1. Warren Silverman MD
Medical Director
ACCESS HEALTH SYSTEMS
Shift Work
Or: What time is it anyway?

2. What is Shift Work?

Regularly scheduled work
outside of the normal daytime
working hours of 7AM-6PM
 Permanent
night shifts
 Afternoon or evening shifts
 Shifts beginning before 6AM

3. 

Condensed work weeks with
extra long weekends
Variable or rotating shifts
 Day
to evening or day to night
 May change weekly or monthly

4. Why do we need shift work?

Critical services on 24 hour basis
Police, fire, military, healthcare, utilities,
transportation,
 A production process > 8 hours or
continuous
 Expensive machinery that must be used
continuously to be profitable
 Support services for other shift workers
 Convenience


5. Who does shift work?







Men do more night and rotating
shifts
Women do more evening and part
time work
Younger > Older workers
African-American > Caucasian
Single > Married
Single Mothers > Married Mothers
In 2 job married couples ¼ - 1/3
have at least one shift worker

7. 


20 Million Americans
do shift work ; 26% of
men, 18% of women
Drop out rate: 20% at
year 1; 33% at 2 years
Tolerance declines with
age
Cumulative effects
 Decreased physiological
reserve > 40


8. Factors describing shift








Permanent (fixed) or rotating
How long?
How many days before a rest day
How many rest days on a “weekend”
Overtime?
Length of rest between shifts
Is there rest during shift
Is Schedule regular and predictable

9. Permanent Nights






Most permanent night workers never
really get used to the schedule
Many nights they feel tired and
sleepy
Fatigue because of return to day
hours on days off
Family and friends active during the
day
Errands and chores during the day
Sleep less during the day

10. Rotating Shifts




Can never adapt to a set work
schedule
Used to be more “fair” to all
workers
Rotating shift workers have
more complaints than others
about physical and
psychological health
Special Risks

11. Special Features

Speed
 The
number of consecutive days
before a shift change

Direction
 Forward
or clockwise (dayevening-night)
 Reverse (day-night-evening)

12. 

Longer rotations (3-4 weeks)
may allow better adaptation to
shift
Shorter (1-2 days) allows no
time to get used to night shift,
but can get through it quickly to
get to rest day. Used more in
Europe than US

13. Work-Rest Ratios




If an 8 hour shift = 16 hours to
do everything else and sleep
If a 12 hour shift, only 12 hours
to do everything else.
Family duties do not decrease
no matter the shift time leading
to less sleep and rest
Fatigue is cumulative

14. Unpredictable schedules




Health care workers with
emergencies or covering call ins
A factory breakdown or last
minute rush order
A last minute “call board”
assignment to move an order
Being on call and getting called
in (Doctors do know about this!)

16. How does the body work



Internal Biological Clock
Circadian rhythm
Regulated by sunlight and
darkness

17. Circadian Rhythm

19. Circadian Rhythm




Different body functions vary
during the 24 hour day
Metabolism (energy from food)
is greatest in the afternoon to
evening
Most people most alert 4-6 PM
and most sleepy 4-6 AM
Personal differences between
people

20. Circadian body rhythms








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Hormone and gastric secretions
Bronchial reactivity
Blood Pressure
Sexual arousal
Anxiety
Work performance
Metabolic Rate
Short term memory
Family interactions

21. 


The body has a natural cycle of
25 hours
Internal and external factors
synchronize us to a 24 hour day
The internal clock is located in
the suprachiasmatic
hypothalmus

22. External clues “Zeitgebers”




Light/Dark cycle
Timing of meals
Social interactions
Actual time clock

23. Sleep ( Not now!)




Night workers get the least
sleep (6.6 hours)
Evening workers get the
most sleep (7.1 hours)
Day workers get medium
amounts (6.7 hours)
Rotating workers sleep the
least of all.

24. 


Sleep during the day is usually
2-3 hours shorter
It is lighter sleep and more
easily disturbed by noise
There are more activities and
noise during the day

26. Sleep

Sleep after night work
 Shorter,
less satisfying or
refreshing

Delta Sleep
 Repair
and Maintenance functions

27. 



Sleep loss makes it easier to fall
asleep at inappropriate times
Will decrease concentration
Increase accidents ( driving,
dangerous machinery)
Sleep can occur in short
episodes lasting a few seconds
without even realizing it. Very
dangerous time.

29. 

