Background

Although the words “fatigue” and “sleepiness” are often used interchangeably, they are distinct phenomena. Sleepiness refers to a tendency to fall asleep, whereas fatigue refers to an overwhelming sense of tiredness, lack of energy, and a feeling of exhaustion associated with impaired physical and/or cognitive functioning.¹ Sleepiness and fatigue often coexist as a consequence of sleep deprivation.

Even though fatigue can be due to a variety of causes (e.g., illness, a vigorous workout, or a period of prolonged concentration), this chapter will focus on the effects of fatigue associated with insufficient sleep (see Key Terms and Definitions). The impact of extended work shifts and the relationship of these work schedules to nurse and patient safety will also be explored. Several practices that show demonstrable potential for reducing the adverse effects of fatigue on patient safety will be reviewed at the end of the chapter.

Insufficient Sleep

Studies suggest that average sleep durations have decreased from 9 hours in 1910 to as little as 6.9 hours on workdays in 2002.^2–6 Objective measurements, however, suggest that mean sleep times may actually be somewhat lower than are typically reported in surveys. For example, 273 randomly selected middle-aged residents of San Diego (40 to 64 years) reported sleeping approximately 7 hours, an amount that appeared to correspond to their time in bed. Mean sleep times obtained from wrist actigraphy, however, revealed that participants slept on average 6.22 hours, approximately 43 minutes less than their subjective reports.⁷

Sleeping longer on weekends and nonworkdays is also common,^{4, 6} suggesting that individuals are obtaining insufficient sleep on workdays, then attempting to “catch up” on weekends. Americans slept on average 36 minutes more on weekends in 2002,⁴ which is somewhat longer than the 23 minutes reported by British adults.⁶ American nurses who participated in a recent survey, however, obtained on average 84 minutes more sleep on nonworkdays than work days (8.2 hours on nonworkdays compared to 6.8 hours on workdays),⁸ which is more than triple the amount reported by British adults and more than double that of other Americans.

Individuals working nights and rotating shifts rarely obtain optimal amounts of sleep. In fact, an early objective study showed that night shift workers obtain 1 to 4 hours less sleep than normal when they were working nights.⁹ Sleep loss is cumulative and by the end of the workweek, the sleep debt (sleep loss) may be significant enough to impair decisionmaking, initiative, integration of information, planning and plan execution, and vigilance.^{10, 11} The effects of sleep loss are insidious and until severe, are not usually recognized by the sleep-deprived individual.^{12, 13}

Finally, it is not uncommon for nurses and other shift workers to acknowledge falling asleep when working nights.^{8, 14, 15} Almost one-fifth of the nurses working permanent night shifts reported struggling to stay awake while taking care of a patient at least once during the previous month.¹⁵ Another survey found that the occurrence of falling asleep during the night shift occurred at least once a week among 35.3 percent of the nurses who rotated shifts, 32.4 percent of the nurses who worked nights, and 20.7 percent of the day/evening shift nurses who worked occasional nights.¹⁶ Objective recordings using ambulatory polysomnographic recorders and actigraphy have verified that nurses, air traffic controllers, and even commercial truck drivers regularly fall asleep for brief periods during the night shift.^17–19

Fatigue Countermeasures and Other Recommended Safety Practices

Fatigue-related problems are believed to cost the United States an estimated $18 billion dollars per year in lost productivity and accidents.¹⁰⁵ More than 1,500 fatalities, 100,000 crashes, and 76,000 injuries annually are attributed to fatigue-related drowsiness on the highway.¹⁰⁵ On-the-job performance also deteriorates: railroad signal and meter reading errors increase at night, minor errors occur more often in hospitals, and switchboard operators take longer to respond to phone calls.¹⁰⁶ Two significant nuclear power plant accidents (Three Mile Island and Chernobyl) and the environmentally disastrous grounding of an oil tanker (Exxon Valdez) occurred at night, during early morning hours when vigilance is at its lowest. In the case of the Exxon Valdez grounding, sleep deprivation was identified as one of the major causal factors of the grounding (the third mate had been awake 18 hours and the ship’s master had not slept in the 36 hours prior to the accident).¹⁰⁷ According to a supplemental report, ¹⁰⁸ sleep deprivation was a contributory, if not causal, factor in the poor decisions made the night before the launch of the Space Shuttle Challenger.

