CONCEPTS
circadian rhythms
A
Rational Approach to Shift Work in
Emergency Medicine
From the Department of Emergency Medicine, Dickinson County Memorial Hospital, Iron Mountain, Michigan;* Department of Emergency Medicine, Bowman Gray School of Medicine, Winston-Salem, North Caroliaa;~ and Department of Emergency Medicine, Bayfront Medical Center, St Petersburg, Florida.~: Receivedfor publication August 23, 1991. Revision received January 23, 1992. Accepted for publication February 25, 1992.
Dennis C Whitehead, MD, FACEP* Harold Thomas, Jr, MD, FACEPt Debra RobertsSlapper, MD, FACEP*
As the only medical specialists who routinely provide continuous 24-hour daily coverage, emergency physicians are all too familiar with the demands of shift work. Although shift work has a pervasive effect on the practice of emergency medicine and is regarded as a major stressor, it has received little attention perse in our literature and in our residency training programs. We review the principles of circadian rhythms and their effects on sleep and alertness, and recommend ways by which emergency physicians can better schedule themselves to mitigate the negative consequences of working shifts, [Whitehead DC, Thomas H Jr, Slapper DR: A rational approach to shift work in emergency medicine. Ann EmergMedOctober1992;21:1250-1258.] INTRODUCTION Shift work is a major stressor in emergency medicine. In a study by the American College of Emergency Physicians (ACEP) Behavioral Emergencies Committee, 1 Deagle and colleagues asked 108 college members to identify the most stressful aspects of emergency medicine. The most common response was "erratic schedule." Zun et al 2 cited shift changes and scheduling difficulties as dominant causes of stress in emergency medicine. Keller and Koenig3 also identified shift work as a major source of career dissatisfaction and as a principal reason for the high rate of attrition seen in emergency medicine. Data from ACEP show a 12% yearly rate of attrition among its members. 4 This suggests the average full-time clinical practice career in emergency medicine lasts about nine years, a much lower average than in other specialties. Fewer than half of ACEP members surveyed expect to be practicing emergency medicine in ten years. Shift work has long been recognized as a cause of mental and physical stress. 4-6 Problems associated with rotating shift work include: • Chronic fatigue syndrome (up to 80% affected) 7 • Chronic sleep disruption and sleep deprivation (average 4.5 hours sleep daily for daytime sleepers working night shifts) 8 • Increased rates of depression, mood swings, divorce 9 • Increased gastrointestinal and immune dysfunction, infertility10 • Higher rates of drug and alcohol abuse n • Chronic hypertension 12
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• Increased cardiovascular mortality (risk worse than smoking a pack of cigarettes p e r day)13,14 • Increased rate of work-related accidents and e r r o r s 15 • Increased risk of accidents driving to and from work 16 • Shift workers in medicine viewing their jobs as extremely stressful 17 Animal models also suggest diminished longevity as a consequence of rotating shifts. 18,19 In J a p a n , there is legal precedent for considering night shift work a compensable cause of p r e m a t u r e death. 2o Although many shift workers believe that their jobs will become easier with time and practice, there is ample evidence that aging makes rotating shift work more difficult.21, 22 This progressive intolerance to shift work may manifest itself in unhealthy ways. In a study by the Wellness Task Force of the Illinois College of Emergency Physicians, Zun et a123 found that 25% of American B o a r d of Emergency Medicine diplomates (average length of practice, 10.3 years) took medication to sleep or stay awake, as c o m p a r e d with 15% of those who had finished an emergency medicine residency within the preceding year.) Other negative indicators, such as substance abuse treatment and psychiatric counseling, also were increased in the diplomate group. As the average age of emergency medicine practitioners continues to increase, more attention must be p a i d to the stressful aspects of the specialty to prevent b u r n o u t and p r e m a t u r e attrition. To devise a rational method for shift scheduling in emergency medicine and to mitigate the deleterious effects of shift work, it is necessary to u n d e r s t a n d the basic nature of circadian rhythms and sleep. CIRCADIAN
PRINCIPLES
AND
PHYSIOLOGY
The term circadian is from the Latin circa diem, meaning "about a day." The first experiment to test circadian rhythms was performed by the F r e n c h astronomer d ' O r t o u s de Mairan 24 in 1729, who demonstrated that plant leaves opened in daytime even when kept in total darkness. In 1832 de Candolle 25 discovered the concept of free running in biologic clocks by noting that mimosa leaves opened and closed on a 22-hour cycle when exposed to constant light. This showed the plant had its own independent " d a y " length. Every mammalian species also seems to have its own inate and genetically transmitted, free-running day length. 26 Controlled experiments have proven that human beings have a free-running 25.1-hour circadian clock 27,28 that is constant and predictable. Volunteers have been studied extensively in the l a b o r a t o r y and in caves over periods as long as six months, during which they were isolated from any zeitgebers (literally, "time givers," or clues to time of day). Subjects were permitted to eat and sleep at the times of their choosing. After one week in a clue-free environment, they lagged behind their usual d a y - n i g h t schedules by almost eight hours. This 25.1-hour human biologic clock has important implications for shift scheduling, implying that our internal clocks have the capabihty of being reset on a daily basis.
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Many physiologic functions follow circadian patterns. Juergensen 29 proved that the temperature cycle is controlled by the biologic clock. Kleitman 30 demonstrated that the temp e r a t u r e cycle could be transposed by keeping subjects awake at night and permitting them to sleep during the day. Other physiologic functions relate to the temperature cycle, which appears to be the most resistant to change of the circadian rhythms. 31 Alertness and potassium excretion have a positive correlation, whereas growth hormone secretion 32 has a negative association with temperature. Cortisot has its own p a t t e r n but follows a regular circadian cycle. 33 Circadian rhythms have both endogenous and exogenous components. 34 The former is dependent on a clocklike mechanism thought to reside in the suprachiasmatic nucleus in human beings, 35 but the latter is driven by external time clues (zeitgebers). It is the endogenous clock that appears responsible for each species' free-running day length. Light/ d a r k cycles have been shown to be important in regulating the human circadian clock.36, 37 SLEEP
PHYSIOLOGY
Coleman has defined sleep as "a state of inertia and loss of consciousness of a t e m p o r a r y n a t u r e from which one can be easily aroused. ''3a There is still debate as to why we need sleep or what amount of sleep is needed for optimal health and mental performance. H o m e 39 has proposed that sleep is necessary in human beings to effect recovery and restitution of the neural and supportive tissues in the cerebral cortex. The p r i m a r y stimulus for spontaneous awakening is a rise in body temperature; thus the duration of the sleep period depends more on the phase of the circadian r h y t h m than on the length of p r i o r wakefulness. 40 This p a r t l y explains why those working short stretches of nights sleep fewer hours during the daytime than those who are entrained to night shifts, as the circadian clock impedes sleep during that Figure 1.
Sleep stages in a typical night's sleep [ ] Stage 1 [ ] Stage 2 [ ] Stages 3 and 4 Stage
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time. 41 There is evidence that those who sleep less than five or more than ten hours daily have increased mortality comp a r e d with those who sleep seven to eight hours daily, a2 Sleep occurs in discrete stages 43 (Figure 1):
Non-rapid eye movement (REM) sleep Stage 1: transition period, usually completed within ten minutes unless sleep disorder is present. Brain activity diminishes and eyes roll slowly from side to side. Vivid hypnagogic imagery may accompany this stage. 44 Most people awakened from stage 1 claim they are not asleep. Stage 2: deeper sleep, characterized by cessation of eye movements. The b r a i n continues to respond to noise and other external stimuli (eg, light) as seen in EEG changes. 45 This stage usually lasts for 20 minutes before progressing. Stage 2 separates blocks of slow wave sleep (SWS) and REM sleep and can be considered the "glue" that maintains the integrity of sleep structure. About half of normal adult sleep is spent in stage 2, and much of so-called "optional" sleep (see below) is comprised of this stage, a6 Stages 3 and 4: also called delta sleep or SWS, characterized on EEG by cortical b r a i n cells firing synchronously in slow large spikes. Stages 3 and 4 are differentiated by the frequency of these delta waves. The bulk of nocturnal SWS occurs early in the sleep period, so it is difficult to arouse someone an hour after onset of sleep. About 25% of adolescent sleep is in this stage, and this percentage declines throughout adulthood until SWS may be absent by the eighth decade of life (Figure 2). 47 After sleep deprivation, SWS is the first stage to be made up, suggesting a restitutive role. Human beings preferentially obtain stage 4 sleep even during periods of frequent sleep disruption, aa The amount of SWS depends on p r i o r wakefulness, not on time of day. 49 Total SWS time is about the same in naturally "long" and " s h o r t " sleepers, with other sleep stages more variable. 5° There seems to be a greater increase
Figure 2. Total sleep stage times by age Minutes of Sleep
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in SWS than in REM sleep in subjects who perform challenging intellectual tasks in the awake period. 51 SWS has been thought to be vital for physical recuperation, because growth hormone is secreted in this stage. 52 There is also evidence that SWS is vital to the maintenance of the immune system. 53 Recent research, however, suggests that SWS deprivation has a more p r o f o u n d effect on the central nervous system than on the rest of the body. Those deprived of SWS will complain of fatigue and muscle aches. 54 REM s l e e p - - b r a i n on, body off Usual onset of the first REM episode occurs after 90 to 120 minutes of nonREM sleep. Hallmarks of REM include a change in E E G to a p a t t e r n similar to wakefulness, dreams, r a p i d conjugate eye movements, absent spinal reflexes, isolated muscle twitches, loss of facial muscle tone, increase in oxygen consumption, increased cerebral blood flow (more than when awake), increased blood pressure, and irregular pulse and respiration, s5 Most sleep periods will have four to six REM episodes. Infants spend over 50% of sleep in REM; the percentage declines to about 25% a r o u n d age 5 years and stays fairly constant throughout life. REM sleep has been thought to be vital for psychological well-being, and those deprived of it complain of irritability and moodiness. 56 REM sleep may also be i m p o r t a n t in the consolidation of complex learning. 57 REM sleep has its own circadian variation 58 (peaking at noon with n a d i r a r o u n d midnight) and thus tends to cluster toward the end of the normal seven- to eighthour nocturnal sleep period. REM stages also become longer as the night goes on, so one is likely to be in the middle of a d r e a m when the morning alarm goes off. Because SWS is replaced first in the sleep deprived, those with shorter sleep periods will likely have REM deprivation. Experimental subjects deprived of REM sleep show some r e b o u n d in REM when allowed to sleep normally.59 Horne 60 r e f e r r e d to the first three SWS cycles (which occur during the first three to four hours and contain the bulk of each sleep period's SWS) as core sleep, with the rest of the sleep period considered "optional" sleep. Only about one t h i r d of lost sleep is made up, consisting mostly of missing stage 4 SWS and about half of missing REM sleep. The sensation of sleepiness may have two components: that of missing core sleep (physiologic) and that of missing optional sleep (psychological). Alcohol, 61 cyclic antidepressants, 62 and nonbenzodiazepine sedative-hypnotics 63 decrease the p r o p o r t i o n of REM sleep. Chronic alcoholics may a p p r o a c h 100% REM sleep during withdrawal, suggesting that delirium tremens may be a form of b r e a k t h r o u g h REM. Alcohol causes greater sleep fragmentation, 64 significantly increasing the number of sleep stage changes p e r night. Alcohol consumption also makes awakening from nocturia more likely. Although some sleep researchers 65,66 proposed the use of triazolam to overcome the insomnia most shift workers face, it does not facilitate reentrainment of the sleep-wake cycle to a new s c h e d u l e s Triazolam also appears to impair learning
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without improving quality sleep. 68 There is no clear evidence triazolam is free of the drawbacks common to other drugs in this class, including the problem of drug dependency. 69 Stimulants, including nicotine and caffeine, 70 impede onset of sleep and normal sleep stage progression.
