Summary of the CROET Seminar: Shift Work

 January 22, 1999
Portland Conference Center
Portland, Oregon



Charles Allen, PhD

Center for Research on Occupational and Environmental Toxicology
Portland, Oregon

Kent Anger, PhD

Center for Research on Occupational and Environmental Toxicology
Portland, Oregon

Gerald Rich, MD

Pacific Northwest Sleep/Wake Disorders Program
Portland, Oregon

Roger Rosa, PhD

National Institute for Occupational Safety and Health
Cincinnati, Ohio

Mark Rosekind, PhD

Alertness Solutions
Cupertino, California

Robert Sack, PhD

Oregon Health Sciences University
Portland, Oregon

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9:00-9:10 Goals of seminar

Charles Allen, PhD
Center for Research on Occupational and Environmental Toxicology
Portland, Oregon

9:10-9:45 Background of Shift Work

Kent Anger, PhD
Center for Research on Occupational and Environmental Toxicology
Portland, Oregon

9:45-10:30 Shift work factors: How they affect us

Mark Rosekind, PhD
Alertness Solutions
Cupertino, California

10:30-10:45 Break

10:45-11:30 Strategies to manage shift work fatigue

Mark Rosekind, PhD
Alertness Solutions
Cupertino, California

11:30-11:45 Questions and answers with Mark Rosekind, PhD

11:45-12:30 Lunch

12:30-1:15 Evaluating your shift work schedule

Roger Rosa, PhD

National Institute for Occupational Safety and Health

Cincinnati, Ohio

1:15-2:00 Biology of sleep and wakefulness

Robert Sack, PhD
Oregon Health Sciences University
Portland, Oregon

2:00-2:15 Break

2:15-3:00 How to improve shift schedules

Gerald Rich, MD
Pacific Northwest Sleep/Wake Disorders Program
Portland, Oregon


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Background Information


Shiftwork involves working outside the normal daylight hours (7 am—6pm) or more than 7 to 8 hours at a time.

Reasons for shiftwork

Critical services needed by the public:

  • Police or Firefighters
  • Security forces such as the military
  • Medical providers such as nurses
  • Transportation
  • Public utilities


Production process is longer than 8 hours.

  • Expensive equipment needs to operate continuously in order to be profitable.
  • 24-hour work schedules increase the need for certain services to be provided on round-the-clock basis: Grocery stores, Gas stations, Restaurants


How many people work on shifts

  • 83 percent of workers are on regular daytime schedules.
  • 5 percent of Americans work in the evening.
  • 4 percent are permanent night workers.
  • 4 percent work irregular schedules.
  • 4 percent work rotating shifts.
  • Total number of shiftworkers is estimated between 11 million (Rosa & Colligan, 1997) and 25 million (Bureau of Labor Statistics, 1998)
  • In general, 2 to 10 percent of almost any occupation works evening, night or rotating shifts.


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Who works shifts

  • Men work more night and rotating shifts.
  • Women work more evening shifts and do more part-time work.
  • Younger people are more likely to work shifts than older people.
  • Single people work more shifts than married people.
  • Blacks are more likely to work night shifts than either Hispanics or Caucasians.


Why people participate in shiftwork

  • Better pay.
  • More time during the day for childcare.
  • More daylight hours for recreation.
  • More time to attend school.
  • Quieter and there are fewer supervisors.

Which occupations utilize shiftworkers

  • 33 percent of the service occupations work shifts.
  • 27 percent of machine operators, assemblers, inspectors, fabricators and laborers work shifts.
  • 10 percent of managers and professional specialty occupations work shifts.
  • 13 percent of technicians, sales personnel and clerical support persons work shifts.
  • 13 percent of crafts, precision products workers, mechanics and construction trade persons work shifts.


Occupations projected to increase in the use of shiftworkers

  • Medical assistants.
  • Nurses aides.
  • Psychiatric aides.
  • Home health aides.


