Fatigue and Shift Work

Fatigue and Shift Work


  • More and more employers, driven by their insatiable need for higher profits, are instituting some form of 24x7 "continuous production"  ... which can have a major impact on the health and well-being of workers
  • Among the issues to consider are workers' physical health ...
  • ... and the effect on worker's mental health ...

Imagine this. The employer calls in the Union Committee and says "We need to increase production and at the same time we need to lower costs. Here’s how we’re going to do it. Starting next month this operation will be on continuous shifts. We’ll be open 7 days a week, 24 hours a day. This means more of you will have to work night shift and in order to make this fair, the shifts will rotate so no one gets stuck on nights permanently."

What effect will this have on the members you represent? There are plenty of questions to ask — and lots of issues to consider.

What are the "pros" (if any) and "cons" about continuous operations? What happens to people when their work schedule changes?  What are the "social" problems of shift work? What happens when a person’s biological rhythms and their social life are disrupted? Are rotating shifts bad for your health? What can be done (if anything) to lessen the effects of shift work? What contractual provisions do we have to insist upon?

Let's take a look.

There are over 20 million workers in the United States that are "shift workers," that is, they work shifts other than regular daytime shifts.

Here are some examples of the percentage of workers working non-daytime shifts:

A sampling of workers engaged in
Non-Daytime Shift Work
Job Type Percent Working
Health Care Workers 30%
Cleaning/Building Services 27%
Precision Production and Repair Workers 13%
Machine Operators, Fabricators, Laborers, Assemblers 27%
The job categories with the least amount of shift workers are management jobs. They average only 8 percent.

Not surprisingly, government surveys show that only 28 percent of people who work evening or night shifts want to be there. Many who answered that they wanted to work nights said they did so for child care reasons, that is, they cared for their children during the day and their partner cared for them at night. Hardly a "voluntary" choice to work night shifts.

In manufacturing, the trend is for employers to run machines 24 hours a day, seven days a week rather than buy more machinery and run them on day shifts. In the service industry we see grocery stores open 24 hours a day and computer processors that are linked to global operations have data entry workers on 24 hour shifts. There have always been some industries that ran continuous shifts: chemicals, plastics, and paper. But now with business being driven to maximize profits with unprecedented fervor, an idle machine is considered lost profits. We all know that concern for the health and well-being of workers ranks a very distant second to employer desires for increased profits.


While there are no set, agreed upon terms used to define shift work, here are basic definitions that we will use for the purposes of this article (note the different approaches that can be used in continuous production):

  • Day Shift – The most common shift for workers, with the hours being between 6 am and 6 pm.
  • Afternoon or evening shift – Most often the hours are between 3:00 pm to midnight
  • Night Shift – The hours being from 11:00 pm to 6:00 am
  • Fixed Rotating Shift – A work schedule where the time of work is always the same (first, evening or night shift) but the days worked changes. This is used in continuous operations.
  • Rotating shift – A work schedule where the shift time changes, usually on a weekly basis and the days worked also change. This is used in continuous operations.
  • Compressed work week – A compressed work week is when workers work 40 hours per week but in less than 5 days, usually for 10 or 12 hours per day.
  • Normal work week – A "normal" work schedule is usually considered 5 days a week, 8 hours per day. This is the most common work schedule for workers in the US. However, as mandatory overtime becomes more common, the "normal work week" is no longer 40 hours but is now about 43 hour per week. In the rest of the industrialized world the work week is getting shorter, not longer.

Human Biological Rhythms

Human beings and most animals naturally wake and sleep according to set ("built-in") biological patterns. The most obvious pattern is that humans must sleep — without it we cannot function well. At some point, a person who is deprived of sleep will fall asleep and cannot be stopped from doing so. The other observation made about humans is that normally we are awake during daylight hours and asleep at night. Scientists have studied these biological rhythms and are just beginning to understand them.

Circadian Rhythms

While there are many different biological rhythms, of diferent lengths, the most recognizable is the 24 hour cycle. These 24 hour cycles are called circadian rhythms from the Latin circa, for around and dies, for day. While humans operate on a basically 24 hour clock, these rhythms are not solely determined by light and dark, although lightness and darkness are key elements that regulate our bodies. We have an internal clock that drives these rhythms. Scientists have now identified hundreds of biological variables in humans that are circadian in nature. This includes physical things like body temperature, hormone production, sleep-wake cycles, and psychological things like memory, and ability to perform mental tasks.

