, 1989; Kogi, 2005;

Paley & Tepas, 1994). The morbidity associated with sleep disorders among shift workers wassignificantly greater than that experienced by daytime workers with identical symptoms, such as

sleep-related accidents, depression, absenteeism, and missed family and social activities (Drake

et al., 2004).

There is growing concern about the ability of individuals to maintain adequate levels ofperformance over long work shifts, particularly when those shifts span nighttime hours. Research

results are mixed on this issue. Gold and colleagues (1992) reported that the main factor

associated with medical errors was shift work. Rouch, Wild, Ansiau, and Marquie (2005)

demonstrated short-term memory disturbances related to circadian rhythm disruption caused byshift work. However, 4 years after workers stopped working shifts, performance seemed to

improve, which suggests a possible reversibility of effects.

Kawada and Suzuki (2002) found that rotating shift work affects the amount of sleep, but not the

rate of errors among workers on a three-shift schedule. Suzuki, Ohida, Kaneita, Yokoyama, and

Uchiyama (2005) found that professional mistakes, such as drug administration errors, incorrectoperation of medical equipment in hospitals by nurses, and needlestick injuries were associated

with the complaint of excessive sleepiness. Suzuki and colleagues (2004) presented no

association between shift work and occupational accidents, but rather found an association

between mental health and medical errors.

Most of the nursing studies rely heavily on the general scientific literature in the field of shift

work and sleep disorders. Assuming that shift work is associated with sleep disorders, the focusof the nursing literature has been on improving the design of the shift system and on offering

strategies for coping with rotating shift work.

Various recommendations have been made in regard to the design of the shift work system, such

as length of shift (8-12 hours); principles of rotation (day, night, evening); scheduling

(clockwise, number of shifts); and adjustment to individual needs ("morning people" vs. "nightpeople") (Thurston, Tanguay, & Fraser, 2000). Recommendations for dealing with shift work

include taking a nap prior to the shift; shift breaks; bright lighting; healthy snack food; and

avoiding coffee, alcohol and smoking before daytime sleep (Cooper, 2003).

Definition of Terms

For the purpose of the present study, we defined "shift work" as a rotating 8-hour shift schedule,including morning, evening, and night shifts. This definition excludes daytime nurses who

permanently work only morning shifts. A "non-adaptive shift worker" is defined as a shift

worker (in our study, a rotating shift nurse) who complains of "difficulties falling asleep afterevening, morning or night shift" and in addition complains about "multiple awaking during day


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sleep after a night shift." These definitions were used by the authors in previous research studies

(Lavie et al., 1989).

Goal and Objectives

The goal of this study was to explore and describe the health complaints and sleep patterns ofhospital nurses who are working rotating shifts and to examine the impact of shift work on nurse

absenteeism and patient safety.

The specific aims of the current study were:

1. To compare subjective medical complaints and sleep disorders between female nursesand male nurses.

2. To compare subjective medical complaints and sleep disorders between daytime nursesand shift nurses.

3. To identify the scope of "non-adaptive shift nurses."4. To compare subjective medical complaints and sleep disorders between "adaptive shiftnurses" and "non-adaptive shift nurses."5. To compare rates of clinical errors and adverse incidents be tween "adaptive shift nurses"

and "non-adaptive shift nurses."

6. To compare rates of absenteeism between "adaptive shift nurses" and "non-adaptive shiftnurses."

Methodology

Subjects. Researchers investigated 738 hospital nurses in a major teaching hospital in northern

Israel during the year 2003. The sample comprised all nurses working only daytime shifts or

rotating shifts. A total of 688 nurses (93.2%) completed all the questionnaire data, including 589females (85.6%) and 99 males (14.4%). Of the total sample, 195 nurses (175 females and 20

males) worked only days and 493 nurses (414 females and 79 males) worked flexible rotating

shifts (mornings, evenings, and night shifts in accordance with the units' and nurses' needs).

The study was approved by the Helsinki Research Ethics Committee of Rambam Medical

Center. All subjects agreed to participate after they were fully informed about the nature of thestudy and of their right to leave at any stage.

Measurements. All nurses completed self-administered questionnaires that included items ondemographics; health history and complaints; and sleep habits and disorders.

