ShiftworkShiftwork

OverviewOverview 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*CCOHS stats

Human kind has evolved as a diurnal Human kind has evolved as a diurnal species that is habitually active during the species that is habitually active during the daylight hours and sleeps at night.daylight hours and sleeps at night.

Shiftwork long been known to disturb this Shiftwork long been known to disturb this “natural” tendency.“natural” tendency.

From both a From both a biologicalbiological and and social social standpoint humans are "meant" to be day standpoint humans are "meant" to be day workers.workers.

It It may notmay not necessarily prove harmful, but necessarily prove harmful, but it does provide a potential source of stress it does provide a potential source of stress for the worker.for the worker.

Systems which entail night work tend to result in Systems which entail night work tend to result in the disruption of the worker's circadian rhythm in a the disruption of the worker's circadian rhythm in a large number of physiological and large number of physiological and psychophysiological parameters.psychophysiological parameters.

Peak activity with regards to physiological, Peak activity with regards to physiological, psychological and social processes, tends to psychological and social processes, tends to coincide with daylight and evening hours.coincide with daylight and evening hours.

This has led to night work being referred to as an This has led to night work being referred to as an "unnatural" mode of work which can result in "unnatural" mode of work which can result in numerous problems for both the individuals numerous problems for both the individuals concerned, and the organizations employing them.concerned, and the organizations employing them.

A reduced worker alertness A reduced worker alertness found to occur during the found to occur during the

night shift has been associated night shift has been associated with:with:

An Increased:

• risk of injury

• accidents

• decreases in productivity due to operational errors.

Reduced alertness and declining Reduced alertness and declining performance has been attributed to: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.

Performance and Safety Performance and Safety Consequences of Night Work !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 taskwork loadpersonal characteristics of the task operators

Situational, task and worker-related differences across shifts which must be kept in mind.

Factors which affect Factors which affect Performance Performance AnalysisAnalysis of human performance in any of human performance in any situation, be it daily living, working or situation, be it daily living, working or sporting activities, requires the sporting activities, requires the consideration of a multitude of variables. consideration of a multitude of variables.

These include the dynamic interaction These include the dynamic interaction between between personalpersonal and and environmentalenvironmental factors.factors.

PERSONAL FACTORSPERSONAL 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 workautonomic processesheart rateblood pressurebody temperature

Circadian RhythmsCircadian 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 Difficult to adjust when the “days off” follow a different schedule (which often happens).schedule (which often happens).

Circadian Rhythms and Your Circadian Rhythms and Your Biological ClockBiological 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.

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.

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

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

More Personal Factors…Several physiological More Personal Factors…Several physiological functions start to deteriorate or decrease with functions start to deteriorate or decrease with

advancing ageadvancing 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.

Effects of Physical ConditioningEffects 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.

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.

Personality-Related DifferencesPersonality-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.

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

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.

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-eveningness 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.

The second circadian type entails The second circadian type entails the quantification of individual the quantification of individual differences along the dimension of differences along the dimension of introversion-extroversion.introversion-extroversion.

Introverts generally tend to be quiet, Introverts generally tend to be quiet, thoughtful, non-impulsive individuals thoughtful, non-impulsive individuals and are often loner.and are often loner.

Extroverts, on the other hand, are Extroverts, on the other hand, are usually carefree, compulsive and highly usually carefree, compulsive and highly sociable with an almost constant need sociable with an almost constant need for stimulation and challenge. for stimulation and challenge.

ENVIRONMENTAL FACTORSENVIRONMENTAL FACTORS

Shift SystemsShift Systems

A review of the available literature on A review of the available literature on shift scheduling indicates that while shift scheduling indicates that while some shift designs are preferential to some shift designs are preferential to others, no ideal shift system is agreed others, no ideal shift system is agreed upon.upon.

There is likely no "best" shift system as There is likely no "best" shift system as any design is a tradeoff between any design is a tradeoff between accommodating the worker's social accommodating the worker's social needs and health and safety aspects. needs and health and safety aspects.

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

ROTATIONAL SHIFTWORKROTATIONAL SHIFTWORK

Shifts rotate or change according to Shifts rotate or change according to a set schedule.a set schedule.

Shifts can be continuous (24/7) or Shifts can be continuous (24/7) or semi-continuous (2-3 shifts/day semi-continuous (2-3 shifts/day without weekends).without weekends).

Workers take turns working all of the Workers take turns working all of the shifts in the system.shifts in the system.

RAPIDLY ROTATING SYSTEMSRAPIDLY ROTATING SYSTEMS

Switches once or twice during a Switches once or twice during a week.week.

Found to cause the least disturbance Found to cause the least disturbance to the endogenous body clock to the endogenous body clock

WEEKLY/MONTHLY ROTATING SYSTEMSWEEKLY/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).

PERMANENT NIGHT SHIFT SYSTEMPERMANENT 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.

Notes on Scheduling:Notes on Scheduling:

An early morning start (before 7:00am) for the morning shift should be avoided.

Shifts should rotate forwardDay → Evening → Night

The schedule should be simple and predictable – people want to plan their lives!

One further variable to consider in terms of the One further variable to consider in terms of the design of shift systems is that of the length of the design of shift systems is that of the length of the shift.shift.

