Some of the world’s biggest disasters, including Chernobyl and the Exxon Valdez oil spill, have been a result of human error attributable in some way to fatigue. In this article we explore the factors that influence fatigue and their effect on human error and accidents.
What is fatigue?
Fatigue is generally considered to be a decline in mental or physical performance resulting from one or a combination of sleep loss, disruption of internal body clock, high workload and prolonged exertion.
It can be affected by social factors such as workload and sleep patterns, or individual factors such as personality, age, diet and fitness. It can also be caused by a wide range of illnesses and diseases. In such cases, a person usually finds they need more rest and sleep than they are getting. This may affect their performance at work. Fatigue is a common symptom of depression.
Shift work, work at night, or working extended hours are the most common causes of work-related fatigue, and can lead to adverse effects on health, particularly for night workers.
Humans have built-in body clocks to regulate all-important body functions. These clocks tell us when to be active and when to rest. They also govern other physiological functions such as body temperature, hormones, digestion and blood pressure. The 24-hour biological rhythms from these clocks do not disappear even if there are changes to the environment (lighting, noise, temperature) and routine (no sleep, changes of meal routine). Even if you are working nights, your body clock will still reduce your body temperature in the early hours of the morning, lower your blood pressure and slow down your digestion. This will make you sleepier and less alert.
Night workers trying to sleep during the daytime will find it harder to get to sleep because their body clock is telling them they should be awake. The reduced quality and quantity of this sleep will lead to more fatigue as a “sleep debt” builds up.
The effects of fatigue
Some people experience severe fatigue at work. This can lead to poor performance on tasks that require attention, decision-making or high levels of skill. For safety-critical work, the effects of fatigue can give rise to increased risks.
Fatigue can affect people differently but could lead to the following health problems:
- Difficulty in falling asleep, and staying asleep
- Difficulty in staying alert and awake at work
- Reduced quality and quantity of sleep
- Gastrointestinal disorders.
All too often, fatigue is seen as a familiar and acceptable part of everyday life. Working long hours may even be accepted in the culture of a workplace as “the thing to do”.
Danger in the early hours
In general, the early hours of the morning, e.g. between 2am and 5am present the highest risk for fatigue-related accidents. Sleep loss can lead to lowered levels of alertness. Cumulative sleep loss over a number of days can result in a “sleep debt” with much reduced levels of productivity and attention. Such sleep loss results from working not only night shifts but also morning shifts with very early start times, and from “on call” situations where it may be difficult to plan when to sleep. The daily rest between shifts needs to be adequate to enable shift workers to return to work fully rested. An adult typically needs seven to eight hours of sleep each night.
Human performance tends to deteriorate significantly when people have been at work for more than 12 hours. For people who have been working for less than 12 hours, the evidence is less clear, and the extent to which fatigue occurs may depend on aspects such as the adequacy of rest breaks, the nature of the work, and the working environment. The effects of fatigue tend to be more marked if the task is monotonous or repetitive.
Employees should be able to recognise the signs of fatigue themselves. When suffering from fatigue, they are less able to recognise the risks and more likely to make poor decisions.
Effects on safety
It is important for organisations to manage fatigue for their employees, because it causes decreased performance in individuals. This can lead to ill health, reduced productivity, accidents and errors.
Fatigue influences individuals in different ways and can lead to a combination of the following aspects of decreased mental and physical performance:
- Reduced attention and awareness
- Reduced ability to process information
- Slower reactions and reduced co-ordination
- Underestimating risk
- Poor decision making
- Increased aggressive behaviour and mood swings
- Lapses in memory.
Up until the 1960s, modelling human and organisational factors in accidents had been rather unsophisticated. These models had not differentiated human elements relevant to accidents beyond rough subdivisions such as skills, personality factors, motivational factors and fatigue. Accidents were seen as undifferentiated problems for which undifferentiated solutions were sought.
An individual’s perception of a given situation is based on two sources of data:
- Information from the senses
- Expected information.
Physical defects of sight or hearing can affect the information presented to us, while fatigue, stress or drugs can alter the expected information.
Managing fatigue in the workplace
High-risk industries have recognised the importance of managing risks from fatigue in the workplace, but it is important for all industries to consider the effects of fatigue on employees for production and safety reasons.
The best practice management approach, which will go beyond what is required by health and safety legislation, is through a multi-component approach that includes:
- Careful planning of shift rotas
- Reviewing maximum hours of duty and time for recovery
- Education on sleep routines, nutrition, effects on family and social life, exercise
- Environmental design changes, especially those aspects that can improve alertness, such as temperature, lighting and comfort levels
- Reducing the number of safety-critical tasks planned for the night shift
- Rotating jobs to reduce levels of boredom
- Providing medical advice for employees, especially for those with existing medical conditions.
These simple steps can significantly reduce human error in the workplace and increase employee concentration, improving both safety and well-being.