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The social and economic burden of shift-work disorder.

Practice recommendations

* Shift-work disorder (SWD) and its defining symptoms can negatively affect health, quality of life, and work performance. The gravity of these consequences necessitates vigilance for the symptoms of SWD by primary care physicians (SOR: B).

* The threshold for treatment intervention for emergency service workers, such as firefighters, who make crucial decisions under shift-work conditions and who are experiencing SWD should be lower than for shift workers in general (SOR: B).

* The economic costs of untreated SWD are likely to be high. Early diagnosis and treatment of SWD may reduce these costs in addition to reducing the human burden of this circadian rhythm sleep disorder (SOR: C).

Shift work is a fundamental component of working patterns across the US workforce and is therefore an integral part of the lifestyle of a large proportion of the population. However, shift workers are at risk of developing the circadian rhythm sleep disorder shift-work disorder (SWD), a clinically recognized condition that develops in some individuals who work at night, start work early in the morning (4 to 7 AM), or work according to a rotating-shift schedule. SWD is more severe than--and distinct from--the sleep disturbances commonly associated with shift work. Provided other sleep/wake disorders can be discounted, SWD is diagnosed by the presence of excessive sleepiness (ES) and/or insomnia for >1 month during which the individual is performing shift work. (1)

Shift work poses a serious public health risk, as it can impair an individual's ability to perform effectively and may lead to occupational or traffic accidents. Furthermore, shift work has numerous negative health effects and infringes on an individual's ability to sleep, eat normally, exercise, and develop relationships. However, SWD is underrecognized in the clinical setting, (2) and data regarding its epidemiology and etiology are scarce in the scientific literature. Published information regarding shift work in general has therefore been used as the foundation for informing the clinical community on the potential burden of SWD. It is incumbent on primary care physicians to be vigilant for SWD in shift workers, make an accurate diagnosis, and initiate appropriate treatment in order to relieve--and prevent--the acute consequences and long-term health sequelae of this disorder, as well as to ensure public safety.

This supplement describes the burden of SWD, discusses the current understanding of the processes that cause this and other circadian rhythm sleep disorders, and describes the recognition and available management strategies for SWD. This article reviews the prevalence of SWD and examines the scale of its social and economic burden, including associated comorbidities. In the second article, Dr Chris Drake explains the causes of SWD and other circadian rhythm sleep disorders by describing the circadian and homeostatic systems and detailing how lifestyle factors, individual susceptibility, morbidity, and genetic components can result in circadian rhythm pathology.

The diagnosis of SWD is particularly challenging because its defining symptoms of ES and/or insomnia are demonstrated by numerous morbidities, including other sleep disorders. Furthermore, normal and abnormal responses to the challenge of shift work are not easily differentiated, and current diagnostic criteria require additional validation? Identification of SWD relies on detailed discussion of a patient's medical history, knowledge of relevant risk factors, and differential diagnosis to rule out other potentially causative medical conditions. Dr Jonathan Schwartz provides a comprehensive guide to recognizing and diagnosing patients with SWD in the third article of this supplement. In the final article, Dr Michael Thorpy discusses the behavioral and pharmacologic options available for patients with SWD in order to address ES and insomnia as well as comorbidities. He also supplies a useful algorithm to assist with the treatment of SWD in the primary care setting.

Epidemiology of SWD, insomnia, and ES in shift workers

For approximately 22 million US adults, shift work is an integral part of their professional life. (4) Of these individuals, about 3.8 million regularly work night shifts, and an additional 3.3 million perform night-shift work on a rotating basis. (5)

Drake and colleagues (6) used a telephone questionnaire to conduct a study of the prevalence of SWD in the general population of Detroit, MI; 2036 day-shift, 360 rotating-shift, and 174 night-shift workers participated. This study used minimum International Classification of Sleep Disorders 2 (ICSD-2) criteria to define SWD (1); namely, subjects with ES and/or insomnia who had been working either a night-shift or a rotating-shift schedule for the past 2 weeks were diagnosed with SWD. In this study, ES was defined by an Epworth Sleepiness Scale (ESS) (7) score of the total sample mean + 1 standard deviation (effectively, an ESS score of [greater than or equal to] 13, compared with the more commonly applied ES diagnostic score of [greater than or equal to] 10). Insomnia was diagnosed using Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Text Revision criteria, (8) ie, the subject had experienced periodic recurrences of difficulty in falling asleep, staying asleep, or nonrestorative sleep for at least 1 month, with a self-reported severity of at least 6 points out of a possible score of 10 on a visual analog scale.

Drake and colleagues (6) reported that 32.1% and 26.1% of night-shift and rotating-shift workers, respectively, met their prespecified ES and/or insomnia criteria, compared with 18.0% of day workers. The differential "true" prevalence of ES and insomnia--and therefore SWD--in night-shift and rotating-shift workers was reported to be approximately 14.1% and 8.1%, respectively. When it is considered that approximately 6% of all workers in the United States perform night- or rotating-shift work, the overall prevalence of SWD in the general population was estimated to be approximately 1%. (6) This result is lower than the 2% to 5% estimated in the ICSD-2 coding manual, (1) and some sleep specialists have argued that the figure put forward by Drake and colleagues (6) is conservative. (3) However, Drake and colleagues (6) also applied the more usual ES diagnostic measure of an ESS score of [greater than or equal to] 10 and, using this criterion, found a much higher prevalence of ES in their study population: 44.8% of night-shift workers and 35.8% of rotating-shift workers were found to have ES and therefore would also be considered to have SWD, provided their symptoms persisted for [greater than or equal to] 1 month.

