Download - Shift Work
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Shift Work By M.H.Davari M.D
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What is shift work?What is shift work?
Shift work is defined as work outside ofthe normal daylight hours from about 7am
until 6 pm
Shift work is defined as work outside ofthe normal daylight hours from about 7am
until 6 pm
Midnight MidnightNoon
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What is Shift Work?
One speaks of shift work if two or more
persons , or teams of persons , work in
sequence at the same work place.
Often , each worker s shift repeats, in same
pattern , over a number of days.
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Production process > 8 hours or
continuous
Expensive machinery that must be used
continuously to be profitable
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7
How many workers work shift work in North America?
13 – 16% of total work force work some shift workTotal of shift workers estimated to be 24 -25 million
• 5-6 % work evening shifts
• 4-5% work permanent night shift
• 4-5 % work rotating shifts
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Why can shift work be difficult?
That is, they are biologically programmed to sleep during the day and be awake at night. e.g. owls,
bats, raccoons
Some animals are what scientists call
NOCTURNAL
DIURNALHumans are what
scientists call
That is, we are biologically programmed to sleep at night and be awake during the day.
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How does the body work
Internal Biological Clock (Circadian rhythm)
External stimulants
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Circadian Rhythm
• Different body functions vary during the 24 hour day
• Metabolism is greatest in the afternoon to evening
• Most people most alert 10 PM-8 AM and most sleepy 2-4 AM
• The body has a natural cycle of 25 hours• External factors synchronize us to a 24 hour day• The internal clock is located in the
suprachiasmatic hypothalmus
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The Suprachiasmatic Nucleus
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Circadian body rhythms
• Hormone and gastric secretions• Body tempreture• Bronchial reactivity• Blood Pressure• Sexual arousal• Anxiety• Metabolic Rate• Short term memory• Work performance
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Biochemistry and
Circadian Rhythms
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External clues “Zeitgebers”
• Light/Dark cycle• Timing of meals• Social interactions• Actual time clock
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In 1879 Thomas Edison invented the light bulb.
In 1879 Thomas Edison invented the light bulb.
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This forever changed our ability to work at night, but not our biological programming
to sleep at night.
This forever changed our ability to work at night, but not our biological programming
to sleep at night.
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The 4 Hazards of Shiftwork
1. Increased risk of errors & accidents in the work and out of the work
2 Insufficient daytime sleep leads to increased fatigue & sleepiness
3. Increase in health problems
4. Increase in social and domestic problems
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• Fatigue affects alertness in many shiftworkers
• 80-90 % of shiftworkers feel sleepy during night shift (?% nap!)
• Studies show increase in accident rate
• Tendency for more severe / serious accidents to occur
Alertness and Accidents
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Fatigue Related AccidentsFatigue Related Accidents
Midnight MidnightNoon
Nu
mb
ers
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Meter Reading ErrorsMeter Reading Errors
Midnight MidnightNoon
Nu
mb
ers
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Fully AlertFully Alert
MidnightMidnight MidnightMidnightNoonNoon
Rela
tive A
lert
ness
Rela
tive A
lert
ness
Biological Rhythms
DrowsyDrowsy
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Dro
wsy
15
10
5
12 15 18 21 00 03 06 09 12
ExxonValdez00:15
Full
Ale
rtne
ss
Time of Day & Major Accidents
Bhopal01:00
Chernobyl01:23
Three Mile Island04:00
MidnightNoon Noon
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Exxon Valdez Disaster
Cleanup cost: $2 Billion
Exxon Fined: $5 Billion
Environmental damage: ?$
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Health Hazards
• Short effects:• sleep disturbance
• Poor concentration • Decrease alertness• Decrease safety
• Prolonged exposure to chemical and biological substances and other hazards
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• Long effects:• GI problem• Reproductive effects• Cancer• Exacerbation of
• Sleep disorders • Asthma • Diabetes mellitus • Coronary Artery Disease
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GI Dis.• 75% of night
workers vs. 20% of day workers
• Complaints– Loss of appetite– Constipation – Dyspepsia– Heart burn– Abdominal pain– Flatulence
• Many problems may not show up until years later
• Reasons– Poor food quality– More caffeine– More alcohol– More tobacco– Drugs used to
keep awake
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Cardiovascular problems
• Increased incidence of ischemic disease
• May be related to:• disturbance of circadian
blood pressure and pulse rate• Substance abuse more likely
in shift workers• Elevated triglyceride levels in
phase advance workers
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Hypertension
• Shift workers were found to have approximately 25% greater chance of developing hypertension than non shift workers
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Cancer
• At least three nights per month for 15 or more years may increase the risk of Colorectal cancer in women 35%
• Shorter durations also have increased risk• Due to the suppression of melatonin production
with nocturnal light exposure. Melatonin has anti-neoplastic properties
• Breast Cancer , Attributed to inhibition of melatonin production by light exposure during the night
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Cognitive Ability
• Recent studies have found deterioration in
cognitive ability in shift workers vs. non shift
workers.
