Chapter 46. Fatigue, Sleepiness, and Medical Errors
Ashish K. Jha, M.D.
University of California, San Francisco School of
Medicine
Bradford W. Duncan, M.D.
Stanford University School of Medicine
David W. Bates, M.D., M.Sc.
Harvard Medical School
Introduction
Fatigue may contribute to the human error component of medical
errors.1-3 Hospitals function around the clock, which necessitates
shift work for many personnel. Physicians, especially those in training,
typically work long hours and are often sleep deprived.4 Personnel
who work during evenings and at night experience disruptions in circadian
rhythms, which may aggravate fatigue. Although little research has focused
specifically on fatigue in hospital personnel and its relationship to medical
error, studies outside the medical field demonstrate the intuitive link between
fatigue and degradation in performance and suggest some safety practices that
may be adopted in medicine. Although both acute and chronic fatigue may have
detrimental effects on the health of medical practitioners,5-7 this
chapter focuses on fatigue's direct effects on patient safety. We review the
literature on problem sleepiness among medical personnel, its impact on
performance, and interventions to address sleep deprivation: limiting work
hours, changes in shift scheduling, napping, and pharmaceutical aids. Although
beyond the scope of this chapter, factors that contribute to fatigue beyond
sleepiness, such as job stress and work load, should be considered as part of a
multifaceted strategy to combat fatigue.
Background
Fatigue and sleepiness may affect patient safety in several
ways. Physicians and nurses need good attention, sound judgment, and often quick
reaction time, especially in emergency situations. Whether evaluating an
electrocardiogram for signs of myocardial ischemia or monitoring a patient
during general anesthesia, degradation of attention, memory, or coordination may
affect performance and lead to adverse events. Research suggests that sleep
requirements and patterns are idiosyncratic, with wide variation across
populations. In order to design interventions that will effectively decrease or
prevent these events, it is important to understand the signs, prevalence, and
impact of sleep deprivation and problem sleepiness.
Sleep Deprivation
Individuals differ in their optimal sleep requirements. Most
sleep experts agree that adults typically need between 6 and 10 hours of sleep
per 24-hour period, with most people requiring approximately 8 hours of sleep
per day.8,9 When adults get less than 5 hours of sleep over a 24-hour
period, peak mental abilities begin to decline.2 For short periods of
time (2-3 days), adult who get 4 hours of sleep can function reasonably well,
but below peak levels.2 However, even with sleep deprivation of just
a couple of days, slower response times and decreased initiatives are
observed.10 After one night of missed sleep, cognitive performance
may decrease 25% from baseline.11,12 After the second night of missed
sleep, cognitive performance can fall to nearly 40% of
baseline.12
With ongoing sleep deprivation (getting 2 to 3 hours less sleep
than optimal), people develop a sleep debt.2 If the sleep debt
continues over 5 to 10 days, they are rarely maximally alert and at some point
general performance, and particularly cognitive performance, become verifiably
worse. Sleep debt also leads to slower response times, altered mood and
motivation, and reduced morale and initiative. A meta-analysis of the effect of
sleep deprivation on performance by Pilcher et al found that humans who are
chronically sleep deprived function at the 9th percentile of
non-sleep-deprived subjects. Further, sleep deprivation affected mood more than
it did cognitive function; both were more affected than motor
function.9
Night-Shifts and Shift Rotation
Shift work usually refers to a schedule in which some employees
begin work at times other than the morning. In hospitals, up to 35% of nurses
may be required to work at times other than the day shift.13 A report
by the Association of Professional Sleep Societies concluded that night-time
operators' fatigue contributed to 4 well known disasters: Exxon Valdez, Bhopal,
Chernobyl, and Three Mile Island.14 Fatigue has also been implicated
in aircraft accidents15 and in poor driving and accidents among truck
drivers.16 It is well documented that shift workers have disturbances
in their circadian rhythm, as measured by changes in their melatonin and
cortisol levels.17 Sleep after night work tends to be shorter than
sleep after day work, leading to greater cumulative sleep
deprivation.18-20 Shift workers have poorer quality of sleep, marked
by less REM sleep, and are less likely to feel refreshed after awaking. Between
