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In occupational health and safety, there is not a single definition of fatigue.
Fatigue is often thought of as the state of feeling very tired, weary or sleepy resulting from various sources such as insufficient sleep, prolonged mental or physical work, or extended periods of stress or anxiety. Boring or repetitive tasks can intensify feelings of fatigue. Fatigue can be described as either acute or chronic.
However, fatigue can include mental, physical, or subjective states. For example, as summarized by the CSA Group’s report on workplace fatigue, these states include:
Everyone should be concerned about the impact of fatigue as it can be considered a form of impairment, making fatigue a workplace hazard. However, fatigue levels are not easily measured or quantified; therefore, it is difficult to isolate the effect of fatigue on incident and injury rates.
Workplace factors that may influence fatigue are shift rotation patterns, balanced workloads, timing of tasks and activities, availability of resources, and the workplace environment (e.g., lighting, ventilation, temperature, etc.).
However, be sure to consider other factors beyond a lack of sleep including mental fatigue, such as mental workloads, demanding mental activities or stress, long periods of anxiety, or long periods of monotonous tasks, etc.
Many studies focus on the amount of sleep required. Some research studies have shown that when workers have slept for less than 5 hours before work or when workers have been awake for more than 16 hours, their chance of making mistakes at work due to fatigue are significantly increased.
Research has shown that the number of hours awake can be similar to blood alcohol levels. One study reports the following:
Fatigue is regarded as having an impact on work performance. Government of Alberta, Labour* reports that most incidents occur when people are more likely to want sleep - between midnight and 6 am, and between 1 to 3 pm. Government of Alberta, Labour also reports that fatigue affects people differently but it can increase a worker's hazard exposure by:
*Source: Fatigue, Extended Work Hours, and Workplace Safety, February 2017. Government of Alberta, