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Fatigue: the insidious risk to health and safety

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.[1]

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 accidents.

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 sleep.

The author, Julie Bell, is a human factors technical specialist here at the Health and Safety Laboratory.


  1. Jean-Claude Marquié, Philip Tucker, Simon Folkard, Catherine Gentil and David Ansiau, 2014:

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