The real cost of sleep debt: inadequate sleep due to extended workdays, overtime, and shift work is increasing health and safety risks for employees and may expose them or their employers to legal liabilities.

We seem to have a new set of heroes in our culture--ambitious, achievement-oriented people who fill every spare moment of the day with activities that will advance their careers. These hard-driving leaders of industry, science, and society seem to believe that leisure time is expendable and that the "useless" time away from work represented by sleep can be eliminated, with no negative consequences.

There is a long history of such thinking. Thomas Alva Edison considered excessive sleep (which he interpreted as eight or more hours a night) to be a waste of time and a sign of laziness, stupidity, and moral weakness. Edison believed that by providing cheap and efficient electric light, he could remove darkness as a common "excuse" for sleeping rather than working.

Edison and other inventors have been successful. The average young adult today reports sleeping about 7 to 7.5 hours each night. In 1910 (before Edison's cheap coiled tungsten filament light bulb was available), the average person slept 9 hours each night. This means that we sleep 1.5 to 2 hours less than our forebears did early in the 20th century (Coren 1997).

We are working a lot longer as well. A recent European Union survey (Costa et al. 2004) found that 84 percent of self-employed workers and 44 percent of employees are working more than 40 hours a week, while 64 percent of the self-employed and 26 percent of employees are working longer than 10 hours each day (and many are working on weekends).

We now live in a world where electric lighting keeps factories, supermarkets, and airports operating around the clock. Trains, planes, and trucks are driven all night and hospitals work on a 24-hour basis. This requires employees to work shifts, which are often variable and long, or to work overtime.

Generally speaking, shift workers can be considered to be a chronically sleep-deprived population. There is substantial evidence that shift work disrupts sleep patterns and substantially reduces the amount of sleep that workers obtain, especially those working evening and night shifts (e.g., Akerstedt 1998). Furthermore, the effects of shift work linger and even disturb sleep on days off work. The level of the disturbance is similar to that seen in clinical insomnia, and the mechanism seems to be a disruption of the normal circadian cycle of sleep and activity

HOW MUCH SLEEP DO WE NEED?

Some people might argue that 7 to 7.5 hours of sleep is sufficient, Studies show, however, that the "natural" sleep duration of humans is probably closer to about 10 hours out of each 24, with a long nighttime sleep and a shorter daytime nap.

One study was conducted at a site well above the Arctic Circle when there was sunlight for the entire 24-hour day (Palinkas, Suedfeld, and Steel 1995). All watches and other timekeeping devices were removed, and only the station's computers knew the times that the team went to sleep and awakened. Individuals conducted their research and chose when to sleep and work according to their "body times."

At the end of the experiment, the researchers found that they slept an average of 10.3 hours each day, with individual averages ranging from 8.8 hours to almost 12 hours. Every member of the team showed an increase in sleep time. This study, like many others, seems to suggest that our biological sleep needs might be closer to the 10 hours per day that is typical of monkeys and apes living in the wild.

Psychological and medical researchers have tended to minimize the effects of sleep insufficiency. They acknowledge that society may be getting too little sleep, but treat the effects of this sleep deprivation as nothing more significant than an inconvenience that makes people feel a bit tired now and then. This view is wrong.

A large body of evidence demonstrates that the immune system operates most efficiently during sleep and that inadequate sleep predisposes individuals to a large variety of medical problems (see Coren 1997 and Lashley 2003 for reviews). For example, sleep-deprived shift workers are more likely to suffer from headaches, stomach problems, heart disease, allergies, skin problems, respiratory difficulties, anxiety and irritability (see Costa et al. 2004 for a review). In addition, recent research suggests that each day with insufficient sleep increases our sleep debt and that when this sleep debt becomes large enough, noticeable psychological problems appear (see Coren 1997 for a review).

Sleep debt-related problems are most predictable at certain times of the day because our physical and mental functions show cyclic increases and decreases in efficiency in the form of circadian rhythms. While our major sleeping/waking rhythm has a cycle length of roughly 24 hours, there are shorter cycles as well, the most important being a secondary cycle that lasts about 12 hours. Because of these cycles, the pressure to fall asleep is greatest in the morning, between 1:00 and 4:00 a.m. There is also a less pronounced but still noticeable increase in sleepiness 12 hours later, between 1:00 and 4:00 p.m. This afternoon low point makes you feel sleepy after lunch and probably was the original reason for the afternoon nap or siesta.

People operating with a sleep debt are less efficient, and this inefficiency is most noticeable when the circadian cycle is at its lowest ebb. Among the common consequences of a large sleep debt are attention lapses, reduced short-term memory capacity, impaired judgment, and the occurrence of microsleeps. A microsleep is a short period of time, usually between 10 seconds to a minute in length, in which the brain actually enters a sleep state regardless of what the person is doing at the time. Although the affected individual often does not know that this momentary blackout has occurred, the effects of microsleeps, combined with attentional lapses, can be dramatic.

