Shiftwork

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Shiftwork
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Overview

• While 24-hour operations have long been a part of
  emergency occupations, the need for "around the-
  clock" workers has increased dramatically in
  industry during recent years ( 25 of North
  American working population).
• This reliance may be attributed to three main
  sources, namely technological, economic and
  social advancements
• Emergency Services (hospitals, police, fire,
  military)
• Production Needs (mills, blasts furnaces, nuclear
  power generators supply and demand)
• Convenience (24-hour shopping, movies)
• CCOHS stats

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• Human kind has evolved as a diurnal species that
  is habitually active during the daylight hours
  and sleeps at night.
• Shiftwork long been known to disturb this
  natural tendency.
• From both a biological and social standpoint
  humans are "meant" to be day workers.
• It may not necessarily prove harmful, but it does
  provide a potential source of stress for the
  worker.

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• Systems which entail night work tend to result in
  the disruption of the worker's circadian rhythm
  in a large number of physiological and
  psychophysiological parameters.
• Peak activity with regards to physiological,
  psychological and social processes, tends to
  coincide with daylight and evening hours.
• This has led to night work being referred to as
  an "unnatural" mode of work which can result in
  numerous problems for both the individuals
  concerned, and the organizations employing them.

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A reduced worker alertness found to occur during
the night shift has been associated with

• An Increased
• risk of injury
• accidents
• decreases in productivity due to operational
  errors.

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Reduced alertness and declining performance has
been attributed to

• the additive effects of a night-time circadian
  low-point in physiological arousal.
• combined with inadequate sleep during daylight
  hours on returning from the night shift.

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Performance and Safety Consequences of Night Work
!

• There is no firm evidence that productivity is
  influenced due to shiftwork.
• Discrepancies with regards to differences in
  accident frequency between day and night have
  also been noted (Bhopal Chemical leak, Chernobyl
  meltdown, Exxon Valdez spill all occurred at
  night).
• But additional factors must be considered when
  examining the relationship between accidents and
  time of day
• time on task
• work load
• personal characteristics of the task operators
• Situational, task and worker-related differences
  across shifts which must be kept in mind.

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• Factors which affect Performance Analysis of
  human performance in any situation, be it daily
  living, working or sporting activities, requires
  the consideration of a multitude of variables.
• These include the dynamic interaction between
  personal and environmental factors.

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PERSONAL FACTORS

• Many functions of the human body have long been
  recognized to exhibit periodic variations (e.g.
  menstrual cycle).
• Of concern are those fluctuations which occur on
  a daily basis, the so-called circadian rhythms.
• Among those body functions which show diurnal
  variations
• Sleep
• readiness to work
• autonomic processes
• heart rate
• blood pressure
• body temperature

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Circadian Rhythms

• Circadin comes from the Latin word circa dies
  which means about a day.
• Sleeping, walking, digestion, secretion of
  adrenalin, body temperature, blood pressure,
  pusle and many other body functions are regulated
  by this 24-25 hour cycle.
• Readies an individual for performance in the
  daytime. While the night is occupied with
  recuperation, relaxation and sleep
• Involvement in shiftwork, in particular night
  work, thus results in a disruption of these
  inherent rhythms.
• These phase shifts occur slowly over a
  considerable period. Some people can start to
  adapt after 2-3 days while some take much longer.
• Difficult to adjust when the days off follow a
  different schedule (which often happens).

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Circadian Rhythms and Your Biological Clock

• A tiny sliver of brain tissue, less than the size
  of a pinhead, regulates the timing of our bodies.
  Within this sliver lies a biological clock that
  keeps track of the time of day, and seasons of
  the year, and marches our bodies and brains in
  step. The small cluster of nerve cells that forms
  the biological clock is called the
  suprachiasmatic nucleus (SCN). Its name derives
  from the location of the SCN, just above where
  the broad optic nerve trunks cross over each
  other (a site known as the "optic chiasm") on
  their way back from the eyes to the visual center
  of the brain.

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• The SCN also receives information about light and
  dark from the eyes, but it has its own dedicated
  pathway of nerves, the retino-hypothalamic tract
  (RHT), which is separate from the main nerve
  bundles carrying visual information to the brain.
• We know that the SCN is a biological clock
  because when it is destroyed in an experimental
  animal by surgical pinpoint lesions of the brain,
  rhythms in sleep and wake, and many other
  rhythms, fade away (interestingly, the animal,
  minus its SCN, runs, eats and drinks the same
  total amount each 24 hours, but these activities
  are now randomly distributed throughout the day
  and night).
• Human biological clocks actually follow a pattern
  of about 25 hours. Hence, if someone lives in a
  cave or an apartment without windows (as people
  have done), their circadian patterns of sleep and
  wakefulness shift "westward" by about one hour a
  day. However, in the regular world, sunlight and
  darkness serve to "reset" the biological clock
  every day and keep us on a 24-hour clock.

