Fatigue at Work Black's... · The Physiology of Circadian Rhythms • Few physiological parameters...
Transcript of Fatigue at Work Black's... · The Physiology of Circadian Rhythms • Few physiological parameters...
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?