A recent study of 4471 US police officers reported that 2.0% of this population had SWD, which was defined by the occurrence of both insomnia and ES in association with a recurrent schedule of work that overlapped the normal rest period?

Epidemiologic data for SWD are sparse and additional studies are warranted. Few overt data exist for the prevalence of SWD. Although the occurrence of insomnia and/or ES has been studied in various shift-working populations, frequently only one symptom is analyzed. Shift-working individuals who have either symptom for [greater than or equal to] 1month should be regarded as meeting the diagnostic criteria for SWD even if this is not stated explicitly by the respective study investigators.

For example, the Helsinki Heart Study examined the occurrence of insomnia and/or ES over a 3-month period in a population of approximately 3000 middle-aged men participating in a coronary heart disease prevention trial. (10) Persistent insomnia was reported by approximately 50% of rotating- and night-shift workers, whereas persistent ES was reported by approximately 25% of shift workers overall; those with ES and/or insomnia therefore met the diagnostic criteria for SWD. (10)

By contrast, a study using the Multiple Sleep Latency Test in a population of shift-working, long-haul bus drivers reported that the criteria for ES were met by 38% to 42% of subjects. (11) However, as the time frame over which patients experienced ES was not measured in this study, these patients should be viewed as being at risk of developing SWD, as opposed to having SWD per se. (11)

Similarly, in a study of police officers, insomnia or hypersomnia were reported by a significantly higher proportion of shift-working personnel compared with their day-working colleagues (insomnia, 25.9% vs 15.8% [P < .001]; hypersomnia, 4.9% vs 2.2% [P < .02]). (12) The absence of data regarding persistence of these symptoms precludes diagnosis of SWD in these patients.

Other studies have reported the prevalence of unplanned napping at work, which may be indicative of ES or sleep deprivation. For example, in a study of almost 700 registered female nurses, approximately 35% and 32% of participants working rotating or night shifts, respectively, reported episodes of unplanned sleep at work and may therefore have been at risk for developing SWD. (13)

Comorbidities associated with shift work and SWD

There are few reported studies regarding comorbidities in patients with SWD, although a large epidemiologic study has reported that patients with SWD are significantly more likely to experience comorbidities than are day workers or shift workers without SWD (P < .05). (6) Shift work has adverse effects on health even in the absence of SWD, although to date there is no evidence that shift work directly affects longevity. (14,15)

Metabolic disturbance and gastrointestinal issues

The relationship between sleep disturbance and obesity is well documented but poorly understood due to its complexity. (16) Sleep deprivation in particular has been implicated in the pathogenesis of weight gain and diabetes, and it may be that recognition and treatment of sleep disorders in general may assist with curtailing the current obesity epidemic. (17)

In a study of 500 male municipal workers in Italy, 3 of the 5 diagnostic symptoms of metabolic syndrome-obesity, elevated cholesterol, and raised triglyceride levels-were found significantly more frequently in nightshift workers than in day workers (P < .001, P < .01, and P < .001, respectively), indicating that shift work is associated with significant metabolic disturbance. (18) This report extended the findings of an earlier study that demonstrated that shift workers at a chemical plant in Italy had a significantly higher mean body mass index (BMI) than their day-working colleagues (27.7 kg/[m.sup.2] vs 26.5 kg/[m.sup.2], respectively; P < .01). (19) In addition, the prevalence of diabetes increased with duration of exposure to shift work, and markers of insulin resistance were more common in shift workers than in day workers. (20,21)

Compared with day workers, shift workers also have higher rates of peptic ulcers and gastrointestinal problems, such as constipation and diarrhea. (22,23) These findings were confirmed by a large trial of US workers, which reported that night-shift workers (odds ratio [OR], 3.13; 95% confidence interval [CI], 1.62-6.05), rotating-shift workers (OR, 2.32; 95% CI, 1.32-4.06), and subjects diagnosed with symptoms of SWD (OR, 4.55; 95% CI, 2.47-8.37) experienced increased rates of peptic ulcers compared with day workers (P < .001 for all comparisons). (6) Furthermore, both the effects of shift work and the symptoms of SWD contributed cumulatively to the increased likelihood of developing an ulcer among patients with SWD. (6)

Metabolic disturbance and gastrointestinal symptoms in shift workers and patients with SWD may arise in response to eating at unusual times of day, as food intake acts as a cue for the synchronization of the circadian clock. Moreover, gastric secretions in the middle of the night oppose the intrinsic circadian rhythm of enzymatic activity set by the light/dark cycle. The increased consumption of caffeine and alcohol used as coping strategies by many shift workers may also lead to gastrointestinal sequelae. (24)

Cardiovascular issues

Heart rate and blood pressure vary throughout the day due to circadian control; however, persistent nocturnal activity due to night work reportedly limits or abolishes the normal nocturnal reductions in blood pressure and decreases heart rate variability. (25,26) Individuals who do not experience circadian-driven fluctuations in blood pressure are likely to develop hypertension, which may lead to further cardiovascular sequelae. (27) In addition, there is some evidence that ES may be a risk factor for hypertension. (28) Shift workers have a 40% increased risk of developing cardiovascular disease compared with day workers. (29) Interestingly, a large study of the general population in Detroit, MI, reported that while nightshift (OR, 2.57; 95% CI, 1.24-5.30) and rotating-shift work (OR, 2.01; 95% CI, 1.06-3.83)were associated with an increased risk of heart disease (P = .01), the symptoms of SWD per se did not additionally exacerbate heart disease. (6) However, a cohort study of nearly 6000 participants (the Cardiovascular Health Study) reported that ES is linked with increased rates of myocardial infarction, total and cardiovascular mortality, and congestive heart failure, (30) although differences between the study populations in this and the study by Drake and colleagues (6) preclude direct comparison of their results.