60 and 70 percent of shift workers complain of sleeping difficulties or problem
sleepiness.21 Several surveys of shift workers have found that those
who work during night shifts are more likely to report sleepiness at
work.18,19,22,23 Alertness on the job is also affected, with
employees showing less alertness during nighttime shifts.24 In
addition, shift workers tend to perform less well on reasoning and
non-stimulating tasks than non-shift workers.22,23
Prevalence and Severity
Fatigue and sleep deprivation are common among medical
personnel. Long work-hours are a tradition during residency,25 with
most interns and residents working 80 to 100 hours a week, often 36 hours at a
time.26 During these shifts their sleep is limited, and is usually
interrupted.27 In a 1991 national survey, second-year residents
reported an average of 37.6 hours as the largest number of hours without sleep
during their first postgraduate year and roughly 25% of the residents reported
being on call in the hospital over 80 hours per week.26 A movement in
the late 1980s, prompted partly by the death of a young woman,28 led
to regulations in New York State dictating that residents could work a maximum
of 80 hours per week, with a maximum of 24 consecutive hours of patient care,
and a minimum of 8 hours off duty between shifts (see also chapter
55).29 Despite these regulations, unannounced inspections of 12
teaching hospitals in New York State in March 1998 found 37% of all residents
worked more than 85 hours per week, 20% of all residents and 60% of surgical
residents worked more than 95 hours per week, and 38% of all residents and 67%
of all surgical residents worked more than 24 consecutive hours.30 In
2000, 8% of programs and institutions reviewed by the Accreditation Council for
Graduate Medical Education were cited as being in violation of their work-hour
requirements.31 Work-hour violations were noted in general surgery
(35%), pediatrics (16%), internal medicine (10%) and other training programs as
well.31
Long hours and sleep deprivation continue after residency.
Healthcare providers, particularly those still in training or who have recently
completed training, occasionally work extra shifts to increase their income
("moonlighting"). One recent survey found that nearly half of all emergency
medicine residents moonlight.32 As many as 65% of internal medicine
residents and fellows moonlight33 and moonlighting is common among
other residencies and fellowships.34, 35 These shifts are often at
odd hours, and therefore are disruptive to normal sleep patterns. Among surgical
staff, fatigue is common, especially since surgical teams can be involved in
long, complicated operative cases that can take 12 to 20 hours at a
time.36,37
Multiple studies have documented the impact of fatigue on
medical personnel performance.38 However, these studies have been
limited by poor study designs or outcomes that may not correlate well with
medical error. One study of nursing fatigue suggests that it may play a role in
increased error. Gold and colleagues administered a questionnaire to nurses at a
large academic hospital and found that nurses who worked a rotating schedule,
when compared with nurses who predominantly worked day shifts, were more likely
to fall asleep at work and get less sleep over all, and were nearly twice as
likely to report committing a medication error.39
Using standardized testing, investigators have found that after
a night of call, sleep deprived physicians may have worse language and numeric
skills,40 retention of information,41 short-term
memory,42 and concentration.43 Performance on standardized
tests may not reflect performance in medical situations. Taffinder et al studied
the impact of sleep deprivation on surgical residents previously trained on a
simulator and found that after a night without sleep, surgeons were slower and
more prone to errors on the simulator than those who had a normal night of
sleep.44 Similarly, Denisco et al studied anesthesia residents after
a night of sleep deprivation and found that those who had been on call and were
sleep deprived scored less well on simulated critical events.45
Smith-Coggins et al compared cognitive and motor performance of emergency
physicians and found that, as the 24-hour study period progressed, physicians
were more likely to make errors during a simulated triage test and while
intubating a mannequin.19 However, other studies have failed to find
an effect of sleep deprivation on cognitive performance by resident
physicians.46-48 Simulators may not reflect actual medical
performance (see chapter 45). Though psychomotor performance seems to be
affected by sleep deprivation, data are inconsistent as to fatigue's impact on
cognitive function and there are inadequate data assessing its impact on
clinical performance.