• This increases with duration of exposure
• The effect seems to diminish 4 years after
discontinuation
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Medical evaluation:
• History:• CAD• GI dx• Sleep dx• Epilepsy• diabetes • Asthma• Difficulty in night vision
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Psychological• Shift workers
demonstrate:• More depression and
despondency• More likely to use
psychotropic drugs or require hospitalization
• Will have magnification of underlying depression or bipolar disorders
• Circadian rhythm disturbance may be a cause for depression
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Social Impact
• Increases• Divorce• Family violence• Social Isolation• Sexual dysfunction• May affect women more than men
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• Impaired logical reasoning and decision-making
• Impaired vigilance and attention
• Slowed mental operations
• Loss of situational awareness
• Slowed reaction time
• Short cuts
Fatigue Effects on Performance
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Major Fatigue Factors
• Time of Day: between midnight and 6 AM
• Cumulative Sleep Debt:
• Acute Sleep Debt:
More than 17 hours since the last sleep period
• Continuous Hours Awake:
Less than eight hours in last 24 hrs.
More than eight hours accumulation.
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Shift work type:
1. Fixed pattern • Night • Evening
2. Rotating pattern• Clockwise (morning- evening- night)
• Rapid (less than 4 days)• slow (more than 4 days)
• Counter clockwise (night-evening- morning)
• Rapid • slow
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3. Oscillating shift work
4. Split shift work
5. Relief Shift work
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Quickly rotating shift system:
• Minimize sleep deprivation (Fischer et al., 1997)
• Minimize circadian rhythm disruption (Knauth 1993, 1995)
• Improve social contacts (Knauth 1993, 1995)
• Improve alertness and well-being (Williamson & Sanderson 1986, Phillips et al., 1991)
Clockwise rotation:• Better tolerated by the
shift workers,Improve production & well-being (Czeisler et al., 1982)
• Improve sleep quality (Folkard 1993)
• Reduce physical, social and psychological problems (Landén 1981)
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Shift work Maladaptation
• 15-20% of workers• Signs & symptoms:
• Sleep dis.• Fatigue• Behavioral dis.• GI dis.• Sedative drugs usage
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Shift work Maladaptation:
• Age > 50• Morning type• Second job or heavy house work• Long sleep time• Fixed & regular sleep pattern• Hx sleep dis.• Hx GI dis.• Hx cardiovascular dis.• Asthma,DM,Epilepsy
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How to keep worker alert?• High illumination level• Breaks• Naps• Occasional stirring music• Stretching or light exercise• Social interaction• Snacks & caffeinated beverages• FDA recommended use Modafinil (Provigil)
for shift work sleep disorder
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Suitable Shift systems:
• Daily work: not be more than 8 hr.• Number of night or evening shifts: as small as
possible.• A full day of free time follow every night shift• Contain consecutive work-free days, preferably
including the weekend • Clockwise rotation• Rapid • Shorter shift ( < 8hr) : heavy manual work• Longer shift (12hr) : light job
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