A variety of industries and professions have developed programs to reduce sleepiness-based errors under the aegis of “fatigue management.”^109–111 These programs usually include an educational component ^112–116 and sometimes include schedule alterations.^{114, 117} Employees are usually given information about circadian rhythms, sleep hygiene measures, shift work and its adverse effects, and a variety of strategies that can be used to reduce fatigue (e.g., judicious use of caffeine and napping during night shifts).^{118, 119} Managers may be urged to consider altering the starting times of shifts whenever possible to make schedules more compatible with circadian rhythms; to avoid scheduling employees to work more than two or three consecutive night shifts; and to provide adequate recovery time between shifts, especially when an employee is rotating off night shift. Hours of service regulations, where applicable, are also considered in the development of a fatigue management program.¹¹⁹

Only limited information about the efficacy of these programs is available to the public. Although several specialized fatigue countermeasures programs have been developed and tested by the U.S Coast Guard, the Crew Endurance Management System,¹¹³ and the Commercial Mariner Endurance Management System,¹¹² information about the efficacy of these programs has not been disseminated. Private companies implementing Fatigue Countermeasures Programs consider their use to be proprietary information. In fact, the only paper describing the efficacy of a fatigue countermeasures program reported only equivocal results.¹¹⁶

Other Recommended Safety Practices

Rest breaks, napping, exercise, bright lights, and pharmacologic measures may be used to provide temporary relief from the symptoms of fatigue during the work shift. Although frequent short rests breaks are usually recommended for the prevention of fatigue, anecdotal information, collective bargaining agreements, and even research studies suggest that nurses are regularly sacrificing their breaks and meal periods to provide patient care.^120–126 In fact, a recent study revealed that hospital staff nurses were completely free of patient care responsibilities during a break or meal period less than half the shifts they worked (2,429 out of 5,221 shifts). There were 334 shifts (10 percent) in which nurses reported having no opportunity to sit down for a break or meal period. The rest of the time (2,249 out of 5,211 shifts) nurses reported having the time for a break or meal, but that they were not relieved of patient responsibilities during that time.¹²⁶ On average nurses reported having only 25.7 minutes break during their entire shift. Nurses working the longest hours were least likely to receive appropriate breaks (e.g., 10 minutes every 2 hours and a 30-minute meal period free of patient care responsibilities).

Studies have shown that short breaks not only improve performance and reduce subjective fatigue,^127–130 they are effective in controlling the accumulation of risk associated with prolonged task performance (e.g., 2 hours sustained work)^{131, 132} and sleepiness.¹²⁹ Other studies however, have shown that rest breaks and tea breaks can decrease fatigue but not necessarily accident risk or errors.^{126, 133}

Napping

Even though napping during breaks or meal periods is often prohibited, both laboratory and field studies suggest that naps (15 minutes to 3 hours) are quite effective in increasing alertness during extended work periods or at night.^134–139 Since few operational settings allow for long naps (e.g., 3 hours), most naps studied in operational settings are short. For example, 20-minute single naps during the first night shift improved the speed of responses on a vigilance task at the end of the shift,¹³⁴ and 26-minute in-seat naps have been shown to increase physiological alertness and psychomotor performance of airline pilots.¹⁴⁰ When pilots were allowed a nap during night flights, their performance improved by 34 percent, and physiologic alertness improved 54 percent compared to the no-nap condition.¹⁴⁰

The alerting effects of naps are varied, with most studies suggesting that improvements in subjective alertness and performance are sustained for up to an hour or more postnap.^{138, 139, 141} Longer naps tend to produce longer periods of alertness and improved performance.¹⁴² Although some studies report sleep inertia, or a period of decreased alertness and performance immediately following a nap,^{138, 139, 141} this effect was not seen in Driskell’s meta-analysis.¹⁴²