Some suggest a shift should not exceed Some suggest a shift should not exceed 8 hours (except where the work is low in physical and mental (except where the work is low in physical and mental demands) while others recommended that demands) while others recommended that extended work periods of 9 to 12 hours may be acceptable.

Extended workdays can be problematic:Extended workdays can be problematic: FatigueFatigue Covering absenteeismCovering absenteeism Limitation of environmental exposure (toxics, heat, Limitation of environmental exposure (toxics, heat,

cold)cold) Increased error rates and accident ratesIncreased error rates and accident rates

Extended WorkdaysExtended Workdays

Fatigue symptomsFatigue symptoms

SleepinessSleepiness IrritabilityIrritability Reduced alertness, concentration and Reduced alertness, concentration and

memorymemory Lack of motivationLack of motivation Increased susceptibility to illnessIncreased susceptibility to illness DepressionDepression HeadachesHeadaches GiddinessGiddiness Loss of appetite and digestive problemsLoss of appetite and digestive problems

Extended Workday Pros/ConsExtended Workday Pros/Cons

Pros:Pros: More days off & more

consecutive days off More family & leisure

time Improved morale Increased job

satisfaction Reduced absenteeism Reduced time of

commuting

Cons: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)

Social FactorsSocial Factors

Married versus SingleMarried versus Single• Pressure on MarriagePressure on Marriage• Research shows more stress for single people – Research shows more stress for single people –

likely because no time to meet new people.likely because no time to meet new people. Less involved in children’s livesLess involved in children’s lives Miss important or fun occasionsMiss important or fun occasions Difficult to participant in sports, clubs, etc.Difficult to participant in sports, clubs, etc. Difficult to make appointments (i.e. Difficult to make appointments (i.e.

dentist, doctors, massages, parent-teacher dentist, doctors, massages, parent-teacher meetings, kids’ concerts, bank, etc.meetings, kids’ concerts, bank, etc.

Shiftwork & Extended Workdays are Shiftwork & Extended Workdays are more difficult for some people than more difficult for some people than others. Some people actually prefer others. Some people actually prefer permanent nightshifts or 12-hour permanent nightshifts or 12-hour shifts.shifts.

Difficult for:Difficult for:• People on medications that have to be People on medications that have to be

taken at a certain time and with food or taken at a certain time and with food or diabetics.diabetics.

• People with health problemsPeople with health problems• People with a lot of home-life People with a lot of home-life

responsibilityresponsibility

Good Practice Guidelines for Shift Good Practice Guidelines for Shift DesignDesign

Talk to employees to see shift preferences. Talk to employees to see shift preferences. Consider time at which shift starts/ends.Consider time at which shift starts/ends. Provide time off during socially advantages times.Provide time off during socially advantages times. Let employees know schedules well in advance.Let employees know schedules well in advance. Allow some flexibility for staff to switch shifts but Allow some flexibility for staff to switch shifts but

make sure people aren’t double-shifting.make sure people aren’t double-shifting. Provide same facilities & support for all shifts.Provide same facilities & support for all shifts. Educate employees on how to cope with shiftwork.Educate employees on how to cope with shiftwork. Consider exposure limits, breaks required, etc.Consider exposure limits, breaks required, etc. Consider different lengths for shifts.Consider different lengths for shifts. Keep schedule regular and predictable.Keep schedule regular and predictable. Keep long shifts and overtime to a minimum.Keep long shifts and overtime to a minimum. Plan for some weekends or holidays off.Plan for some weekends or holidays off.

Good Practice Guidelines for the Good Practice Guidelines for the Work EnvironmentWork Environment

Adequate lighting & proper heatingAdequate lighting & proper heating Same facilities available for each shiftSame facilities available for each shift Access to healthy mealsAccess to healthy meals Encourage interaction between employeesEncourage interaction between employees Keep in contact about employees about Keep in contact about employees about

their concernstheir concerns Encourage exerciseEncourage exercise Encourage breaks when sleepyEncourage breaks when sleepy

Hints & Tips for Shift Workers: Hints & Tips for Shift Workers: How to CopeHow to Cope

Pay attention to food/nutritionPay attention to food/nutrition ExerciseExercise Figure out how to optimize sleep timeFigure out how to optimize sleep time Get information on shiftwork health risksGet information on shiftwork health risks Have a social lifeHave a social life Seek advice from doctor if you have health conditionsSeek advice from doctor if you have health conditions Take more frequent breaks when fatiguedTake more frequent breaks when fatigued Talk to family and friends about sleep scheduleTalk to family and friends about sleep schedule Restrict or avoid caffeine, cigarettes and alcohol consumptionRestrict or avoid caffeine, cigarettes and alcohol consumption Avoid long commutes when sleepyAvoid long commutes when sleepy Use co-workers to keep you awake on the jobUse co-workers to keep you awake on the job Talk to co-workers for tips on how to copeTalk to co-workers for tips on how to cope Don’t leave the boring tasks for the end of the shift when most Don’t leave the boring tasks for the end of the shift when most

fatigued. Switch things up when you can to stay interested.fatigued. Switch things up when you can to stay interested. Try not to alter sleep schedule too much on “days off”Try not to alter sleep schedule too much on “days off”

Interesting Web Sources…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/