What is fatigue?

Fatigue is generally considered to be a decline in mental and/or physical performance that results from prolonged exertion, sleep loss and/or disruption of the internal clock. Here, we are more concerned with mental fatigue than physical fatigue – especially the impact that mental fatigue can have on human reliability.

There’s no point in having a competent workforce if they are too tired to work safely!
Fatigue needs to be actively managed, just like any other hazard.

Arrangements for managing the risks from fatigue should be documented and incorporated into the safety management system. 

This topic is related to staffing levels – if staff are regularly working high levels of overtime then there may be insufficient resources.

What causes fatigue?

The current economic climate and expectations mean many people now work longer hours than a couple of decades ago. Trying to balance our work with our family, social and personal commitments means that sometimes we don’t get as much sleep as we need. Between seven hours and seven and a half hours sleep is generally recognised as an average and normal need. If you get less than this each night you will build up a ‘sleep debt’, which can only be rectified by several good nights’ sleep.

However, not all fatigue-inducing factors are under the control of individuals. Millions of people across the world work a variety of shift patterns, including those employed in the oil, gas, chemical, mining, nuclear and utility industries, defence, emergency services, manufacturing and healthcare. The design of shift work patterns and working hours arrangements significantly impact on fatigue in the workplace. Poorly-designed working time arrangements and a lack of rest and recovery time can result in accidents, injuries, ill health and reduced productivity.

Some of the main causes of fatigue are:

  • working when you would normally be asleep;
  • sleeping when you would normally be awake;
  • getting less than normal sleep;
  • getting poor sleep;
  • working very long hours;
  • having no time to rest and recover from work;
  • workload (workers are more easily fatigued if their work is machine-paced, complex or monotonous);
  • alcohol (for example, alcohol consumed in the afternoon may be twice as potent in terms of producing sleepiness as the same amount taken in the evening);
  • prescribed or over-the-counter medication may cause sleepiness as a side effect, and
  • suffering medical sleep problems.

These factors often prevent adequate rest, leading to increased tiredness.

What are the consequences of fatigue in the workplace?

Fatigue impacts on many of the abilities of individuals that organisations rely on to ensure safety to workers, their colleagues and the public. Fatigue is a strong Performance Influencing Factor, and can result in:

  • slower reactions;
  • reduced ability to process information;
  • impaired ability to make effective judgments;
  • memory lapses;
  • absent-mindedness;
  • decreased awareness;
  • impaired reactions to changes in a situation;
  • lack of attention;
  • reduced self-monitoring of performance;
  • underestimation of risk;
  • reduced coordination, and
  • reduced communication.

Recent research has compared fatigue with blood alcohol level. For example, if you haven’t slept for 17-18 hours, your performance on tasks will be affected as if you had a blood alcohol level of 0.05% (the legal limit for driving in some countries). Not sleeping for 24 hours or more compares with a blood alcohol level of 0.1%.

The link between fatigue and work-related accidents

In 2009, a railway maintenance worker in Western Australia was killed when struck by a moving train. The deceased was working his first nightshift of a fly-in fly-out roster and, including travel, flight and work arrangements, potentially had been awake for nineteen hours before the accident.

The UK HSE states that:

“It is important not to underestimate the risks of fatigue. For example, the incidence of accidents and injuries has been found to be higher on night shifts, after a succession of shifts, when shifts are long and when there are inadequate breaks”. 

Fatigue is often a cause of accidents at work, in all industries.  It is often a root cause of major accidents for example, see Herald of Free Enterprise, Buncefield, Chernobyl, Texas City, Clapham Junction, Challenger and Exxon Valdez. Your arrangements for the investigation of accidents and ill-health should consider fatigue as a contributory factor.

Fatigue and road traffic accidents

Fatigue has also been implicated in 20% of accidents on major roads and research indicates that around 30 per cent of fatal crashes can be attributed to driver fatigue. Not sleeping for 17-18 hours doubles your risk of having a crash. Not sleeping for over 24 hours and your crash-risk increases tenfold. Shift workers who switch from day to night shifts are up to six times more likely to be involved in a ‘fatigue-related’ road crash than other workers. Government agencies around the world agree that the only cure for fatigue is to stop, take a complete break from driving and sleep.

Accidents caused by fatigue tend to have more severe outcomes because there is little or no braking, and fatigued drivers are less likely to take avoidance action.

Are you getting enough?

The quality of our sleep is important. If sleep is disturbed, for example due to on-call working or a noisy-environment (particularly relevant for night workers), then a ‘sleep debt’ can result, making us more vulnerable to fatigue. Clearly, the amount and quality of sleep that we receive is a key factor. It is thought that the brain uses the time that we are sleeping to eliminate waste products from our brain cells. This video from the TED Talks series explains:

It’s about sleep!

