Shift work contributes significantly to the UK economy but
it can lead to fatigue and poor safety
performance.Julie Bell looks at
how best to manage shift schedules to reduce fatigue risk.
Research published in Occupational & Environmental
Medicine in November 2014, which looked at the chronic effects
of shift work on cognition, showed that shift work is associated
with impaired cognitive function.
This association was strongest for those who had been employed
in shift work for more than ten years and was equivalent to an
additional 6.5 years of age-related decline. HSE states that over
the last 25 years, there has been a gradual increase in the number
of people who undertake shift work in the UK, with around 5-20 per
cent of the working population now engaged in shift work that
involves night work. This equates to 3-6 million workers.
The Health and Safety Laboratory (HSL) works with HSE to draw
together current research and the results of accident
investigations, to provide advice on the risk from fatigue on
health and safety performance as a result of shift working. Shift
work, particularly that which requires people to work at night
(around 11pm until around 4am), interferes with the human's
biological need for night time sleep and can result in both acute
(within shift) and chronic (over a longer period) fatigue.
This can have a negative impact on cognitive functions such as
vigilance, decision-making and situational awareness, with the
potential to contribute to poor safety performance and ultimately
incidents, such as the Buncefield explosion in 2005. In the longer
term, shift work has been associated with health impacts such as
gastrointestinal and cardiovascular problems, along with a possible
link with breast cancer. The research by Marquié et al now
indicates a potential for a long-term cognitive impact too.
The direct causal link between shift work, fatigue, safety
performance and health consequences is yet to be established.
However, the link between fatigue and safety outcomes is very clear
in circumstances where the impact of poor performance/ human error
can be immediate, such as with drivers and road traffic
In more complex, high hazard, low-risk occupational environments
where accidents are low frequency events, the link between fatigue,
poor performance and incidents is less clear. This is because
additional layers of defence are used to protect against human
error, such as the use of automatic shut off valves in the
petrochemical industry. In these circumstances, fatigue is
acknowledged as a contributory factor to incidents.
It is clear that shift work is necessary in our society but it
will always have the potential to result in fatigue because of the
implicit disruption to the sleep/wake cycle. However, the fatigue
risk can be managed like any other health and safety risk and,
while fatigue is not directly measurable, it can be minimised by
well-designed and well-managed shift schedules.
Incident investigations, such as the one into the Buncefield
explosion, often reveal simple organisational factors that increase
the risk from fatigue. Typically, this means not enough staff to
work the planned shift schedule, or not enough people in some
roles, or insufficient flexibility in the schedule to cope with
work demands. A well-designed shift schedule should be informed by
taking a risk-assessment approach to managing the fatigue risk; it
will need to include good arrangements to cover absence, training,
and other demands on staff time.
Ultimately, the only way to reduce the impact of fatigue on
performance and safety is through quality rest and recovery
periods. This is further reinforced by the Marquie et al research,
which indicates that those who had been out of shift work for more
than five years showed signs that their cognitive performance had
recovered. The conclusion is that we all need a good night's
The author, Julie Bell, is a human factors technical
specialist here at the Health and Safety Laboratory.
- Jean-Claude Marquié, Philip Tucker, Simon Folkard, Catherine
Gentil and David Ansiau, 2014: http://bit.ly/1Be6SyQ