Stimulants

Caffeine is probably the most commonly used fatigue countermeasure.¹⁴³ Its effects have been studied alone,¹⁴⁴ as well as in combination with rest breaks, naps, and other stimulant medications.^145–147 Generally, caffeine’s onset of action occurs approximately 15–30 minutes after ingestion and its effects last 3–4 hours. Although tolerance can develop, significant increases in alertness and performance can be obtained with 200 mg of caffeine (approximately the amount of caffeine in one to two cups of coffee), with positive effects occurring with doses ranging from 100 mg to 600 mg.^{143, 145} Although caffeine alone improved alertness and performance during a laboratory study, the combination of napping and caffeine was more efficacious than just napping or just caffeine alone in a field study of evening and night shift workers.¹⁴⁶ Six hundred milligrams of caffeine was also as effective as 20 mg d-amphetamine and 400 mg modafinil in producing short-term performance and alertness during prolonged sleep loss.¹⁴⁸ Modafinil has also been shown to be effective in increasing alertness on laboratory measures of performance among workers diagnosed with shift work sleep disorder (see Table 1 for a description of the disorder),^149–151 but produced mixed results when evaluated during a randomized, double-blind cross-over study of sleep-deprived emergency room physicians. Even though modafinil improved some aspects of cognitive functioning and perceived alertness, participants had difficulties falling asleep when given an opportunity.¹⁵² Although other compounds have been recommended (e.g., melatonin), their efficacy has not been established.^{153, 154}

Table 1

Adverse Effects of Restricted Sleep on Patient Safety and the Health of Nurses

Bright light

Although a number of studies have shown that bright lighting in control rooms, work areas, and laboratory environments can increase alertness at night and facilitate entrainment to night shift work,^154–157 this strategy may not help nurses as much as other types of workers. Protocols typically involve exposure to bright lights (approximately 2,500 lux) or normal lighting (approximately 150 lux) while working at a desk for periods of 2 to 6 hours. No one has evaluated the efficacy of intermittent exposure to bright lights or the effects of alternating exposure to bright lights with the dim lighting typically found in patient rooms at night.

Exercise

Exercise typically produces increased subjective alertness and improved cognitive performance in both sleep-deprived and nonsleep-deprived subjects.^{158, 159} Exercising for 10 minutes, however, produces only transient (30–50 minutes) increases in subjective alertness. In one study there were no effects on performance after exercise, but within 50 minutes there were signs of increased drowsiness on electroencephalogram (EEG) recordings.¹⁶⁰ As a result of this finding, the authors of the study caution that people who use exercise as an intervention for maintaining alertness during a period of sleep loss may end up sleepier than if they had not exercised.

Research Evidence

There is a very large, strong body of evidence showing that insufficient sleep has adverse effects on cognition, performance, and mood. These effects have been documented by at least two meta-analyses^{22, 150} and several clinical trials,^{32, 161, 162} as well as by studies using somewhat less robust designs including time series, cross-sectional, before-and-after designs, and noncomparative descriptive studies.^{11, 30, 37, 163–167} The adverse effects of insufficient sleep have also been documented in a variety of settings ranging from tightly controlled laboratories^{11, 32, 162, 163, 166} to field studies, ^{30, 37, 164–167} and in a variety of occupational groups.

The studies demonstrating a relationship between adverse effects on health and obtaining less than 7 hours sleep per night tend to use less robust designs (e.g., cross-sectional designs, time series designs, comparative and noncomparative descriptive designs), but they often include large numbers of participants. Although survey and cross-sectional designs may not be as rigorous as controlled clinical trials, the number of recent studies suggesting similar relationships between insufficient sleep, altered glucose metabolism,^{56, 168} and increased risks of developing diabetes mellitus^{54, 169} and obesity^{53, 54} is powerful and convincing evidence that a relationship exists between these variables. Longer sleep durations (e.g., more than 8 to 9 hours per night) were also associated with greater risks of dying or developing a chronic illness such as DM or cardiovascular disease,^{29, 56, 168} leading researchers to speculate that individuals who routinely obtain higher than normal amounts of sleep may have preexisting health problems.²⁹