The sleep questionnaires consisted of a 10-question Sleep Disorder Questionnaire, which wasrated on a 7-point Likert scale ranging from "never" to "all the time" (a Cronbach=0.74) (Zomer,

Peled, Rubin, & Lavie, 1985), and a sleep habit questionnaire reflecting respondents' perceptions

of sleep time and sleep quality. In both sleep questionnaires, there were questions about daytime

fatigue and sleepiness, as well as overall well-being.

Results


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Sample demographics. Significant differences were found be tween male and female nurses in all

the demographic variables. In comparison to the male nurses, the female nurses weresignificantly older, had higher rate of divorce, more children, older children, and longer seniority

at work. Body Mass Index (BMI) was significantly higher in the males, and more male nurses

were single than female nurses (seeTable 2). Assuming that family status, number, and age of

children and seniority at work are age dependent, the observed demographic findings indicatesignificant differences in age and BMI. Of a total 688 nurses, 70% (414) of the female nurses

were working rotating shifts, compared to 80% (79) of the male nurses.

Medical history and complaints: Gender comparison. The first aim of the study was to compare

medical complaints and sleep disorders between female and male nurses. The results of thereported medical history and complaints revealed that the female nurses complained significantly

more about thyroid problems (p


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(336 nurses) were defined as adaptive nurses. No significant differences were found be tween the

females and males in either the adaptive or the non-adaptive groups (c[2]

=2.236,p=0.134).

Medical history, health complaints: Adaptive versus non-adaptive nurses. Comparison of the

medical history, health complaints, and sleep disorders between adaptive versus non-adaptive

shift nurses was the fourth aim of the study. No significant differences were found in anyreported medical histories or health complaints between the adaptive nurses and the non-adaptive

nurses (seeTable 6).

Sleep disorders:Adaptive vs. non-adaptive. In addition to the difficulties falling asleep and mid-

sleep awakenings after a night sleepthe criteria for maladaptation to the shift systemnon-adaptive shift nurses complained more about early morning awakening, use of sleeping pills,

headaches in the morning, morning fatigue, and restless sleep. Adjustments for age and BMI did

not change the results (seeTable 6).

Errors and incidents at work. The fifth aim of this study was to compare clinical errors and ad

verse incidence report between adaptive and non-adaptive shift nurses. During the 1-yearresearch period, 205 clinical errors and adverse incidences (e.g., medication errors, patient falls)

were reported by 201 night shift nurses. No significant differences were found between the group

of 153 adaptive nurses (45%), and the group of 48 non-adaptive nurses (37%) (p=0.14).

Adjustments for age, gender, and BMI did not change the results.

Absentees at work. The last aim of this study was to compare rates of absenteeism between"adaptive" and "non-adaptive" shift nurses. The number of absentees was divided into three

categories during the 1-year research period: none, one to three times a year, and more than four

times a year. As demonstrated inTable 7, no significant differences were found between the

adaptive and non-adaptive nurses for all three categories (c[2]

=0.49, NS). Adjustments for age,

gender, and BMI did not change the results. It is interesting to note that over 50% of the non-adaptive nurses did not miss work even once a year because of a health problem and only 8%

missed work more than four times a year.

Discussion

It is well established that 20% of the workers in our society are shift workers (night shifts androtating shifts) and that approximately half of them complain of difficulties with their sleep

(Drake et al., 2004). There is also evidence in the scientific literature of the adverse physiological

and psychological effects of shift work, including disruption to biological rhythm, sleep

disorders, health problems, diminished performance at work, job dissatisfaction, and social

isolation (Morshead, 2002; Muecke, 2005; Westfall-Lake, 1997).

Our study was aimed at examining the phenomenon of shift work among a group of female and

male workers in the same profession, namely nursing. We compared the results of health

problems and sleep disorders between female and male nurses, between daytime and shift nurses,and between sleep-adjusted and non-sleep-adjusted shift nurses. Given the lack of research on

the impact of shift work and sleep deprivation on nurses' performance and patient care (Brown,


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2004), we also explored the relationship between adjustment to shift work and organizational

outcomes (errors and incidents and absenteeism from work).