In a widely-cited article on managing fatigue, subtitled “It’s about sleep” (2005), Drew Dawson and Kirsty McCulloch describe two aspects as being key to managing fatigue:

  1. a roster or schedule provides, on average, an adequate opportunity to obtain sufficient sleep and
  2. an individual actually obtaining sufficient sleep.

A model proposed in this paper to assist in determining whether an individual is likely to be fatigued considers three aspects: the amount of prior sleep in the past 24 and 48 hours, along with the time awake (from wake-up until the end of the working shift).

The authors proposed:

“a shift away from prescriptive HOS (Hours Of Service) approaches to one in which fatigue is no longer managed as an industrial or labor relations issue but rather, as part of an organization’s overall SMS (Safety Management System)” (p.378).

Fatigue warning signs

As individuals become more fatigued they become increasingly less able to recognise that their performance is deteriorating. Therefore, look-out for the warning signs in yourself and colleagues, which include:

  • Feeling you have lost time;
  • Feeling dazed;
  • Day dreaming;
  • Loss of concentration (e.g. forgetting what you were doing);
  • Poor coordination;
  • Easily distracted;
  • Excessive blinking;
  • Heavy or droopy eyelids;
  • Blurred, dimmed vision;
  • Yawning;
  • Squinting;
  • Head nodding and microsleeps;
  • Errors on tasks, and
  • Changes in mood (e.g. being irritable or ‘grumpy’).

If you experience several of these symptoms (or observe them in colleagues), take action to manage the risks; which may include postponing high-risk activities, moving the individual to low-risk activities, or breaks from work to enable rest. If this happens on several occasions, then the organisation may need to consider working hours arrangements, the individual should review their sleeping arrangements, and it may be necessary to investigate the possibility of sleep disorders.

Can fatigue make you ill?

There is evidence that heart disease and rates of some cancers are increased in individuals who perform shift work. For example, the International Agency for Research on Cancer (IARC, 2010) concluded that shift work which involves circadian disruption is “probably” carcinogenic to humans.

However, it should be noted that it may not be the shift work itself which is responsible for increased risk to these diseases, but more likely due to poor coping behaviours. Recent research suggests that individuals who are sleep-deprived experience a rise in blood glucose levels, snack more frequently and opt for less-healthy food options with increased risk of a variety of health issues. Shift-workers should be provided with appropriate education and support.

The difficulties that shift workers face in maintaining social relationships and activities can also influence the health of individuals (for example, by weakening their social and support networks).

Checklist for organisations

Many countries have set working time limits (e.g. the European Working Time Directive, implemented in the UK as the Working Time Regulations) – however, it is likely that these will not in themselves manage the risks of fatigue.

As a minimum, identify who could be affected by fatigue when carrying out critical work; set appropriate standards and good practice for working hours and working patterns, and ensure that staff adhere to these standards. There should be a system in place to identify when these standards have not or will not be met. The limits that have been set should only be exceeded in exceptional cases – and with prior approval following risk assessment.

These arrangements should be reviewed and assessed when there have been changes to the job or organisation; when fatigue has been identified as a causal factor in an investigation; when standards and limits have been exceeded on a regular basis; or when there is a significant incidence of safety critical workers being declared unfit due to fatigue.

Provide all workers under your supervision, management or control with information on the risks to health and safety due to fatigue and on your arrangements for managing fatigue.

Designing shift patterns

There is a large body of research that can inform shift design, but there are some key principles to follow. Design working patterns so that they (i) minimise the build-up of fatigue by restricting the number of consecutive night or early-morning shifts, (ii) allow fatigue to dissipate by ensuring adequate rest between shifts and blocks of shifts, and (iii) minimise sleep disturbance.

The working arrangements should take into account foreseeable causes of fatigue including job design, workload, overtime, on-call working, travel time, planned maintenance, training courses etc.

There is no single working pattern that can be recommended as ideal; therefore, organisations have to design a shift schedule that is appropriate for the nature of their work.

I’ve often found that the workforce prefer certain shift patterns – and these may not be the most effective arrangements in preventing fatigue. For example, workers may prefer to work more consecutive shifts in order to take a block of days off afterwards, but this will increase the risk of higher levels of fatigue from more shifts worked. Although the workforce should be consulted on their working hours and shift patterns, most countries have imposed a legal duty on organisations to manage the risks and this should be above the preference of individuals.

What is an FRMS or a FRMP?