The evidence regarding shift duration, however, is less clear-cut. Although some studies suggest that reductions in the work hours of resident physicians and interns is associated with fewer errors,³⁵ other studies suggest that the implementation of work hour limitations has not decreased the number of adverse events.^169,170 Although there are numerous literature reviews,^171–173 descriptive and other comparative studies,^{14, 25, 26, 69, 174–176} there are no meta-analyses and only one systematic review¹⁷⁷ focusing on the impact of work hours on medical errors or work performance. The strongest study, involving 20 critical care residents and interns and direct observation of errors, found that traditional schedules were associated with 35 percent more serious errors, and shortened workdays (16 hours) were associated with both fewer order-writing errors and diagnostic errors.³⁵ Unfortunately, this study has not been replicated outside of the critical care setting or at any other institution.

The evidence demonstrating a relationship between working long hours and adverse effects on health is stronger. Not only are there several large-scale studies documenting higher injury rates when people worked overtime or extended shifts,^{82, 178, 179} there are several literature reviews^{83, 170} and three meta-analyses examining the effects on worker health.^{78, 79, 83}

Clinical trials that would provide more definitive answers to questions regarding shift duration and adverse health effects have not been done, nor are they likely to be done because of ethical issues.

Although more than 170,000 employees from a variety of industries (including aviation, rail, trucking, maritime, health care, petrochemical, nuclear energy, and law enforcement) have been exposed to fatigue countermeasures programs,¹¹⁵ there is very limited information about their efficacy. Typical reports indicate that some aspects of a particular program were successful (e.g., employees slept longer at night,¹⁸⁰ napping improved alertness on duty,¹²⁹ and that participants used most of the suggested strategies),¹¹⁶ but the reports rarely assess the efficacy of the program as a whole for improving alertness on the job and reducing errors. The only published study describing the outcomes of a fatigue countermeasures program for resident physicians involved a very small sample (n = 6) and produced mixed results.¹¹⁶ Although participants reported increased subjective alertness after using the suggested strategies for a month, there were no improvements in their performance, mood, or the amount of sleep obtained when working the night shift.

There is strong evidence that short naps can improve alertness during night shifts and prolonged periods of wakefulness. Data obtained from several small clinical trials,^{134, 138, 140, 146} and a meta-analysis¹⁴² all support the use of this strategy for improving alertness at night. In addition, there are several small clinical trials that suggest a short daytime nap can improve alertness during the afternoon.^181–184

The effects of rest breaks were more variable. Study designs evaluating the efficacy of rest breaks on performance and alertness also tended to be weaker, involving quasi-experimental designs^{128, 130, 131, 133, 185} rather than randomized clinical trials¹²⁹ or meta-analyses. Given that almost all of the aforementioned studies were field studies conducted at actual worksites during regular work hours, the choice of somewhat less rigorous designs is understandable.

There is strong evidence that use of caffeine, either alone or in combination with a nap, can increase alertness. Although there are no meta-analyses evaluating the efficacy of caffeine, the utility of caffeine for increasing alertness has been demonstrated through numerous clinical trials,^{144, 145, 147} and its widespread use by adults. (Mean caffeine consumption in the United States is estimated at 238 mg or slightly more than two cups of coffee per day per person.)¹⁸⁶ Other measures to increase alertness, such as bright lighting and exercise, either lack sufficient evidence or may not be practical for nurses.

Evidence-Based Practice Implications

Although studies have not always been able to document that the cognitive deficits associated with insufficient sleep lead to medical mishaps, there is enough evidence to suggest that insufficient sleep can have adverse effects on patient safety and the health of nurses. The effects, summarized in Table 1, provide the basis for the two recommendations in Table 2.