Shift work and gender. The main demographic gender-related differences in this study indicate

that the female nurses are significantly older and have lower BMI than the male nurses. In

addition, the female nurses complained more about health problems (thyroid problems,backache, and leg pain) and sleep disorders (mid-sleep awakenings, headaches on awakening,

and morning fatigue) than the male nurses. One question that should be raised is whether theseresults reflect a general tendency of females to complain more than males about their health and

sleep. Another question that needs examination is whether the females' subjective complaints

about their health problems and sleep disorders can be supported by objective evidence. Toanswer these questions, we designed a second phase of this study that was aimed to test objective

indicators of health condition and sleep patterns among the sample.

Shift work, health problems, and sleep disorders. Surprisingly, in contrast with the wealth ofliterature on the adverse effects of shift work on workers' health, our results indicate that daytime

nurses complained significantly more than shift nurses about health problems and sleepdisturbances. The main predictors of health symptoms and sleep disturbances were age and BMI.

The phenomenon of non-adaptive shift nurses. In our study, 27.7% of the nurses were non-

adaptive to shift work, compared to the 5% to 10% reported for sleep disorders in the scientificsleep literature (Drake et al., 2004). The differences might stem from methodological, gender, or

cultural differences. Methodologic problems can stem from different definitions of the terms

"non-adaptive" and "sleep disorder" or from non-standardized criteria for shift workers (e.g.,type, length, duration of shift).

The findings may indicate true differences between male and female shift workers or may

suggest sociocultural differences. Lavie and colleagues (1989) re ported about 15% non-adaptiveshift workers among a group of male workers, which is less than that found among male and

female non-adaptive nurses. Even though we used only two questions to define adaptiveness,

there were many more differences between the two groups. Those differences may presentorganizational culture effects. Further research is needed to address these differences.

Shift work and organizational outcomes. In the present study, we investigated the impact of sleep

disturbances on shift nurses and on two organizational outcomes: errors and incidents and

absenteeism from work. Based on our literature review (Morshead, 2002; Muecke, 2005;Westfall-Lake, 1997), we expected that "non-adaptive shift nurses" would report on more

involvement in errors and adverse incidents as compared to "adaptive shift nurses." We also

assumed that non-adaptive nurses, who by definition have more sleep-related complaints, would

have higher absenteeism rates due to illness compared to their adaptive colleagues. Neither ofour hypotheses was supported by the results of this study.

It is known that there is a tendency toward under-reporting on professional errors and incidents;however, there is no reason to believe that the non-adaptive nurses would avoid reporting more

or less than the adaptive nurses. We found lower absenteeism rates among the shift work nurses


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(both adaptive and non-adaptive) than among the daytime nurses, which may be explained by

differences in age.

There is a need to further explore the reasons that the "non-adaptive" nurses in the present study

were not more involved in professional errors and incidents and did not have higher absenteeism

rates from work than the "adaptive" nurses. We can only conclude that there is no relationshipbetween reported sleep disorders and performance, as demonstrated by this study's findings.

Conclusions

It appears that gender, age, and weight are more significant factors than shift work indetermining the well-being of nurses. Moreover, nurses who were identified as being non-

adaptive to shift work based on their complaints about sleep were found to work as effectively

and safely as their adaptive colleagues in terms of absenteeism from work and involvement in

professional errors and accidents.

It is important to emphasize that the decision to define a nurse as "adaptive" or "non-adaptive"was solely based on two subjective complaints about sleep disorders. The fact that we foundhigher rates of nurses who were not adjusted to shift work than reported in the literature thus far,

might be attributed to differences in gender, age, BMI, and the definition of "adapting" versus

"non-adapting" nurses employed in our study. It is well-established that the ability to cope withrotating night shifts is diminished with age and that BMI is rising with age (Learhart, 2000; Reid

& Dawson, 2001; Reilly, Waterhouse, & Atkinson, 1997).

As for gender, most research on sleep disturbances associated with shift work has been

conducted among male workers, and there is not enough evidence for comparison with females.

It has yet to be investigated whether the differences in adjustment to shift work between male

and female workers are supported objectively or whether they are attributable to the tendency offemale workers to express more complaints. In this context, it would be interesting to investigate

the impact of organizational culture and social culture on workers' norms of complaining.

In conclusion, this research adds two additional findings to the field of shift work studies. The

first finding is that female shift workers complain significantly more about sleep disorders than

male shift workers. The second finding is that although we found high rates of nurses whosesleep was not adapted to shift work, we did not find a more adverse impact on their health,

absenteeism rates, or performance (reported errors and incidents), compared to their "adaptive"

and "daytime" colleagues. In other words, shift work by itself was not a risk factor for nurses'

health and organizational outcomes in this study.

Policy Implications

Nurses are expected to deliver high-quality care and to assure patient safety 24 hours a day in

health care facilities. Taking into account that nursing is a predominantly female profession with

an increasingly aging workforce and a prolonged shortage of human resources, it is theresponsibility of health care leaders to identify health risks and their effects on work patterns

(absenteeism) among nursing personnel as well as risks to patient safety.


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Policymakers should consider the impact of the aging nursing workforce. Daytime nursing

personnel tend to be in managerial positions, as they are older and have more seniority andexperience. However, with the increasing age of nurses, we already find growing numbers of

older nurses who are required to work rotating shifts, including night shifts. This should be a

point of concern for both the nurses and the patients.

The work scheduling policy for the nurses in the hospital where this study was conducted is to

schedule 8-hour flexible rotating shifts according to employee preferences and organizationalneeds. There is some research evidence in the literature indicating that in general, nurses who

work their preferred shifts and their preferred work weeks report more positive work outcomes

and less interference with their non-work activities (Havlovic, Lau, & Pinfield, 2002).

While there is not much that can be done about age and gender, other than to take these factors

into account in shift planning, there is a need to address the increasing obesity among health care

professionals, such as by encouraging a balanced diet and exercise regime.

Future studies should continue to explore the effects of shift work through objective indicatorsfor measuring sleep disorders, adaptation to shift work, and biological markers of health

problems. It is of importance to further explore gender differences among shift workers, as well

as the effects of different organizational cultures and different occupations (industrial workers,

helping professions) on adjustment to shift work and its impact on employees' health andorganizational outcomes.

___________________________________________________________

Surviving Shiftwork

Type: Union News Subject: OHS

1 November 2005

Dr Delwyn Bartlett


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Shiftwork is a loathsome aspect of the nursing that's almost impossible to avoid. Researchpsychologist Dr Delwyn Bartlett shared some tips with conference delegates on how get moreand better sleep when you're caught in the shiftwork zone.

When you're working nightshift it may seem that everyone else is off having a good night's sleep.

But you're not alone. Around 20% of workers work nightshift, said Dr Bartlett.

'When you are working nightshift you lose around five to seven hours' sleep per week,' she said.

'Twice the number of accidents happen on nightshift than dayshift and nightshift workers are

more vulnerable to car accidents on the way to and from work.'

So how much sleep do we need? Around 7-8 hours said Dr Delwyn. However, some people need

as little as 4 hours per night, and others need 10 hours.

According to Dr Bartlett, shiftwork means you are working against your body's natural rhythm.

'Shiftwork is very stressful. You are pushed into a state of hyperarousal,' she said.

'When you are stressed muscular tensions increases, memory can be affected, you become

moody, you can suffer stomach upsets and diarrhoea, more frequent illnesses like colds and fluand sleep disturbance is common.

'In extreme cases individuals suffer from a clinical condition called shiftwork sleep disorder(SWSD) where they cannot maintain a normal sleep duration despite attempts to optimise

environmental conditions for sleep. Around 2-5% of shiftworkers are thought to suffer

from SWSD.'

To maximise sleep after a nightshift, Dr Bartlett recommends you wear dark sunglasses with side

shields on the way home from work. 'The darker the better but you need to be able to see.'

'Go home and get into bed as soon as possible. Avoid doing anything else.

'Make your sleep environment as dark as possible. Use black plastic bags on the windows if need

be and have background white noise like a fan. Keep your bedroom cool. Don't forget to pull out

the phone and leave a note on the front door telling all callers that you are sleeping.'

Whether you're working nightshift or not, Dr Bartlett has some tips for a better night's (or day's)

sleep:

Use your bed for sleep and sex only Get out of bed if you haven't fallen asleep after 20 minutes. Sit on the floor for five minutes thenget back in to bed.

'If you are not sleeping well it is important to check out whether you have a sleeping disordersuch as insomnia, restless legs syndrome, obstructive sleep apnoea,' said Dr Bartlett. 'It's also

important to check out the possibility of other medical conditions or psychological disorders.'


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Sleep can be disturbed by increased stress. Disturbed sleep also predicted by increased work

demands, high physical workload, being female aged over 45 years and having a high body massindex.