Changes in hormone secretion, autonomic and sympathetic cardiac control, metabolism, and heart rate while working at night are implicated in shift-work-related cardiovascular problems. (18,31) Other factors, such as heightened levels of stress relating to work dissatisfaction and an absence of social support, may also play a part. (29,32) Furthermore, increased rates of smoking and more frequent rates of overweight contribute to the increased risk of developing cardiovascular problems in this patient population. (18,29)


Increased rates of breast, prostate, and colorectal cancer have been reported in occupations typically associated with night-shift work, such as firefighting, health care, and law enforcement. (33-39) For example, a study of long-term shift-working nurses reported that this population was at a moderately increased risk of breast and colorectal cancer. Nurses who had worked for [greater than or equal to] 20 years on a rotating night-shift schedule had a relative risk of breast cancer of 1.79 (95% CI, 1.06-3.01) compared with non-shift-working nurses. (39) The risk of developing breast cancer increased with longer working hours and increased duration of night-shift working. (34) The relative risk of colon cancer in nurses who had worked a rotating night-shift for [greater than or equal to] 15 years compared with nurses who never worked night shifts was 1.35 (95% CI, 1.03-1.77). (38)

Women who are awake during what would normally be the period of peak melatonin production (ie, at night) due to work commitments or poor sleep habits have been shown to have an increased risk of developing breast cancer (OR, 1.14 for each night per week; 95% CI, 1.01-1.28). (34) It may be that increased rates of cancer in shift-working populations are due to a reduction in night-time melatonin production, which has been shown to increase the incidence of tumors in animal models. (40,41) Dysregulation of circadian genes in cancer-related pathways or altered hormone production have also been implicated in raising the risk of cancer in shift-working individuals. (42,43)

Reproductive health

In addition to an increased risk of developing breast cancer, shift-working women are also more likely than day workers to experience irregular menstruation, reduced fertility, and problems during pregnancy. (44-46) Moreover, women working rotating shifts have more difficulty becoming pregnant than night-shift working women. (47,48)

Sleep disorders

The chronic sleep deprivation experienced by individuals with insomnia, including shift workers and those with SWD, is linked to reduced serum iron levels, which in turn leads to additional sleep problems such as restless legs syndrome or periodic limb movement disorder. (12,49) Periodic limb movement disorder occurs in 8.5% of shift workers, compared with 4.2% of non-shift workers (P < .005). (12) Fatigue (weariness without feeling sleepy) is frequently reported by shift workers and is often a manifestation of an underlying sleep disorder that is disrupting sleep quality. (50) The reported prevalence of sleep disorders other than SWD in shift workers is approximately 30%. (51)

Mood and anxiety disorders

High rates of depression have been reported in shift workers, particularly in women. (52) Furthermore, depression and SWD can both manifest as impairment in memory and concentration and may also result in apathy and lethargy. It is therefore vital that shift-working patients who present with symptoms of depression are asked about their sleep habits in order to avoid misdiagnosis of a mood disorder.

Shift work is thought to exacerbate existing mood disorders; this may be due to a lack of bright light exposure, as is the case with patients who experience seasonal affective disorder. (53) A large epidemiologic study has reported that symptoms of SWD were associated with elevated rates of depression (OR, 2.57; 95% CI, 2.01-3.27). (6) Interestingly, rates of depression did not differ between day, night-shift, and rotating-shift workers who did not have SWD. The findings indicate that, although SWD may be associated with depression, shift work alone does not elevate the risk of developing this mood disorder. (6) Assessment of shift-working radar controllers in the US Air Force using the Zung Anxiety and Depression Scales showed that shift workers with SWD had a greater likelihood of experiencing anxiety than did their shift-working colleagues without SWD (P < .01), and they were also significantly more prone to depression (P < .01). (54)

Cognitive effects associated with shift work and SWD

Memory consolidation, learning, alertness, and performance are severely affected by sleep deprivation, even in the absence of circadian misalignment. (55,56) Moreover, ES has detrimental effects on memory, impedes concentration, and impairs learning and work performance, regardless of its etiology. (57-59) A recent study has assessed learning in healthy patients who lived under shift-work conditions in a laboratory devoid of time cues by measuring improvements in the Mathematical Addition Test and the Digit Symbol Substitution Task. (60) Circadian misalignment was found to be detrimental to learning in subjects who failed to adapt to their imposed schedule of sleep and wake. (60) Thus individuals who experience ES, sleep deprivation, and sleep/wake synchronization issues as a result of SWD are likely to be particularly affected in this respect.

