Wednesday, June 7, 2023
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The term shift work describes regular employment outside the normal daytime hours. Therefore, shift workers experience a circadian rhythm dysynchronization, which is a recurrent or persistent misalignment between a patient's sleep pattern and societal norms. The patient cannot sleep when sleep is desired, needed, or expected, and thus, will suffer from chronic sleep loss. In fact, the more than 30 million shift workers in this country average 5-10 hours less sleep per week than nonshift workers, and this chronic sleep loss affects a shift worker's health, social activities, and family life.[1]
Recent history provides abundant examples in which severe fatigue at night resulted in disaster in the workplace: the Exxon Valdez oil spill in Alaska's Prince William Sound; the nuclear reactor meltdown in Chernobyl, Russia; the chlorine gas release in Bhopal, India; the radiation gas cloud at Three Mile Island, Pennsylvania; and NASA's Challenger disaster.
One of the gravest concerns to society is the risk of workplace injuries and mistakes. In a 2003 interview, John W. Mayo, PhD, dean of the Georgetown University School of Business in Washington, DC, and executive director of the school's Center for Business and Public Policy, stated, "Workplace death and injury is our nation's hidden epidemic, costing U.S. businesses and taxpayers more than $170 billion yearly in lost productivity and higher worker compensation, health care, and insurance costs.[12]" He asserted that approximately 17 Americans die in work-related accidents every day and that over 6 million people per year will be injured or suffer an illness related to work.[12]
According to the Bureau of Labor Statistics,[13,14] the most common shift work professions include:
These categories represent at least 20% of the workforce; this high percentage emphasizes the need to obtain an occupational history from patients in the workforce.
A significant number of these workers may experience severe enough consequences from their misaligned sleep-wake schedule to carry the diagnosis of shift work sleep disorder (SWSD). The International Classification of Sleep Disorders (ICSD) classifies SWSD as one of the dyssomnias, disorders with symptoms of either excessive sleepiness or insomnia.[5] All patients with SWSD will have 1 of these 2 symptoms (and often both) as the primary presenting complaint.
Estimating the prevalence of SWSD is difficult because of a number of factors, including a general lack of awareness of the disorder, the wide variety of terms used to describe SWSD (eg, night shift, irregular hours, and transient excessive sleepiness), and different definitions of "shift work." One study of shift workers showed that 25% of those who worked night or rotating shifts met the criteria for SWSD.[15] Patients with SWSD experience sleep attempts during the daytime (when circadian wake propensity is high) that are shortened and fragmented. The lack of restorative sleep significantly increases the sleep drive during waking hours, such as during the work shift, which leads to accidents and poor control of chronic diseases, such as hypertension and diabetes.[1,16,17] This could be the reason that a physician may have difficulty adequately controlling his or her shift worker patient's glucose or blood pressure.
Closely related to the ICSD criteria for SWSD are the criteria for the diagnosis of circadian rhythm sleep disorder, shift work type, in the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV). The DSM-IV criteria require that insomnia occurs during the major sleep period or that excessive sleepiness occurs during the major awake period, and that these symptoms are associated with night shift work or frequently changing shift work. In addition, all DSM-IV circadian rhythm sleep disorders require a finding of clinically significant distress or impairment in social, occupational, or other important areas of functioning.
In one survey of shift workers, evening and rotating workers were likely to experience higher levels of job strain, greater physical demands, more relationship problems, and higher personal stress levels than day workers.[18] Shift workers have greater sleep loss, unhealthy lifestyle behaviors (eg, smoking, poor diet, alcohol abuse, and lack of exercise), increased stress levels, and a higher incidence of cardiovascular disease, hypertension, and gastrointestinal disorders.[19,20] Shift workers' altered sleep schedules can lead to marital strain and disruption of social and/or family life; they can also increase the risk for drug or alcohol addiction, because patients often self-medicate with these substances to improve sleep and reduce waking episodes.[21]
The shift workers with the lowest mean hours of daily sleep are truck drivers, at 3.5 hours/24 hours.[22] This fact should wake us all up! A National Transportation Safety Board study examined the effects of duty shifts and sleep patterns on drivers of heavy trucks involved in single-vehicle accidents and found that 62 of 107 accidents (58%) reported by drivers were deemed to be "fatigue-related." More than half of these accidents occurred between 5:00 am and 7:00 am, around the end of the night shift schedule. Nineteen of the drivers reported falling asleep while driving.