Few studies have looked at the impact of fatigue in hospital
personnel on adverse events. A retrospective study by Haynes et al of 6371
surgical cases, found that the risk of postoperative complications among
patients undergoing surgery was not increased when the surgical resident was
sleep deprived.49 These results may not be surprising for several
reasons. First, the authors did not measure the residents' error rate, which may
have been higher with sleep deprivation. Second, the study did not measure the
role attending physicians or other operating room personnel may have played in
averting adverse events when residents erred. The supervisory aspect of system
design can (and should) reduce both the frequency of individual mistakes
(error prevention) and the likelihood of adverse events given that errors
are inevitable (error absorption).1 Finally, the rate of
adverse events, including those that did not result in operative complications
("near misses"), may have been higher but under reported. Well-designed studies
that evaluate the effects of fatigue among medical personnel on rates of medical
errors or adverse events would be useful. In the meantime, the lack of
convincing data linking fatigue with poor patient outcomes should not deter us
from tackling the issue of fatigue among medical personnel.
Practice Descriptions
Hours of Service
We reviewed the evidence for 2 potential safety practices
concerning hours of service: 8-hour versus 12-hour length shifts and regulations
limiting maximum shift length and/or total hours worked. Most observational
studies on optimal shift length to reduce fatigue and maximize performance are
in non-medical settings and present inconsistent findings. In a study of
work-place accidents in Germany, Hanecke et al found accident risk increased
exponentially after the 9th hour at work and was highest among
workers whose shift began in the evening or night.50 The authors
concluded that shifts that last longer than 8 hours might lead to more worker
fatigue and higher risk of accidents. Axelsson and colleagues studied workers at
a power plant and found no difference in sleepiness or performance between those
who worked 8-hour shifts and those who worked 12-hour shifts.51
Another group found that switching from 8- to 12-hour shifts led to increased
alertness on the job and improved recovery time after night shifts.52
Overland has proposed that work that requires complex cognitive tasks may be ill
suited for longer shifts, whereas work with limited cognitive demands may be
well suited for longer shifts.53 Because the components of work vary
dramatically within and across industries, shift durations that maintain
performance in one setting may be ineffective in another.
We identified 9 observational studies comparing 8-
versus 12-hour shifts for medical personnel. Two studies of nursing care on 10
wards found that quantity54 and quality55 of care were
significantly lower with 12-hour shifts. Six studies of nurses56-61
and one of physicians62 measured outcomes including self-reported
alertness, self-reported performance, and/or worker satisfaction. While 2 nurse
studies found that self-reported alertness, performance, and satisfaction wane
with longer shifts,56,57 Urgovics and Wright found that ICU nurses
reported higher job satisfaction and subjectively improved clinical performance
with 12-hour shifts.60 The 3 remaining studies in nurses found no
difference in either satisfaction or self-reported performance between 8- and
12-hour shifts.58,59,61 A survey of emergency department physicians
found that those who worked 12-hour shifts were less likely to be satisfied than
those who worked 8-hour shifts.62 The relationship between these
subjective outcomes measures and medical error is not clear.
Hours of service regulations as an effort to reduce errors due
to fatigue are standard in some non-medical fields. Truck drivers are typically
allowed to work no more than 10 hours at a time and no more than 60 hours in one
week. Airline pilots and air traffic controllers work regulated hours and some
data suggest waning performance as work-hours increase.24,63-65
Although most healthcare personnel are not subject to work-hour standards, many
physicians-in-training are, either by statutory regulations or by being in an
accredited training program. In a retrospective cohort study, Laine and
colleagues found the aforementioned New York State regulations limiting resident
work-hours had no effect on patient outcomes such as mortality or transfers to
the intensive care unit but were associated with increased rates of medical
complications and delays in diagnostic tests.66 These negative
effects may have been related to discontinuity of care and/or fewer
physician-hours per patient. As the authors noted, "better care may be provided
by a tired physician who is familiar with the patient than by a rested physician
who is less familiar with the patient."66 In a case-control study,
Petersen and colleagues found that when patients were cared for by a physician
other than their primary resident, they were 6 times as likely to suffer a
preventable adverse event.67 Thus, fewer physician work hours may
lead to more physician discontinuity and potentially, more adverse events and
poorer outcomes for patients.