Night workers have a drop in
alertness at 2-4 AM
Accidents at 3 Mile Island,
Bhopal, Chernobyl, and the
Exxon Valdez oil spill each
occurred between midnight and
4 AM

30. Sleep deprivation



Mild sleep disruption may not
have significant impact
Cumulative increasing each
night
Disordered sleep is
compounded by circadian
dysrhytmia

31. Sleep Deprivation


Six days of restricted sleep (4 hours
per 24-hour period) caused changes
to the sleep architecture similar to
the changes seen in people suffering
from depression.
changes in several natural body
rhythms of hormone secretion
Melatonin
 cortisol
 thyroid-stimulating hormone
 leptin
 Prolactin
 growth hormone.


32. What happens if we remove cues
and disturb the internal clock?

Desynchronosis:


Core body temperature and digestive
secretions may remain near daily mean
levels
Entrainment
When we try to regain our rhythms with
light dark cycles
 Different physiologies may entrain at
different rates and we may lose the
normal phase relationship of one to
another


33. Signs of desynchronosis





Sleep disturbance
Short term fatigue
Irritability
Loss of Appetite
Judgment alteration

34. What does The Dark do?

Triggers changes leading to
sleep
 Dropping
blood pressure
 Dropping heart rate
 Dropping breathing rate
 Dropping temperature
 Slowed digestion

35. 
Two physiologies most critical to
work and safety are core body
temperature and
sleep/wakefulness

36. Rotation

While forward rotation works
better with circadian rhythms of
the body, reverse rotation is
more common in the US
(workers pick up an extra “day
off” going from night to evening)

37. Clockwise shift rotation




Phase delaying: places less
strain on the human internal
clock
Higher worker satisfaction
Fewer health complaints and
work schedule complaints
20% increased productivity c/w
phase advanced shifts

38. Counter clockwise

Phase advancing:
 For
every hour of advancement a
full day is needed for entrainment
(ie: phase advancement to an
earlier shift every 7 days
necessitates a week or longer to
adapt after each rotation)
 25% of workers may not adapt

39. Other observations

Air travel:
 Entrainment
is much easier
westbound than eastbound


“Night owl” type personalities
adapt better to night and
rotating shifts than “morning
larks”
Rotation every 21 days results
in 70% fewer complaints than
every 7 days

40. Sleep stages

41. Stage 1




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Initial part of sleep
10-15 minutes
Slow rolling eye movements
EEG = Alpha waves
If awakened during this phase,
will deny sleeping

42. Stage 2





Largest part of sleep @ 50%
Infrequent or absent eye
movement
EEG = occasional sleep spindle
bursts
Deprivation of this stage may
lead to total sleep loss
Not usually “made up” after
sleep deprivation

43. Stages 3 & 4






Slow wave sleep (SWS): deep
Muscle tone; variable
Arousal; difficult
EEG: High voltage; Delta waves
Important to body repair
Not as susceptible to circadian
factors

44. REM






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After 1-2 hours
Paralysis of muscles with occasional
twitches
Body loses some thermoregulatory ability
Heart rate and blood pressure very variable
Restorative and dream sleep
Important for psychosocial adjustment and
development
Greatly influenced by circadian factors

46. Cycling between stage 4 and
REM





Increased with caffeine
REM suppressed with
alcohol
Sedatives increase
stage 2 non restorative
sleep
Older less SWS, more
frequent awakenings
and less sleep time
Younger greater
frequency and longer
REM intervals

48. Health Effects
Immediate
Long term

49. Health Hazards





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Gastrointestinal Problems
Cardiovascular problems
Sleep and stress related disorders
Drug and Alcohol use
Risks from prolonged exposure to
chemical and biological substances
and other hazards
Effects on pregnancy

50. Digestive




Increased incidence of ulcers.
Often eat at night when
digestion and other body
functions are slowed down
May eat less nutritious foods at
night (snack foods)
Drink more caffeine products at
night

51. GI Upsets


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
Used to keep
awake

52. Cardiovascular problems



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Increased incidence of ischemic
disease
Elevated triglyceride levels in
phase advance workers
May be related to disturbance of
circadian blood pressure and
pulse rhythms
Substance abuse more likely in
shift workers

53. Hypertension

Shift workers were found to
have approximately 25% greater
chance of developing significant
hypertension than non shift
workers

54. 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

55. 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


56. Social Risks




Number 1 problem: missing family
and friends
Would rather loose sleep than miss
social opportunities
Some activities are flexible ( ie:
gardening, woodworking, fixing cars)
Some are not (clubs, team sports,
childcare, school activities)

57. Social Impact

Increases
 Divorce
 Family
violence
 Social Isolation
 Sexual dysfunction
 May affect women more than men

58. Circadian rhythm related
issues


Peak bronchial reactivity between 4-7 AM
 Asthma may be worse in workers
exposed to irritants
Shift work increases glucose levels in
insulin dependent diabetics.