How you think is how you feel, warns Dr Bartlett. 'Negative thoughts can keep you awake so it's

important to distract negative thoughts in bed. Focus on something calming and try to thinkrealistically about sleep and being awake at night, instead of catastrophising about the

consequences of not sleeping.'

Health effects of shift work and extended hours of work

1. J M Harrington1. Professor J M Harrington Institute of Occupational Health, University of Birmingham,

Birmingham B15 2TT, [email protected]

Normal hours of work are generally taken to mean a working day with hours left for recreationand rest. Rest is a night time activity, work a daytime activity. This review is concerned with

those who work other schedules either on shifts or with extended hours which transcend the day-

night work-sleep pattern.

Such abnormal working hours are not a modern phenomenon. Ramazzini (16331714) notedthat bakers, innkeepers, and soldiers worked such hours. The advent of the industrial revolution

led to many people working long hours until legislation was introduced to curtail the worst

vicissitudes of the new factory based economy.

SHIFT SCHEDULES

Today, about one in five workers in Europe are employed on shift work involving night workand over one in 20 work extended hours . Shift systems involve periods of 612 hours work at a

time with the shift crews alternating on two, three, or four shifts in any 24 hour period. The

traditional three shifts start at 0600, 1400, and 2200 hours but there are many variations on this.

Some workers only work on the two day shifts, some only nights, while others rotate through allthree shifts with variable degrees of speed of rotation and direction of rotation. Extended hours

of work is generally accepted to mean working more than 48 hours a week. This can occur on

either day work or shift work due to either a high number of hours worked per day or a higher

number of days worked per week.

Box 1: Summary of EC Working Time Directive

No more than 48 hours a week averaged over a 17 week period A minimum daily rest period of 11 consecutive hours A minimum weekly rest period of 24 or 48 consecutive hours averaged over 14 days A minimum of 20 minutes rest in any work period of more than 6 hours A maximum of 8 hours night work every 24 hours averaged over a 17 week period
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Free health assessments for night workers Paid annual leave of at least 4 weeks

WORKING TIME DIRECTIVE

During the 1990s, substantial changes took place in international legislation on working time.The new European Directive on Working Hours (1993) introduced specific measures relating to

the scheduling of shifts and rest periods whereas on a broader scale, the International LabourOrganisation (ILO) introduced in 1990 radical new standards for working patterns. The object of

each of these measures was to limit hours worked because long or abnormal work patterns are

deemed to be hazardous to health. The main features of the European Directive as incorporated

into United Kingdom law are found in box 1. The reasons why shift work and now extendedwork has continued into the 21st century are threefold.

Society's needs for services and emergency cover Technical need for maintaining continuous process industries Economic need for offsetting plant obsolescence.

Although the shift worker of 50 years ago was likely to be factory based, increasing demand for

services, both business and pleasure, has extended to those employed in more traditionally

white collar occupations. E-commerce will lead to the need for 24 hour services for most retailand service organisations.

There are extensive publications on the health and social effects of shift work.

The quality of the papers does not always match the quantity. There are considerable

methodological issues concerned with this subject. The most obvious is the fact that a large

proportion of shift workers are a self selected population and those that remain shift workers foryears are a survivor population. Many of the studies published are cross sectional, as there are

difficulties in selecting appropriate comparison populations for longitudinal studies. Finally,

some of the outcome measures in studies of shift work involve relatively soft measures such asfatigue, mood, and performance. Nevertheless, some excellent studies have provided the basis

for what follows in this article. Some recent reviews have also highlighted the current state of

knowledge in this area.1-4

Biological and social aspects

CIRCADIAN RHYTHMS

One of the most important physiological problems associated with shift work and the night shift

in particular, is that working, eating, and sleeping phases are changed.

Mammals have a natural rhythmicity to many bodily functions and these circadian rhythms exist

in humans, with many operating on a 25 hour cycle. Such free running cycles, which includebody temperature, respiratory rate, urinary excretion, cell division, and hormone production, can
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be modulated by exogenous factors such as light-dark cycle, social climate, and of course, work

schedules.