It is important to note that sleep debt is cumulative. Research shows that individuals who sleep 3 to 7 hours in each 24-hour period for 2 weeks suffer reduced psychological performance efficiencies comparable to those of people who are deprived of sleep for a continuous period of 3 days and nights (Rogers and Grunstein 2005). Most important from a safety viewpoint, the majority of such individuals fail to recognize their level of impairment, which means that simply asking people to self-monitor their own conditions is not a sufficient safeguard to prevent sleepiness from becoming an accident risk.

IMPACT OF SLEEP DEBT

There is now evidence that many major disasters have resulted from sleep debt-related effects, including the oil spill of the Exxon Valdez, the nuclear accidents at Chernobyl and Three Mile Island, and the explosion of the space shuttle Challenger (see Coren 1997 for a review). The U.S. National Commission on Sleep Disorders conducted a study to determine the direct impact of sleep debt and found that sleep-related accidents in the United States cost more than $56 billion each year and cause 25,000-plus deaths and 250,000 disabling injuries (Leger 1994).

A recent study shows just how much impact the cumulative effect of sleep deprivation can have on behavior (Barger et al. 2005). The study looked at 2,737 medical interns, many of whom work extended or double shifts that can last up to 24 hours. The researchers analyzed the likelihood that these medical personnel would be involved in motor vehicle crashes or near-miss incidents after extended work shifts. They found that for every extended work shift scheduled in a given month, the risk of a motor vehicle crash during that month increased by 9 percent.

Problems associated with sleep loss are beginning to have legal ramifications as well. For example, after a driver in Selby, England, caused two trains to crash, killing 10 people and injuring more than 70 others, authorities learned he had not slept the previous night. His behavior was deemed to be criminally negligent and he was sentenced to five years in prison. Meanwhile, an Australian court found an employer liable for the crash-related death of one of its truck drivers, who had not slept for two days before the crash because of work demands (Rogers and Grunstein 2005). There have also been several cases in which doctors and hospital staff have been successfully prosecuted for deaths due to mistakes and diagnostic errors caused by fatigue from extended work hours and lack of sleep (e.g., Coren 1997).

What can be done to limit sleep deprivation and its impact? As with many other areas, it is easier when dealing with sleep deprivation and shift work to outline the problems than to put forward solutions. However, some recommendations have emerged which seem to help.

The first is quite simple. Shift workers rarely receive on-the-job training to help them cope better with the rigors of working nights, evenings, and early mornings. Several studies suggest that such direct instruction can produce improvements in health and fatigue indices and an increase in daytime sleep length (c.f., Akerstedt 1998).

Shifts should be changed in a forward rotation--that is, moving from morning work to evening work to the night shift--to make it easer for workers to adapt (Akerstedt 1998). Shifts should not be rotated rapidly, and workers should stay on a particular shift schedule as long as possible, as fixed shifts seem to produce the best results overall in terms of adapting to schedules and getting adequate sleep.

Overtime, double shifts, and extended schedules should be avoided. All of the available evidence suggests that 12-hour shifts result in more accidents, illnesses, and absences than 8-hour shifts (Folkard, Lombardi, and Tucker 2005).

Be aware of the daily cycles of workers. If flexibility permits, workers should avoid complex activities that involve sustained concentration--e.g., plant safety checks or tasks involving numerous mathematical computations--during the 1:00-4:00 hours when sleep pressure is greatest. These "low" points are better suited to routine activities such as filing papers, taking inventory, or performing simple assembly projects.

A short nap immediately before the beginning of a night shift also seems to help (Garbarino et al. 2004), but employers typically do not want to pay people for naps and employees often feel that such demands are infringements on their personal time. Education and instruction may convince shift workers of the usefulness of this practice.

There are also some improvements that can be made to the workplace itself that may help. Some of these improvements are obvious, such as providing canteen facilities and creating a pleasant, stimulating environment. In addition, bright light quickly resets the biological clock and can improve alertness during the night shift (Czeisler et al. 1990), especially when combined with complete darkness in bedrooms and strict adherence to daytime sleep schedules. For settings such as vehicle driving, such changes are not practical.

Given the realities of the modem workplace, it does not seem possible to completely eliminate the negative effects of sleep deprivation and shift work schedules. It is, however, certainly possible to reduce them.

With the passage of the Americans with Disabilities Act (ADA), employers need to know about reasonable accommodations for people with sleep disorders. Following are brief descriptions of common sleep disorders:

* Insomnia A condition that causes difficulty initiating or maintaining sleep for days, weeks, months, or years; may have other medical or psychiatric conditions present.