ES can be severe in night-shift workers (defined by an ESS score [greater than or equal to] 18) (7) and becomes most pronounced in terms of impaired performance between 3 and 6 AM. (55) Reductions in sleep duration of between 1 and 4 hours per day have been reported in night-shift populations, and this sleep deprivation may account for a large proportion of the ES associated with SWD. (61-63) Moreover, the quality of night-shift workers' sleep is often poor due to premature awakening and reductions in rapid eye movement and stage 2 slow wave sleep, which is associated with memory consolidation and learning. (62-66) Restriction of sleep time by as little as 2 hours per night for 1 week has been shown to significantly affect scores on vigilance tasks. (67) Furthermore, the persistent sleep debt incurred by shift workers may lead to reduced attention and performance equivalent to that demonstrated by intoxicated persons or study subjects required to remain awake continuously for 24 hours. (67,68) Of concern, significantly lower levels of alertness and performance have been recorded in nuclear power plant night-shift workers vs day- and evening-shift workers. (69,70)

Alertness and cognitive processes may be especially impaired during the transition from day work to a series of night shifts, as many individuals will attempt to stay awake throughout the whole first day and night. (71) Response times in tests of visual selective attention were significantly (P < .05) affected on the first night shift in a shift-work simulation study. (71) These results indicate that the potential for accidents is increased in affected night-shift workers from as early as their first shift; productivity is also likely to be affected almost immediately in such workers. (71)

Social and quality of life burden of SWD

Shift work negatively affects quality of life. In a study of Air Force radar controllers, shift workers in general experienced higher levels of anxiety (P < .001) and irritability (P < .05) and demonstrated a greater tendency to ignore stress (P < .001) than did day workers. (54) Importantly, this study also demonstrated that SWD imparts a significantly greater detriment to quality of life than does shift work alone. Quality of life for shift workers with SWD was significantly poorer than that of shift workers without this disorder for the Sickness Impact Profile domains of sleep and rest (P < .001), emotional behavior (P < .001), home management (P < .05), mobility (P < .05), social interaction (P < .01), ambulation (P < .05), alertness behavior (P < .001), work (P < .05), and recreational pastimes (P < .01). (54) Subjects with SWD also experienced greater impairments, compared with other shift workers, for the Illness Behavior Questionnaire domains of general hypochondriasis (P < .001), disease conviction (P < .001), affective inhibition (P < .001), affective disturbance (P < .001), and the Whiteley Index of Hypochondriasis (P < .001). (54)

Moreover, a large epidemiologic study of the general US population found that individuals with SWD are more likely to be unable to attend social and family interactions due to sleep problems than those without SWD. (6) Permanent night workers with SWD missed 8.6 days of family or social activity per month compared with 1.5 days in those without SWD; rotating-shift workers with SWD missed 10.1 days of family or social activity each month vs 1.0 day in their colleagues without SWD. (6)

A set of self-report questionnaires--the Standard Shiftwork Index (SSI)--was developed specifically to monitor problems relating to shift work, including changes in alertness, coping, job satisfaction, sleep, psychological well-being, and physical health. (72) A number of studies have used the SSI in shift-work populations and have demonstrated that this measure can differentiate between shift schedules of differing types and length. (73-79) However, a number of analyses have intimated that several of the scales incorporated in the SSI are psychometrically weak, and further evidential support for this set of questionnaires may be required. (80,81)


Shift workers are more likely to have work-related accidents than are day workers. (82) Considering that the shift-work population includes nurses, physicians, firefighters, police officers, military personnel, pilots, and drivers, the potential ramifications of SWD are disconcerting. Early treatment intervention should be considered in emergency workers presenting with SWD symptoms so that they can continue to perform their roles safely. Transportation accidents due to ES, suboptimal treatment of patients under the care of shift-working clinicians, and injuries to the clinicians themselves are commonplace, yet SWD remains a poorly documented condition. (2)

The likelihood of a medical resident experiencing a percutaneous injury (with a scalpel or needle) was found to be twice as high during a night shift than during a day shift (OR, 2.04; 95% CI, 1.98-2.11). (83) The odds of reporting an accident or error due to ES were twice as high among nurses on a rotating-shift schedule compared with nurses on a fixed day or evening shift. (13)


Other workers with vital roles are also affected by the demands of shift work. Police officers required to work shifts were reported to be significantly more likely to experience a sleep-related accident at work or at home than were their non-shift-working colleagues (OR, 2.24; P < .0005); data concerning the types of accidents experienced by these police officers were not collected in this study. (12)

More accidents are reported by workers commuting home after the night shift than by day workers. (84,85) For example, 40% of motor vehicle accidents experienced by medical residents in their first postgraduate year occurred during the commute home after shift work. (88) Moreover, 74% of motor vehicle crashes involving emergency medicine residents occurred after they had worked a night shift, compared with 12% after a day shift. (85) Among night-shift working nurses, 79% reported experiencing at least one episode of drowsiness on the commute home in a 4-week study. (87)

Driving as part of a shift-based occupation also presents risks for accidents, with approximately 25% of police officers reporting that they have fallen asleep at the wheel while driving at work. (88) It is not surprising that the vast majority of single-vehicle accidents occur early in the morning, when drivers are sleepiest (89,90) (FIGURE 1).

Early-morning sleepiness is also thought to be responsible for the increased rate of military flight accidents at this time of day. (91) Twelve percent of US Air Force non-aircrew shift workers admit that they have experienced a fatigue-related operational error, although only 31% of those affected officially reported such an event. Of concern, work/rest guidelines used by shift-working US Air Force aircrew do not appear to greatly improve matters, as fatigue was found to be a factor in 13% of serious aviation mishaps recorded between 1972 and 2000. (92)

Although these data are illuminating, it is apparent that very few studies have been published on the rate of accidents specifically caused by SWD. Considering that patients with SWD are particularly vulnerable to the circadian issues created by shift work, it seems likely that they must make up a significant proportion of the shift-working population that experiences work-related and traffic accidents. However, until further studies are performed that specifically analyze accidents involving patients with SWD, we can only anticipate that the incidents that these individuals experience are more harmful and occur more frequently compared with the general shift-working population.