ALERTNESS AND SLEEPINESS For personnel on a daytime schedule, sleepiness is greatest around 0300, with a "siesta" trough also noted a r o u n d 1400 (Figure 3). 71 A siesta will produce a higher p r o p o r t i o n of REM than sleep at other times because of the circadian nature of REM sleep. The m a j o r determinants of alertness include circadian phase (especially temperature), total sleep time and amount of SWS before testing, and the regularity of the sleep-wake schedule. 72 Studies on sleep deprivation show the ability to perform challenging intellectual tasks is slowed but otherwise relatively unchanged; however, motivation to p e r f o r m routine tasks is diminished. 73,74 Sleep-deprived subjects have more errors of omission in work-paced tasks (eg, monitoring, telemetry, suturing), whereas in self-paced tasks (eg, problem solving, writing orders) speed is impaired but accuracy remains high. 75 Emergency medicine clearly has both these types of tasks. An extreme form of amotivation caused by sleepiness is called automatic behavior, wherein subjects who a p p e a r to be awake show hght sleep on EEG, sometimes for several minutes. 76 When a sufficient stimulus occurs, the subject becomes awake on EEG, but there is no anticipation of events while one is on "autopilot. ''77 Automatic behavior is most common during routine tasks when concentration is difficult and may actually be a form of stage 1 sleep. Figure 3. Alertness as measured by multiple sleep latency test Median Sleep Latency (rain) 20-o
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Amotivation and impaired performance are also seen after prolonged intense mental endeavors such as emergency medicine. It is reasonable to plan shorter shifts and/or more frequent work breaks the more intense the patient contact. 78 One study of emergency physicians on night shift showed general psychomotor and cognitive impairment, with errors tending to increase toward the end of the shift. 79 Because the quality of emergency medical practice often depends on p r o p e r l y performing routine tasks that may follow prolonged periods of intellectual exertion, it is imperative for physicians who work different shifts to schedule themselves in ways that minimize patient risk.
CHAN61NG SHIFTS Most people who have little trouble with shift work can be classified as "night owls" on standardized tests.80, 81 Those intolerant of shift change are more hkely to be "morning types" (larks), who characteristically show a s h a r p e r rate of t e m p e r a t u r e rise after morning awakening than do owls.82, 83 Tolerant shift workers, however, show higher amphtudes of circadian functions, especially temperature, when entrained to new shifts. 84 Monk a5 divided the ill feeling one gets when working different shifts into two separate categories: • Circadian d i s h a r m o n y - - t h e "jet lag" malaise one experiences until adaptation to a new shift occurs • I n a p p r o p r i a t e p h a s i n g - - t r y i n g to stay awake or go to sleep when the circadian clock says otherwise A worker who prefers to avoid prolonged night shift rotations p r o b a b l y abhors the feeling associated with circadian disharmony more than i n a p p r o p r i a t e phasing, whereas the Opposite would be true for one who prefers to work a particular shift for an extended Period of time. The latter will be able to overcome circadian disharmony in a short time, whereas, the former must contend with i n a p p r o p r i a t e phasing every night shift he or she works. F o r many years, industrial shift rotation has been a weekly counterclockwise rotation, often called the Southern Swing. It has fallen out of favor because of recent circadian research but is still widely used in the mining and civil service industries. Weekly counterclockwise rotations are undesirable for the following reasons: 1. The human free-running cycle is 25 hours, making it easier to delay sleeping than advancing it. The internal clock adjusts easily to a two-hour sleep delay or advance, but little sleep will be h a d if sleep time is advanced four to eight hours to accommodate the Southern Swing. (In like fashion, it's easier to adjust flying west across time zones than it is flying east. 86) 2. Shift workers on counterclockwise rotations take at least one week to reset their biological clocks, so the weekly change of the Southern Swing means the worker never becomes entrained to any shift.
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3. Weekly shift changes are enormously disruptive of family and social life. Czeisler et a187 studied shift workers at a potash plant that used the weekly counterclockwise schedule. Based on p r e l i m i n a r y findings, a three-week clockwise rotation was field tested for two years. With the new schedule, productivity increased 20%, and there was m a r k e d improvement in job satisfaction and sick time. Employee acceptance of this schedule after one y e a r was 60%, growing to 90% after two years. Based on these and similar studies,a8-90 many chronobiologists recommend clockwise shift rotation no more often than monthly, with an adequate period of time between rotations to effect circadian stabilization. 91 ALTERNATIVE STRATEGIES Emergency medicine has lagged behind other industries in applying circadian principles to shift scheduling. P e r h a p s this is because emergency physicians function in small groups, which is different from most other continuously operating industries in which the greater n u m b e r of workers affords the luxury of eight-hour shifts and more latitude in formulating shift patterns. Because of these unique problems, emergency physicians have explored alternative strategies in dealing with the problems of scheduling continuous coverage, Many shift workers favor 12-hour shifts to increase the number of days off, and this is a common shift length in emergency medicine. 92 Most industries on 12-hour shifts rotate weekly, but even when the rotations are of greater length it takes longer to reset the biological clock rotating across a 12-hour change than it does for an eight-hour adjustment. In a mentally and physically demanding job such as emergency medicine, there is a tendency to fatigue in the last few hours of a 12-hour shift, 93 especially during a new night rotation when alertness would be down anyway. Literature references to shifts longer than 16 hours are mainly about house officers in medical training programs.94-96 The use of very long shifts (more than 16 hours) should be limited to low-volume emergency departments, in which the physician can reliably expect to obtain several hours of continuous sleep during the duty period. Planned napping during night shifts is p o p u l a r in J a p a n , where it has been found that a nap of at least three hours (similar in duration to core sleep) enhances work efficiency and safety. 97 Night naps also have the a d d e d benefit of helping to maintain d i u r n a l rhythms, which would be i m p o r t a n t for those working very long shifts in low-volume EDs, where the bulk of patients would be seen during daytime hours. Many E u r o p e a n shift workers use what is known as the F r e n c h system, which features a clockwise rotation through day, evening, and night shifts over three successive days, on the theory that it is too diffibult to reset the biological clock, so the sooner you get it over with the better. Circadian fatigue during night shifts is not addressed in this method.
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The circadian "gold s t a n d a r d " for any industry requiring continuous coverage is not to change shifts at all. Some groups are now paying a premium to have physicians work nights exclusively. Several emergency physician megagroups are now offering day shifts exclusively to those with ten to 15 years of continuous service. Relatively few physicians opt for the former category, and few qualify for the latter. Those working only night shifts must maintain a daytime sleep pattern, even during days off, to avoid disrupting their biological clocks. 98 Reentrainment to d i u r n a l circadian rhythms can occur after as few as three to four days off night work, which is much quicker than the time needed for most subjects to adjust to nocturnal activity. 99 Most emergency physicians resist the idea of forced d i u r n a l sleeping, as it becomes difficult to participate in daytime family and social functions or to be involved regularly in administrative activities. In addition, there should be adequate time off and appropriate use of supportive strategies for the physician to adjust to a nocturnal schedule before beginning an extended block of night shifts. Objection to losing out on daytime activities is the primary reason some physicians also disparage the notion of monthly rotations, but in both cases there is a compromise of anchor sleep, which minimizes circadian desynchronization. Anchor sleep is a period of at least four hours during which one sleeps every day while on a p a r t i c u l a r shift rotation. F o r example, if one sleeps from 0800 to 1600 after working nights and from 0400 to 1200 when off, the overlapping interval from 0800 to 1200 is anchor sleep (Figure 4). Sleeping until noon is preferable to sleeping all day for most people with families or other daytime commitments. By sleeping through at least half of the time normally reserved for sleep, circadian rhythms are " a n c h o r e d " to a p a r t i c u l a r schedule and minireally disrupted, lo0,1ol The planned nighttime napping during very long shifts described above is a form of anchor sleep for diurnal orientation. Some emergency physiciansl02j 03 advocated a singlenight shift system, wherein each member of a group works a solitary night shift attached to " n o r m a l " scheduling. A group of five physicians, however, would still wind up working at Figure 4. Anchor sleep period for night shift worker
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least every fifth night. Again, the issue of circadian fatigue during these single-night shifts is problematic but may be mitigated by napping before work. Large groups able to adopt this system exclusively would have an inappropriately phased physician working on e v e r y night shift, which could conceivably affect morale of nonphysician co-workers. In general, those who espouse the solitary night shift solution agree with Monk lo4 that the hazards of circadian disharmony outweigh the problem of inappropriate phasing, whereas the opposite is true for those who champion long rotations on a particular shift. In any case, the practice of weekly shift rotation, whether clockwise or not, has no support in the recent literature. A worker so scheduled would suffer from both circadian disharmony and inappropriate phasing. One of the authors has proposed a system that combines longer night shift rotations with isolated night shifts. One member of the group works a month (or longer) on nights, while the other group members work isolated night shifts on his or her nights off. Small groups could work this system with little difficulty, and it would be a very attractive alternative in a group of any size where even only one member preferred working nights. For those working short stretches of nights, there is the compromise of split sleep periods. Because this short rotation will not allow for effective shift of the sleep/wake cycle, the goal is to prevent circadian rhythms from shifting and still stay awake and alert during the night. One sleeps in two four-hour periods adjacent to the normal sleep time. A physician who normally sleeps from 2300 to 0700 who must work during that time should sleep for four hours immediately before and immediately after work. Sleeping close to the beginning and the end of the normal sleep period maintains some consistency in zeitgebers. Because the aim of this strategy is to prevent the shift of circadian rhythms, no more than two night shifts should be worked consecutively because the usual diurnal temperature peak is likely to prevent one from obtaining normal amounts of sleep, causing excessive fatigue at work. Flattening of the normal temperature cycle1°5 by working a longer stretch defeats the purpose of this strategy. After working an isolated night shift, sleeping as soon as possible after work and then getting up after four hours promotes immediate resumption of the normal nocturnal sleep pattern. Sleeping longer than four hours after working may significantly retard the next night's sleep, likely causing REM deprivation if one needs to be up early for day shift the next morning. Napping between shifts seems to have use for the shift worker. SWS appears in daytime naps, especially in the sleep deprived, lo6 reflecting the body's drive to compensate for missing SWS. SWS obtained during daytime napping in subjects not sleep-deprived is "subtracted" from the following night's usual SWS amount, lo7 suggesting residual benefit for the night shift worker. Because siestas coincide with an
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alertness trough in human circadian rhythms, most people are able to sleep during this period even if they have trouble napping at other times of the day. A two-hour nap is thought to be restorative and useful in preventing performance deterioration during subsequent night work, even if mood is not improved.108 Napping before work seems to provide some subjective advantage, although the objective benefit is less clear. 1°9 It is suggested that at least 20 minutes elapse between awakening and starting work, so that sleep inertia has dissipated. Sleep inertia, often described as a groggy or "hung over" feeling, is also noticed by those who nap during long shifts.