* Sleep Apnea A condition in which a person stops breathing for 30 seconds or more, several hundred times a night. Heavy snoring can signal this condition.

* Narcolepsy A disorder that causes irresistible sleep attacks; it might include sudden attacks of sleep, excessive daytime sleepiness, muscular weakness, hallucinations and sudden attacks of rapid eye movement (one stage of sleep).

* Restless Legs Syndrome A discomfort in the legs that is relieved by moving or stimulating the legs. The discomfort might keep the individual from getting restful sleep.

* Hypersomnia A condition for which the predominant complaint is excessive sleepiness for at least one month, but not because of narcolepsy or any other identifiable cause.

* Sleepwalking Disorder A condition that causes repeated episodes of rising from bed during sleep, then walking. On awakening, the person has amnesia of the episode.

Employers have several options for accommodating workers with these disorders. A common option is to allow for a flexible work schedule so a person with a sleep disorder can adjust to daily changes. For example, the option of starting work between 7:00 and 10:00 and ending between 3:00 and 6:00 could be considered. This may need to be decided daily at the discretion of the worker.

Another type of flexible schedule allows a worker to take breaks as needed, meaning that a worker entitled to an hour for lunch and a 15-minute break in the morning and afternoon could choose to skip the morning break, spend only 30 minutes eating lunch, then take an hour-long break in the afternoon. The individual could also choose to take several 10-minute breaks during the day and use only 30 minutes to eat lunch.

A less common approach is to permit a worker to take a nap during the time of day s/he is most sleepy. The employer can adjust the workday so the individual makes up the time at the end or beginning of the work shift.

If the employee's job is sedentary, restructure the work environment so the individual can alternate sitting and standing. Because people with sleep disorders sometimes forget the purpose of a task after beginning it, encourage them to use a checklist, organizer, or pacesetter device with an audible alarm to serve as a task reminder.

--Excerpted from "Work-Site Accommodation Ideas for Individuals with Sleep Disorder," Office of Disability Employment Policy, U.S. Department of Labor.

References

Akerstedt, T. 1998. "Shift work and disturbed sleep/wakefulness." Sleep Medicine Reviews 2 (2): 117-128.

Barger, L.K., B.E. Cade, N.T. Ayas, J.W. Cronin, B. Rosner, F.E. Speizer, and C.A. Czeisler. 2005. "Extended work shifts and the risk of motor vehicle crashes among interns." New England Journal of Medicine 352 (2): 125-134.

Coren, S. 1997. Sleep Thieves. New York: Simon & Schuster Inc.

Costa, G., T. Akerstedt, F. Nachreiner, F. Baltieri, J. Carvalhais, S. Folkard, M.F. Dresen, C. Gadbois, J. Gartner, H.G. Sukalo, M. Harma, I. Kandolin, S. Sartori and J. Silverio. 2004. "Flexible working hours, health, and well-being in Europe: some considerations from a SALTSA project." Chronobiology International 21 (6): 831-844.

Czetsler, C.A., M.P Johnson, J.F. Duffy, E.N. Brown, J.M. Ronda, and R.E. Kronauer. 1990. "Exposure to bright light and darkness to treat physiologic maladaptation to night work." New England Journal of Medicine 322 (18): 1253-1259.

Garbarino, S., B. Mascialino, M.A. Penco, S. Squarcia, F. De Carli, L. Nobili, M. Beelke, G. Cuomo and F. Ferrillo. "Professional shift-work drivers who adopt prophylactic naps can reduce the risk of car accidents during night work." Sleep 27 (8): 1446-1448.

Folkard, S., D.A. Lombardi and P.T. Tucker. 2005. "Shiftwork: safety, sleepiness and sleep." Industrial Health 43 (1): 20-23.

Lashley, F.R. 2003. "A review of sleep in selected immune and autoimmune disorders." Holistic Nursing Practice 17 (2): 65-80.

Leger, D. 1994. "The cost of sleep-related accidents: a report for the National Commission on Sleep Disorders Research." Sleep 17: 84-93.

Palinkas, L.A., P. Suedfeld and G.D. Steel. 1995 "Psychological functioning among members of a small polar expedition." Aviation, Space, & Environmental Medicine 66 (10): 943-950.

Rogers N.L. and R.R. Grunstein. 2005. "24/7 Health. Second annual Sleep Loss Symposium: working and sleeping around the clock." Medical Journal of Australia 182 (9): 444-445.

Stanley Coren, Ph.D., FRSC 

Stanley Coren is a professor in the Department of Psychology at the University of British Columbia in Vancouver, Canada. He can be reached by e-mail at [e-mail].