Fatigued Workers: A True Safety Concern

Court documents suggest fatigue played a critical role in an accident aboard a Navy submarine in which 10 pounds of mercury were spilled into San Diego Bay. In September, the Navy said the cost to clean up the spill was $1.78 million. The accident aboard rescue vehicle Mystic occurred at 7 a.m. on July 1, 1996, at North Island Naval Air Station, when a technician inadvertently opened a valve on the emergency ballast system during daily maintenance. Testimony during the court martial showed fatigue probably contributed to the error. For months leading up to the accident, the sub's crew worked 12 to 20 hours a day, with a day off every two or three weeks, in an effort to get the sub ready for duty. During a subsequent court martial, the technician who made the error was convicted of "negligently failing to perform his duties" and making a false statement about his actions afterward. In a tearful plea for leniency before a military judge, the technician said: "After months and months of sleepless nights and work that never seemed to end, we were all mentally and physically drained...I'm sorry my actions have caused so much trouble. But I still hold onto the fact I am only human. I'm not a robot. And as humans do, I made a mistake." A few months before the accident, an engineer passed out from stress and exhaustion, and had to be hospitalized for three days. "The whole crew was fairly well mentally and physically burned out," the engineer testified. "I can't even describe how we were operating. We were all just dog tired." Dr. Daniel Kripke, a psychiatry professor at the University of California, in September publicly criticized the Navy for failing to recognize the dangers of fatigue and its potential risk to public safety. "This was an accident waiting to happen," he said. "Had it not been this tragedy, it would have been another. It is fortunate nobody was killed outright." While it's difficult to discern what the first step towards eliminating this problem should be, there is a strong contingency claiming altering "circadian rhythms" should be the first step. With data collected on circadian rhythms, and studies offering methodology to "delay" those rhythms, it's a powerful argument, especially when combined with the findings of a UK study revealing the "peak accident times" during a worker's shift. Then again, perhaps recent labor battles regarding the limiting of overtime could be the answer. An academic review by a renowned British shiftwork researcher draws a remarkable conclusion: The accident risk is highest during the early hours of a shift - even for work shifts of 12 hours. "Surprisingly, risk does not show a monotonic increase over time on task," concluded Folkard, a psychologist at the University of Wales Swansea in the United Kingdom. "Rather, there is a transient 2-4 hour peak in risk...Only when individuals have been working for 12 hours or more will their risk rise above that found during the 2-4 hour peak." Folkard also pointed out very short work shifts - such as four-hour shifts used in the marine industry and in some public transport operations to cover rush hours - seem particularly perilous. Such shifts "would appear to have 20 percent increased risk relative to 8-hour duties," Folkard said. "Only when duty periods are extended to 14 hours or more will the overall risk exceed that on four-hour duties." Folkard's observations are primarily based on the results of three transportation studies: The first, by M.L. Pokorny in 1981, looked at accidents among Dutch bus drivers. Pokorny found a peak in the accident risk in the third or fourth hour of shifts, which was independent of the shift start time. The peak "was followed by a period of relatively low risk, and only when the drivers had been working for over eight hours did risk start increasing again," Folkard said. The second study, by P. Hamelin in 1987, focused on British truck drivers. "The risk in the first four hours was higher than in all subsequent hours unless the drivers had been working for over 12 hours," Folkard said. The third, by H.L. Wharf in 1993, studied locomotive engineers at British Rail. Wharf's study found a distinct peak in "signals passed at danger" rates in the second and third hours of duty followed by a relatively low level for up to 12 hours of duty. Folkard then used mathematical formulas to combine the results of all three studies. One result is the chart at left (8-2#37) showing the overall relative risks associated with shifts of different lengths. The findings raise the question of whether trends derived from transportation studies can be generalized to all shiftwork operations - and the subject of how 12-hour shifts stack up against 8-hour shifts. Folkard suggested it isn't a huge leap, since his own reviews of industrial occupational injury rates found "a remarkably similar and consistent peak" early in work shifts. Why accidents peak early isn't known. One theory Folkard cited is at the beginning of a shift people make a conscientious effort to follow safety procedures. Later on, work performance "may place greater reliance on less effortful, automated processing." The accident peak, then, is the result of the middle zone between the two safer extremes. Folkard says he believes this explanation "is a feasible one" that deserves further investigation. Another theory is that fluctuations in circadian rhythms interact with the shift start times. For example, due to the afternoon circadian dip in alertness, a truck driver who drives from noon to midnight is more likely to have an accident at 3 p.m. than 9 p.m. Folkard emphasized his overall findings "should be treated with considerable caution" because they are based on limited data. His aim, he said, "is simply to draw attention to the potentially important practical implications of the transient 2-4 hour peak in risk with a view to encouraging further research in this area." The average person who has a hard time with shiftwork typically follows a fairly generic pattern: After feeling pretty good for the first few hours of a shift, he struggles to stay alert through the overnight hours. From 4 a.m. to 6 a.m., he battles to avoid falling asleep on the job. He makes it through the morning to the morning shift changeover, and goes to bed at 8 a.m. But sleep is difficult, lasting four or five hours, with frequent awakenings. What can workers who have on-duty alertness lapses and off-duty sleep problems do to rectify this problem? One potential avenue is to make a deliberate effort to "phase shift" one's circadian rhythms so they're more attuned to being awake at night and asleep in the morning. This approach is most relevant to people who work fixed night shifts. Researchers have identified four major factors that can shift circadian rhythms: changing one's "sleep/wake" cycle, bright light, exercise and melatonin. Before looking at these factors one by one, it's worthwhile to understand exactly what phase shifting circadian rhythms is all about. As you may know, circadian rhythms - body