SUPPORTIVE STRATE61ES Because emergency physicians rarely have the opportunity to work permanent day shifts, it is important to take advantage of supportive strategies that can mitigate circadian disruption. Exercise improves health and reduces stress. Vigorous aerobic exercise after awakening was shown to decrease the time needed to shift the circadian sleep/wake cycle from eight to 1.5 days in one animal study. 11o Human beings may similarly benefit. Light exposure between 7,000 and 12,000 lux in the work place during night shifts improves alertness and performance. 111 Bright light (more than 10,000 lux) for two hours after awakening markedly shortens the time needed to entrain circadian rhythms to the night shift, reducing to three days the time needed to change the sleep/wake cycle by 12 hours. 112 Fullspectrum lights that mimic natural sunshine are available for both screw-in and fluorescent fixtures. Diet should be balanced and in harmony with circadian rhythms. 113 Start "day" with high-protein meal, Switching to complex carbohydrates toward bedtime. Maintaining regular meals during the waking period aids in sleep and in general alertness. 114 Avoid caffeine, nicotine, and alcohol near bedtime. Social life is important for the shift worker. 115 Maintaining close ties with family and friends helps to relieve stress and mitigates the sense of temporal isolation shift workers face. Planning for quality social time is as vital as planning for work.
Personal attitude toward one's work has a great deal to do with overall job satisfaction. The enthusiastic professional committed to excellence in his or her craft will have less difficulty tolerating necessary shift work than will someone who is poorly motivated. 116 A precipitous decline in adaptability to night work may indicate burnout or other serious underlying problem.
RECOMMENDATIONS We make the following recommendations for emergency physicians who must perform shift work: 1. Given the right set of circumstances, the best strategy is to work the same shift all the time and keep the same sleep
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pattern. Consider additional compensation for those willing to work night shifts for extended periods. 2. For those unable to maintain consistent sleep patterns, use compromise strategies such as anchor sleep, spli t sleep periods, and napping to mitigate circadian disruptions. 3. Rotate all shifts in the clockwise direction, with at least one-month minimum time per rotation. 4. Isolated night shifts may be the best option for larger groups, or in groups in which one or more physicians are working nights permanently or for an extended period. This concept is gaining more acceptance among emergency physicians, mainly because of the obvious a p p e a l of fewer clustered night shifts. It is difficult logistically for most small groups. The brevity of the isolated night shift rotation should not disrupt circadian rhythms. 5. Sleep in a quiet, d a r k e n e d room, minimizing disruptions. Give the work schedule to likely daytime callers when on nights. 6. Start the awake period with a high-protein meal, switching to complex c a r b o h y d r a t e s toward bedtime. Avoid caffeine and high-calorie/high-fat snack food before sleep. Eat meals regularly. 7. Use bright light ~more than 10.000 lux for two hours after rising) as an adjunct for adjusting to new shifts. 8. Get regular exercise, which is very i m p o r t a n t for the well-being of the shift worker. Vigorous aerobic exercise after rising may diminish the time needed to adjust to new shifts. Avoid heavy exertion before attempting to sleep. 9. Work with family and friends to plan regular quality time together. 20. Do not try to live a day shift lifestyle while worldng night shifts. Hold administrative meetings early in the morning or late in the afternoon when working night shifts. Respect the circadian rights of those working nights by excusing them from meetings held during the day. SUMMARY
Emergency physicians are among the 7.5 million Americans who are at work every night. About 27% of the workforce in the United States works nights permanently or as p a r t of a rotation through different shifts. 117 Emergency physicians are not immune to the well-documented ill effects and difficulties suffered by shift workers in other industries. The feeling of many physicians, that they are unaffected by the vicissitudes of life that afflict their patients, has n o place in emergency medicine, where suboptimal job performance can have disastrous consequences. Because shift work seems largely responsible for the high attrition rate in emergency medicine, it is incumbent on those Of us who practice it to take good care of ourselves so that we may continue to take good care of others. Practicing in an environment that respects circadian principles means improved quality of care for our patients and improved personal and professional well-being for us.
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REFERENCES 1. Beagle J: Chair, American College of Emergency Physicians Behavioral Emergencies Committee, unpublished data, 1985. 2. Zun L, Kebernick M, Howes B: Emergency physician stress and morbidity. Am J Emerg Meal 1988;6:378-374. 3. Keller K, Koenig W: Sources of stress and satisfaction in emergency medicine. J Emerg Meal 1989;7:293-299. 4. Keller M: Health risks related to shift work: An example of time-contingent effects of long term stress. Int Areh Occup Envir Health 1983;53:59-75. 5. LaDoa J: Health effects of shift work. West J Med 1982;137:525-530. 6. Frese M, Semmer N: Shiftwork, stress, and psychosomatic complaints: A comparison between workers in different shift-work schedules, nen-shiftworkers, and former shiffworkers. Ergonomics 1986;29:99-114. 7. Akerstedt T: Sleepiness as a consequence of shift work. Sleep 1988;11:17-34. 8. Frese M, Harwich C: Shiftwork and the length and quality of sleep. J Occup Meal 1984;26:561-566. 9. Frese M, Okenek K: Reasons to leave shiftwork and psychological and psychosomatic complaints of former shiftwarkers. J Appl Psycho11984;69:509-514. 10. Akerstedt T: Psychological and psychophysiological effects of shift work. Scand J Work Environ Health 1990;16(suppl 1):67-75 11. Gordon N, Cleary P, Parker C, eta[: The prevalence and health impact of shift work. Am J Pubfic Health 1986;76:1225-1228. 12. Chau NP, Mallion JM, de 6audemaris R, et al: Twenty-four hour ambulatory blood pressures in shift workers. Circulation 1989;80:341-347. 13. Akerstedt T, Knutssen A, Alfredssen L, et al: Shift work and cardiovascular disease. Seanfl J Work Environ Health 1984;10:490-414. 14. Binder LS, Allison EJ Jr, Presser Ri.et al: 24-hour coverage in academic emergency medicine: Ways of dealing with the issue. Ann Emerg Meal 1990;19:430-434. 15. Mitler MM, Carskadon MA, Czeisler CA, et al: Catastrophics, sleep, and public policy: Consensus report. Sleep 1988;11:100-109. 16. Costa G, Apostoli P, Chiesi AM, et al: The Journey from Home to Work: The Impact on the Safety and Health of Workers~Commuters. Dublin, EURF Publ, 1984. 17. Milne D, Watkins F: An evaluation of the effects of shift rotation on nurses' stress, coping and strain. IntJ Nurs Stuff 1986;23:139-146. 18. Ascheff J, yon St Paul U, Wever R: )Lifetime of flies under influence of time displacement.] Naturwissenschaften 1971;58:574. 19. Halberg F, Nelson W, Cadotte G: Living routine shifts simulated on mice: Biweekly manipulation of light/dark cycle, in TwelfthInternational Conference Proceedings of the International Society of Chrnnobiology. Milan, II Ponte, 1977, p 133-138. 20. Makihara K: Death of a salaryman. InflHealth 1991;5:40-50. 21. Feret J, Bensimon 6, Benoit O, et al: Quality of sleep as a function of age and shift work. J Hum Ergo11982;11(suppl):149-154. 22. Weitzman ED, Moline ML, Czeisler CA, et al: Chronobiolegy of aging; Temperature, sleep-wake rhythms and entrainment. NeurobiolAging 1982;3:299-309. 23. Zun L, Chen E, Carrisen DM, et al: Longitudinal study of emergency physician wellness: Initial impressions (abstract). Ann Emerg Meal 1990;19:496. 24. d'Ortous de Mairan J J: Observation botanique, in Histoire de I'Acad~mie Reyale des Sciences, vo135. Paris, 1729. 25. de Candolle AP: Physiologie v@Gtale, ou exposition des forces et des fonctions vitales des v@Gtaux, in Memoires des Sarans I~trangers de I'lnstitut. Paris, Bechet Jaune, 1832. 26. Pittendrigh CS, Minis BH: Circadian systems--Longevity as a function of circadian resonance in Drosiphila melenogaster. Proc NaflAeadSci(USA) 1972;69:1537-1539. 27. Aschoff J, Wever R: Spentanperiodik des Menschen bei Ausschluss alter Zeitgeber. Naturwissenschaften 1962;49:337-342.
ANNALS OF EMERGENCY MEDICINE
21:10
OCTOBER1992
SHIFT W O R K
Whitehead, Thomas & Slapper
I
28. Czeisler CA: Human circadian physiology: Internal organization of temperature, sleep-wake and neuroendocrine rhythms monitored in an environment free of time cues. PhO dissertation, Stanford University, 1978.
I
56. McGrath M J, Cohen DB: REM sleep facilitation of adaptive waking behaviour: A review of the literature. Psycholog Bull 1978;85124-57.
29. Juergensen T: Die Korperwarme des gesunden Menschen. Leipzig, 1873.
57. Smith C: Sleep states and learning: A review of the animal literature. Neurosci Biobehav Rev 198519:157-168.
30. Kleitman N: Sleep and Wakefulness, ed 2. Chicago, University ef Chicago Press, 1963,p 172-184.
58. Czeisler CA, Guilleminault C: REM sleep: A workshop on its temporal distribution. Sleep 1980;2:265-287.
31. Zulley J, Wever RA: Interaction between the sleep-wake cycle and the rhythm of rectal temperature, in Aschoff J, Dean S, Oroos 6A (eds): Vertebrate Circadian Systems,Berlin, Springer-Verlag, 1982, p 253-261.
59. Pearlman CA: Sleep structure variation and performance, in Webb WB (ed): BiologicalRhythms, Sleep, and Performance. Chichester, Wiley and Sons, 1982, p 143173.
32, Quabbe HJ: Chronobiology of growth hormone secretion. Chronobiologia1977;4:217246,
60. Home J: Why We Sleep. Oxford, Oxford University Press, 1988, p 79-101. 61. Prinz PN, Roehrs TA, Vitaliano PP, et el: Effect of alcohol on sleep and nighttime plasma growth hormone and cortisol concentrations. J Clin EndocrinolMetab 1980151:759-764.
33. Weitzman ED: Temporal patterns of neuroendocrine secretion in man: Relationship to the 24 hour sleep-waking cycle, in Ascoff J, Ceresa F, Halberg F (eds): ChronobiologicalAspects of Endocrinology,Stuttg art, Sc hatta ua r-Ve rla g, 1974, p 169184.
62. Vogel GW: Evidence for REM sleep deprivation as the mechanism of action of antidepressant drugs. Prog NeuropsychopharmacolBiolog Psychiatry 1983;7:343-349.
34. Minors DS, Waterhouse JM: The use of constant routines in unmasking the endogenous component of human circadian rhythms. Chronobiollnt1984;l:205-216.
63. Roehrs T, Zorick F, Wittig R, et el: Effects of acute administration of brotizolam in subjects with disturbed sleep. BrJ Clin Pharmaco11983;16:371S-376S.
35. Moore RY: The suprachiasmatic nucleus and the organization of the circadian system. TrendsNeurosci1982;5:404+407.
64. Lester OK, Rundeg OH, Cowden LC, et al: Chronic alcoholism, alcohol and sleep. Adv Exp Med Bio11973;35:261-279.
36. Czaisler CA, Richardson 6S, Zimmerman JC, et al: Entrainment of human circadian rhythms by light-clark cycles: A reassessment. PhotochemPhotobio11981;34:239-247.
65. Turek FW, Losee-Olsen S: A benzodiazepine used in the treatment of insomnia phase shifts the mammalian circadian clock. Nature 19861321:167-168.
3/. Wever RA, Polasek J,Wildgruber CM: Bright light affects human circadian rhythms. PflugersArch 1983;396:85-87.
66. Van Reeth O, Turek FW: Adaptation of circadian rhythmicity to shift in light-dark cycle accelerated by a benzediazepine. Am J Physio11987;253:R204-207.
38. Coleman RM: WideAwake at3:OOAM. New York, Freeman and Co, 1986, p 88.
67. Walsh J K, Muehlbach M J, Schweitzer PK: Acute administration of triazolam for the daytime sleep of rotating shift workers. Sleep 1984;7:223-229.