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• Individuals with high amplitudes in their
  circadian rhythms were better able to cope with
  the frequent rhythm disturbances caused by
  shiftwork. These high amplitudes, which are
  believed to result in an increased stability of
  the circadian rhythms, are reported to occur in
  physically fit individuals

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• Circadian rhythm phase shifts induced by
  shiftwork can have significant effects on the
  worker in terms of
• performance efficiency
• motivation
• sleep patterns
• family and social life
• health

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More Personal FactorsSeveral physiological
functions start to deteriorate or decrease with
advancing age.

• Visual and auditory processes.
• Maximum heart rate and maximal oxygen
  consumption.
• It is these reduced and failing capacities which
  are believed responsible for the problems
  generally experienced by older workers.
• Adjustment to shiftwork, and night work in
  particular, has been found to become more
  difficult with age, and is accompanied by a
  decrease in resistance to the stresses imposed by
  these modes of work.
• The combined effects of ageing and aberrant work
  hours could thus place older shiftworkers at a
  greater risk than younger individuals and may
  lead to a substantial reduction of performance
  efficiency.

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Effects of Physical Conditioning

• Prevention of heart disease by decreasing
  hypertension and blood cholesterol levels.
• Reduction in occurrence of musculoskeletal
  injuries such as a lower back pain (LBP) via an
  increase in flexibility and muscular strength.
• Physically conditioned individuals should thus be
  well equipped to cope with demands, both
  qualitative and quantitative, imposed on them by
  the work environment.

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• One of the recognized problems associated with
  shiftwork is that of passivity following a
  reduced, or lack of, regular participation in
  physical activity - this state of hypokinesis
  appears to stem primarily from the disruption of
  the worker's social and recreational lifestyle
  due to the continuous alternation of work hours.
  Time off work tends to be used predominantly for
  sleep and family contact with limited time
  remaining for participation in physical activity.
• Moderate physical training was found to improve
  the general fitness of a group of shiftworkers,
  whilst further decreasing work-dependent fatigue
  and musculoskeletal problems. These effects were
  observed to be most pronounced during the night
  shift where worker alertness was lowest.
• Several studies have indeed shown an increase in
  tolerance to shiftwork in physically conditioned
  workers.

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Personality-Related Differences

• The psychological make-up of humans has long been
  recognized as being a significant contributor to
  both intra- and inter-individual differences with
  regards to nature of performance in various
  situations.
• Personality has been described as being a
  relatively stable set of psychological structures
  and processes which organize human experience and
  determine an individual's actions and reactions
  to the environment.

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There two broad classifications of personality
associated with "circadian type".

• The first circadian type involves the
  differentiation between "morning larks" and
  "night owls".
• The larks are commonly referred to as "morning
  types" (M- types), while the owls are known as
  "evening types" (E-types).
• M-type individuals tend to have early bedtimes
  and waketimes and are more alert during the
  mornings.
• E-types on the other hand, are more aroused later
  at night and experience difficulty in waking up
  early. Self-assessment questionnaires are
  commonly used for identifying morningness and
  eveningness characteristics. (http//www.circadian
  .com/learning_center/lark_owl_test.htm)

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• M-types are generally found to be less tolerant
  to shiftwork, in particular, the night shift.
  Three reasons have been proposed
• M-types find it extremely hard to stay awake at
  night, or to sleep late in the morning, which is
  exactly the behaviour required of night workers.
• M- types appear to be more susceptible to
  environmental zeitgebers (time cues).
• When M-types are isolated from all time cues,
  they exhibit "free-running" circadian rhythms
  with an approximate length of 24.3 hours in
  comparison to E-types who tend to have slower
  rhythms of approximately 25.5 hours.

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• Night work is best suited to those individuals
  with a longer running period as this leads to a
  phase delay in behaviour, for example a later
  bedtime.
• It would therefore seem that E-types would better
  cope with the demands of working at aberrant
  hours.
• It has been queried whether morningness-eveningnes
  s is a stable, genetically determined trait, or
  simply a reflection of a recently developed
  habit.
• An M-type individual could thus temporarily
  acquire E-type characteristics, yet may revert
  back to their morningness tendency at a later
  stage.

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• The second circadian type entails the
  quantification of individual differences along
  the dimension of introversion-extroversion.
• Introverts generally tend to be quiet,
  thoughtful, non-impulsive individuals and are
  often loner.
• Extroverts, on the other hand, are usually
  carefree, compulsive and highly sociable with an
  almost constant need for stimulation and
  challenge.

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ENVIRONMENTAL FACTORS

• Shift Systems
• A review of the available literature on shift
  scheduling indicates that while some shift
  designs are preferential to others, no ideal
  shift system is agreed upon.
• There is likely no "best" shift system as any
  design is a tradeoff between accommodating the
  worker's social needs and health and safety
  aspects.

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Rosa, R. and Colligan, M. (1997). Plain Language
About Shiftwork. U.S. Dept. of Health and Human
Services.
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ROTATIONAL SHIFTWORK

• Shifts rotate or change according to a set
  schedule.
• Shifts can be continuous (24/7) or
  semi-continuous (2-3 shifts/day without
  weekends).
• Workers take turns working all of the shifts in
  the system.

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RAPIDLY ROTATING SYSTEMS

• Switches once or twice during a week.
• Found to cause the least disturbance to the
  endogenous body clock

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WEEKLY/MONTHLY ROTATING SYSTEMS

• Changes every week or every month.
• provide for both the physical and social needs of
  the worker.
• Where rotation of shifts occurs, a forward
  direction (morning-afternoon/evening-night) is
  favoured as this causes minimum disturbance of
  diurnal rhythms.
• weekly rotating shifts are generally regarded as
  being the worst system as disruptions to the
  circadian rhythms lead to a cumulative sleep
  debt.
• It would appear however, that these systems tend
  to be the most commonly used (employment equity).

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PERMANENT NIGHT SHIFT SYSTEM

• an acceptable level of circadian rhythm
  adjustment can normally be achieved and this
  nocturnal orientation may in turn improve sleep
  and performance.
• Permanent night shifts are preferred when safety
  is crucial learn to work in the environment.
• these shifts are not desirable to most people as
  they hinder social contacts.
• Many family units appear to prefer permanent
  night work as it facilitates the organization of
  domestic responsibilities.

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Notes on Scheduling

• An early morning start (before 700am) for the
  morning shift should be avoided.
• Shifts should rotate forward
• Day ? Evening ? Night
• The schedule should be simple and predictable
  people want to plan their lives!

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Extended Workdays

• One further variable to consider in terms of the
  design of shift systems is that of the length of
  the shift.
• Some suggest a shift should not exceed 8 hours
  (except where the work is low in physical and
  mental demands) while others recommended that
  extended work periods of 9 to 12 hours may be
  acceptable.
• Extended workdays can be problematic
• Fatigue
• Covering absenteeism
• Limitation of environmental exposure (toxics,
  heat, cold)
• Increased error rates and accident rates

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Fatigue symptoms

• Sleepiness
• Irritability
• Reduced alertness, concentration and memory
• Lack of motivation
• Increased susceptibility to illness
• Depression
• Headaches
• Giddiness
• Loss of appetite and digestive problems

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Extended Workday Pros/Cons

• Pros
• More days off more consecutive days off
• More family leisure time
• Improved morale
• Increased job satisfaction
• Reduced absenteeism
• Reduced time of commuting

• Cons
• Long travelling time or exhausting recreation may
  cause fatigue on return to work
• Decline in safety alertness
• Slower pace of work
• Workers need more breaks

Some occupations have regulations against
extended workdays (e.g. Airlines)
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Social Factors

• Married versus Single
• Pressure on Marriage
• Research shows more stress for single people
  likely because no time to meet new people.
• Less involved in childrens lives
• Miss important or fun occasions
• Difficult to participant in sports, clubs, etc.
• Difficult to make appointments (i.e. dentist,
  doctors, massages, parent-teacher meetings, kids
  concerts, bank, etc.

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• Shiftwork Extended Workdays are more difficult
  for some people than others. Some people
  actually prefer permanent nightshifts or 12-hour
  shifts.
• Difficult for
• People on medications that have to be taken at a
  certain time and with food or diabetics.
• People with health problems
• People with a lot of home-life responsibility

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Good Practice Guidelines for Shift Design

• Talk to employees to see shift preferences.
• Consider time at which shift starts/ends.
• Provide time off during socially advantages
  times.
• Let employees know schedules well in advance.
• Allow some flexibility for staff to switch shifts
  but make sure people arent double-shifting.
• Provide same facilities support for all shifts.
• Educate employees on how to cope with shiftwork.
• Consider exposure limits, breaks required, etc.
• Consider different lengths for shifts.
• Keep schedule regular and predictable.
• Keep long shifts and overtime to a minimum.
• Plan for some weekends or holidays off.

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Good Practice Guidelines for the Work Environment

• Adequate lighting proper heating
• Same facilities available for each shift
• Access to healthy meals
• Encourage interaction between employees
• Keep in contact about employees about their
  concerns
• Encourage exercise
• Encourage breaks when sleepy

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Hints Tips for Shift Workers How to Cope

• Pay attention to food/nutrition
• Exercise
• Figure out how to optimize sleep time
• Get information on shiftwork health risks
• Have a social life
• Seek advice from doctor if you have health
  conditions
• Take more frequent breaks when fatigued
• Talk to family and friends about sleep schedule
• Restrict or avoid caffeine, cigarettes and
  alcohol consumption
• Avoid long commutes when sleepy
• Use co-workers to keep you awake on the job
• Talk to co-workers for tips on how to cope
• Dont leave the boring tasks for the end of the
  shift when most fatigued. Switch things up when
  you can to stay interested.
• Try not to alter sleep schedule too much on days
  off

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Interesting Web Sources

• http//www.circadian.com/
• A company that consults in shiftwork jobs
• http//www.sleepfoundation.org
• http//www.ccohs.ca/oshanswers/work_schedules/
• http//www.hse.gov.uk/humanfactors/shiftwork/