For example, under normal living conditions, body temperature peaks in the late afternoon with

its lowest point occurring in the early hours of the morning. Under experimental conditions, it is

possible to reverse this cycle but rotating shift workers usually only succeed in flattening thecurves. Body temperature records are often used as a surrogate measure of disruption of

circadian rhythm, but it is probably too simplistic to link this measure directly to performance.5

EFFICIENCY OF PERFORMANCE

Human error is often cited as an important factor in work accidents and this may depend to some

extent on sleep related factors and circadian rhythm. In general, efficiency of performance seems

to parallel the circadian variation in body temperature. The disruption of circadian rhythm,

combined with sleep deficit and fatigue, can lead to workplace inefficiency, particularly in theearly hours of the morning. This pattern of cause and effect has been reported for many groups of

shift workers. A dip after lunch has also been described for lowered efficiency of performanceand this is only partially dependent on the meal itself.6

The shortening of the sleep period caused by an early start at work has also been shown to be

associated with an increase in errors and accidents in transport workers.

FAMILY AND SOCIAL LIFE

Workers who engage in shift work or who work long hours can experience considerable

disruption of family and social activities as many of these rhythms of the general population are

oriented around the day. Saturday and Sunday work, for example, can preclude involvement in

sporting events or religious activities. Shift work can thus lead to social marginalisation.

Family and marital responsibilities can be severely disrupted by shift work or long hours.

Childcare, housework, shopping, and leaving a partner alone at night can all lead to marital strainand family dysfunction. On the positive side, for those shift workers who like relatively solitary

leisure pursuits or who abhor the crowds often find that shift scheduling provides them with

greater opportunities to do what they want to do in their non-working time.

Health effects

Box 2: Summary of health effects of shift work

Reduction in quality and quantity of sleep Widespread complaints of fatigue Anxiety, depression, and increased neuroticism Increasing evidence of adverse cardiovascular effects Possible increase in gastrointestinal disorders Increased risk of spontaneous abortion, low birth weight, and prematurity.
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SLEEP

There is general agreement in publications that the effects of long hours of work or shift work

has a deleterious effect on sleep. Perhaps the most authoritative review concludes that despite

considerable variation between people, sleep loss is a major effect of shift work.7This is most

noticeable after the night shift. The quantity of sleep may be reduced by up to 2 hours a day butthere is also an effect on the quality of sleep. Rapid eye movement (REM) sleep and stage 2

sleep have been shown to be reduced. Such sleep deficits can lead to sleepiness at work, with

some data showing that inadvertent napping at work can result. Overall, the effect of shift workhas been likened to a long distance traveller working in San Francisco and returning to London

for any rest days.

FATIGUE

Fatigue is a common complaint among those working abnormal hours. It is particularly

noticeable after the night shift, less so on the morning shift, and least on the afternoon shift.

Fatigue, however, is a complaint that is exceedingly difficult to measure. Some publishedevidence exists to suggest that there is a reduction in complaints of fatigue after objective

improvement in physical fitness. Nevertheless, it remains an important, if vague, symptom whichis often cited as a major reason for intolerance to shift work.

MENTAL HEALTH

Shift working can be a potential psychosocial stressor. Stress is, however, a difficult concept to

define, let alone measure. Many published reports on working hours cite stress as a problem but

such reports all too commonly lack scientific rigour, acquiring these data from self administered

questionnaires and case reports. The increasing use of validated questionnaires such as the

general health questionnaire (GHQ) and, more specifically, the standard shift work index (SSI)developed by Barton and Folkard8 has improved the researchers' ability to characterise and

measure the effects of shift work on mental health.

Anxiety and depression indices also point to the likelihood of an adverse effect on mental healthfrom shift work and long working hours. Nevertheless it must be remembered that, by and large,

shift workers are a self selected population. Thus the question of whether shift work causes

psychiatric mortality or shift workers have pre-existent psychiatric problems is not entirely

resolved. There seems to be increased neuroticism with increasing years of shift work, butneuroticism in itself does not predict health related shift problems.

CARDIOVASCULAR DISORDERS

In 1978, the general consensus was that there was no firm evidence that cardiovascular disease

was more prevalent in shift workers than other groups.9Today, that opinion would have to berevised, although much of the new evidence comes from Scandinavian studies. A recent reviewof the data suggests that shift workers have a 40% increase in risk.10Causal mechanisms are not

well defined but contributing factors include disruption of circadian rhythm, disturbed
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sociotemporal patterns and social support, stress, smoking, poor diet, and lack of exercise. The

health outcomes are mainly angina pectoris, hypertension, and myocardial infarction.