On the other hand, Gottlieb studied changes in a medical
service staffing schedule that allowed for reduced sleep deprivation, improved
distribution of admissions throughout the week, and improved continuity of
inpatient care.68 After these changes were instituted, patients had
shorter lengths of stay, fewer ancillary tests, and fewer medication errors.
Although it is difficult to ascribe the improvements to changes in work-hours
because several other changes were made as well, it does appear that changes in
work-hours can be made without adversely affecting patient outcomes. Any effort
to change duty hours for healthcare personnel in an effort to reduce fatigue
should factor in and continuously monitor numerous variables, including the
potential costs of discontinuity, medical complications and unnecessary hospital
days, to ensure that the measures do not compromise patient care. The costs
needed to maintain adequate staffing in face of lost physician work-hours has
been estimated to be $360 million in New York State alone.69 However,
the difficult task of estimating other costs and potential savings from
implementing these regulations has not been accomplished.
Finally, some authors have expressed concern that restriction
of resident physician work-hours may lead to poorer quality training and
decreased professionalism among doctors.70 They argue that restricted
working hours will decrease a sense of obligation to patients and will sanction
self-interest over the well-being of patients. However, there are no data to
substantiate these concerns.
Direction and Speed of Rotation of Shift Work
The direction of shift rotation may impact worker
fatigue. For workers who change from one shift to another, a forward
rotation of shift work (morning shifts followed by evening shifts followed by
night shifts) may lead to less fatigue on the job than backward rotation (day
shift to night shift to evening shift).71-74 Forward rotation appears
easier to tolerate physiologically since the natural circadian rhythm tends to
move forward and it is more difficult to fall asleep earlier than the normal
bedtime. Several studies in non-medical personnel have shown that forward
rotation allows for better acclimation of the circadian
rhythm.2,12,75 However, 2 other studies found no significant
difference in forward versus backward shift rotation.76,77 None of
these studies measured worker performance or error rates and we found no studies
that evaluated direction of shift work rotation among medical personnel.
Another variable in scheduling is the speed of shift work
rotation. Studies suggest that slow rotation (e.g., changing from one shift to
another every one to two weeks) may allow for better adaptation of the circadian
rhythm than fast rotation (e.g., changing shifts every 2-3
days).71,73,78,79 Slow shift rotation results in greater sleep length
at home, less sleepiness on the job, better self-reported performance, and fewer
errors.74,79 In some cases, fast rotation may increase worker
satisfaction80 but the effects of such satisfaction on safety have
not been assessed. Shift rotation at an extremely slow rate approximates fixed,
non-rotating shifts (permanent night shifts, permanent day shifts). Permanent
shifts are associated with better adaptation to changes in the circadian
rhythm78 and better performance than rotating shifts.79
However, daytime commitments and social obligations often prevent workers from
completely adapting to permanent night shifts and worker satisfaction is
poor.71
Improving Sleep: Education about Sleep Hygiene
Good sleep hygiene, including the avoidance of alcohol and
caffeine before bedtime, and maintaining a healthy sleep environment, may aid in
decreasing sleep debt and fatigue. Studies of sleep hygiene have focused on
treatment of persons with insomnia or other chronic sleep
disorders.81-83 We found no clinical studies that measure the
efficacy of good sleep hygiene among shift workers. Generally, most employers
cannot dictate how their workers spend their hours off-duty and compliance with
recommendations may be poor. One study of law-enforcement officers working
rotating shifts found significant increases in awareness and knowledge after a
training session on sleep hygiene practices but no change on a post-sleep
inventory assessed at one-month follow-up.84 The effectiveness of
educational programs about sleep hygiene to improve shift worker performance
requires further study.