Economic impact of SWD

As described in "Cognitive effects associated with shift work and SWD" on page $6 of this article, shift work is associated with significant neurocognitive deficits and reduced efficiency at work. The costs due to lost productivity and accidents associated with shift workers performing at suboptimal level are, therefore, likely to be substantial. To date, studies of the direct and indirect costs of shift work and SWD have not been published; however, an indication of the scale of the economic burden can be gained by looking at the costs associated with the 2 key symptoms of SWD: ES and insomnia.

A study of the economic consequences of ES (performed using 1988 data) reported that ES of any etiology was responsible for motor vehicle accidents costing between $29 billion and $38 billion annually ($53 billion and $69 billion, when adjusted to 2009 values) and work-related accidents (including deaths and disabling injuries) costing between $10 billion and $13 billion annually ($18 billion and $24 billion when adjusted to 2009 values). (93)


Studies of patients with insomnia of unspecified etiology reveal the extent of the cost burden of this symptom. An observational US study found that average 6-month total costs (le, direct and indirect costs) were approximately $1253 higher for an adult (age 18-64 years) with insomnia than for a matched control without insomnia. (94)

A recently reported Canadian study highlighted the large contribution of indirect costs to the total costs associated with insomnia. (95) Direct costs included those for doctors' visits, transportation to the visits, and prescription and over-the-counter drugs. Indirect costs associated with insomnia included those for lost productivity and job absenteeism; these accounted for 91% of all costs. On average, the total annual costs incurred by a patient with insomnia syndrome (defined as those who used a sleep-promoting agent [greater than or equal to] 3 nights per week and/ or were dissatisfied with sleep, had insomnia symptoms [greater than or equal to] 3 nights per week for [greater than or equal to] 1 month, and experienced psychological distress or daytime impairment) (95) were C$5010 (C$293 direct and C$4717 indirect). For a patient with insomnia symptoms, average annual total costs were calculated to be C$1431 (C$160 direct and C$1271 indirect). By comparison, a good sleeper (ie, a study subject who reported being happy with his or her sleep, did not report symptoms of insomnia, and did not use sleep-promoting medication) was found to incur average annual costs of C$421. (95)

More detailed assessment is required of the costs incurred specifically in patients with SWD, but there is clearly an economic rationale for early diagnosis and treatment of the symptoms of SWD.


What is clear from this review is that, while information on shift work is relatively abundant, data concerning SWD are meager. For example, epidemiologic data on SWD are sparse, in part because many investigators in studies of shift workers do not take the seemingly logical step of assessing SWD in their subjects. However, differentiating between shift workers who experience transient symptoms associated with adapting to a new shift schedule and individuals with SWD is complex and may lead to underrecognition of this condition. Similarly, there are few data on the comorbidities experienced by individuals diagnosed with SWD and further studies are warranted. The increased risk of illness demonstrated by shift-working individuals may be even greater in patients with SWD due to their intrinsic--and poorly understood-vulnerability to the effects of shift work.

The studies described here show that the burden of SWD is multifactorial, and it includes impairment of patients' relationships and health and reduces their efficiency at work. (6) Again, there are very few data on the economic burden of SWD, although reduced productivity and the cost of accidents in the workplace and while driving are likely to be high. Additional research is needed in this area.

Shift workers, including public service workers, must make difficult decisions during times of day when they are not functioning optimally. Emergency clinicians in particular have great responsibility and must work under these trying conditions. In addition to the increased rates of traffic and workplace accidents encountered by such clinicians, many will also have difficulty adapting to shift and on-call work, lose recreation time with their families, and experience insomnia, ES, sleep deprivation, and comorbidities (FIGURE 2). Not surprisingly, these factors lead to high rates of dissatisfaction and attrition in specialized roles, (96) including health care workers, air traffic controllers, and power-plant workers. A lack of support for shift workers dealing with such issues has economic and safety consequences for society in general; recognition and treatment of SWD are therefore vital.


(1.) American Academy of Sleep Medicine. International Classification of Sleep Disorders: Diagnostic and Coding Manual. 2nd ed. Westchestet, IL: American Academy of Sleep Medicine; 2005.

(2.) Schwartz JRL, Roth T. Shift work sleep disorder: Burden of illness and approaches to management. Drugs. 2006;66:2357-2370.

(3.) Sack RL, Auckley D, Auger R, et al. Circadian rhythm sleep disorders: part I, basic principles, shift work and jet lag disorders. Sleep. 2007;30: 1460-1483.

(4.) McMenamin TM. A time to work: recent trends in shift work and flexible schedules. Monthly Labor Review, Dec 2007:3-15. artlfull.pdf. Accessed April 2, 2009.

(5.) US Bureau of Labor Statistics. Workers on flexible and shift schedules in May 2004. Washington, DC: US Department of Labor, Bureau of Labor Statistics; 2005.

(6.) Drake CL, Roehrs T, Richardson G, et al. Shift work sleep disorder: prevalence and consequences beyond that of symptomatic day workers. Sleep. 2004;27:1453-1462.

(7.) Johns MW. A new method for measuring daytime sleepiness: the Epworth Sleepiness Scale. Sleep. 1991;14:540-545.

(8.) American Psychiatric Association. Diagnostic and Statistical Manual of Mental Health Disorders, 4th ed, text rev. Washington, DC: American Psychiatric Association; 2000.