The effect of overtime or long hours of work has been less extensively investigated. One

mortality study from California showed increased rates of arteriosclerotic heart disease for male

occupational groups in increasing proportions of the population who worked more than 48 hoursa week.11The 48 hour week cut off was an arbitrary one with information taken from censuses,

and the study has not been replicated. The publicity surrounding the Japanese phenomenon ofKaroshi (sudden vascular death) and overwork is relevant here but the published studies are little

more than case series and thus lack epidemiological rigor.

GASTROINTESTINAL DISORDERS

Many shift workers complain of digestive disorders, which may be a reflection on the poor

quality of catering on some shifts. Night workers seem to have the most complaints of dyspepsia,heartburn, abdominal pains, and flatulence. The data in these studies are not particularly robust.

It is necessary to realise that psychosomatic disorders are common in the general population andto recognise the influence of several other factors including Helicobactor pylori, infection, family

history, and lifestyle.

REPRODUCTIVE EFFECTS

There is increasing evidence to suggest that shift work and particularly night work, may present

special risks to women of child bearing age.4The causative factors probably include disruption

of the menstrual cycle and increased stress from the conflicts created by night work on familylife. Specific health outcomes linked to shift work include increased risk of spontaneous

abortion, low birth weight, and prematurity. The evidence for subfertility is less convincing.

Safety effects

Box 3: Summary of safety effects of shift work

Poorer performance especially at night Increased rate of accidents especially at night

PERFORMANCE

This area has already been alluded to. Until relatively recently, much of the evidence for a

performance decrement associated with long hours of work relates to some excellent studiesundertaken by Vernon et al11 on munitions workers in the first world war. The studies are

thorough, well designed, and clearly show that reducing hours of work by between 7 and 20 perweek (down to 5055 hours per week) resulted in an improvement in the quality and quantity of

units produced. Vernon et al also showed that pauses of 10 minutes in the morning and afternoon

could increase production by 512%.
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Since these studies, much of the research effort has been concentrated on laboratory based work

because comparability of working conditions between shifts is difficult to find in the worksituation. Some well designed workplace studies, however, support the laboratory based

research. In short, there is a persuasive body of evidence to suggest that performance (output) is

poorer at night. However, performance of tasks with a high working memory component is less

dependent on endogenous circadian rhythm and thus may have relatively rapid adjustment tonight work. This implies the need to view the task as well as the person in tailoring the shift

system.

ACCIDENTS

The cause of industrial accidents is exceedingly complex but the link between increased fatiguewith lowered performance and subsequent high rates of accidents would seem logical.

Publications on working hours do not support this very well, largely because many of the studies

have inadequate analytical procedures, or failed to allow for the many confounding factors that

can influence accident statistics. Furthermore, the night shift, which might intuitively be

associated with more accidents, is often the time for easy runs of a particular task on what isoften a less supervised shift. However, some recent well designed studies have shown an

increased risk of accidents on the night shift and with long working hours .4

Several studies have shown peak accident rates at around 1000 and 1100 and again between

1300 and 1600 but this probably reflects peaks in work activities as performance capabilities dueto circadian rhythms should be relatively high at these times.

Finally, on an anecdotal note, it is interesting that some major catastrophes such as Three Mile

Island, Chernobyl, Exxon Valdez, and the space shuttle Challenger all started in the early hours

of the morning with errors by people who had been on duty for long hours.

EXPOSURE TO TOXIC CHEMICALS

This is an area that has received scant attention but clearly could be important in terms of longworking hours or possible chemical variation in pharmokinetic handling of absorbed chemicals.What is clear is that occupational exposure limits are almost invariably calculated on the basis of

an 8 hour day, 5 day week. Scaling down these limits to accommodate long working shifts such

as 10 or 12 hours or making allowances for diurnal variation in metabolic processes is no easytask and no rules are available to accomodate these variations in working hours. There is a

potential toxicological problem here but no solutions at present.

