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Or: What time is it anyway?

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1 Or: What time is it anyway?
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 Direction
The number of consecutive days before a shift change Direction Forward or clockwise (day-evening-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
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 Delta Sleep
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 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 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 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
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
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 Decreased vigilance
Alert to suddenly severe fatigue Worse with monotonous tasks 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
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 Tailor supervision: 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 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: Pros: 3-4 days of 10-12 hour shifts
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 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

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