39. Horne J: Why We Sleep: The Functions of Sleep in Humans and Other Mammals. Oxford, Oxford University Press, 1988, p 310-313. 40. Czeisler CA, Weitzman ED, Moore-Edy MC, et al: Human sleep: Its duration and organization depend on circadian phase. Science 19861210:1264-1267,
68. Penetar DM, Belenky G, Garrigan J J, et el: Triazalam impairs learning and fails to improve sleep in a long-range aerial deployment. AviatSpace EnvironMed 1989;60:594- 598,
41. Strogatz SH, Kronauer RE, Czeisler CA: Circadian pacemaker interferes with sleep onset at specific times each day: Role in insomnia. Am J Physio11987;253:R172-178.
69. Schneider-Helmert D: Why low-dose benzodiazepine-dapendent insomniacs can't escape their sleeping pills. Acta Psychiatr Scand 1988178:706-711.
42. Wingard DL, Berkman LF: Mortality risk associated with sleeping patterns among adults. Sleep 1983;6:102-107.
70, Johnson LC, Spinweber CL, Gomez SA, et al: Daytime sleepiness, performance, mood, nocturnal sleep: The effect of benzodiazepine and caffeine on their relationship. Psychepharmacology(Berlin) 1990;101:160-167.
43. Baker TL: Introduction to sleep and sleep disorders. Med Clin North Am 1985;69:1123-1153. 44. Vogel 6W: An alternative view to the neurobiology of dreaming. Am J Psychiatry 19781135:1531-1535. 45. Oswald I, Taylor AM, Treisman M: Discriminative responses to stimulation during human sleep. Brain 1960;83:440-453.
71. Richardson GS, Carskadon MA, Flagg W, etal: Excessive daytime sleepiness in man: Multiple sleep latency measurement in narcoleptic and control subjects. Electroenceph Clin Neurophysio11978;45:621-627. 72. Coleman RM: WideAwake at3:OOAM. New York, Freeman and Co, 1986, p 166-167.
46. Horne J: Why We Sleep. Oxford, Oxford University Press, 1988, p 210- 212.
73. Home JA, Anderson NR, Wilkinson RT: Effects of sleep deprivation on signal detection measures of vigilance: Implications for sleep function. Sleep 1983;6:347-358.
47. Blois R, Feinbarg I, 6alliard J-M, et al: Sleep in normal and pathological aging. Experientia 1983;39:551-558.
74. Bonnet, MH: Effect of sleep disruption on sleep, performance, and mood. Sleep 1985;8:11-19.
48. Bonnet MH: Performance and sleepiness following disrupted sleep allowing or prohibiting slew wave sleep. Sleep Res 1986115:68,
75. Johnson LC: Sleep deprivation and performance, in Webb WB (ed): Biological Rhythms, Sleep, and Performance. Chichester, Wiley and Sons, 1982, p 111-141.
49. Minors OS, Waterhouse JM: Circadian Rhythms and the Human. Bristor, Wright PSB, 1981,p 95-117.
76. Torsvall L, Akerstedt T: Sleepiness on the job: Continuously measured EEG changes in train drivers. Electroencephalogr Clin Neurephysio11987166:502-511.
50. Akerstedt T, 6Jllberg M: A dose-response study of sleep loss and spontaneous sleep termination. Psychephysiology1986;23:293-297.
77. Coleman RM: WideAwake at3:OOAM, New York, Freeman and Co, 1986, p 20-21.
61. Home J: Why We Sleep: The Functions of Sleep in Humans and Other Mammals, Oxford, Oxford University Press, 1988, p 150-156.
78. Rosa RR, Colligan M J, Lewis P: Extended work days: Effects of eight-hour and twelve-hour rotating shift schedules on performance, subjective alertness, sleep patterns, and psychosocial variables. Work and Stress 1989;3:21-32.
52. Sassin JF, Parker DC, Mace JW, et al: Human growth hormone release: Relocation to slow wave sleep and sleep-waking cycles. Science 1969;165:513-515.
79. Smith-Coggins R, Rosekind MR, Hurd S, Buceino K: Relationship of day versus night sleep to physician performance and mood (abstract). Ann EmergMeal1991;20:455.
53. Moldofsky H, Lue,FA, Eisen J, at el: The relationship of interleukin-1 and immune function to sleep in humans. Psychosomatic Med1986148:309-318.
80. Home JA, Ostberg O: A self-assessment questionnaire to determine morningnesseveningness in human circadian rhythms. IntJ Chronobio11976;4:97-110.
54. Agnew HW, Webb WB, Williams RL: Comparison of stage four and 1-REM sleep deprivation. Percept Mot Skills 1967;24:851+ 858.
81. Hildebra ndt G: Individual differences in susceptibi)ity to night- and shift work, in Halder M, Koller M, Cervinka R (ads): Nightand Shiftwork: Longterm Effects and Their Prevention. Frankfurt, Verlag Peter Lang, 1985, p 109-115.
55. 6uilteminault C, Pool P, Motta J, et al: Sinus arrest d'uring REM sleep in young adults. N EnglJ Meal 1985;31t :1006-1007.
OCTOBER1992
21:10
ANNALS 0F EMERGENCY MEDICINE
82. Blake M J: Relationship between circadian rhythm of body temperature and introversion-extroversion. Nature 19671215:896-897.
1257/119
SHIFT WORK
Whitehead, Thomas & Slapper
83. Blake M J: Temperature and time of day, in Colquhoun WP (ed): BiologicalRhythms and Human Performance. New York, Academic Press, 1971. 84. Reinberg A, Andlauer P, Guillet P, et al: 0ral temperature, circadian rhythm amplitude, aging and tolerance to shift work. Ergonomics 1980;23:55-64. 85. Monk TH: Advantages and disadvantages of rapidly rotating shift schedules--A circadian viewpoint. Human Factors 1986;28:553-557. 86. Klein KE, Wegemann H, Hunt BI: Desynchrenization of body temperature and performance circadian rhythms as a result of outgoing and homecoming transmeridian flights. Aerospace Med 1972;43:119-132. 87. Czeisler CA, Moore-Edy MC, Coleman RM: Rotating shift work schedules that disrupt sleep are improved by applying circadian principles. Science 1982;217:480-463. 88. Raymond CA: Shifting work, sleep cycles are on the way to becoming another public health issue. JAMA 1988;259:2958-2959.
109. Binges DF, 0rne MT, Whiteheuse WG, et al: Temporal placement of nap for alertness: Contributions of circadian phase and prior wakefulness. Sleep 1987;10:313329. 110. Mrosovsky N, Salmon PA: A behavioural method for accelerat ing re-entrainment of rhythms to new light-dark cycles. Nature 1987;330:372-373, 111. Czeisler CA, Johnson MP, Duff,/JF, et al: Exposure to bright light and darkness to treat physiologic maladaption to night work. NEnglJMed1990;322:1253-1259. 112. Czeisler CA, Kronauer RE, Allan JS, et el: Bright light induction of strong (type 0) resetting of the human circadian pacemaker. Science 1989;244:1328-1333. 113. Reinberg A, Migraine C, Apfelbaum M, et al: Circadian and ultradian rhythms in eating behavior and nutrient intake of oil refinery operators. Chronobiologia 1979;suppl 1:89-102.
89. Guilleminault C, Czeisler CA, Coleman RM, et el: Circadian rhythm disturbances and sleep disorders in shift workers. Electroencephalogr Clin Neurophysiol 1982;36(sup pl):709-714.
114. Apfelbaum M, Reinberg A, Lacatis D: Effects of meal timing on circadian rhythms in nine physiologic variables of young healthy but obese women during a caloric restriction, in Jequier E (ed): Second International Congress: Energy Balance and Man. Geneva, Medicine and Hygiene, 1975, p 22-26.
90. Vieux N, Ghata J, laporte A, et al: Adjustment of shift workers adhering to a three- to four-day rotation (Study 2). Chronobiologia 1979;suppl 1:37-42.
115. Lortie M, Foret J, Teiger C, et el: Circadian rhythms and behaviour of permanent nightworkers. Int Arch Occup Environ Health 1979;44:1-11.
91. Winget CM, Hughes L, LaBou J: Physiological effects of rotational work shifting: A review. J Occup Med 1978;20:204-210,
116. Patkai P, Akerstedt T, Pettersson K: Field studies of shift workers: I. Temporal patterns in psychophysiolegical activation in permanent night shift workers. Ergonomics 1977;20:611-619.
92. Whitehead DC: Chair, American College of Emergency Physicians Wellness Task Force, unpublished, 1990. 93. Rissman BS: Shift work indicated as a possible health hazard. Hasp Empl Health 1991;10:69-72. 94. Sharp KH: Circadian rhythms and disrupted sleep/wake cycles in resident physicians: A paradigm for change. PhD dissertation, Walden University, 1986. 95. Dean/I J, Tait R: Effects of sleep disruption on cognitive performance and mood in medical house officers. BrMedJ1987;295:1513-1516. 96. Ford CV, Wentz DK: The internship year: A study of sleep, mood states and psychophysiologic parameters, South MedJ 1984;77:1435-1441.
117. Mellor EF: Shift work and flexitime: Hew prevalent are they? Men Labor Rev 1986;Nov:14-21. Address for reprints: Dennis C Whitehead, MD, FACEP Department of Emergency Medicine Dickinson County Memorial Hospital Iron Mountain, Michigan 49801
97. Sakai K, Kogi K: Conditions for three-shift workers to take nighttime naps effectively, in Halder M, Keller M, Cervinka R (eds): Nightand Shiftwork: Longterm Effects and Their Prevention. Frankfurt, Verlag Peter Lang, 1985, p 173-180. 98. Folkard S, Monk TH, Lobban MC: Short and long-term adjustment of circadian rhythms in "permanent" night nurses, in Colquheun WP, Rutenfranz J (eds): Studies of Shiftwork. London, Taylor and Francis Ltd, 1980. 99. Knauth P, Rutenfranz J, Hermann G, at al: Reentrainment of bodytemperature in experimental shift-work studies. Ergonomics 1975;21:775-783. 10E Webb WB, Agnew HW: Variables associated with split period sleep regimes. A erosp Med 1971;45:701-704. 101. Hume KI, Mills JN: Rhythms of REM and slow wave sleep in subjects living on abnormal time schedules. Waking and Sleeping 1977;1:291-296. 102. Michaels HE: Night shift work. Ann Emerg Med 1984;13:201-202. 103. Thomas H: Coping with shift work. North Carolina EPICSpring 1990, p 8. 104. Monk TH: Advantages and disadvantages of rapidly rotating shift schedules--A circadian viewpoint. Human Factors 1986;28:553-557. 105. Akerstedt T: Adjustments of physiological circadian rhythms and the sleep-wake cycle to shiftwork, in Folkard S, Monk TH (eds): Hours of Work. Chichester, John Wiley, 1985, p 185-198. 106. Maren L, Rechtschaffen A, Wolpert EA: Sleep cycle during napping. Arch Gen Psychiatry 1964;11:503-50& 107. Karaean I, Williams RL, Finley WW, Hursch CJ: The effects of naps on nocturnal sleep: Influence on the need for stage- 1 REM and stage 4 sleep. BiolPsychiat 1970;2:391-399. 10& Binges DF, Orne MT, Orne EC, et al: Napping to sustain performance and mood: Effects of circadian phase and sleep loss, in Ha!der M, Keller M, Cervinka R (eds): Night and Shiftwork: Longterm Effects and Their Prevention. Frankfurt, Verlag Peter Lang, 1985, p 23-30.