(9.) Rajaratnam SMW, Barger LK, Lockley SW, et al. Screening for sleep disorders in North American police officers [abstract]. Sleep. 2007;30(suppl): A209.

(10.) Harma M, Tenkanen L, Sjoblom T, et al. Combined effects of shift work and life-style on the prevalence of insomnia, sleep deprivation and daytime sleepiness. Scand J Work Environ Health. 1998;24:300-307.

(11.) Santos EH, de Mello MT, Pradella-Hallinan M, et al. Sleep and sleepiness among Brazilian shift-working bus drivers. Chronobiol Int. 2004;21:881-888.

(12.) Garbarino S, De Carli F, Nobili L, et al. Sleepiness and sleep disorders in shift workers: a study on a group of Italian police officers. Sleep. 2002;25:648-653.

(13.) Gold DR, Rogacz S, Bock N, et al. Rotating shift work, sleep, and accidents related to sleepiness in hospital nurses. Am J Public Health. 1992;82: 1011-1014.

(14.) Taylor PJ, Pocock SJ. Mortality of shift and day workers 1956-1968. Br J Ind Med. 1972;29:201-207.

(15.) Boggild H, Saudicani P, Hein HO, et al. Shift work, social class, and ischaemic heart disease in middle aged and elderly men; a 22 year follow up in the Copenhagen male study. Occup Environ Med. 1999;56:640-645.

(16.) Wolk R, Somers VK. Sleep and the metabolic syndrome. Exp Physiol. 2007;92:67-78.

(17.) Knutson KL, Spiegel K, Penev P, et al. 3he metabolic consequences of sleep deprivation. Sleep Med Rev. 2007;11:163-178.

(18.) Biggi N, Consonni D, Galluzzo V, et al. Metabolic syndrome in permanent night workers. Chronobiol Int. 2008;25:443-454.

(19.) Di Lorenzo L, De Pergola G, Zocchetti C, et al. Effect of shift work on body mass index: results of a study performed in 319 glucose-tolerant men working in a Southern Italian industry. Int J Obes Relat Metab Disord. 2003;27:1353-1358.

(20.) Kawachi I, Colditz GA, Stamfer ML et al. Prospective study of shift work and risk of coronary heart disease in women. Circulation. 1996;92:3178-3182.

(21.) Nagaya T, Yoshida H, Takahashi H, et al. Markers of insulin resistance in day and shift workers aged 30-59 years. Int Arch Occup Environ Health. 2002;75:562-568.

(22.) Knutsson A. Health disorders of shift workers. Occup Med (Lond). 2003;53:103-108.

(23.) Segawa K, Nakazawa S, Tsukamoto Y, et al. Peptic ulcer is prevalent among shift workers. Dig Dis Sci. 1987;32:449-453.

(24.) Garbarino S, Beelke M, Costa G, et al. Brain function and effects of shift work: implications for clinical neuropharmacology. Neuropsychobiology. 2002;45:50-56.

(25.) Su TC, Lin LY, Baker D, et al. Elevated blood pressure, decreased heart rate variability and incomplete blood pressure recovery after a 12-hour night shift work. J Occup Health. 2008;50:380-386.

(26.) Yamasaki E Schwartz JE, Gerber LM, et al. Impact of shift work and race/ethnicity on the diurnal rhythm of blood pressure and catecholamines. Hypertension. 1998;32:417-423.

(27.) Birkenhager AM, van den Meiracker AH. Causes and consequences of a non-dipping blood pressure profile. Neth J Med. 2007;65:127-131.

(28.) Thurnheer R. Obstructive sleep apnea and cardiovascular disease--time to act! Swiss Med Wkly. 2007;137:217-222.

(29.) Boggild H, Knutsson A. Shift work, risk factors and cardiovascular disease. Scand J Work Environ Health. 1999;25:85-99.

(30.) Newman AB, Spiekerman CF, Enright P, et al. Daytime sleepiness predicts mortality and cardiovascular disease in older adults. The Cardiovascular Health Study Research Group. J Am Geriatr Soc. 2000;48:115-123.

(31.) Furlan R, Barbic F, Piazza S, et al. Modifications of cardiac autonomic profile associated with a shift work schedule of work. Circulation. 2000;102:1912-1916.

(32.) Harma M. Shift work and cardiovascular disease--from etiologic studies to prevention through scheduling. Scand J Work Environ Health. 2001;27:1057-1079.

(33.) Hansen J. Increased breast cancer risk among women who work predominantly at night. Epidemiology. 2001;12:74-77.

(34.) Davis S, Mirick DK, Stevens RG. Night shift work, light at night, and risk of breast cancer. J Natl Cancer Inst. 2001;93:1557-1562.

(35.) Demers PA, Checkoway H, Vaughan TL, et al. Cancer incidence among firefighters in Seattle and Tacoma, Washington (United States). Cancer Causes Control. 1994;5:129-135.

(36.) Megdal SP, Kroenke CH, Laden F, et al. Night work and breast cancer risk: a systematic review and meta-analysis. Eur J Cancer. 2005;41:2023-2032.

(37.) Schernhammer ES, Laden F, Speizer FE, et al. Rotating night shifts and risk of breast cancer in women participating in the Nurses' Health Study. J Natl Cancer Inst. 2001;93:1563-1568.

(38.) Schernhammer ES, Laden F, Speizer FE, et al. Night-shift work and risk of colorectal cancer in the Nurses' Health Study. J Nat Cancer Inst. 2003;95:825-828.