Lighting at Work
The body's regulation of circadian rhythm is mediated by the
effects of light and darkness. A 1986 survey found that 7.3 million Americans
work at night.71 These employees, who work during dark hours and
sleep during daylight hours, are often chronically sleep deprived and may suffer
adverse health effects,85 partially due to poor synchrony of
circadian rhythm to work schedule. Since scheduled light exposure can produce a
phase shift in the endogenous circadian rhythm,71, 86 investigators
have studied changes in lighting at work and home to improve adjustment to the
shift cycle. Foret et al studied 8 young men in a sleep lab and found exposure
to bright lights during the night produced a beneficial effect on subjective
alertness.87 Czeisler and colleagues found that subjects who were
exposed to bright light at night and nearly complete darkness during the day had
better cognitive performance and subjective alertness, and longer daytime sleep
(7.7 vs. 5.7 hours, p=0.01).88
Manipulation of light and dark is much easier in sleep labs
than in the field,89 where unintended exposure to bright light is
common and may adversely impact attempts to alter workers' circadian
rhythm.90 The National Aeronautics and Space Administration (NASA)
has studied the efficacy of bright lights on shuttle astronauts. Their
encouraging results suggest that alterations in circadian rhythm can be obtained
upon on exposure to light at night.89,91 The United States Nuclear
Regulatory Commission has also implemented bright lighting for its night workers
and found less fatigue and better alertness on the job.92 Field
studies are needed to determine how bright artificial light affects objective
measures of performance in healthcare workers and medical error. Bright light
may not be appropriate for all areas of the hospital. For example, Bullough and
Rea have noted that while bright light might help workers in neonatal care
units, it may also be detrimental to patients.93
Nonetheless, lighting can be a relatively inexpensive
intervention using existing equipment. Keeping lights bright at night, and
educating workers about using heavy shades at home may have an important impact
on worker performance on night shifts.
Napping
Napping is common among shift workers and is perceived as a way
to combat fatigue.94,95 One study of shift workers in a steel plant
found that over half reported napping at home either before or after their
shifts.94 The efficacy of naps has been studied in 3 settings: prior
to periods of sleep deprivation (prophylactic naps), during periods of
sleep deprivation (therapeutic naps) and during work hours
(maintenance naps). Most studies have been conducted in sleep labs in
healthy, young, male subjects.
A number of studies in the non-medical literature have studied
the efficacy of prophylactic napping. Gillberg and colleagues studied 8 male
subjects who were allowed only 4 hours of sleep at night. When subjects took a
30-minute nap in the middle of the prior day, they had better subjective
alertness, 20% improvement in vigilance performance, and less overall sleepiness
than when they had not been allowed to nap.96 Others have also found
benefits of prophylactic naps on subjective and objective measures of alertness
and performance in healthy volunteers undergoing extended periods of sleep
deprivation.97-100 Bonnet and Arand studied prophylactic versus
therapeutic naps in 12 healthy young men who underwent 24 hours of sleep
deprivation to simulate sleep patterns of medical housestaff.101 One
group of subjects had a 4-hour prophylactic nap in the evening and caffeine
during the 24 hours, while the second group had four, 1-hour naps during the
24-hour work period and no caffeine. Those in the prophylactic nap and caffeine
group had a 15% increase in reasoning and overall improved subjective alertness
compared with the group that had only short naps. There was no impact on mood.
