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Shift Work and
Long Work Hours
By : Dr. Ar. SafaeianOccupational medicine
specialist
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Shift work
Shift work involves work at times other than daytime hours of approximately 7:00 A.M. to 6:00 P.M.
Almost 15% of full-time workers (or 15 million Americans) work on evening, night, rotating, split, or employer-arranged irregular shifts
Social needs and economic factors promote the use of shift work and long hours.
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Critical services with shift work
1. police
2. fire protection
3. health care
4. transportation
5. communications
6. public utilities
7. military service
8. industries require continuous processing
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Shift Work Schedules
What is the best or worst work schedule?
☻There is no simple answer to this question because there is no ideal schedule that fits every situation.
☻Both good and bad points can be found in most work schedules.
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Types of Work Schedules
Different schedules might be used by the same occupation, the same industry, or even the same workplace.
5 days on a single shift followed by 2 days off (max).
Depending on the job, it is even possible to work 7, 10, or 14 days in a row.
☻Offshore oil rig workers, might work 2 weeks out on the rig followed by 2 weeks off at home.
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Time of Shift
24 hour operations usually are divided into 2 or 3 shifts. Start- and end-times depend on the length of the shift.
☻Day shift (also called morning or first shift) starts around 5 to 8 a.m. and ends around 2 to 6 p.m.
☻Evening shift (also called afternoon or second shift) starts around 2 to 6 p.m. and ends around 10 p.m. to 2 a.m.
☻Night shift (also called third, “graveyard,” or “mid” shift) starts around 10 p.m. to 2 a.m. and ends around 5 to 8 a.m.
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2nd-shift worker efficiency levels are typically 3–5% below 1st shift
3rd shift 4–6% below 2nd shift
The productivity level, i.e. cost per employee, is often 25% to 40% lower on 2nd and 3rd shifts due to fixed costs which are "paid" by the first shift.
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Permanent versus Rotating Schedules:
Permanent :
☻Most permanent night workers never really get used to the schedule.
Fatigue occurs because most night workers go back to a day schedule on their days off.
They sleep less during the day, so they don’t recover from fatigue.
Over several days, fatigue can accumulate to unsafe levels.
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Rotating :
☻Often used because they are considered fairer to all workers
☻ they can never completely adapt to a set work schedule.
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Speed and Direction of Rotation:
Speed :
●the number of consecutive day, evening, or night shifts before a shift change occurs.
Direction :
●Forward rotation, from day to evening to night shift.
●Backward rotation, from day to night to evening shift.
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SPEED OF ROTATION
Longer rotations (3-4weeks of working the same hours) allow workers more time to get used to night shifts. However, workers usually return to a day schedule on their days off.
A fast rotation (every 2 days) allows no time to get used to night work.
☻Some researchers prefer the fast rotation, because the worker quickly pass the hard shifts and then has a couple of days off.
☻Very fast rotations are used in Europe more than in America.
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DIRECTION OF ROTATION
Can affect the ability of circadian rhythms to adapt to the change in work times.
Forward rotation is better for helping a worker adjust to new sleep times(because it is easier to go to bed later and wake up later than earlier).
Backward rotations work against the body rhythm by forcing the worker to go to sleep earlier and earlier.
backward rotation schedules are used frequently in US.
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Work-Rest Ratios
The more a person works, the less time he or she will have for rest.
How many breaks during the shift and the length of breaks ?
-Several short breaks might be better than a few long breaks.
How many days works in a row
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How Regular or Predictable?
Most jobs have a very regular, set schedule. HCW, breakdown at a factory, Railroad
workers It is difficult to get adequate rest. Maybe they are on call and never get deep,
satisfying sleep because they are always listening for the phone. Some people call this “sleeping with one eye open.”
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Table 1: Work Schedule FeaturesExample Particulars Feature
Day, evening or night
Time of Shift
Shift Rotation
Fixed shift times (no rotation)
Permanent
Changing shift times Rotating
Rapid: 2 days per shift Number of workdays before shift change
speed
Slow: 21 days per shift
Clockwise: day to evening to night
Clockwise (forward) or counterclockwise (backward) change
direction
Counter: day to night to evening
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Example Particulars Feature
Work-Rest Ratios
5 workdays/2 rest days
7 workdays/3 rest days
Number of workdays to number of rest days Overtime workdays
Weekly
8 h work/16 h rest12 h work/12 h restLunch, coffee break
Work hours to rest hoursRest breaks within a dayOvertime work hours
Daily
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Example Particulars Feature
How Regular or Predictable?
Emergency or “on-call”part of the schedule Unplanned overtimeDemand-based schedulingor working off a “call board”
Can affect any otherpart of the schedule
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Shift work
The relationship between shift work and health and safety is influenced by :
work schedule the job the worker the work environment others (ergonomic ,organizational factors, job
demands, workers' personalities, sociodemographic characteristics, geographic location, recreational resources, housing arrangements, sociometric patterns, and social support)
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Risks Associated with Shift Work
Sleep, Sleepiness Circadian Rhythms, Performance, and Safety Social and Familial Disruptions Long-term Effects and Vulnerable Groups
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Sleep, Sleepiness
The most direct effect of shift work is the reduction in the length and quality of sleep
Night-shift workers have lighter, more fragmented, and less restful daytime sleep
Rotating shift workers obtain less sleep, than permanent schedules.
No adaptation
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Circadian rhythms refer to biologic rhythms that show a cyclic rise and fall about once a day.
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Circadian Rhythms, Performance, and Safety
The timing of the circadian rhythms are slow to change and generally take several days to readjust after abrupt
Disturbances in circadian rhythms lead to reductions in the length and quality of sleep, increase negative, GI symptoms
Injury risk increased :18% during afternoon/evening shift and 34% during the night
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Social and Familial Disruptions
Shift workers often work in the evening and sleep during the day
The disruptions depend on: worker's schedule, family, gender of the worker, presence of children, the degree of flexibility in the worker's social contacts and leisure pursuits.
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Long-term Effects
32% of night workers and 26% of rotating shift workers experience long-term insomnia and excessive sleepiness and are unable to adapt their sleep adequately on these shifts.
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Vulnerable Groups
Unstable angina or MI
HTN requiring regular medications
IDDM Asthma requiring
regular medication Psychiatric illnesses
requiring regular medication
Alcohol or drug abuse
GI diseases Sleep disorders Epilepsy requiring
medication within the past year
Renal impairment Thyroid and
suprarenal pathologies
Malignant tumors Pregnancy
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Long-term Effects
Aging is associated with less tolerance of shift work
The sleep changes may begin as early as the 30s and 40s, so some workers who initially adapted well to shift work during their younger years may show more symptoms as they grow older
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Long Work Hours
Working a minimum of 50 hours per week
Estimated that over 26% of U.S. men and 11% of U.S. women worked long hours in 2000.
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Risks Associated with Long Work Hours
The overtime work is associated with small but significant increases in adverse physical and psychological outcomes like:
poorer perceived general health increased injury rates more illnesses increased mortality
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Countermeasures
Efforts to promote adaptation to or ease the difficulties of coping with shift work and long work hours include
strategies for employers strategies for workers
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Countermeasures Work schedules /rest breaks during work Sleep strategies Altering circadian rhythms (bright or blue light) Optimally timing physical activity Improving physical conditioning Pharmacologic aids or using caffeine Dietary regimens Stress reduction techniques Social support groups Providing family counseling.