Fatigue at Work

Dr Alan Black

Consultant in Occupational Medicine

Learning Points

• The main factors that cause fatigue

• How fatigue affects an individual

• How to avoid or reduce fatigue

• The risks associated with coping with fatigue

• How to create an affective system for managing

fatigue

• Comparing shift patterns and identification of when

risks are highest

• Good practice shift rota design

Fatigue*

“Fatigue is the decline in mental and/or physical

performance that results from prolonged

exertion, lack of quality sleep or disruption of

the internal body clock. The degree to which a

worker is prone to fatigue is also related to

workload. For example, work that requires

constant attention, is machine paced, complex

or monotonous will increase the risk of

fatigue.

“Fatigue is the decline in mental and/or physical

performance that results from prolonged exertion,

lack of quality sleep or disruption of the internal

body clock. The degree to which a worker is prone

to fatigue is also related to workload. For example,

work that requires constant attention, is machine

paced, complex or monotonous will increase the

risk of fatigue.”

Fatigue*

*Health & Safety Executive

Fatigue

• A vague and imprecise term

• A normal emotional and physiological consequence

of work

• A subjective symptom

• Distinct from weakness or excessive drowsiness

• Does not automatically denote ill health

• Can be pleasant, but usually regarded as unpleasant

tiredness, weariness or exhaustion

• Can affect mental performance

Neurasthenia*

“The simplest form of neurasthenia is that which is

often met with towards the end of a years work.

The patient is mentally and physically overdone,

work becomes an effort, there is lack of

concentration, and mere trifles are magnified out

of all proportion to their importance. Neurasthenia

may thus be so slight an affliction as to be cured

by the usual annual holiday. On the other hand, it

may develop into a serious affection shading off

into melancholia or hypochondriasis.”

*The Complete Family Doctor cira 1920

Disasters Attributed to Fatigue

• Chernobyl

• Exxon Valdez

• Challenger

• Clapham Junction

• Bhopal pesticide plant

The Physiology of Circadian Rhythms

• Few physiological parameters are constant, but

rather show a rhythm throughout 24 hours

• Body regulated by internal clock (supra-chiasmatic

nucleus -SCN), running 25 hour day

• SCN influenced by external environmental cues, esp.

light through melatonin (Zeitgebers)

• Growth hormone, melatonin, cortisol peak at night

• Cardiac output, blood pressure, core temperature

peak during the day

Adverse health affects of working shifts

• Workers who have poor tolerance of night work tend to leave

it – healthy worker effect

• Gastro-intestinal disease

– Mechanism of action unknown

– role of use of coffee, smoking, alcohol?

– Glucose metabolised less readily at night

• Cardiovascular disease

• Cancer

– Endometrial

– Non-Hodgkin’s lymphoma

– Prostate

– Breast – females working over 30 years on nights

Pregnancy and Shift Work

• No significant differences until “late”

pregnancy (last trimester)

• No automatic ban but total working hours

should not exceed 40 / week

• Should avoid prolonged standing

• Insufficient evidence to insist on worker

stopping nights

Identify at Risk workers

• young workers

• older workers

• new and expectant mothers

• workers with pre-existing health conditions

• workers taking time-dependent medication such as

insulin

• sub-contractors

• On call workers, having to work through from a full

days work

Key Risk Factors

• Workload

• Work activity

• Shift timing and duration

• Direction of rotation

• Number and length of breaks during and

between shifts

Good Practice for Shift Design (1)

• Night shifts

– Restrict number of night shifts to 4 maximum if

possible.

– Allow at least 2 days off following night shift.

– Avoid keeping workers on permanent night shifts.

Good Practice for Shift Design (2)

• Early starts

– Move early shift starts before 6am forward (e.g.

7am not 6am start).

– Limit the number of successive early starts ie

before 7am (to 4 maximum if possible)

– Shifts involving an early start should be shorter in

length to counter the impact of fatigue later in the

shift.

Good Practice for Shift Design (3)

• Shift length

– If 12-hour shifts worked then no overtime worked

in addition.

– Avoid long working hours (more than 50 hours per

week).

– If 8/10 hour shifts then no more than 4/2 hours

additional overtime to be worked.

– Restrict ‘back to backs’ with 8 hour shifts and

avoid entirely with 12 hour shifts.

Good Practice for Shift Design (4)

• Rest periods

– Allow minimum of 12 hours between shifts and

avoid ‘quick return’ of 8 hours if possible. (Rest

period between shifts should permit sufficient

time for commuting, meals and sleep.)

– Plan some weekends off, advisably at least every 3

weeks.

Good Practice for Shift Design (5)

• Rotation

– Rotate shifts quickly (e.g. every 2-3 days)

– Avoid rotating shifts every 1-2 weeks.

– Use forward rotation (morning/afternoon/night)

for preference.

Good Practice for Shift Design (6)

• Social Considerations

– Arrange start/finish times of the shift to be

convenient for public transport, social and

domestic activities.

– Consider travelling time of workforce.

– Allow some individual choice where possible to

accommodate larks/owls and family

commitments.

– Keep the timing of shifts regular and predicable

but also allow employees to have some flexibility

to choose their own work schedule.

Managing Fatigue – Key Principles (1)

• Fatigue needs to be managed

• Higher risk of accidents and injuries

• Legal duty on employer to manage risk – reliance on

Working Time Directive alone is insufficient

• Needs to be risk assessed – HSEs Fatigue Risk Index

• Consult employees

• Develop policy that sets limits on overtime, shift

swapping and working hours

Managing Fatigue – Key Principles (2)

• Implement, monitor and enforce

• Problems with shift swapping / overtime may

be due to inadequate staffing levels

• No single optimal shift pattern that suits

everyone – owls v. larks

• Sleep disturbance can lead to sleep debt

Assessment Tools

• HSE’s Fatigue and Risk Index Tool

– www.hse.gov.uk/research/rrpdf/rr446cal.xls

• The Epworth Sleepiness Scale

– Johns M W ‘A new method for measuring daytime sleepiness: The

Epworth sleepiness scale’ Sleep 1991 14 (6) 540-545

• The Standard Shiftwork Index

– A battery of questionnaires for assessing shift-related problems’ Work

and Stress 1995 9 (1), 4-30

• Swedish Occupational Fatigue Inventory

– A Perceived Quality of Fatigue during Different Occupational Tasks.

Development of a Questionnaire’ International Journal of Industrial

Ergonomics 1997 20 (2) 121-135

Questions?