Table 2

Evidenced-Based Recommendations for Practice Related to Sleep Duration

To implement these recommendations, many nurses will have to be willing to make substantial changes in their behavior. Despite their more sophisticated knowledge about health and illness, the sleep habits of nurses mirror those of other Americans. Only a little more than one-fourth of the participants in the Staff Nurse Fatigue and Patient Safety Study (27.2 percent) obtained at least 6 hours sleep prior to every shift they worked during the 28-day study period; more than one-quarter of the 11,387 shifts studied (29.1 percent) were worked by nurses who obtained less than 6 hours sleep, an amount that has been associated with higher risks of errors (Dawson, personal communication, 2005). Although few nurses would consider coming to work if they were legally drunk, the data suggest that many nurses are unaware of or disregard the equally serious risks associated with insufficient sleep.

Although it might be argued that family responsibilities prevented hospitals staff nurses from obtaining sufficient sleep, regression analysis has shown that this is not the case. Neither childcare nor elder care responsibilities were associated with reduced sleep times on workdays. Instead, longer work shifts, longer commutes, higher caffeine intakes, complaints of poor sleep, and older age (of the nurse) were associated with shorter sleep durations.¹⁸⁸ Childcare responsibilities, however, were associated with shorter sleep times on nonworkdays.

Several authorities have recommended that work shifts be limited to 12 hours in a 24-hour period and employees limited to working no more than 48 to 60 hours per week.^{171, 173, 189, 190} Although 12-hour shifts are quite popular among nurses, most authorities do not recommend the use of 12-hour shifts unless there are sufficient rest breaks, there are adequate arrangements for coverage of absentees, overtime will not be added, and shift systems are designed to minimize the accumulation of fatigue.^{173, 190, 191} Rosa¹⁷³ also recommends that 12-hour shifts not be adopted if there are staffing shortages, citing the dangers associated with an already fatigued worker covering part or all of a vacant shift.

In fact, legislation pending in the Massachusetts State legislature would (1) prohibit resident physicians from working more than 10 consecutive hours in all high-intensity settings, (e.g., emergency departments, intensive care units, etc.); (2) limit resident physician workhours to 18 consecutive hours in all other areas; (3) mandate 16 consecutive hours off after an 18-hour shift and require 10 consecutive hours off between all other work shifts; and (4) require all physicians, not just trainees, to notify patients before providing care if the physician has been awake 22 hours out of the prior 24 hours.¹⁹² Although the workhours of most nurses will not be altered by this legislation, limiting the duration of nursing shifts and mandating sufficient rest periods between shifts would also be of benefit for nurses and the patients they care for.

Table 3

Evidenced-Based Practice Recommendations Related to Shift Duration and Number of Workhours During a Week

The emphasis on maximizing opportunities for sleep is intentional. Because long workhours are often associated with insufficient sleep,^{25, 36, 196} some authorities believe that fatigue on the job is more likely to be associated with a lack of sleep than the number of hours spent working.^{191, 197} Workers who report high workloads, stressful workweeks, or who score higher on burnout indexes have shorter sleep times,^{198, 199} as well as more arousals, greater sleep fragmentation, more wake time after sleep onset, lighter sleep, and less deep sleep.^{200, 201} Fatigue and daytime sleepiness associated with stressful working conditions and burnout is believed to be a result of insufficient sleep, rather than a direct result of stressful working conditions or burnout.

Although employer support will be required to implement schedule changes, there are several strategies that nurses can adopt to improve their ability to remain alert throughout their entire shift. Even though the following three fatigue countermeasures were developed mainly for night shift workers, the first two recommendations are also appropriate for nurses working other shifts.

Practice Recommendations for Use of Caffeine

1. Caffeine should be used therapeutically. Caffeine should not be consumed on a regular basis or when alert. Instead, caffeine consumption should occur only at the beginning of a shift or about an hour before an anticipated decrease in alertness (e.g., between 3 a.m. and 5 a.m.). To reduce the possibility of insomnia, caffeine consumption should stop at least 3 hours before a planned bedtime.²⁰²
2. Nurses should be allowed to nap during their break and meal periods. Naps should be short, e.g., less than 45 minutes, to reduce the likelihood of awakening from deep sleep and experiencing sleep inertia.¹⁴³ Some nurses may prefer to take a shorter nap, and have a 15-minute wake up period before they resume patient care.
3. Nurses, particularly those who start their shift at 11 p.m. or midnight, should consider napping prior to starting their shift. Not only are nurses who work at night required to be awake and vigilant when their body temperature is lowest and their sleep tendency is greatest, they are typically awake longer before the beginning of their shift than workers on other shifts.²⁰³