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circadian rhythms
A
Rational Approach to Shift Work in
Emergency Medicine
From the Department of Emergency Medicine, Dickinson County Memorial Hospital, Iron Mountain, Michigan;* Department of Emergency Medicine, Bowman Gray School of Medicine, Winston-Salem, North Caroliaa;~ and Department of Emergency Medicine, Bayfront Medical Center, St Petersburg, Florida.~: Receivedfor publication August 23, 1991. Revision received January 23, 1992. Accepted for publication February 25, 1992.
Dennis C Whitehead, MD, FACEP* Harold Thomas, Jr, MD, FACEPt Debra RobertsSlapper, MD, FACEP*
As the only medical specialists who routinely provide continuous 24-hour daily coverage, emergency physicians are all too familiar with the demands of shift work. Although shift work has a pervasive effect on the practice of emergency medicine and is regarded as a major stressor, it has received little attention perse in our literature and in our residency training programs. We review the principles of circadian rhythms and their effects on sleep and alertness, and recommend ways by which emergency physicians can better schedule themselves to mitigate the negative consequences of working shifts, [Whitehead DC, Thomas H Jr, Slapper DR: A rational approach to shift work in emergency medicine. Ann EmergMedOctober1992;21:1250-1258.] INTRODUCTION Shift work is a major stressor in emergency medicine. In a study by the American College of Emergency Physicians (ACEP) Behavioral Emergencies Committee, 1 Deagle and colleagues asked 108 college members to identify the most stressful aspects of emergency medicine. The most common response was "erratic schedule." Zun et al 2 cited shift changes and scheduling difficulties as dominant causes of stress in emergency medicine. Keller and Koenig3 also identified shift work as a major source of career dissatisfaction and as a principal reason for the high rate of attrition seen in emergency medicine. Data from ACEP show a 12% yearly rate of attrition among its members. 4 This suggests the average full-time clinical practice career in emergency medicine lasts about nine years, a much lower average than in other specialties. Fewer than half of ACEP members surveyed expect to be practicing emergency medicine in ten years. Shift work has long been recognized as a cause of mental and physical stress. 4-6 Problems associated with rotating shift work include: • Chronic fatigue syndrome (up to 80% affected) 7 • Chronic sleep disruption and sleep deprivation (average 4.5 hours sleep daily for daytime sleepers working night shifts) 8 • Increased rates of depression, mood swings, divorce 9 • Increased gastrointestinal and immune dysfunction, infertility10 • Higher rates of drug and alcohol abuse n • Chronic hypertension 12
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• Increased cardiovascular mortality (risk worse than smoking a pack of cigarettes p e r day)13,14 • Increased rate of work-related accidents and e r r o r s 15 • Increased risk of accidents driving to and from work 16 • Shift workers in medicine viewing their jobs as extremely stressful 17 Animal models also suggest diminished longevity as a consequence of rotating shifts. 18,19 In J a p a n , there is legal precedent for considering night shift work a compensable cause of p r e m a t u r e death. 2o Although many shift workers believe that their jobs will become easier with time and practice, there is ample evidence that aging makes rotating shift work more difficult.21, 22 This progressive intolerance to shift work may manifest itself in unhealthy ways. In a study by the Wellness Task Force of the Illinois College of Emergency Physicians, Zun et a123 found that 25% of American B o a r d of Emergency Medicine diplomates (average length of practice, 10.3 years) took medication to sleep or stay awake, as c o m p a r e d with 15% of those who had finished an emergency medicine residency within the preceding year.) Other negative indicators, such as substance abuse treatment and psychiatric counseling, also were increased in the diplomate group. As the average age of emergency medicine practitioners continues to increase, more attention must be p a i d to the stressful aspects of the specialty to prevent b u r n o u t and p r e m a t u r e attrition. To devise a rational method for shift scheduling in emergency medicine and to mitigate the deleterious effects of shift work, it is necessary to u n d e r s t a n d the basic nature of circadian rhythms and sleep. CIRCADIAN
PRINCIPLES
AND
PHYSIOLOGY
The term circadian is from the Latin circa diem, meaning "about a day." The first experiment to test circadian rhythms was performed by the F r e n c h astronomer d ' O r t o u s de Mairan 24 in 1729, who demonstrated that plant leaves opened in daytime even when kept in total darkness. In 1832 de Candolle 25 discovered the concept of free running in biologic clocks by noting that mimosa leaves opened and closed on a 22-hour cycle when exposed to constant light. This showed the plant had its own independent " d a y " length. Every mammalian species also seems to have its own inate and genetically transmitted, free-running day length. 26 Controlled experiments have proven that human beings have a free-running 25.1-hour circadian clock 27,28 that is constant and predictable. Volunteers have been studied extensively in the l a b o r a t o r y and in caves over periods as long as six months, during which they were isolated from any zeitgebers (literally, "time givers," or clues to time of day). Subjects were permitted to eat and sleep at the times of their choosing. After one week in a clue-free environment, they lagged behind their usual d a y - n i g h t schedules by almost eight hours. This 25.1-hour human biologic clock has important implications for shift scheduling, implying that our internal clocks have the capabihty of being reset on a daily basis.
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Many physiologic functions follow circadian patterns. Juergensen 29 proved that the temperature cycle is controlled by the biologic clock. Kleitman 30 demonstrated that the temp e r a t u r e cycle could be transposed by keeping subjects awake at night and permitting them to sleep during the day. Other physiologic functions relate to the temperature cycle, which appears to be the most resistant to change of the circadian rhythms. 31 Alertness and potassium excretion have a positive correlation, whereas growth hormone secretion 32 has a negative association with temperature. Cortisot has its own p a t t e r n but follows a regular circadian cycle. 33 Circadian rhythms have both endogenous and exogenous components. 34 The former is dependent on a clocklike mechanism thought to reside in the suprachiasmatic nucleus in human beings, 35 but the latter is driven by external time clues (zeitgebers). It is the endogenous clock that appears responsible for each species' free-running day length. Light/ d a r k cycles have been shown to be important in regulating the human circadian clock.36, 37 SLEEP
PHYSIOLOGY
Coleman has defined sleep as "a state of inertia and loss of consciousness of a t e m p o r a r y n a t u r e from which one can be easily aroused. ''3a There is still debate as to why we need sleep or what amount of sleep is needed for optimal health and mental performance. H o m e 39 has proposed that sleep is necessary in human beings to effect recovery and restitution of the neural and supportive tissues in the cerebral cortex. The p r i m a r y stimulus for spontaneous awakening is a rise in body temperature; thus the duration of the sleep period depends more on the phase of the circadian r h y t h m than on the length of p r i o r wakefulness. 40 This p a r t l y explains why those working short stretches of nights sleep fewer hours during the daytime than those who are entrained to night shifts, as the circadian clock impedes sleep during that Figure 1.
Sleep stages in a typical night's sleep [ ] Stage 1 [ ] Stage 2 [ ] Stages 3 and 4 Stage
•
REM
,//
REM 3-4 2 1
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1
2
3
4
5
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SHIFT WORK Whitehead, Thomas & Slapper
time. 41 There is evidence that those who sleep less than five or more than ten hours daily have increased mortality comp a r e d with those who sleep seven to eight hours daily, a2 Sleep occurs in discrete stages 43 (Figure 1):
Non-rapid eye movement (REM) sleep Stage 1: transition period, usually completed within ten minutes unless sleep disorder is present. Brain activity diminishes and eyes roll slowly from side to side. Vivid hypnagogic imagery may accompany this stage. 44 Most people awakened from stage 1 claim they are not asleep. Stage 2: deeper sleep, characterized by cessation of eye movements. The b r a i n continues to respond to noise and other external stimuli (eg, light) as seen in EEG changes. 45 This stage usually lasts for 20 minutes before progressing. Stage 2 separates blocks of slow wave sleep (SWS) and REM sleep and can be considered the "glue" that maintains the integrity of sleep structure. About half of normal adult sleep is spent in stage 2, and much of so-called "optional" sleep (see below) is comprised of this stage, a6 Stages 3 and 4: also called delta sleep or SWS, characterized on EEG by cortical b r a i n cells firing synchronously in slow large spikes. Stages 3 and 4 are differentiated by the frequency of these delta waves. The bulk of nocturnal SWS occurs early in the sleep period, so it is difficult to arouse someone an hour after onset of sleep. About 25% of adolescent sleep is in this stage, and this percentage declines throughout adulthood until SWS may be absent by the eighth decade of life (Figure 2). 47 After sleep deprivation, SWS is the first stage to be made up, suggesting a restitutive role. Human beings preferentially obtain stage 4 sleep even during periods of frequent sleep disruption, aa The amount of SWS depends on p r i o r wakefulness, not on time of day. 49 Total SWS time is about the same in naturally "long" and " s h o r t " sleepers, with other sleep stages more variable. 5° There seems to be a greater increase
Figure 2. Total sleep stage times by age Minutes of Sleep
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t0
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40 Age (yr)
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in SWS than in REM sleep in subjects who perform challenging intellectual tasks in the awake period. 51 SWS has been thought to be vital for physical recuperation, because growth hormone is secreted in this stage. 52 There is also evidence that SWS is vital to the maintenance of the immune system. 53 Recent research, however, suggests that SWS deprivation has a more p r o f o u n d effect on the central nervous system than on the rest of the body. Those deprived of SWS will complain of fatigue and muscle aches. 54 REM s l e e p - - b r a i n on, body off Usual onset of the first REM episode occurs after 90 to 120 minutes of nonREM sleep. Hallmarks of REM include a change in E E G to a p a t t e r n similar to wakefulness, dreams, r a p i d conjugate eye movements, absent spinal reflexes, isolated muscle twitches, loss of facial muscle tone, increase in oxygen consumption, increased cerebral blood flow (more than when awake), increased blood pressure, and irregular pulse and respiration, s5 Most sleep periods will have four to six REM episodes. Infants spend over 50% of sleep in REM; the percentage declines to about 25% a r o u n d age 5 years and stays fairly constant throughout life. REM sleep has been thought to be vital for psychological well-being, and those deprived of it complain of irritability and moodiness. 56 REM sleep may also be i m p o r t a n t in the consolidation of complex learning. 57 REM sleep has its own circadian variation 58 (peaking at noon with n a d i r a r o u n d midnight) and thus tends to cluster toward the end of the normal seven- to eighthour nocturnal sleep period. REM stages also become longer as the night goes on, so one is likely to be in the middle of a d r e a m when the morning alarm goes off. Because SWS is replaced first in the sleep deprived, those with shorter sleep periods will likely have REM deprivation. Experimental subjects deprived of REM sleep show some r e b o u n d in REM when allowed to sleep normally.59 Horne 60 r e f e r r e d to the first three SWS cycles (which occur during the first three to four hours and contain the bulk of each sleep period's SWS) as core sleep, with the rest of the sleep period considered "optional" sleep. Only about one t h i r d of lost sleep is made up, consisting mostly of missing stage 4 SWS and about half of missing REM sleep. The sensation of sleepiness may have two components: that of missing core sleep (physiologic) and that of missing optional sleep (psychological). Alcohol, 61 cyclic antidepressants, 62 and nonbenzodiazepine sedative-hypnotics 63 decrease the p r o p o r t i o n of REM sleep. Chronic alcoholics may a p p r o a c h 100% REM sleep during withdrawal, suggesting that delirium tremens may be a form of b r e a k t h r o u g h REM. Alcohol causes greater sleep fragmentation, 64 significantly increasing the number of sleep stage changes p e r night. Alcohol consumption also makes awakening from nocturia more likely. Although some sleep researchers 65,66 proposed the use of triazolam to overcome the insomnia most shift workers face, it does not facilitate reentrainment of the sleep-wake cycle to a new s c h e d u l e s Triazolam also appears to impair learning
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without improving quality sleep. 68 There is no clear evidence triazolam is free of the drawbacks common to other drugs in this class, including the problem of drug dependency. 69 Stimulants, including nicotine and caffeine, 70 impede onset of sleep and normal sleep stage progression.