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How to Examine Work Schedules

Types of work schedules

  • Most common - Five days on a single shift followed by two days off.
  • Rotating shift schedule ­ worker will change to a new shift after days off.
  • Work will be 7, 10 or 14 days in a row.
  • Length of shift is 8, 10 or 12 hours.


Work schedule features

  • How long is the shift?
  • How many shifts are worked before a rest day?
  • How many rest days are on weekends?
  • Is there overtime?
  • How much rest is taken between shifts?
  • How much rest is taken during the shift?
  • Is the work schedule regular and predictable?


Time of shift

  • Twenty-four hour operations may be divided up into two or three shifts:
  • Day shift - Begins 5 to 8 am and ends around 2 to 6 pm.
  • Evening shift - Begins 2-6 PM and ends around 10 PM to 2 am.
  • Night shift - Begins around 10 PM to 2 am and ends around 5 to 8 am.
  • People who work in the late night or early morning hours often feel sleepy and fatigued.
  • Circadian rhythm, or internal clock, controls our sleep and wake cycles.
  • Night shift workers are awake when their circadian rhythm tells them to sleep


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Permanent versus rotating schedules

  • Permanent night workers never really get used to night shift.
  • Fatigue occurs because most night workers go back to a day schedule on their days off.
  • Night workers also sleep less during the day and do not recover from fatigue.
  • Rotating schedules are utilized to make shift work more fair for all involved.
  • Rotating shift workers are always trying to adjust to changing work times.
  • Rotating shift workers have more complaints than other workers about physical health and psychological stress.


Speed and direction of rotation

  • Adaptation to rotating shifts can be affected by the speed of rotation and the direction of rotation.
  • Speed of rotation means the number of consecutive day, evening or night shifts before a shift change occurs.
  • Direction means the order of shift change:
  • Forward rotation is in the clockwise direction (day to evening to night)
  • Backward rotation is in the counterclockwise direction (day to night to evening)


Work-rest ratios

  • The more a person works, the less time he or she will have for rest.
  • People who work an 8-hour shift have 16 hours left in the day to rest and complete necessary tasks.
  • People who work a 12-hour shift have only 12 hours to rest and complete necessary tasks.
  • Overtime reduces workers ability to rest and take care of home duties.


Work versus rest breaks

  • Depending on the type of work and length of the shift several short breaks may be better than a few long breaks.
  • Fatigue builds up over several workdays as well as over a single workday.
  • How tired a worker is depends partly on how many days in a row he or she works.
  • Fatigue is cumulative and can accumulate to unsafe levels.


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Regular or predictable work schedules

  • Most jobs have a very regular, set schedule allowing workers to schedule sleep.
  • Workers can not get adequate sleep if they can not predict their work schedules.
  • Health care workers might respond to emergencies that keep them on shift longer than anticipated.
  • Factory workers could be kept at work to deal with an equipment breakdown or a last-minute call for product.
  • Railroad workers sometimes work off a "call board" and can not anticipate their next work shift.
  • Workers who are "on-call" may never get deep satisfying sleep because they are listening for a phone call. This is described as 'sleeping with one eye open'.


Improving Shiftwork Schedules*

  • Avoid permanent (fixed or non-rotating) night shift.
  • Keep consecutive night shifts to a minimum.
  • Avoid quick shift changes.
  • Plan some free weekends.
  • Avoid several days of work followed by four- to-seven-day
  • "mini-vacations."
  • Keep long work shifts and overtime to a minimum.
  • Consider different lengths for shifts.
  • Examine start-end times.
  • Keep the schedule regular and predictable.
  • Examine rest breaks.


* Source: Plain Language About Shiftwork, Rosa & Colligan, 1997. DHHS Publication N. 97-145.

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Health and Safety Effects of Shiftwork


  • Night workers get the least amount of sleep.
  • Evening shift workers get the most sleep.
  • Day shiftworkers get a medium amount of sleep.
  • Rotating shiftworkers sleep the least of all.
  • Day sleep is shorter than night sleep ­ 2 t3 hours shorter.
  • Day sleepers don't sleep as deeply as they do at night.