Personal issues

Box 4: Summary of personal issues and prevention

Sex women>men Age older>younger Personality introversion/extroversion Design shift schedules on physiological grounds
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Physical fitness.SEX

Many countries have long banned the employment of women on shift work. The emergence of

equal opportunity legislation has questioned the basis for such prohibition. It seems that womencomplain of more sleepiness on shift work (4) but the physiological basis for this is difficult to

substantiate. Some of the increased difficulties that women have on shift work are related to theirgreater domestic obligations and to the broad based assertion that women tend to report health

symptoms more often than men. Also there does seem to be some evidence for an adverse

reproductive effect already noted.

AGE

Intuitively, it might be proposed that shift working would be better tolerated the older the worker

becomes. They might have less domestic pressures from small children, more experience of

coping in general, and older people seem to require less sleep than younger people. Furthermore,the shift worker who has been working such schedules for decades is, of course, part of a

survivor population.

In fact, the research findings support the opposite. The evidence all points in the direction of

asserting that the aging worker tolerates shift work less well than younger colleagues. With age,sleep becomes shorter and more fragmented. This does not necessarily reflect a need for less

sleep but simply an inability to achieve so easily what is needed. What is clear, therefore, is that

whereas the aging shift worker may cope, it is inadvisable to begin shift work at an older age.

PERSONALITY

It has been proposed that almost one in five workers leave shift work because they cannot

tolerate it, about 10% positively enjoy it, and the rest tolerate it to a greater and lesser

extent.9Personality may play a part in this as there is an association between neurotic

introversion and intolerance to shift work. It may be simplistic to view introvert-extrovertpersonality types in this way but there is some physiological support for the importance of

personality if people are viewed as morning types and evening types. People who are at their best

in the morning face more difficulties in adjusting their circadian rhythms to night work comparedwith those who feel better in the evening. By contrast, evening types have greater problems with

the early morning shift. Physical factors may also play a part and are discussed later.

Prevention

DESIGN OF WORK SCHEDULE

Most of the work on minimising the deleterious effects of shift work has concentrated on thethree 8 hour shift rotation. As the night shift seems to cause a disproportionate amount of the

problems of shift work, night work should be reduced as much as possible, perhaps by increasing

the number of crews involved. Rapid rotation of shifts (a change every few days) is preferable to
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slow rotation as this schedule produces less interference with circadian rhythm. Clockwise

rotation (morning, afternoon, night) is preferable to counter clockwise rotation as quickchangeoversfor example, the morning and the night shift in the same 24 hour periodare

avoided and this rotation allows longer rest periods between shifts. Finally, a later start for the

morning shift which is traditionally 0600 reduces the truncation of the previous sleep period,

particularly for REM sleep.

On balance, the duration of shift should not be extended to 10 or 12 hours as complaints offatigue are greater on the long shifts. However, the evidence that this translates into poorer

performance and increased accidents is lacking.13Many workers favour the longer shifts, not

because they are longer but because the breaks between shift weeks are longer often 34 days.

Finally, there is some evidence that allowing the workers to design their own shift schedules

encourages good work performance as they take responsibility for achieving the work output

targets.

Other factors which can ameliorate shift schedules include workplace improvements in catering,supervision, health care, transportation, and recreational facilities. There is some limited

evidence that bright light might be useful on the night shift to offset some of the circadian effects

of the day-night changes.

PERSONAL ISSUES

Physical fitness does seem to be important in helping workers to cope with shift work, so adviceon exercise, diet, and sleep management helps the person to manage his or her approach to shift

work.

Finally, there is the much debated issue of health surveillance. The Working Time Directive callsfor health checks for night workers, although it is unclear what a health check might be! Some

suggestions for an effective, and to some extent, an evidence based approach has been proposedby Costa et al.4A sensible and measured stance has also been promulgated in a guidance booklet

published jointly by the Society of Occupational Medicine and the Faculty of Occupational

Medicine in the United Kingdom.14

Conclusions

Work involving long hours or abnormal night-day schedules has been in existence for centuries.There is evidence to suggest that such schedules are here to stay, for one reason or another, for

one in five workers. The main physiological consequence of such shift schedules is disruption ofcircadian rhythm which can have a deleterious effect on performance, sleep patterns, accident

rates, mental health, and cardiovascular mortality. Reproductive outcome effects may be linkedto disruption of menstrual cycles. Individual issues such as sex, age, and personality are also

important.
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Coping with these potentially harmful work schedules involves helping people to cope and by

designing workplace environments and shift scheduling schemes that lead to the least disruptionto mental, physical, and social wellbeing.

shift work in nursing

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