(39.) Schemhammer ES, Kroenke CH, Laden F, et al. Night work and breast cancer risk. Epidemiology. 2006;17:108-111.

(40.) Anisimov VN. The light-dark cycle regimen and cancer development. Neuro Endocrinol Lett. 2002;23:28-36.

(41.) Anisimov VN, Baturin DA, Popovich IG, et al. Effect of exposure to light-at-night on life span and spontaneous carcinogenesis in female CBA mice. Int J Cancer. 2004; 111:475-479.

(42.) Davis S, Mirick DK. Circadian disruption, shift work and the risk of cancer: a summary of the evidence and studies in Seattle. Cancer Causes Control. 2006; 17:539-545.

(43.) Stevens RG, Black DE, Brainard GC, et al. Meeting report: the role of environmental lighting and circadian disruption in cancer and other diseases. Environ Health Perspect. 2007;115:1357-1362.

(44.) Nurminen T. Shift work and reproductive health. Scand J Work Environ Health. 1998;24:28-34.

(45.) Uehata T, Sasakawa N. ]he fatigue and maternity disturbance of night workwomen. J Hum Ergol (Tokyo). 1982; 11:465-474.

(46.) Miyauchi F, Nanjo K, Otsuka K. Effects of night shift on plasma concentrations of melatonin, LH, FSH and prolactin, and menstrual irregularity [in Japanese]. Sangyo Igaku. 1992;34:545-550.

(47.) Ahlborg G Jr, Axelsson G, Bodin L. Shift work, nitrous oxide exposure and subfertility among Swedish midwives. Int J Epidemiol. 1996;25: 783-790.

(48.) Bisanti L, Olsen J, Basso O, et al. Shift work and subfecundity: a European multicenter study. J Occup Environ Med. 1996;38:352-358.

(49.) Barton JC, Wooten VD, Acton RT. Hemochromatosis and iron therapy of restless legs syndrome. Sleep Med. 2001;2:249-251.

(50.) Shen J, Botly LCP, Chung SA, et al. Fatigue and shift work. J Sleep Res. 2006;15:1-5.

(51.) Palm SL, Pires MLN, Bittencourt LRA, et al. Sleep complaints and polysomnographic findings: a study of nuclear power plant shift workers. Chronobiol Int. 2008;25:321-331.

(52.) Scott AJ, Monk TH, Brink LL. Shiftwork as a risk factor for depression: a pilot study. Int J Occup Environ Health. 1997;2(suppl 2):S2-S9.

(53.) Cole RJ, Loving RT, Kripke DE Psychiatric aspects of shiftwork. Occup Med. 1990;5:301-314.

(54.) Puca FM, Perrucci S, Prudenzano MP, et al. Quality of life in shift work syndrome. Funct Neurol. 1996;11:261-268.

(55.) Dijk DJ, Duffy JF, Czeisler CA. Circadian and sleep/wake dependent aspects of subjective alermess and cognitive performance. J Sleep Res. 1992;1:112-117.

(56.) Walker MP, Stickgold R. It's practice, with sleep, that makes perfect: implications of sleep-dependent learning and plasticity for skill performance. Clin Sports Med. 2005;24:301-317.

(57.) Rajaratnam SM, Arendt J. Health in a 24-h society. Lancet. 2001;358:999-1005.

(58.) Reimer MA, Flemons WW. Quality of life in sleep disorders. Sleep Med Rev. 2003;7:335-349.

(59.) Alapin I, Fichten CS, Libman E, et al. How is good and poor sleep in older adults and college students related to daytime sleepiness, fatigue, and ability to concentrate? J Psychosom Res. 2000; 49:381-390.

(60.) Wright KP Jr, Hull JT, Hughes RJ, et al. Sleep and wakefulness out of phase with internal biological time impairs learning in humans. J Cogu Neurosci. 2006;18:508-521.

(61.) Akerstedt T. Work schedules and sleep. Experientia. 1984;40:417-422.

(62.) Tilley AJ, Wilkinson RT, Warren PSG, et al. The sleep and performance of shift workers. Hum Factors. 1982;24:629-641.

(63.) Walsh JK, Tepas DI, Moses PD. The EEG sleep of night and rotating shift workers. In: Johnson LC, Tepas DI, Colquhoun WP, eds. Biological rhythms, sleep and shift work. New York, NY: Spectrum Publications; 1981:371-381.

(64.) Akerstedt T. Shift work and disturbed sleep/ wakefulness. Occup Med (Lond). 2003;53:89-94.

(65.) Akerstedt T, Torsvall L, Gillberg M. Sleepiness and shift work: field studies. Sleep. 1982;5(suppl 2):S95-S106.

(66.) Knauth P, Landau K, Droge C, et al. Duration of sleep depending on the type of shift work. Int Arch Occup Environ Health. 1980;46:167-177.

(67.) Czeisler CA. The Gordon Wilson Lecture: work hours, sleep and patient safety in residency training. Trans Am Clin Climatol Assoc. 2006;117: 159-188.

(68.) Van Dongen HP, Maislin G, Mullington JM, et al. The cumulative cost of additional wakefulness: dose-response effects on neurobehavioral functions and sleep physiology from chronic sleep restriction and total sleep deprivation. Sleep. 2003;26:117-126.

(69.) Smith L, Folkard S. The impact of shiftwork on nuclear power personnel: an exploratory study. Work Stress. 1993;7:341-350.