  • Sleepiness can affect performance on and off the job.
  • Driving to and from work is a major concern with sleep loss.
  • Sleepiness affects our ability to concentrate or pay attention which driving or operating machinery requires.
  • Microsleeps occur without the individual realizing they have had a brief period of sleep lasting only a few seconds.
  • If something dangerous happens during microsleeps the worker or somebody else could get seriously hurt.


Circadian Rhythm, Performance and Safety

  • Circadian rhythm is a major body rhythm with regular ups and downs during the 24-hour day.
  • Body systems are active at certain times of the day and not active at others.
  • Body's ability to produce energy from food is highest in the afternoon to evening.
  • Most people feel most active and alert around 4 to 6 PM and sleepiest at 4 to 6 am.
  • There are personal differences in circadian rhythms:
  • Larks ­ 'morning people'
  • Owls ­ 'evening people'
  • People perform best when alertness and internal body activity is high and worst when alertness and activity are low.
  • The day-work and night-sleep situation is best for performance. This means it also is best for safety.
  • Night shift workers are awake when circadian rhythm is low and asleep when it is high_ when performance is at its worst.
  • If a night shift worker has lost sleep, fatigue could combine with the circadian low-point to double the effect on one's ability to perform
  • Accident studies show an increased risk at night when circadian rhythm is low and sleep has been lost.


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Interference with social and family life

  • A shiftwork schedule affects not only the worker, but also the rest of the family.
  • Shift work determines when a worker can see family and friends.
  • Parents who work evening shift may not see their children during their work week.
  • Workers on evening or night shifts often miss out on social or family activities.
  • Shiftworkers would rather lose sleep to participate in social or family activities compromising their alertness.
  • Shiftwork affects participation in activities that are on a strict time schedule such as clubs, team sports or visits to a child's school.
  • Solitary activities such as gardening or woodworking that are not on a strict time schedule work well.


Long-term health effects

  • Workers who quit doing shift work often point to health problems as a major reason for quitting.
  • Major stresses such as marriage problems or caring for a relative combine with the stresses of shiftwork to compromise a person's health.
  • Poor health habits such as using stomach alcohol or tobacco will aggravate an existing health problem.


Digestive problems

  • Research suggests that shiftworkers have more upset stomachs, constipation and stomach ulcers than day workers.
  • Regular eating and digestive patterns are disrupted by switching work and sleep times
  • Digestive problems also could be caused by lack of nutritious food available during the evening and night shifts.


Heart Disease

  • Heart problems have been noted more often among shiftworkers than day workers.


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Improving Shiftwork Throughout the Organization

The changing workplace

  • There are few laws or regulations governing work hours or work scheduling in the U.S.
  • U.S. economy is changing into a more service-based economy where many shiftwork jobs exist.
  • Economic expansion and downsizing lengthen the work week for many.
  • Employers are experimenting with compressed work weeks and rotation shifts.
  • At least 1/2 of US occupations are believed to regularly exceed the eight-hour work day.
  • New technologies can change both the physical and mental demands placed on a worker.
  • A well-designed work schedule can improve health and safety, worker satisfaction and productivity.


Changing work schedules

  • Designing a work schedule has a large and immediate impact on all workers.
  • Any work schedule change should first be temporary and evaluated carefully.
  • All aspects of job and home life must be considered when changing a work schedule.
  • Consider alternatives to permanent night shift
  • Most workers never really get used to night shift because they go back to a daytime schedule on their days off.
  • Some workers on fixed night shifts lose contact with management and the rest of the workers in the organization.
  • If possible utilize a rotating night shift schedule.