The Sleep Cycle


Are human beings biologically programmed to nap? Divergent lines of evidence, both direct and indirect, suggest that midafternoon napping is an inherent aspect of human behavior. No other species exhibits exclusively once-a-day, or monophasic, sleep patterns. Indeed, as children develop, the midafternoon nap is generally relinquished only when school interferes. Adult napping is more prevalent than most Americans realize, especially in other cultures and among persons who may be sleep-deprived, More than 50 percent of all college students, for example, nap at least once a week. Napping also appears to increase among retired Americans.

There are other indications that a midafternoon nap is natural in humans.

When human circadian rhythms are analyzed in a time-free environment, napping is common. The postlunch dip, or the mid-afternoon decrease in human performance regardless of food intake, may reflect a proclivity for sleep at that time. Decreased human performance presumably accounts for the midafternoon peak in traffic accidents. Moreover, the decline in human performance corresponds to peaks in sleepiness. Measures of sleepiness using the multiple sleep latency test demonstrate a more rapid onset of sleep in the afternoon. Pathological conditions, such as narcolepsy, or frequent, uncontrolled sleeping, also exhibit a midafternoon peak in sleep episodes.

Insight into human napping behavior may have some practical implications.

While mood and subjective feelings of sleepiness may not be affected by napping, performance during extended periods of work can be improved. In addition, the scheduling of brief episodes of sleep during sustained periods of work maybe optimized: research suggests that napping before, rather than after, extended periods of work is best for reducing the effects of sleep loss.

SOURCE: Office of Technology Assessment 1991, "Biological Rhythms: Implications for the Worker"

The average human requires 8 hours of sleep per day and the time for sleep is when it's dark outside. There are people who differ, of course, but this is the norm. Studies show that when this 8 hours is reduced there is a corresponding reduction in the ability of the person to perform. Some studies show that people begin to build up a "sleep bank" consisting of the hours of sleep they have missed. This is why many people who do not get 8 hours of sleep a night will "sleep in" on weekends or whenever they can. Their body is demanding the extra sleep it needs to function (at times when the body is deprived of sleep it will even shut down for very quick periods called microsleeps).

Within the sleep cycle itself there are periods of deep sleep where the body and brain activity slow down considerably, and lighter sleep, when dreaming occurs and brain activity increases to be on par with brain activity of awake people. When certain of these cycles are interrupted, the benefits of sleep are lessened. Many shift workers have a real problem in getting enough uninterrupted sleep.

The Temperature Cycle

The temperature of a person’s body also follows a circadian rhythm. Beginning about 6:00 am the body temperature begins rising and reaches its peak in the late afternoon, 5 or 6 pm. It then begins falling until it again begins rising in the next early morning. It is easy to see that people regularly sleep when their body temperature is at its lowest and are active when their temperature is rising. Studies have shown that people who try to sleep when their body temperature is beginning to rise, have the least restful sleep and suffer from problems of fatigue.

The Problem

Working when the body is programmed to sleep will cause problems. Trying to sleep when the body is programmed to be awake causes problems. Not getting the body’s required amount of uninterrupted sleep causes problems. Add to this mix longer shifts, such as twelve hours and fatigue must be figured in. 

Social Problems of Shift Work

Most of human society is geared towards the daylight hours. That is when most of the work is done. The early evening is for social life, and nighttime is for sleeping.

Studies show that many shift workers suffer from additional stress caused by missing out on important parts of their social life. It is harder for shift workers to spend time with their children and to attend school functions with them. Spouses may work the opposite shift, thus causing less time together. Unmarried shift workers miss out on the social life that most daytime workers have.

Sleeping becomes a problem, especially for workers whose shift ends in the morning. They have been awake all night, when their body wanted to sleep and now have to sleep when they should be awake. They also have to try to sleep when the rest of the world is awake and often noisy.

Workers bodies can adjust to working nights if a strict schedule of sleeping during the day is maintained. The body’s internal clock will change somewhat to accommodate for the new regular schedule. The problem comes when the worker, in order to be with friends and family, switches back to a daytime schedule on weekends or on days off. This causes the internal clock to switch back to the normal day-night schedule.

Scientists have also found that if the workplace is brightly lit on the off shifts, this helps the body adjust to staying awake. 

Note: As we went to press, two studies were released that linked working night shifts to increases in breast cancer in women, especially where there were bright lights. The speculation is that working under bright lights at night reduces the amount of melotonin, the hormone that makes one sleep and in women this may increase the amount of estrogen.

Shift Premiums

Negotiated extra pay is one way that UE and other unions have developed to compensate shift workers for the extra hardship they face. Stewards need to remind employers that this isn’t just a "nothing" bonus but a justifiable compensation. Shift workers have extra stresses, both physical and social that must be compensated.