ALERTNESS AND SLEEPINESS For personnel on a daytime schedule, sleepiness is greatest around 0300, with a "siesta" trough also noted a r o u n d 1400 (Figure 3). 71 A siesta will produce a higher p r o p o r t i o n of REM than sleep at other times because of the circadian nature of REM sleep. The m a j o r determinants of alertness include circadian phase (especially temperature), total sleep time and amount of SWS before testing, and the regularity of the sleep-wake schedule. 72 Studies on sleep deprivation show the ability to perform challenging intellectual tasks is slowed but otherwise relatively unchanged; however, motivation to p e r f o r m routine tasks is diminished. 73,74 Sleep-deprived subjects have more errors of omission in work-paced tasks (eg, monitoring, telemetry, suturing), whereas in self-paced tasks (eg, problem solving, writing orders) speed is impaired but accuracy remains high. 75 Emergency medicine clearly has both these types of tasks. An extreme form of amotivation caused by sleepiness is called automatic behavior, wherein subjects who a p p e a r to be awake show hght sleep on EEG, sometimes for several minutes. 76 When a sufficient stimulus occurs, the subject becomes awake on EEG, but there is no anticipation of events while one is on "autopilot. ''77 Automatic behavior is most common during routine tasks when concentration is difficult and may actually be a form of stage 1 sleep. Figure 3. Alertness as measured by multiple sleep latency test Median Sleep Latency (rain) 20-o
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Amotivation and impaired performance are also seen after prolonged intense mental endeavors such as emergency medicine. It is reasonable to plan shorter shifts and/or more frequent work breaks the more intense the patient contact. 78 One study of emergency physicians on night shift showed general psychomotor and cognitive impairment, with errors tending to increase toward the end of the shift. 79 Because the quality of emergency medical practice often depends on p r o p e r l y performing routine tasks that may follow prolonged periods of intellectual exertion, it is imperative for physicians who work different shifts to schedule themselves in ways that minimize patient risk.
CHAN61NG SHIFTS Most people who have little trouble with shift work can be classified as "night owls" on standardized tests.80, 81 Those intolerant of shift change are more hkely to be "morning types" (larks), who characteristically show a s h a r p e r rate of t e m p e r a t u r e rise after morning awakening than do owls.82, 83 Tolerant shift workers, however, show higher amphtudes of circadian functions, especially temperature, when entrained to new shifts. 84 Monk a5 divided the ill feeling one gets when working different shifts into two separate categories: • Circadian d i s h a r m o n y - - t h e "jet lag" malaise one experiences until adaptation to a new shift occurs • I n a p p r o p r i a t e p h a s i n g - - t r y i n g to stay awake or go to sleep when the circadian clock says otherwise A worker who prefers to avoid prolonged night shift rotations p r o b a b l y abhors the feeling associated with circadian disharmony more than i n a p p r o p r i a t e phasing, whereas the Opposite would be true for one who prefers to work a particular shift for an extended Period of time. The latter will be able to overcome circadian disharmony in a short time, whereas, the former must contend with i n a p p r o p r i a t e phasing every night shift he or she works. F o r many years, industrial shift rotation has been a weekly counterclockwise rotation, often called the Southern Swing. It has fallen out of favor because of recent circadian research but is still widely used in the mining and civil service industries. Weekly counterclockwise rotations are undesirable for the following reasons: 1. The human free-running cycle is 25 hours, making it easier to delay sleeping than advancing it. The internal clock adjusts easily to a two-hour sleep delay or advance, but little sleep will be h a d if sleep time is advanced four to eight hours to accommodate the Southern Swing. (In like fashion, it's easier to adjust flying west across time zones than it is flying east. 86) 2. Shift workers on counterclockwise rotations take at least one week to reset their biological clocks, so the weekly change of the Southern Swing means the worker never becomes entrained to any shift.
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3. Weekly shift changes are enormously disruptive of family and social life. Czeisler et a187 studied shift workers at a potash plant that used the weekly counterclockwise schedule. Based on p r e l i m i n a r y findings, a three-week clockwise rotation was field tested for two years. With the new schedule, productivity increased 20%, and there was m a r k e d improvement in job satisfaction and sick time. Employee acceptance of this schedule after one y e a r was 60%, growing to 90% after two years. Based on these and similar studies,a8-90 many chronobiologists recommend clockwise shift rotation no more often than monthly, with an adequate period of time between rotations to effect circadian stabilization. 91 ALTERNATIVE STRATEGIES Emergency medicine has lagged behind other industries in applying circadian principles to shift scheduling. P e r h a p s this is because emergency physicians function in small groups, which is different from most other continuously operating industries in which the greater n u m b e r of workers affords the luxury of eight-hour shifts and more latitude in formulating shift patterns. Because of these unique problems, emergency physicians have explored alternative strategies in dealing with the problems of scheduling continuous coverage, Many shift workers favor 12-hour shifts to increase the number of days off, and this is a common shift length in emergency medicine. 92 Most industries on 12-hour shifts rotate weekly, but even when the rotations are of greater length it takes longer to reset the biological clock rotating across a 12-hour change than it does for an eight-hour adjustment. In a mentally and physically demanding job such as emergency medicine, there is a tendency to fatigue in the last few hours of a 12-hour shift, 93 especially during a new night rotation when alertness would be down anyway. Literature references to shifts longer than 16 hours are mainly about house officers in medical training programs.94-96 The use of very long shifts (more than 16 hours) should be limited to low-volume emergency departments, in which the physician can reliably expect to obtain several hours of continuous sleep during the duty period. Planned napping during night shifts is p o p u l a r in J a p a n , where it has been found that a nap of at least three hours (similar in duration to core sleep) enhances work efficiency and safety. 97 Night naps also have the a d d e d benefit of helping to maintain d i u r n a l rhythms, which would be i m p o r t a n t for those working very long shifts in low-volume EDs, where the bulk of patients would be seen during daytime hours. Many E u r o p e a n shift workers use what is known as the F r e n c h system, which features a clockwise rotation through day, evening, and night shifts over three successive days, on the theory that it is too diffibult to reset the biological clock, so the sooner you get it over with the better. Circadian fatigue during night shifts is not addressed in this method.
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The circadian "gold s t a n d a r d " for any industry requiring continuous coverage is not to change shifts at all. Some groups are now paying a premium to have physicians work nights exclusively. Several emergency physician megagroups are now offering day shifts exclusively to those with ten to 15 years of continuous service. Relatively few physicians opt for the former category, and few qualify for the latter. Those working only night shifts must maintain a daytime sleep pattern, even during days off, to avoid disrupting their biological clocks. 98 Reentrainment to d i u r n a l circadian rhythms can occur after as few as three to four days off night work, which is much quicker than the time needed for most subjects to adjust to nocturnal activity. 99 Most emergency physicians resist the idea of forced d i u r n a l sleeping, as it becomes difficult to participate in daytime family and social functions or to be involved regularly in administrative activities. In addition, there should be adequate time off and appropriate use of supportive strategies for the physician to adjust to a nocturnal schedule before beginning an extended block of night shifts. Objection to losing out on daytime activities is the primary reason some physicians also disparage the notion of monthly rotations, but in both cases there is a compromise of anchor sleep, which minimizes circadian desynchronization. Anchor sleep is a period of at least four hours during which one sleeps every day while on a p a r t i c u l a r shift rotation. F o r example, if one sleeps from 0800 to 1600 after working nights and from 0400 to 1200 when off, the overlapping interval from 0800 to 1200 is anchor sleep (Figure 4). Sleeping until noon is preferable to sleeping all day for most people with families or other daytime commitments. By sleeping through at least half of the time normally reserved for sleep, circadian rhythms are " a n c h o r e d " to a p a r t i c u l a r schedule and minireally disrupted, lo0,1ol The planned nighttime napping during very long shifts described above is a form of anchor sleep for diurnal orientation. Some emergency physiciansl02j 03 advocated a singlenight shift system, wherein each member of a group works a solitary night shift attached to " n o r m a l " scheduling. A group of five physicians, however, would still wind up working at Figure 4. Anchor sleep period for night shift worker
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least every fifth night. Again, the issue of circadian fatigue during these single-night shifts is problematic but may be mitigated by napping before work. Large groups able to adopt this system exclusively would have an inappropriately phased physician working on e v e r y night shift, which could conceivably affect morale of nonphysician co-workers. In general, those who espouse the solitary night shift solution agree with Monk lo4 that the hazards of circadian disharmony outweigh the problem of inappropriate phasing, whereas the opposite is true for those who champion long rotations on a particular shift. In any case, the practice of weekly shift rotation, whether clockwise or not, has no support in the recent literature. A worker so scheduled would suffer from both circadian disharmony and inappropriate phasing. One of the authors has proposed a system that combines longer night shift rotations with isolated night shifts. One member of the group works a month (or longer) on nights, while the other group members work isolated night shifts on his or her nights off. Small groups could work this system with little difficulty, and it would be a very attractive alternative in a group of any size where even only one member preferred working nights. For those working short stretches of nights, there is the compromise of split sleep periods. Because this short rotation will not allow for effective shift of the sleep/wake cycle, the goal is to prevent circadian rhythms from shifting and still stay awake and alert during the night. One sleeps in two four-hour periods adjacent to the normal sleep time. A physician who normally sleeps from 2300 to 0700 who must work during that time should sleep for four hours immediately before and immediately after work. Sleeping close to the beginning and the end of the normal sleep period maintains some consistency in zeitgebers. Because the aim of this strategy is to prevent the shift of circadian rhythms, no more than two night shifts should be worked consecutively because the usual diurnal temperature peak is likely to prevent one from obtaining normal amounts of sleep, causing excessive fatigue at work. Flattening of the normal temperature cycle1°5 by working a longer stretch defeats the purpose of this strategy. After working an isolated night shift, sleeping as soon as possible after work and then getting up after four hours promotes immediate resumption of the normal nocturnal sleep pattern. Sleeping longer than four hours after working may significantly retard the next night's sleep, likely causing REM deprivation if one needs to be up early for day shift the next morning. Napping between shifts seems to have use for the shift worker. SWS appears in daytime naps, especially in the sleep deprived, lo6 reflecting the body's drive to compensate for missing SWS. SWS obtained during daytime napping in subjects not sleep-deprived is "subtracted" from the following night's usual SWS amount, lo7 suggesting residual benefit for the night shift worker. Because siestas coincide with an
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alertness trough in human circadian rhythms, most people are able to sleep during this period even if they have trouble napping at other times of the day. A two-hour nap is thought to be restorative and useful in preventing performance deterioration during subsequent night work, even if mood is not improved.108 Napping before work seems to provide some subjective advantage, although the objective benefit is less clear. 1°9 It is suggested that at least 20 minutes elapse between awakening and starting work, so that sleep inertia has dissipated. Sleep inertia, often described as a groggy or "hung over" feeling, is also noticed by those who nap during long shifts.