We identified one study of napping by medical personnel. Harma and colleagues
studied 146 female hospital nurses and nurses' aides and found that those who
napped prior to their night shifts were less likely to report on the job
fatigue.95
Most studies evaluating the efficacy of therapeutic napping
during prolonged periods of sleep deprivation have found beneficial effects when
compared with no napping.102-108 On the other hand, Gillberg and
colleagues found no difference in simulated driving between the 2 groups of
sleep deprived truck drivers, one group having taken a 30-minute nap during the
middle of the previous night.109
Maintenance naps are naps that occur on the job, during the
shift. These naps could compensate for daytime sleep deprivation or could bridge
the nighttime low point in circadian somnolence.110 Many Japanese
industries have provided their employees with the option of on the job napping
and nearly half of nighttime shift workers take advantage of this
opportunity.111 Though no systematic studies of the impact of
maintenance naps exist in shift workers, one investigation found that short naps
in the middle of the night improved performance for the rest of the
shift.98 Napping over several successive shifts has not been
studied.110
An important consideration in napping is the phenomena of
sleep inertia, a period of transitory hypo-vigilance, confusion,
disorientation of behavior and impaired cognitive performance that immediately
follows awakening.112 Sleep inertia is well
documented112-116 and lasts up to 30 minutes after
awakening.116-118 The duration of deep sleep and the time of the nap,
relative to the circadian cycle, seem most related to the severity of sleep
inertia.8 Strategies for napping on the job to reduce fatigue should
be designed to avoid possible detrimental effects of sleep inertia. Another
potential negative effect of lengthy naps is that they can disrupt the quantity
and quality of later sleep periods.119
In summary, there is strong evidence that therapeutic naps and
maintenance naps combat the effects of fatigue and sleep loss. They can help
subjects adapt better to circadian rhythm disturbances and perform better during
acute sleep deprivation. Their application in the medical field is not
well known. While prophylactic and therapeutic napping result in loss of social
time at home, maintenance napping results in loss of work time. Costs associated
with naps have not been reported. The financial impact of reduced worker fatigue
due to napping has not been evaluated in medicine.
Medical Therapies
Melatonin is the major hormone responsible for circadian rhythm
regulation. James et al studied the effect of oral melatonin supplementation on
circadian rhythm and adaptation to night shifts among medical
personnel.120 They and others have found no effect among medical
shift workers.121-123 Though melatonin continues to be studied for
chronic insomnia and other conditions, there currently is insufficient evidence
to recommend its use to combat the fatigue associated with changing
workshifts.
Some studies have looked at the potential benefits of
benzodiazepines and other sedatives for short-term insomnia associated with
shift work, but no data exist on long-term use. Stimulants and caffeine can
boost performance acutely but do not address the underlying sleep
deprivation,124 and thus are not a viable long-term solution.
Furthermore, concern over side effects, addiction, and performance degradation
with current pharmacologic interventions makes their use as a safety practice
unlikely.
Comment
Sleep deprivation and disturbances of circadian rhythm lead to
fatigue, decreased alertness, and poor performance on standardized testing.
Although data from non-medical fields suggest that sleep deprivation leads to
poor job performance, this link has not yet been established in medicine.
Although the link with fatigue seems intuitive, promoting interventions designed
to combat medical errors should be evidence-based. Limits on physician duty
hours must account for potentially detrimental effects of discontinuity in
patient care. Forward rather than backward shift rotation, education about good
sleep hygiene, and strategic napping before or during shifts may reduce fatigue
and improve performance. High face validity, low likelihood of harm, and ease of
implementation make these promising strategies, although more evidence of their
effectiveness in medicine is warranted. Studies on the use of bright light in
the medical workplace are needed before it can be embraced.
As Gaba points out,125 in most high-hazard
industries the assumption is that fatigue and long, aberrant work hours lead to
poor performance, and the burden of proof is in the hands of those who believe
that such work practices are safe. In medicine, concerns over discontinuity of
care, and difficulties in changing medical culture have pushed the burden of
proof into the hands of those who wish to change the status quo. Given
that medical personnel, like all human beings, probably function suboptimally
when fatigued, efforts to reduce fatigue and sleepiness should be undertaken,
and the burden of proof should be in the hands of the advocates of the current
system to demonstrate that it is safe.
Finally, fatigue among medical personnel may not be fully
remediable and human errors are, in the end, inevitable. The ultimate solution
for healthcare organizations will likely require a systems-based approach that
both limits the potential for human error and intercepts errors that do occur
before they reach patients.
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