A multivariate analysis showed that the most important factors in predicting an accident were the duration of a driver's last sleep period, the total hours of sleep obtained in the past 24 hours, and split sleep patterns.[23] With this in mind, the first law to criminalize sleep-deprived drivers was passed in New Jersey in 2003 and is called "Maggie's Law," named after Maggie McDonnell who was killed by a driver who fell asleep after going without sleep for 30 hours. The law enables the police to charge anyone involved in a fatal accident after not sleeping for 24 hours with vehicular homicide.
Adolescents are not considered to be shift workers but they operate in a sleep-deprived environment. Approximately 40% of high school and college students are estimated to be sleep-deprived, with documented performance decrements. This group is significantly represented among drowsy driving crashes.[24,25] Furthermore, a Minneapolis School District study found that simply changing the high school start times from 7:15 am to 8:40 am resulted in an hour more sleep per night and improved attendance rates.[26]
The medical profession has vast experience with, yet, little understanding of shift work consequences. In a study of emergency physicians, the mean total sleep time was reduced by 33% in those working night shifts vs those working day shifts (total sleep, 329 minutes vs 497 minutes, respectively; P = .02).[27] In another study, Landrigan and associates[28] demonstrated that intensive care unit interns working a traditional every third night extended 24-hour call schedule executed 5.6 times as many serious diagnostic errors than when they worked an intervention schedule that eliminated extended work shifts and reduced the number of hours worked per week.
Barger and colleagues[29] showed that residents with extended 24-hour schedules had a 9.1% increase in automobile accidents while driving home. Steele and associates[30] surveyed emergency medicine physicians to compare the incidence of accidents or near misses in regular day shift vs evening or night shift workers, and found that 76 residents reported 96 accidents, and 553 reported 1146 near misses during the commute home. Nearly three quarters of the accidents and 80% of the near misses occurred following a night shift. The number of incidents was significantly related to the number of night shifts worked per month.
Gold and coworkers[31] conducted a study of 687 nurses who were assigned to rotating shift schedules vs fixed day or night schedules. Compared with those working fixed shifts, the rotating shift workers reported a higher number of occupational difficulties and accidents. Those working a rotating schedule were twice as likely to report accidents or errors (including medication errors, work-related injuries, or accidents on the commute home), and 2.5 times more likely to report "near-miss" accidents or errors. The investigators concluded that the excessive sleepiness related to rotating shift work is associated with "frequent lapses of attention and increased reaction time, leading to increased error rates.[31]"
In 2003, the Accreditation Council for Graduate Medical Education implemented requirements for work hours for all resident physicians.[32] According to the guidelines, residents should work no more than 80 hours a week, have a maximum shift duration of 24 hours, have at least 10 hours off between shifts, have 1 day off per week, and have overnight call assignments no more than every third night.
This is a good start, but further restrictions and enforcement are necessary. Commercial airline pilots are restricted to no greater than 40 hours of flight time per month. These restrictions were mandated by law because a substantial body of literature has demonstrated that crew fatigue is a concern in military operations. The published scientific literature is replete with evidence that fatigue compromises cognition, judgment, and performance in all types of operational personnel.[33,34]
Military and commercial aviation operations have recognized the threat of additive fatigue factors in shift work: 12% to 25% of their most severe military mishaps were related to fatigue.[33,34] Multiple studies have concluded that performance errors increase significantly when continuous work hours exceed 12 hours.[35-37] Aircraft and other equipment can function for extended periods without adverse effects, but human operators need periodic sleep for the restoration of both body and brain.[35] Prolonged periods of wakefulness produce attention lapses and slower reaction times, which are associated with poor performance.[36,37]
Sleep-deprived personnel lose approximately 25% to 30% of their ability to perform useful mental work with each 24-hour period of sleep loss.[38,39] In fact, a 2003 study on the impact of fatigue on F-117 pilots revealed that 27-33 hours of sleep deprivation (1 night of sleep loss) degrade basic piloting skills by more than 40% below normal.[40]
Many continuous work time limits have been mandated by law, with long-haul truck driver limits set at 12 hours; US maritime industry sea pilots' limits set at 8 hours; railroad engineers' limits set at 12 hours; commercial carrier pilot maximum awake time from "on-call to crew rest" set at 16 hours; single-pilot flight schedule limits set at 6.5 hours; and the US Air Force's maximum pilot awake time set at 16 hours, with a single-pilot flight schedule limit set at 12 hours. Similar kinds of limits should be considered for medical professionals.