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Improving shiftwork schedules

  • Keep consecutive night shifts to a minimum. Two to four nights in a row should be worked before a couple of days off. This keeps circadian rhythms from being overly disrupted.
  • Avoid quick shift changes. A break of only seven to ten hours should be avoided before rotating to a new shift. At the end of a night shift a break of at least 24 hours is recommended before rotating to another shift. 48 hours would be better.
  • Plan some free weekends. If a seven-day schedule is required, allow one or two full weekends off each month. Weekends are the best time to meet family and friends who are on a day schedule.
  • Avoid several days of work followed by four to seven day "mini-vacations". Some schedules require 10 t14 days of work followed by five to seven days off. Older workers find it difficult to recover from this extended work period during their time off. Poor recovery from fatigue can produce accidents and damage health.
  • Keep long work shifts and overtime to a minimum. Extra work hours add to fatigue. If 12-hour shifts are used two or three shifts in a row should be the maximum.
  • Consider different lengths for shifts. Try adjusting shift length to the workload. Heavy physical or mental work or monotonous work is especially difficult at night. If possible, move heavy work to shorter shifts and lighter work to longer shifts.
  • Examine start and end times. Flexible start-end times can be useful for those with child care needs or a long commute time. Consider moving start-end time away from rush hour. Morning shifts should not start too early (5 t6 am) because night sleep often is cut short.
  • Keep the schedule regular and predictable. Workers should know their schedule well ahead of time, so they can plan their rest, child care, recreation and contact with family and friends. Irregular schedules contribute to accidents by producing sleep loss and fatigue.
  • Examine rest breaks. Sometimes the standard lunch and coffee break are not enough to recover from fatigue. In jobs requiring repetitive physical or heightened concentration, brief rest breaks each hour seem to be best for recovery from fatigue.


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Workload Distribution

  • When possible schedule heavy or demanding work at times when workers are most alert or at peak performance.
  • Avoid doing the heaviest or most dangerous work in the middle of the night, during early morning hours or at the end of a 12-hour shift. Extra fatigue from long work hours can combine with early morning sleepiness to increase accident risk.


Work Environment

  • Poor working conditions add to the strain of shiftwork. Adequate lighting, clean air, proper heat and air conditioning and reduced noise will avoid adding to the shiftworker's burden.
  • Circadian rhythm changes make the body more sensitive to toxic exposures at certain times of the day.
  • Workers should have access to hot and nutritious meals during evening and night shifts. A microwave will allow workers to heat meals brought from home or foods bought from vending machines.


Electronic Monitoring

  • Worker performance could be monitored through computer technology. If a worker slows too much, it could be a sign of fatigue.
  • The feeling of being watched constantly can be very stressful to workers It is suggested that computer monitoring be used only when the workers themselves choose it for safety purposes.


Access to Health Care and Counseling

  • Shiftwork may interfere with health care or counseling appointments.
  • If services are not available within the organization, a directory of health care organizations with expanded hours should be provided.


Training and Awareness Programs

  • New shiftworkers need to be made aware of the ups and downs of shiftwork. Invite family members to these meetings.
  • Personal experiences of shiftworkers should be shared with the new workers to help them understand they are not alone.


Social Programs

  • Organizing get-togethers, hobby clubs, sports or game activities, through work, can lessen the feeling of isolation.


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Coping Strategies for the Individual

Get Enough Good Sleep

  • When to sleep after the night shift. This is different for each individual. Keep a written record of when you go to sleep, when you wake up and how rested you feel to help you in identifying the sleep schedule that works for you. Many night workers need 2 shorter sleep periods to get enough sleep after the night shift. It is a good idea to go to bed right after the night shift and take advantage of the natural tendency to be sleepy in mid-afternoon for a nap.
  • Does rest equal sleep? Resting without sleep is not enough. The brain has to have sleep, but rest without sleep is valuable for body and muscle recovery. Schedule at least seven hours in bed even if you don't sleep the entire time.
  • What is the Minimum Amount of Sleep? The majority of workers need at least six hours of sleep, but most need more than this.
  • Switching Back to Days When switching back to days after the night shift it is best to get most of your sleep the following night. Sleep a few hours shortly after night shift to shake off sleepiness.
  • Napping. A short afternoon or evening nap will help fight sleepiness during the night shift. Allow enough time for drowsiness to wear off before starting work. Twenty to thirty minutes should be the minimum for a nap during a work break. Naps work best when they are extra sleep time and not a substitute for lost sleep.


