Chapter 7: Level 3 Controls: Assessing Symptoms of Fatigue

Learning Outcomes

On completing this chapter, you will be able to:

  • Explain the purpose of including fatigue-related symptom checklists within an FRMS.

  • Recognize symptoms of fatiguerelated impairment.

  • Describe some of the major sleep disorders.

  • Outline appropriate action to be taken by a company if an employee is thought to suffer from a sleep disorder.

Level 3 Controls: Assessing Symptoms of Fatigue

Hazard-Control Model for Fatigue Risk Management
Click to enlarge image

Hazard-Control Model for Fatigue Risk Management

Even when sufficient sleep opportunity has been provided (Level 1 controls) and employees feel they have obtained sufficient sleep (Level 2 controls), they may still show fatigue-related symptoms. Level 3 controls assess individual employees for symptoms that could lead to fatigue-related error.

Level 3 controls play two main roles:

  1. Identify employees who continue to exhibit fatigue-related symptoms, despite getting sufficient sleep.

  2. Assess the effectiveness of Level 1 and 2 controls. For example, where employees fail to report they did not get enough sleep, monitoring for fatigue-related symptoms adds an additional layer of defence.

Identifying At-Risk Individuals

Fatigue-related symptoms can be divided into three categories: physical, mental, and emotional. The table below outlines some of the major symptoms under each category. If employees experience three or more of the symptoms outlined below, they may be experiencing some level of fatigue or reduced alertness. Fatigue is not the only cause of the symptoms presented below, but when they occur together it likely indicates fatigue-related impairment.

An employee who presents three or more symptoms in a short period of time
is likely to be experiencing fatigue-related impairment.
Physical Symptoms Mental Symptoms Emotional Symptoms


Heavy eyelids


Head drooping


Difficulty concentrating on tasks

Lapses in attention

Difficulty remembering what you are doing

Failure to communicate important information

Failure to anticipate events or actions

Accidentally doing the wrong thing

Accidentally not doing the right thing

More quiet or withdrawn than normal

Lacking in energy

Lacking in motivation to do the task well

Irritable or grumpy with colleagues, family or friends

Many companies teach employees how to identify symptoms, both in themselves and others, that may indicate an increased risk of making a fatigue-related error. Raising awareness about the signs and symptoms of fatigue can be an effective strategy to reduce the number and severity of fatigue-related errors and incidents.

To further reinforce the importance of monitoring fatigue-related symptoms, employees can be provided with aids, such as a checklist to be filled out at the start of every shift, or a wallet-sized card listing the most common symptoms to watch out for.

If employees consistently exhibit fatiguerelated behaviour, potential reasons should be investigated. It may simply be that the employee has a personal problem (e.g., sickness in the family, new child or concern, or poor sleeping environment). Employees who say they get enough sleep and cannot explain their fatigue-related symptoms should undergo screening for a sleep disorder. The first step is some kind of paper-based screening, such as a questionnaire, to determine whether they are at risk. At-risk employees should then be referred to a sleep clinic.

Another way to check how fatigued employees feel is to ask them to rate their alertness at various intervals within a shift. The Karolinska Sleepiness Scale3 can be used to determine whether fatigue is a problem for an individual without determining the root cause for the lack of sleep. As shown below, the scale requires employees to select the statement that best describes them at the time. The scale can be used as an assessment of sleepiness/fatigue at any point in time: at work, while driving, on waking in the morning, etc.

Screening for Sleep Disorders
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Screening for Sleep Disorders

Karolinska Sleepiness Scale

  1. Extremely alert
  2. Very alert
  3. Alert
  4. Rather alert
  5. Neither alert nor sleepy
  6. Some signs of sleepiness
  7. Sleepy, but no effort to keep awake
  8. Sleepy, some effort to stay awake
  9. Very sleepy, great effort to keep awake, fighting sleep

Employees who report fatigue-related symptoms on a regular basis may have a sleep disorder. An example of a paperbased test to identify the severity of fatigue is the Epworth Sleepiness Scale4, which asks individuals to determine how likely they are to fall asleep or doze off during a variety of activities. Subjects are instructed to provide answers based on their usual way of life over the past several months. Even if they have not done some of these things recently, they are instructed to try and work out how they might have been affected in each situation. Employees who score above 10 are likely to have problems with their sleep patterns and should be referred to a sleep specialist.

Epworth Sleepiness Scale
Situation Chance of

0 = would never doze
1 = slight chance of dozing
2 = moderate chance of dozing
3 = high chance of dozing

A score of less than 8 indicates normal sleep function

8-10 = mild sleepiness
11-15 = moderate sleepiness
16-20 = severe sleepiness
21-24 = excessive sleepiness

Sitting & Reading  
Watching TV  
Sitting inactive in a public place
(e.g. theatre)
As a passenger for an hour without a break  
Lying down to rest in the afternoon  
Sitting & talking to someone  
Sitting quietly after lunch without alcohol  
In a car, while stopping for a few minutes in traffic  
Total Score  

There are several types of sleep disorder that affect daytime functioning. A polysomnographic (PSG) recording of sleep at a sleep clinic can help determine the root cause of the fatigue. This process includes analysis of electrical brain activity, eye movements, and breathing throughout the sleep period.