The best method for shift premiums is a percentage basis. Here’s why. First the union fights for a rate of pay that is fair for the work being done. For example $20 dollars per hour for a machinist. As that rate of pay increases due to inflation and because workers are owed a better life, so should the shift premium increase. If the premium is a percentage then it will automatically increase as the wages are increased.

Rotating Shifts

Average Length of Sleep
Permanent and Rotating Shift Workers
Rotating shift workers on the night shift have the shortest sleep averages.
Chart comparing hours of sleep received by workers on permanent vs. rotating shifts.

All across the United States employers are trying to make workers work 12 hour-rotating shifts. A 12 hour rotating shift might work like this. For three days you work 12 hours during the day, have two days off; work 12 hours on nights for 4 days, have 3 days off; work 12 hours on days for 3 days etc. Of course there are many variations on this theme.

The Worst Possible Schedule

Why do employers want these shifts? The first reason is they want continuous production, 24 hours a day, seven days a week. They think 12 hour shifts are more productive because shift changes are supposed to be "unproductive." With 12 hour shifts there are fewer shift changes. Most will claim that by rotating the shifts, no one is stuck with working nights all the time. This is the worst possible shift schedule!

Most union and scientific studies show that this kind of shift is the most stressful, both mentally and physically. Worse, many unions realize that employers institute these shifts in order to make older workers quit. They want to have work-forces that are young (fewer vacation days; lower insurance and pension costs). But, in fact, it is not just "older" workers that cannot take the disruption in  their personal lives and the fatigue caused by 12 hour shifts.

With a rotating shift the body never gets accustomed to working one time period. Studies show that workers on rotating shifts get far less sleep than do workers who work a steady night shift. With less sleep comes more fatigue and more accidents.

Employers like to entice workers to try these shifts by claiming that "you work fewer days per year for the same pay". While it is true that fewer days are worked because of the 12 hour shifts, studies show that most workers spend much of their extra "free" time sleeping.

Remember, it is the job of UE stewards to make sure the union remains united and not let the employer divide the workers based upon age. Don’t let the employer pit young workers against the older workers with promises of "more time off." Young workers will become "old" workers soon enough.

What About 12 Hour Non-Rotating Shifts?

These sound enticing because of the additional days off per year but, here again, there are real problems. Employers usually want to do away with overtime after 8 hours. They want to do away with automatic overtime for weekend work, claiming that weekends are now just regular work days.

Bonus pay for working weekends started not just because an employee was working a sixth or seventh day but because weekends are supposed to be for time spent with family and friends.

Employers often want to do away with many holidays as well, claiming that holidays were negotiated at 8 hours pay, therefore taking a 12 hour shift as a holiday is really equal to one and a half holidays. When an employee is out sick they lose 12 hours pay instead of 8, and a 40 hour vacation now only allows a worker 3 days off from work, instead of 5 days! Many employers begin insisting on mandatory overtime to make workers fill in for workers who are out sick, again because 12 hours work instead of 8 will be lost.

The union should fight against losing hard earned contract provisions and fight to gain these provisions in all our contracts:

  • Time and one half pay after 8 hours work;
  • Time and one half pay for work on Saturday;
  • Double time for work on Sunday;
  • No mandatory overtime;
  • Shift differentials for second and third shifts based on a percentage of the hourly rate.

Other Forms of Continuous Operations

There are other shift schedules that allow employers to operate continuously without having to face rotating shifts. Many plants that work 8 hour shifts, the same shift every day but the days worked change. People on these shifts work 5 days a week but everyone takes turns working the weekends. These shift schedules eliminate the bad effects of rotating and the bad effects of 12 hours, but workers loose many of their weekends off. Of course, with this arrangement, shift differentials and overtime pay for weekend work must be retained.

In some UE shops where continuous operations are unavoidable, the union has negotiated shift premiums and overtime pay into the hourly rate. This is done by calculating the average number of hours per year that would be worked on weekends and nights; how much premium pay would be earned; and then what that equals in cents or dollars per hour. The advantage in doing this is that "bonus pay" is then earned for vacation pay, holiday pay etc. Any additional overtime that is worked is paid at the regular overtime rates.

The best form of continuous operations is having a weekend shift. In one UE shop, workers employed for the weekend shift worked 2-twelve hour shifts and were paid for 40 hours. There was a system worked out for how holidays and vacations were taken. Because only 2 days were worked, the twelve hour shifts were manageable, and some of the weekend workers could be available if needed during the week.

UE stewards should keep in mind the union’s policy is that all workers should be able to earn decent pay and standard of living on 40 hours pay per week. Of course, what we really need is a shorter work week at 40 hours pay.

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