functions such as body temperature, heart rate, blood pressure and hormone production that fluctuate over 24-hour periods - are at the root of many shiftwork-related problems. Basically, circadian rhythms - which are strongly influenced by the daily cycle of sunlight and darkness - "program" a person to be sleepy at night and awake in the daytime. Shiftworkers' fundamental problem is that their circadian rhythms are out of synch with their schedule of working at night and sleeping in the morning. Fluctuations in body temperature - which loosely equate with ups and downs in human alertness - illustrate this concept well. Body temperature drops during the overnight hours, even when one is awake. It typically reaches its lowest point between 4 and 5 a.m. Researchers refer to the temperature minimum as the "T-min." - and it's no coincidence this is the hour when most shiftworkers have the most difficulty staying alert. Once body temperature reaches its nadir, it begins rising again. So when a shiftworker's head hits the pillow at 8 a.m., body temperature - along with other alertness-activating circadian rhythms - is on the upswing, making it hard to fall asleep and stay asleep. With a concerted effort, individuals can move their circadian rhythms to later hours, a process known as "phase delaying." A person who phase delays the T-min. from 5 a.m. to 11 a.m. will find it much easier to stay awake through the overnight hours and sleep during the morning and early afternoon. Under most circumstances, circadian rhythms can only be delayed an hour or two per day. So with each successive night shift, someone using these tactics might see his or her T-min. move from 5 a.m. to 7 a.m. to 9 a.m. to 11 a.m. Sleep/wake cycle: The sleep/wake cycle reflects when a person goes to sleep and wakes up. Delaying one's bedtime will delay the body temperature minimum. This means shiftworkers who want to delay circadian rhythms -and then keep them phase delayed - should make an effort to stay up as late as possible on days off between night shifts. In pursuing this strategy, it's often helpful to supplement one's main sleep block with naps to avoid building up a sleep debt. Bright light: Research has established exposure to elevated light levels before the T-min. delays circadian rhythms, while such exposure after the T-min. "advances" them. (Advancing circadian rhythms would mean moving the T-min. from 5 a.m. to 4 a.m.) To delay the T-min., people should expose themselves to as much light as possible between about midnight and 3 a.m. Options include increasing the illumination in the work environment, spending breaks in a particularly well-lit room, or sitting in front of a commercially-manufactured light box for 15 to 30 minutes. A crucial point here is one should also minimize exposure to light in the morning. Exercise: Researchers started looking at how exercise affects circadian rhythms only recently. A few studies have found that vigorous exercise - such as several 20-minute workouts on a stationary bike or treadmill, or one longer one - shift circadian rhythms (as well as providing an immediate alertness boost and contributing to overall good health). Although it's not yet known for certain, exercise may prove to work in a similar fashion to bright light, with exercise before the T-min. delaying circadian rhythms. So if working conditions permit it, shiftworkers should exercise between midnight and 3 a.m. Melatonin. The final - and most controversial - method of shifting circadian rhythms is use of synthetic melatonin. Melatonin is a sleep-inducing hormone produced by the brain's pineal gland. A synthetic version is available at health food and drug stores in the U.S. and via prescription in Canada. Research has confirmed taking synthetic melatonin shifts circadian rhythms. Melatonin works in an opposite fashion as bright light and exercise: Taking it before the T-min. advances circadian rhythms and taking it after the T-min. delays them. So workers can phase delay by taking it after night shifts, before going to sleep in the morning. Melatonin remains controversial because its long-term effects are unknown. Researchers who study it disagree on whether it presents health risks. Anyone considering taking it should first consult his or her physician. Those who do decide to take it should take the minimum effective dose. Although it's typically available in 3 mg. doses, research has found that doses from 0.1 to 1 mg. are sufficient to promote phase shifting. Recent collective bargaining agreements suggest mandatory overtime - and limits on the amount employees can be required to work - may emerge as a key issue in 24-hour industries. In telecommunications, mandatory overtime was a focal point of strikes at US West and Bell Atlantic. Following a 15-day strike at US West, the company signed a new agreement with the Communications Workers of America (CWA) restricting mandatory overtime to 16 hours a week. In January 2001, this level will fall to eight hours. In addition, the new contract guarantees workers at least one five-day work-week a month starting in January, and two five-day work weeks per month in 2001. At Bell Atlantic, 73,000 workers struck for two days before a new agreement was signed in which the company agreed to: · Limit mandatory overtime to 10 and 15 hours per week, depending on the time of year · Avoid scheduling back-to-back six-day weeks · Accept reasonable excuses for declining overtime. Prior to the agreements, employees were commonly working 60- and 70-hour weeks and having vacation requests denied, said CWA spokeperson Candace Johnson. A number of forces are combining to make mandatory overtime increasingly a subject of debate. Companies seem to be relying on it more because the high cost of employee benefits discourages them from hiring additional workers. And with unemployment under 5 percent in the U.S., even companies that want to hire more people often cannot find qualified applicants - so they boost existing employees' hours. From an employee perspective, the strong U.S. economy has led to growth in real wages and greater job security, positioning more workers to demand limits on overtime. It's unclear whether mandatory overtime limits will move from notable trend to a major labor issue in coming years. One force working against it is the fact that overtime is a complex issue that inspires a range of feelings among workers. Many workers welcome overtime as a way to boost their overall income and raise their standard of living. There are others who would choose to work only their scheduled hours - and then a middle group who desire overtime only from time to time. Excerpted from various issues of ShiftWork Alert. Reprinted with permission of Circadian Information (Cambridge, Mass.) Readers can request a free sample issue by contacting 800-878-0078, [email protected], or visiting the http://www.circadian.com. Circadian Information provides publications, research, training and consulting services to improve performance, alertness, health and safety in 24-hour operations.