(70.) Smith L, Peter T, Folkard S. Shiftwork effects in nuclear power workers: a field study using portable computers. Work Stress. 1995;9:235-244.

(71.) Santhi N, Horowitz T, Duffy JF, et al. Acute sleep deprivation and circadian misalignment associated with transition onto the first night of work impairs visual selective attention. PLoS ONE. 2007;2:e1233.

(72.) Barton J, Spelten E, Totterdell P, et al. The Standard Shiftwork Index: a battery of questionnaires assessing shiftwork-related problems. Work Stress. 1995;9:4-30.

(73.) Barton J, Folkard S. Advancing versus delaying shift systems. Ergonomics. 1993;36:59-64.

(74.) Barton J, Smith L, Totterdell P, et al. Does individual choice determine shift system acceptability? Ergonomics. 1993;36:93-99.

(75.) Poissonnet CM, Iwatsubo Y, Cosquer M, et al. A cross-sectional study of the health effects of work schedules on 3212 hospital workers in France: implications for the new French work schedules policy. J Hum Ergol (Tokyo). 2001;30:387-391.

(76.) Takahashi M, Tanigawa T, Tachibana N, et al. Modifying effects of perceived adaptation to shift workers on health, wellbeing, and alertness on the job among nuclear power plant operators. Ind Health. 2005;43:171-178.

(77.) Tucker P, Barton J, Folkard S. Comparison of eight and 12 hour shifts: impacts on health, wellbeing, and alertness during the shift. Occup Environ Med. 1996;53:767-772.

(78.) Tucker P, Smith L, Macdonald I, et al. Shift length as a determinant of retrospective on-shift alertness. Scand J Work Environ Health. 1998;24 (suppl 3):49-54.

(79.) Tucker P, Smith L, Macdonald I, et al. Effects of direction of rotation in continuous and discontinuous 8 hour shift systems. Occup Environ Med. 2000;57:678-684.

(80.) Smith C, Gibby R, Zickar M, et al. Measurement properties of the Shiftwork Survey and Standard Shiftwurk Index. J Hum Ergol (Tokyo). 2001;30:191-196.

(81.) Tucker P, Knowles SR. Review of studies that have used the Standard Shiftwork Index: evidence for the underlying model of shiftwork and health. Appl Ergon. 2008;39:550-564.

(82.) Ohayon MM, Lemoine P, Amaud-Briant V, et al. Prevalence and consequences of sleep disorders in a shift worker population. J Psychosom Res. 2002;53:577-583.

(83.) Ayas NT, Barger LK, Cade BE, et al. Extended work duration and the risk of self-reported percutaneous injuries in interns. JAMA. 2006;296:10551062.

(84.) Akerstedt T, Peters B, Anund A, et al. Impaired alermess and performance driving home from the night shift: a driving simulator study. J Sleep Res. 2005; 14:14-20.

(85.) Steele MT, Ma OJ, Watson WA, et al. The occupational risk of motor vehicle collisions for emergency medicine residents. Acad Emerg Med. 1999;6:1050-1053.

(86.) Barger LK, Cade BE, Ayas NT, et al. Extended work shifts and the risk of motor vehicle crashes among interns. N Engl J Med. 2005;352:125-134.

(87.) Scott LD, Hwang WT, Rogers AE, et al. The relationship between nurse work schedules, sleep duration, and drowsy driving. Sleep. 2007;30: 1801-1807.

(88.) Vila B, Kenney DJ. Tired cops: the prevalence and potential consequences of police fatigue. National Institute of Justice Journal. 2002;248: 16-21.

(89.) Hamelin P. Lorry driver's time habits in work and their involvement in traffic accidents. Ergonomics. 1987;30:1323-1333.

(90.) Lavie P, Gopher D, Wollman M. Thirty-six hour correspondence between performance and sleepiness cycles. Psychophysiology. 1987;24: 430-438.

(91.) Price W, Holley DC. The last minutes of flight 2860: an analysis of crew shift work scheduling. In: Reinberg A, Vieux N, Andlauer E eds. Night and shift work: biological and social aspects. Oxford, UK: Pergamon Press; 1981:287-298.

(92.) Tvaryanas AP, Thompson WT. Fatigue in military aviation shift workers: survey results for selected occupational groups. Aviat Space Environ Med. 2006;77:1166-1170.

(93.) Leger D. The cost of sleep-related accidents: a report for the National Commission on Sleep Disorders Research. Sleep. 1994;17:84-93. 94. Ozminkowski RJ, Wang S. Walsh JK. The direct and indirect costs of untreated insomnia in adults in the United States. Sleep. 2007;30:263-273.

(95.) Daley M, Morin CM, LeBlanc M, et al. 3he economic burden of insomnia: direct and indirect costs for individuals with insomnia syndrome, insomnia symptoms, and good sleepers. Sleep. 2009;32:55-64.

(96.) Waeckerle JF. Circadian rhythm, shift work, and emergency physicians. Ann Emerg Med. 1994;24:959-961.

Larry Culpepper, MD, MPH

Department of Family Medicine

Boston University Medical Center

Boston, Massachusetts

Dr Culpepper reports that he serves as a consultant to AstraZeneca, Eli Lilly and Company, Pfizer Inc, Wyeth, sanofi-aventis, and Takeda Pharmaceuticals North America, Inc, and on the speakers bureau of Wyeth.
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Author:Culpepper, Larry
Publication:Journal of Family Practice
Geographic Code:1USA
Date:Jan 1, 2010
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