One study shows a 35% increased risk for
developing diabetes
Sleep deprivation lowers seizure threshold
Increases frequency of migraines
The absorption, excretion, metabolism and
peak effect of medications is affected by
circadian rhythms

59. Colorectal Cancer



data suggest that working a rotating
night shift 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
This may be due to the suppression
of melatonin production with
nocturnal light exposure. Melatonin
has anti-cancer properties

60. Breast Cancer

Attributed to inhibition of
melatonin production by light
exposure during the night

61. Shift Work Sleep Disorder

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Circadian Rhythm disruption
Insomnia
Disrupted sleep schedules
Reduced performance
Difficulties with personal
relationships
Irritability/depressed mood
Sleep apnea 11.6% vs 5% in general
population

62. Increased accidents


To and from work
Microsleeps
Alert to suddenly severe fatigue
 Worse with monotonous tasks


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Decreased vigilance
Lower performance
Higher error rates
20% increase in ergonomic workers
compensation cases

63. Making an Impact
Strategies to WAKE UP

64. Administrative Controls
1.
2.
3.
Limit shift work to essential jobs
Schedule toughest most dangerous
tasks for early in the shift. Less
demanding tasks for later in the
shift
Avoid scheduling demanding or
dangerous tasks at the beginning
of an early morning shift

65. 1.
Tailor supervision:
1.
2.
3.
2.
Extra supervision between 3:30 AM
and 5:30 AM
Younger workers have more accidents
at the start of a shift following
weekends
Older workers have more accidents at
the end of a shift.
Supervise inexperienced workers
more closely until they learn their
job

66. 


Encourage good eating
habits at night.
Encourage light meals
that are nutritious and
easy to digest
Allow adequate meal
and rest breaks
Have good emergency
plans in place for odd
shifts (nighttime
emergency responders
may be fewer than day)

68. Odd Shift Out

Compressed workweek:
 3-4

days of 10-12 hour shifts
Pros:
 More
time off and between work
schedules
 More opportunities for family and
social activities

69. 
Cons:
 Increased
fatigue
 Decreased performance by the
end of the shift
 Daily exposure to chemical,
biological and physical hazards
my be increased
 Some families may have trouble
arranging childcare or eldercare

70. Permanent afternoon, evening
or Night shift


Pro: More time to adjust
Con:
 Disruptive
to social life
 Permanent night workers may
accumulate a greater sleep
deficiency over time

71. Rotating or Variable shifts

Length of rotation:
 Workers
rotated to a new shift
schedule too rapidly or without
sufficient break may have trouble
functioning

72. 
Speed of rotation

Longer rotations of 10-14 days may
allow more time to adjust.





Circadian rhythm may require 3 weeks to
fully adjust to a new shift
Mental functions adjust more rapidly
More trouble with the first 4 shifts
Faster rotations of 2-3 days do not allow for
circadian rhythm adjustment
Faster rotation allows workers to get through
the more difficult night shift rotation quicker

73. 
Direction of the rotation
 Clockwise
rotation from morning
to afternoon to night causes fewer
problems than the reverse order

74. Engineering controls



Reduce night traffic, noise and
distractions
Be aware of hazards. Calculate toxic
exposures based upon shift duration
(i.e.: 8H TWA vs. 12 hour shift)
Promote alertness:
Keep area brightly lit
 Reduce glare and reflective surfaces
 If feasible, allow workers to play music
that will keep them awake


75. 
Maximizes safety and health controls
Good ventilation
 Temperature control
 Machine guarding



Avoid isolating workers.
Communicate often
Provide food preparation areas, rest
areas, consider and exercise facility

76. Provide worker education and
instruction




Treat shift training like Hazcom
Talk about health and safety
difficulties
Emphasize performance and
accident risks
Teach employees to recognize
social and family problems

77. They should know….



How to recognize health
problems which may be related
to shift work
How to control shift work
hazards and methods that can
be used to do so.
How to minimize the effects of
shift work on themselves

78. They can do this by…

Protecting their sleep periods
 Maintaining
regular rest and wake
routines
 Avoid exercising for 2 hours
before going to bed
 Keep light out the bedroom
 Disconnect the phone
 Maintain a quiet sleep area

79. 


Eat nutritious meals
Keep a regular eating routine
Select foods high in
carbohydrate rather than heavy
fatty high protein meals before
sleep

80. 



Family and friends should be
made aware of the potential
harmful consequences of shift
work
Adjust family and social life to
maximize interaction
Maintain physical fitness
Learn strategies to remain
awake at work

81. One last note:


Modafilin aka Provigil
Sept 2003: FDA advisory panel
recommended use for shift work
sleep disorder
Different mechanism than
amphetamines
 Well tolerated
 Memory improving
 mood brightening
 No jittery feeling
 ?anxiolytic