SUPPORTIVE STRATE61ES Because emergency physicians rarely have the opportunity to work permanent day shifts, it is important to take advantage of supportive strategies that can mitigate circadian disruption. Exercise improves health and reduces stress. Vigorous aerobic exercise after awakening was shown to decrease the time needed to shift the circadian sleep/wake cycle from eight to 1.5 days in one animal study. 11o Human beings may similarly benefit. Light exposure between 7,000 and 12,000 lux in the work place during night shifts improves alertness and performance. 111 Bright light (more than 10,000 lux) for two hours after awakening markedly shortens the time needed to entrain circadian rhythms to the night shift, reducing to three days the time needed to change the sleep/wake cycle by 12 hours. 112 Fullspectrum lights that mimic natural sunshine are available for both screw-in and fluorescent fixtures. Diet should be balanced and in harmony with circadian rhythms. 113 Start "day" with high-protein meal, Switching to complex carbohydrates toward bedtime. Maintaining regular meals during the waking period aids in sleep and in general alertness. 114 Avoid caffeine, nicotine, and alcohol near bedtime. Social life is important for the shift worker. 115 Maintaining close ties with family and friends helps to relieve stress and mitigates the sense of temporal isolation shift workers face. Planning for quality social time is as vital as planning for work.
Personal attitude toward one's work has a great deal to do with overall job satisfaction. The enthusiastic professional committed to excellence in his or her craft will have less difficulty tolerating necessary shift work than will someone who is poorly motivated. 116 A precipitous decline in adaptability to night work may indicate burnout or other serious underlying problem.
RECOMMENDATIONS We make the following recommendations for emergency physicians who must perform shift work: 1. Given the right set of circumstances, the best strategy is to work the same shift all the time and keep the same sleep
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pattern. Consider additional compensation for those willing to work night shifts for extended periods. 2. For those unable to maintain consistent sleep patterns, use compromise strategies such as anchor sleep, spli t sleep periods, and napping to mitigate circadian disruptions. 3. Rotate all shifts in the clockwise direction, with at least one-month minimum time per rotation. 4. Isolated night shifts may be the best option for larger groups, or in groups in which one or more physicians are working nights permanently or for an extended period. This concept is gaining more acceptance among emergency physicians, mainly because of the obvious a p p e a l of fewer clustered night shifts. It is difficult logistically for most small groups. The brevity of the isolated night shift rotation should not disrupt circadian rhythms. 5. Sleep in a quiet, d a r k e n e d room, minimizing disruptions. Give the work schedule to likely daytime callers when on nights. 6. Start the awake period with a high-protein meal, switching to complex c a r b o h y d r a t e s toward bedtime. Avoid caffeine and high-calorie/high-fat snack food before sleep. Eat meals regularly. 7. Use bright light ~more than 10.000 lux for two hours after rising) as an adjunct for adjusting to new shifts. 8. Get regular exercise, which is very i m p o r t a n t for the well-being of the shift worker. Vigorous aerobic exercise after rising may diminish the time needed to adjust to new shifts. Avoid heavy exertion before attempting to sleep. 9. Work with family and friends to plan regular quality time together. 20. Do not try to live a day shift lifestyle while worldng night shifts. Hold administrative meetings early in the morning or late in the afternoon when working night shifts. Respect the circadian rights of those working nights by excusing them from meetings held during the day. SUMMARY
Emergency physicians are among the 7.5 million Americans who are at work every night. About 27% of the workforce in the United States works nights permanently or as p a r t of a rotation through different shifts. 117 Emergency physicians are not immune to the well-documented ill effects and difficulties suffered by shift workers in other industries. The feeling of many physicians, that they are unaffected by the vicissitudes of life that afflict their patients, has n o place in emergency medicine, where suboptimal job performance can have disastrous consequences. Because shift work seems largely responsible for the high attrition rate in emergency medicine, it is incumbent on those Of us who practice it to take good care of ourselves so that we may continue to take good care of others. Practicing in an environment that respects circadian principles means improved quality of care for our patients and improved personal and professional well-being for us.
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REFERENCES 1. Beagle J: Chair, American College of Emergency Physicians Behavioral Emergencies Committee, unpublished data, 1985. 2. Zun L, Kebernick M, Howes B: Emergency physician stress and morbidity. Am J Emerg Meal 1988;6:378-374. 3. Keller K, Koenig W: Sources of stress and satisfaction in emergency medicine. J Emerg Meal 1989;7:293-299. 4. Keller M: Health risks related to shift work: An example of time-contingent effects of long term stress. Int Areh Occup Envir Health 1983;53:59-75. 5. LaDoa J: Health effects of shift work. West J Med 1982;137:525-530. 6. Frese M, Semmer N: Shiftwork, stress, and psychosomatic complaints: A comparison between workers in different shift-work schedules, nen-shiftworkers, and former shiffworkers. Ergonomics 1986;29:99-114. 7. Akerstedt T: Sleepiness as a consequence of shift work. Sleep 1988;11:17-34. 8. Frese M, Harwich C: Shiftwork and the length and quality of sleep. J Occup Meal 1984;26:561-566. 9. Frese M, Okenek K: Reasons to leave shiftwork and psychological and psychosomatic complaints of former shiftwarkers. J Appl Psycho11984;69:509-514. 10. Akerstedt T: Psychological and psychophysiological effects of shift work. Scand J Work Environ Health 1990;16(suppl 1):67-75 11. Gordon N, Cleary P, Parker C, eta[: The prevalence and health impact of shift work. Am J Pubfic Health 1986;76:1225-1228. 12. Chau NP, Mallion JM, de 6audemaris R, et al: Twenty-four hour ambulatory blood pressures in shift workers. Circulation 1989;80:341-347. 13. Akerstedt T, Knutssen A, Alfredssen L, et al: Shift work and cardiovascular disease. Seanfl J Work Environ Health 1984;10:490-414. 14. Binder LS, Allison EJ Jr, Presser Ri.et al: 24-hour coverage in academic emergency medicine: Ways of dealing with the issue. Ann Emerg Meal 1990;19:430-434. 15. Mitler MM, Carskadon MA, Czeisler CA, et al: Catastrophics, sleep, and public policy: Consensus report. Sleep 1988;11:100-109. 16. Costa G, Apostoli P, Chiesi AM, et al: The Journey from Home to Work: The Impact on the Safety and Health of Workers~Commuters. Dublin, EURF Publ, 1984. 17. Milne D, Watkins F: An evaluation of the effects of shift rotation on nurses' stress, coping and strain. IntJ Nurs Stuff 1986;23:139-146. 18. Ascheff J, yon St Paul U, Wever R: )Lifetime of flies under influence of time displacement.] Naturwissenschaften 1971;58:574. 19. Halberg F, Nelson W, Cadotte G: Living routine shifts simulated on mice: Biweekly manipulation of light/dark cycle, in TwelfthInternational Conference Proceedings of the International Society of Chrnnobiology. Milan, II Ponte, 1977, p 133-138. 20. Makihara K: Death of a salaryman. InflHealth 1991;5:40-50. 21. Feret J, Bensimon 6, Benoit O, et al: Quality of sleep as a function of age and shift work. J Hum Ergo11982;11(suppl):149-154. 22. Weitzman ED, Moline ML, Czeisler CA, et al: Chronobiolegy of aging; Temperature, sleep-wake rhythms and entrainment. NeurobiolAging 1982;3:299-309. 23. Zun L, Chen E, Carrisen DM, et al: Longitudinal study of emergency physician wellness: Initial impressions (abstract). Ann Emerg Meal 1990;19:496. 24. d'Ortous de Mairan J J: Observation botanique, in Histoire de I'Acad~mie Reyale des Sciences, vo135. Paris, 1729. 25. de Candolle AP: Physiologie v@Gtale, ou exposition des forces et des fonctions vitales des v@Gtaux, in Memoires des Sarans I~trangers de I'lnstitut. Paris, Bechet Jaune, 1832. 26. Pittendrigh CS, Minis BH: Circadian systems--Longevity as a function of circadian resonance in Drosiphila melenogaster. Proc NaflAeadSci(USA) 1972;69:1537-1539. 27. Aschoff J, Wever R: Spentanperiodik des Menschen bei Ausschluss alter Zeitgeber. Naturwissenschaften 1962;49:337-342.
ANNALS OF EMERGENCY MEDICINE
21:10
OCTOBER1992
SHIFT W O R K
Whitehead, Thomas & Slapper
I
28. Czeisler CA: Human circadian physiology: Internal organization of temperature, sleep-wake and neuroendocrine rhythms monitored in an environment free of time cues. PhO dissertation, Stanford University, 1978.
I
56. McGrath M J, Cohen DB: REM sleep facilitation of adaptive waking behaviour: A review of the literature. Psycholog Bull 1978;85124-57.
29. Juergensen T: Die Korperwarme des gesunden Menschen. Leipzig, 1873.
57. Smith C: Sleep states and learning: A review of the animal literature. Neurosci Biobehav Rev 198519:157-168.
30. Kleitman N: Sleep and Wakefulness, ed 2. Chicago, University ef Chicago Press, 1963,p 172-184.
58. Czeisler CA, Guilleminault C: REM sleep: A workshop on its temporal distribution. Sleep 1980;2:265-287.
31. Zulley J, Wever RA: Interaction between the sleep-wake cycle and the rhythm of rectal temperature, in Aschoff J, Dean S, Oroos 6A (eds): Vertebrate Circadian Systems,Berlin, Springer-Verlag, 1982, p 253-261.
59. Pearlman CA: Sleep structure variation and performance, in Webb WB (ed): BiologicalRhythms, Sleep, and Performance. Chichester, Wiley and Sons, 1982, p 143173.
32, Quabbe HJ: Chronobiology of growth hormone secretion. Chronobiologia1977;4:217246,
60. Home J: Why We Sleep. Oxford, Oxford University Press, 1988, p 79-101. 61. Prinz PN, Roehrs TA, Vitaliano PP, et el: Effect of alcohol on sleep and nighttime plasma growth hormone and cortisol concentrations. J Clin EndocrinolMetab 1980151:759-764.
33. Weitzman ED: Temporal patterns of neuroendocrine secretion in man: Relationship to the 24 hour sleep-waking cycle, in Ascoff J, Ceresa F, Halberg F (eds): ChronobiologicalAspects of Endocrinology,Stuttg art, Sc hatta ua r-Ve rla g, 1974, p 169184.
62. Vogel GW: Evidence for REM sleep deprivation as the mechanism of action of antidepressant drugs. Prog NeuropsychopharmacolBiolog Psychiatry 1983;7:343-349.
34. Minors DS, Waterhouse JM: The use of constant routines in unmasking the endogenous component of human circadian rhythms. Chronobiollnt1984;l:205-216.
63. Roehrs T, Zorick F, Wittig R, et el: Effects of acute administration of brotizolam in subjects with disturbed sleep. BrJ Clin Pharmaco11983;16:371S-376S.
35. Moore RY: The suprachiasmatic nucleus and the organization of the circadian system. TrendsNeurosci1982;5:404+407.
64. Lester OK, Rundeg OH, Cowden LC, et al: Chronic alcoholism, alcohol and sleep. Adv Exp Med Bio11973;35:261-279.
36. Czaisler CA, Richardson 6S, Zimmerman JC, et al: Entrainment of human circadian rhythms by light-clark cycles: A reassessment. PhotochemPhotobio11981;34:239-247.
65. Turek FW, Losee-Olsen S: A benzodiazepine used in the treatment of insomnia phase shifts the mammalian circadian clock. Nature 19861321:167-168.
3/. Wever RA, Polasek J,Wildgruber CM: Bright light affects human circadian rhythms. PflugersArch 1983;396:85-87.
66. Van Reeth O, Turek FW: Adaptation of circadian rhythmicity to shift in light-dark cycle accelerated by a benzediazepine. Am J Physio11987;253:R204-207.
38. Coleman RM: WideAwake at3:OOAM. New York, Freeman and Co, 1986, p 88.
67. Walsh J K, Muehlbach M J, Schweitzer PK: Acute administration of triazolam for the daytime sleep of rotating shift workers. Sleep 1984;7:223-229.