An FRMS is a Fatigue Risk Management System (sometimes called a FRMP, Fatigue Risk Management Plan). It considers much more than prescriptive working time limits, and so the establishment and implementation of this is a positive step towards reducing and managing the risks of fatigue. The Energy Institute defines such a risk management system as:

“a risk-based plan or system of controls that identifies, monitors and manages fatigue risk, with the aim of ensuring that, so far as reasonably practicable, employees are performing with an adequate level of alertness (2014).

In effect, fatigue should be managed using the principles of a safety management system (SMS) – just like any other safety hazard. A useful summary of the development and implementation of an effective fatigue management is provided by the New South Wales Government (NSW, Australia, 2009):

  1. making a firm policy commitment to effective fatigue management
  2. early and on‐going consultation
  3. establishment of roles and responsibilities
  4. risk identification, assessment, control and evaluation
  5. documentation of the plan
  6. implementation of the plan
  7. development and implementation of assessment and monitoring procedures, and
  8. regular review and resultant modification of the plan.

More information on fatigue

Fatigue and shift work Extract from HSE publication Reducing error and influencing behaviour (HSG48, ISBN 978 0 7176 2452 2, Second edition, published 1999). Contains a good summary of key fatigue issues.

Managing fatigue risks. Extract from HSE Inspectors Human Factors Toolkit. This 6-page guide introduces the topic, provides some good practice on shift roster design and contains questions for assessing an organisation’s management of fatigue.

Managing shift work – Health and safety guidance HSG 256 (HSE, 2006). Aims to improve the understanding of shift work and its impact on health and safety. The guidance (i) provides advice on risk assessment, design of shift-work schedules and the shift-work environment; (ii) suggests measures to reduce the negative impact of shift work; and (iii) aims to reduce tiredness, poor performance and accidents by enabling employers to control, manage and monitor the risks of shift work.

Fatigue management – A worker’s guide, Safe Work Australia (2013). A helpful, 2-page briefing note that outlines what fatigue is, why it’s an issue in the workplace, and outlines the role that workers play in  reducing the risk of being involved in a work incident caused by fatigue.

Tips for avoiding fatigue, Australian Civil Aviation Safety Authority (CASA). One-page information sheet that presents 8 tips relating to factors such as sleep, diet and exercise.

Fatigue Risk Management Chart, New South Wales Government (NSW, Australia). A one-page Chart based on Appendix 2 of the joint Worksafe Victoria/NSW Workcover Report ‘Fatigue prevention in the workplace’, 2008. This Chart outlines the key hazards, supports assessment of risk and provides options for risk control.

Development and implementation of a Fatigue Management Plan for the NSW mining and extractives industry (2009). New South Wales Government (NSW, Australia). A practical guide originally written for the mining industry, but is actually a useful guide to developing and implementing a fatigue management plan for any industry.

Guidance for managing shiftwork and fatigue offshore, HSE Information Sheet 7 (2008).  Provides advice on good practice approaches specifically in relation to shift working in the offshore oil and gas industry.

Policy on working hours offshore, HSE Information Sheet 8 (2008). Contains general principles for a working hours policy for offshore facilities, along with key issues to consider.

Managing rail staff fatigue, Office of Rail Regulation (2012). This guidance gives advice on good practice in managing fatigue associated with work in the rail industry. It builds on the more general guidance applicable to all industries in HSE’s guidance booklet HSG256 above. Although this guidance is specific to the rail industry (particularly the legal duties), all organisations managing safety-critical work will find this extremely useful.

Assessing risks from operator fatigue, published by IPIECA and IOGP (2014).  This guidance document for the oil and gas industry describes a structured approach to implementing a fatigue risk assessment (FRA). It offers a standardized method for documenting and reporting an assessed level of fatigue risk.

The development of a fatigue /risk index for shiftworkers, Research Report RR446, HSE (2006). This report describes the work carried out to revise and update a Fatigue Index, which can be used to assess the risks from fatigue associated with rotating shift patterns. The Fatigue Risk Calculator is available as an Excel spreadsheet. Prior to using this calculator, please review the User guidance.

Managing fatigue – It’s about sleep. Drew Dawson and Kirsty McCulloch (2005). Sleep Medicine Reviews (2005) 9, 365–380. Freely available from researchgate.net. Key article that proposed a shift from prescriptive Hours of Service limitations, toward a broader Safety Management System (SMS) approach.

Fatigue Prevention Guidelines for the Refining and Petrochemical Industries, RP 755. (American Petroleum Institute, API, 2019). Employers should note that the ‘hours of service guidelines’ or limits outlined in API RP 755  are intended to act as triggers for further risk assessment – and not as working time limits. Consistently working to the limits is not sustainable and may lead to chronic sleep debt. This would be considered unacceptable in certain countries (such as the UK) where rapid rotation of shifts and shorter weekly hours are considered good practice.

Up ↑