Some of the major sleep disorders are outlined below. Any of these conditions can result in bouts of daytime sleepiness, reduced alertness, and overall lack of energy. Physicians trained in sleep medicine are best equipped to diagnose and treat these problems. A primary care physician should be able to refer clients to a sleep specialist for evaluation, diagnosis, and treatment.


Insomnia is a disorder characterized by difficulty falling or staying asleep, and/or frequent awakenings during the sleep period. There are a number of factors that may contribute to insomnia, including (but not limited to):

  • short-term or long-term stress such as trauma or chronic illness

  • psychological condition

  • the presence of another sleep disorder

  • poor sleep hygiene (i.e., not following good sleep practices)

Sleep Apnea

Sleep apnea causes a person to stop breathing for brief periods several times during sleep. This condition can affect all common in men and is particularly prevalent in obese people. The disorder exists in two forms:

  1. Obstructive sleep apnea is the most common and occurs when the airways close while a person is sleeping, blocking the flow of air and preventing adequate oxygen flow to the body. This awakens the sleeper many times a night, disrupting the normal structure of sleep, and resulting in sleepiness and reduced alertness at work.

  2. Central sleep apnea is less common and occurs when muscles required for breathing do not receive a signal from the brain, causing the sleeper to stop breathing.

Untreated sleep apnea can lead to cardiovascular tissue damage caused by reduced oxygen levels and can lead to excessive sleepiness when a person is awake. Excessive sleepiness can lead to accidents and injuries, particularly while driving or operating safety sensitive systems.

Restless Leg Syndrome and Periodic Limb Movement

Restless Leg Syndrome and Periodic Limb Movement are sleep disorders that are characterized by involuntary limb movements, usually a leg, many times over the course of a night. Movements can occur as often as every 10 seconds, disrupting sleep and leaving the individual suffering significant daytime sleepiness.


Narcolepsy is characterized by a sudden irresistible desire to go to sleep that lasts from minutes to hours at a time. It is associated with cataplexy (the sudden loss of tone in one or more muscle groups) and with vivid auditory or visual hallucinations when falling asleep. This is understood to be a malfunction of the mechanism that controls rapid eye movement (dreaming) sleep. Excessive daytime sleepiness and the tendency to fall asleep uncontrollably may render individuals unable to carry on working, and may put themselves or others at risk.

Sleep Clinics

An employee suspected of having a sleep disorder should be encouraged to consult a sleep specialist. Usually, the employee will need a doctor’s referral. The Canadian Sleep Society offers a list of sleep medicine clinics in Canada:

Assessing the effectiveness of other levels of control

In Chapter 6, we discussed Level 2 controls (i.e., obtaining sufficient sleep) as they related to Level 1 controls (providing sufficient sleep opportunity). We established that assessing the actual amount of sleep obtained provides a measure of how effective the Level 1 controls are in providing sufficient sleep opportunity. In the same way, Level 3 controls offer a way to measure the effectiveness of the two previous levels of control.

In Chapter 2 we discussed organizational and individual responsibilities in managing fatigue. The organizational responsibilities included two subcomponents:

  1. Fatigue related to hours of work

  2. Fatigue related to workload and environment

Fatigue related to hours of work should be managed by providing employees with sufficient sleep opportunity between shifts (Level 1 controls). Assessing actual hours of sleep (Level 2 controls) lets you double-check that sleep opportunity is sufficient.

Some employees may find it difficult to quantify how much sleep they actually get, particularly if sleep is disturbed. Some may also choose to be dishonest about the actual amount of sleep they obtain and fail to report when they may be at risk of fatigue-related error. Level 3 controls (monitoring for fatigue-related behaviours or symptoms) provide a further check to ensure that sufficient sleep opportunity has been provided (Level 1) and that employees are obtaining sufficient sleep (Level 2).

The tasks involved in a job can significantly affect fatigue. Some tasks are more fatiguing than others. As shown in the figure below, this can occur at both ends of the spectrum – mundane tasks can be just as fatiguing as highly complex, demanding tasks.

Similarly, some aspects of the work environment can affect fatigue more than others. For example, fatigue-related behaviour tends to be more prevalent in workplaces that have high levels of vibration or noise, or high temperatures. The level of lighting (lux) in a workplace can also affect fatigue. Since these factors would not be identified in the Level 1 or 2 controls, watching for specific fatiguerelated symptoms in the workplace provides an additional level of control to further enhance the safety management system.

Relationship between Task Complexity and Fatigue
Relationship between Task Complexity and Fatigue

3 Åkersted, T., & Gillberg, M. (1990). Subjective and objective sleepiness in the active individual. International Journal of Neuroscience, 52 (1-2), 29-37.

4 Johns, M. W. (1991). A new method for measuring daytime sleepiness: the Epworth sleepiness scale. Sleep, 14 (6), 540-545.

- Describe the role of Level 3 controls in an FRMS.
- List seven signs or symptoms of fatigue.
- Describe two of the major sleep disorders.

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