39. Horne J: Why We Sleep: The Functions of Sleep in Humans and Other Mammals. Oxford, Oxford University Press, 1988, p 310-313. 40. Czeisler CA, Weitzman ED, Moore-Edy MC, et al: Human sleep: Its duration and organization depend on circadian phase. Science 19861210:1264-1267,
68. Penetar DM, Belenky G, Garrigan J J, et el: Triazalam impairs learning and fails to improve sleep in a long-range aerial deployment. AviatSpace EnvironMed 1989;60:594- 598,
41. Strogatz SH, Kronauer RE, Czeisler CA: Circadian pacemaker interferes with sleep onset at specific times each day: Role in insomnia. Am J Physio11987;253:R172-178.
69. Schneider-Helmert D: Why low-dose benzodiazepine-dapendent insomniacs can't escape their sleeping pills. Acta Psychiatr Scand 1988178:706-711.
42. Wingard DL, Berkman LF: Mortality risk associated with sleeping patterns among adults. Sleep 1983;6:102-107.
70, Johnson LC, Spinweber CL, Gomez SA, et al: Daytime sleepiness, performance, mood, nocturnal sleep: The effect of benzodiazepine and caffeine on their relationship. Psychepharmacology(Berlin) 1990;101:160-167.
43. Baker TL: Introduction to sleep and sleep disorders. Med Clin North Am 1985;69:1123-1153. 44. Vogel 6W: An alternative view to the neurobiology of dreaming. Am J Psychiatry 19781135:1531-1535. 45. Oswald I, Taylor AM, Treisman M: Discriminative responses to stimulation during human sleep. Brain 1960;83:440-453.
71. Richardson GS, Carskadon MA, Flagg W, etal: Excessive daytime sleepiness in man: Multiple sleep latency measurement in narcoleptic and control subjects. Electroenceph Clin Neurophysio11978;45:621-627. 72. Coleman RM: WideAwake at3:OOAM. New York, Freeman and Co, 1986, p 166-167.
46. Horne J: Why We Sleep. Oxford, Oxford University Press, 1988, p 210- 212.
73. Home JA, Anderson NR, Wilkinson RT: Effects of sleep deprivation on signal detection measures of vigilance: Implications for sleep function. Sleep 1983;6:347-358.
47. Blois R, Feinbarg I, 6alliard J-M, et al: Sleep in normal and pathological aging. Experientia 1983;39:551-558.
74. Bonnet, MH: Effect of sleep disruption on sleep, performance, and mood. Sleep 1985;8:11-19.
48. Bonnet MH: Performance and sleepiness following disrupted sleep allowing or prohibiting slew wave sleep. Sleep Res 1986115:68,
75. Johnson LC: Sleep deprivation and performance, in Webb WB (ed): Biological Rhythms, Sleep, and Performance. Chichester, Wiley and Sons, 1982, p 111-141.
49. Minors OS, Waterhouse JM: Circadian Rhythms and the Human. Bristor, Wright PSB, 1981,p 95-117.
76. Torsvall L, Akerstedt T: Sleepiness on the job: Continuously measured EEG changes in train drivers. Electroencephalogr Clin Neurephysio11987166:502-511.
50. Akerstedt T, 6Jllberg M: A dose-response study of sleep loss and spontaneous sleep termination. Psychephysiology1986;23:293-297.
77. Coleman RM: WideAwake at3:OOAM, New York, Freeman and Co, 1986, p 20-21.
61. Home J: Why We Sleep: The Functions of Sleep in Humans and Other Mammals, Oxford, Oxford University Press, 1988, p 150-156.
78. Rosa RR, Colligan M J, Lewis P: Extended work days: Effects of eight-hour and twelve-hour rotating shift schedules on performance, subjective alertness, sleep patterns, and psychosocial variables. Work and Stress 1989;3:21-32.
52. Sassin JF, Parker DC, Mace JW, et al: Human growth hormone release: Relocation to slow wave sleep and sleep-waking cycles. Science 1969;165:513-515.
79. Smith-Coggins R, Rosekind MR, Hurd S, Buceino K: Relationship of day versus night sleep to physician performance and mood (abstract). Ann EmergMeal1991;20:455.
53. Moldofsky H, Lue,FA, Eisen J, at el: The relationship of interleukin-1 and immune function to sleep in humans. Psychosomatic Med1986148:309-318.
80. Home JA, Ostberg O: A self-assessment questionnaire to determine morningnesseveningness in human circadian rhythms. IntJ Chronobio11976;4:97-110.
54. Agnew HW, Webb WB, Williams RL: Comparison of stage four and 1-REM sleep deprivation. Percept Mot Skills 1967;24:851+ 858.
81. Hildebra ndt G: Individual differences in susceptibi)ity to night- and shift work, in Halder M, Koller M, Cervinka R (ads): Nightand Shiftwork: Longterm Effects and Their Prevention. Frankfurt, Verlag Peter Lang, 1985, p 109-115.
55. 6uilteminault C, Pool P, Motta J, et al: Sinus arrest d'uring REM sleep in young adults. N EnglJ Meal 1985;31t :1006-1007.
OCTOBER1992
21:10
ANNALS 0F EMERGENCY MEDICINE
82. Blake M J: Relationship between circadian rhythm of body temperature and introversion-extroversion. Nature 19671215:896-897.
1257/119
SHIFT WORK
Whitehead, Thomas & Slapper
83. Blake M J: Temperature and time of day, in Colquhoun WP (ed): BiologicalRhythms and Human Performance. New York, Academic Press, 1971. 84. Reinberg A, Andlauer P, Guillet P, et al: 0ral temperature, circadian rhythm amplitude, aging and tolerance to shift work. Ergonomics 1980;23:55-64. 85. Monk TH: Advantages and disadvantages of rapidly rotating shift schedules--A circadian viewpoint. Human Factors 1986;28:553-557. 86. Klein KE, Wegemann H, Hunt BI: Desynchrenization of body temperature and performance circadian rhythms as a result of outgoing and homecoming transmeridian flights. Aerospace Med 1972;43:119-132. 87. Czeisler CA, Moore-Edy MC, Coleman RM: Rotating shift work schedules that disrupt sleep are improved by applying circadian principles. Science 1982;217:480-463. 88. Raymond CA: Shifting work, sleep cycles are on the way to becoming another public health issue. JAMA 1988;259:2958-2959.
109. Binges DF, 0rne MT, Whiteheuse WG, et al: Temporal placement of nap for alertness: Contributions of circadian phase and prior wakefulness. Sleep 1987;10:313329. 110. Mrosovsky N, Salmon PA: A behavioural method for accelerat ing re-entrainment of rhythms to new light-dark cycles. Nature 1987;330:372-373, 111. Czeisler CA, Johnson MP, Duff,/JF, et al: Exposure to bright light and darkness to treat physiologic maladaption to night work. NEnglJMed1990;322:1253-1259. 112. Czeisler CA, Kronauer RE, Allan JS, et el: Bright light induction of strong (type 0) resetting of the human circadian pacemaker. Science 1989;244:1328-1333. 113. Reinberg A, Migraine C, Apfelbaum M, et al: Circadian and ultradian rhythms in eating behavior and nutrient intake of oil refinery operators. Chronobiologia 1979;suppl 1:89-102.
89. Guilleminault C, Czeisler CA, Coleman RM, et el: Circadian rhythm disturbances and sleep disorders in shift workers. Electroencephalogr Clin Neurophysiol 1982;36(sup pl):709-714.
114. Apfelbaum M, Reinberg A, Lacatis D: Effects of meal timing on circadian rhythms in nine physiologic variables of young healthy but obese women during a caloric restriction, in Jequier E (ed): Second International Congress: Energy Balance and Man. Geneva, Medicine and Hygiene, 1975, p 22-26.
90. Vieux N, Ghata J, laporte A, et al: Adjustment of shift workers adhering to a three- to four-day rotation (Study 2). Chronobiologia 1979;suppl 1:37-42.
115. Lortie M, Foret J, Teiger C, et el: Circadian rhythms and behaviour of permanent nightworkers. Int Arch Occup Environ Health 1979;44:1-11.
91. Winget CM, Hughes L, LaBou J: Physiological effects of rotational work shifting: A review. J Occup Med 1978;20:204-210,
116. Patkai P, Akerstedt T, Pettersson K: Field studies of shift workers: I. Temporal patterns in psychophysiolegical activation in permanent night shift workers. Ergonomics 1977;20:611-619.
92. Whitehead DC: Chair, American College of Emergency Physicians Wellness Task Force, unpublished, 1990. 93. Rissman BS: Shift work indicated as a possible health hazard. Hasp Empl Health 1991;10:69-72. 94. Sharp KH: Circadian rhythms and disrupted sleep/wake cycles in resident physicians: A paradigm for change. PhD dissertation, Walden University, 1986. 95. Dean/I J, Tait R: Effects of sleep disruption on cognitive performance and mood in medical house officers. BrMedJ1987;295:1513-1516. 96. Ford CV, Wentz DK: The internship year: A study of sleep, mood states and psychophysiologic parameters, South MedJ 1984;77:1435-1441.
117. Mellor EF: Shift work and flexitime: Hew prevalent are they? Men Labor Rev 1986;Nov:14-21. Address for reprints: Dennis C Whitehead, MD, FACEP Department of Emergency Medicine Dickinson County Memorial Hospital Iron Mountain, Michigan 49801
97. Sakai K, Kogi K: Conditions for three-shift workers to take nighttime naps effectively, in Halder M, Keller M, Cervinka R (eds): Nightand Shiftwork: Longterm Effects and Their Prevention. Frankfurt, Verlag Peter Lang, 1985, p 173-180. 98. Folkard S, Monk TH, Lobban MC: Short and long-term adjustment of circadian rhythms in "permanent" night nurses, in Colquheun WP, Rutenfranz J (eds): Studies of Shiftwork. London, Taylor and Francis Ltd, 1980. 99. Knauth P, Rutenfranz J, Hermann G, at al: Reentrainment of bodytemperature in experimental shift-work studies. Ergonomics 1975;21:775-783. 10E Webb WB, Agnew HW: Variables associated with split period sleep regimes. A erosp Med 1971;45:701-704. 101. Hume KI, Mills JN: Rhythms of REM and slow wave sleep in subjects living on abnormal time schedules. Waking and Sleeping 1977;1:291-296. 102. Michaels HE: Night shift work. Ann Emerg Med 1984;13:201-202. 103. Thomas H: Coping with shift work. North Carolina EPICSpring 1990, p 8. 104. Monk TH: Advantages and disadvantages of rapidly rotating shift schedules--A circadian viewpoint. Human Factors 1986;28:553-557. 105. Akerstedt T: Adjustments of physiological circadian rhythms and the sleep-wake cycle to shiftwork, in Folkard S, Monk TH (eds): Hours of Work. Chichester, John Wiley, 1985, p 185-198. 106. Maren L, Rechtschaffen A, Wolpert EA: Sleep cycle during napping. Arch Gen Psychiatry 1964;11:503-50& 107. Karaean I, Williams RL, Finley WW, Hursch CJ: The effects of naps on nocturnal sleep: Influence on the need for stage- 1 REM and stage 4 sleep. BiolPsychiat 1970;2:391-399. 10& Binges DF, Orne MT, Orne EC, et al: Napping to sustain performance and mood: Effects of circadian phase and sleep loss, in Ha!der M, Keller M, Cervinka R (eds): Night and Shiftwork: Longterm Effects and Their Prevention. Frankfurt, Verlag Peter Lang, 1985, p 23-30.
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ANNALS OF EMERGENCY MEDICINE
21:10
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