Protect Sleep

  • Block out noise. Switch off the phone, disconnect the doorbell and use earplugs. Ask the family to use headphones when using the television or stereo and set strict times for noisy activities such as vacuuming. Locate your bedroom in the quietest place in the house, soundproof the room with insulation and heavy curtains. Put signs out to say you are sleeping and tell friends and neighbors when not to call.
  • Keep a regular sleep routine. Make the bedroom as dark as possible. Always sleep in the bedroom. Follow your regular bedtime routine. Don't read, eat or watch TV in your bed, use it for sleeping.
  • Avoid heavy foods and alcohol before sleep. Heavy, greasy foods cause stomach upsets making it difficult to sleep Eat a light snack if you must eat at all. Alcohol may make you feel sleepy, but it will wake you up too quickly after falling asleep. Don't drink alcohol in the hour or two before sleep.


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  • Regular exercise keeps a person from becoming tired too quickly and helps resist stress and illness.
  • Timing of exercise is important. Twenty minutes of aerobic exercise before work will help a worker wake up and keep the heart in shape.
  • Try to avoid exercise in the three hours before sleep.


Relaxation Techniques

  • Determine what is best for you personally to help you relax best. Give yourself time to relax and get rid of work-time stresses.



  • Stick to a diet that, along with exercise, helps a person stay physically fit. This means avoiding fatty and sugary foods, which make a person gain too much weight.
  • Eating lighter meals in the middle of the night helps reduce stomach upsets.


Bright Light

  • Recent research tells us that bright light can affect our circadian rhythm. The high-point and the low-point of the circadian rhythm can be changed by exposure to bright light.
  • Bright light affects melatonin, a chemical produced by the brain, that makes us feel sleepy.
  • In laboratory research, people exposed to a few hours of bright light in the morning felt alert earlier in the day. Bright light exposure in the evening will reduce melatonin levels making workers feel more alert for a longer period of time.
  • A well-timed exposure of bright light could increase alertness at night.


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Caffeine, Alcohol and Other Drugs

  • Caffeine. It is a mild stimulant that helps a person feel more alert, perhaps perform better and is the most widely used drug in the world to maintain alertness and performance. If you drink caffeinated beverages, do so before the shift or early in the shift. Try to avoid caffeine late in the shift. Caffeine interferes with sleep and makes sleep lighter and less satisfying.
  • Amphetamines, Diet Pills, "Uppers". These drugs are very strong stimulants that increase alertness and can eliminate sleep all together. Most of these drugs can only be obtained by prescription. They are easy to become addicted to and frequent use produces extreme nervousness, mood changes and performance actually becomes worse.
  • Alcohol. One or two alcoholic drinks per day (one drink = eight to twelve ounces of beer, four to six ounces of wine, or one ounce of hard liquor) taken with food is OK for relaxation and to be social. Alcohol can make a person sleepy, but alcohol actually disturbs sleep. After drinking alcohol a person sleeps lightly and wakes up more often than without alcohol. Avoid alcohol for one to two hours before sleep.
  • Sleeping Pills. There are two general types of sleeping pills, prescription and nonprescription. Nonprescription sleeping pills make a person drowsy and help them fall asleep. They are fairly long acting and may make the user feel drowsy after waking up. If they are used too often their effect expires. Prescription sleeping pills work to help a person fall asleep and stay asleep. Regular use has the potential to cause dependency.
  • Melatonin. This chemical is produced by the brain, is controlled by bright light and makes a person feel sleepy. Research needs to be conducted to learn the proper dosage and best time to take melatonin for a particular work shift.