Table 4

Evidenced-Based Recommendations for Practice Related to Improving Alertness on the Job

Finally, nurses should realize that most people are not accurate judges of how impaired they are by fatigue or sleep loss.^{204, 205} Few adults can perform at high levels for more than 12 consecutive hours or function adequately with less than 6 hours sleep. Figure 1 illustrates the risks associated with combining insufficient sleep with extended shifts and outlines strategies to reduce fatigue-related errors.

Figure 1

Risks Associated With Various Combinations of Sleep Duration, Shift Duration, and Shift Time, and Strategies To Mitigate the Effects of Insufficient Sleep and Extended Work Shifts

Research Implications

More research is needed to understand the effects of fatigue on patient safety. Controlled trials are needed to determine optimal work schedules in hospital settings and test fatigue countermeasures. Since night shifts cannot be eliminated, the efficacy of fatigue countermeasures, naps during break periods, therapeutic use of caffeine, and other measures should be tested in hospital environments. Since the use of naps and caffeine have been shown to increased alertness during prolonged sleep deprivation and during night shift work, these measures should also be evaluated to determine if they would be effective for increasing alertness on day and evening shifts.

Finally, there is no information about the sleep of nurses working outside of hospital environments, and only limited information about the workhours of nurses in nursing homes and extended-care facilities. Nor is there any information about the sleep and performance of nurses who work 24-hour shifts (e.g., nurse-midwives and some advanced practice nurses) or who are required to take call. These issues and others need to be examined to improve both the safety of patients and the nurses who care for them.

Although many questions remain unanswered, “We do know enough,” according to L. G. Olson and A. Ambrogetti, “to end the worse abuses of the human sleep-wake cycle, and we need to see a shift by both hospital employers and the medical [nursing]^* profession towards addressing this issue”²⁰⁶ (p. 416). The service regulations written during the first two decades of the 20th century recognized that people cannot work for long periods of time each day without adequate time to sleep. Eighty years later, at the beginning of the 21st century, it is perhaps time to acknowledge that nurses cannot provide safe care when they are fatigued, have worked for more than 12 consecutive hours, and/or have not had at least 12 to 16 hours off between shifts.

Table 5

Critical Research Questions

Conclusion

The evidence is overwhelming that nurses who work longer than 12 consecutive hours or work when they have not obtained sufficient sleep are putting their patients’ health at risk; risk damaging their own health; and if they drive home when they are drowsy, also put the health of the general public at risk. Nurses, nurse managers, nursing administrators, and policymakers need to work together to change the culture that not only allows, but often encourages nurses to work long hours without obtaining sufficient sleep.

Key Terms and Definitions

Table 6

Key Definitions

Search Strategy

Relevant papers for this review were identified from three databases (MEDLINE,^® CINHAL,^® and PsychLit) using the period 1990–2006. Several older, classical works were also cited. Hand searches were also performed examining journals such as the Journal of Sleep Research and Sleep. Only those papers that focused on the effects of chronic partial or total sleep deprivation for a single night, extended work shifts, and strategies to reduce fatigue-related errors and accidents were included in this review. Search terms included “caffeine,” “chronic partial sleep deprivation,” “fatigue,” “fatigue countermeasures,” “extended work shifts,” “napping,” “overtime,” “performance,” “resident physicians,” “registered nurses,” “rest breaks,” “sleep loss,” “sleep restriction,” “staff nurses,” “total sleep deprivation,” and “vigilance.”

Evidence Table 1

Effects of Insufficient Sleep on Patient Safety and Health of Individuals

Evidence Table 2

Extended Work Hours

Evidence Table 3

Fatigue Countermeasures

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