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Caffeine Content of Popular Drinks

12-ounce beverage milligrams

Jolt 71.2
Sugar-Free Mr. Pibb 58.8
Pepsi One 55.5
Mountain Dew 55.0
Diet Mountain Dew 55.0
Mellow Yellow 52.8
Surge 51.0
Tab 46.8
Coca-Cola 45.6
Diet Coke 45.6
Shasta Cola 44.4
Shasta Cherry Cola 44.4
Shasta Diet Cola 44.4
Mr. Pibb 40.8
Sunkist orange 40.0
Dr. Pepper 39.6
Storm 38.0
Pepsi-Cola 37.2
Diet Pepsi 37.0
RC Cola 36.0
Diet RC 36.0
Barq's Root Beer 23.0
Diet Rite Cola 0
Sprite 0
7-Up 0
Mug Root Beer 0
Minute Maid Orange 0

Other Beverages: (8 ounces) milligrams

Coffee, Drip 115-175
Coffee, Brewed 80-135
Coffee, Espress(2 ounces) 100
Coffee, Instant 65-100
Tea, iced (12 ozs.) 70
Tea, brewed, imported 60
Tea, brewed, U.S. 40
Tea, instant 30
Tea, green 15
Hot cocoa1 4
Coffee, Decaf, brewed 3-4
Coffee, Decaf, instant 2-3

SOURCES: National Soft Drink Association, US Food and Drug Administration, Bunker and McWilliams, Pepsi.


Alward, Ruth R. and Monk, Timothy H., The Nurse's Shift Work Handbook, American Nurses Publishing, 1993.

Rosa, Roger R. and Colligan, Michael J., Plain Language About Shiftwork DHHS (NIOSH) Publication N. 97-145 July 1997.

Rosekind, Roger, "Shiftwork Factors: How they affect us.", Alertness Solutions, 1999.

Rosekind, Roger, "Strategies tmanage shift work fatigue.", Alertness Solutions, 1999.

United States Department of Labor, Bureau of Labor Statistics.

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Recommended Reading

  1. Authors: Corlett, E.N., Quiennec, Y., and Paoli, P.
    Title: Adapting Shiftwork Arrangements
    Publisher: European Foundation for the Improvement of Living and
    Working Conditions, Dublin, Ireland
    Year Published: 1988
  2. Authors: Folkard, S. and Monk, T.H. (editors)
    Title: Hours of Work: Temporal Factors in Work-Scheduling
    Publisher: John Wiley and Sons, New York
    Year Published: 1985
  3. Author: Lamberg, L.
    Title: Bodyrhythms: Chronobiology and Peak Performance
    Publisher: William Morrow and Company, New York
    Year Published: 1994
  4. Author: Monk, T.H.
    Title: How to Make Shift Work Safe and Productive
    Publisher: American Society of Safety Engineers, Des Plaines, Illinois
    Year Published: 1988
  5. Authors: Monk, T.H. and Folkard, S.
    Title: Making Shiftwork Tolerable
    Publisher: Taylor and Francis, London
    Year Published: 1992
  6. Author: Scott, A.J. (editor)
    Title: Shiftwork: Occupational Medicine State of the Art
    Reviews, Volume 5, Number 2.
    Publisher: Hanley and Belfus, Inc., Philadelphia
    Year Published 1991
  7. Author: U.S. Congress, Office of Technology Assessment
    Title: Biological Rhythms: Implications for the Worker
    Publisher: U.S. Government Printing Office, Washington, D.C.
    Year Published: 1991
  8. Author: Wedderburn, A.
    Title Guidelines for Shiftworkers
    Publisher: European Foundation for the Improvement of Living and
    Working Conditions, Dublin, Ireland
    Year Published: 1991


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Web Sites

NASA Ames Research Center


National Sleep Foundation

Sleep Medicine Home Page

American Sleep Disorders Association

Department of Transportation: The Human Fatigue Resource Directory

AAA Foundation for Traffic Safety

NIOSH Plain Language About Shiftwork #97-145

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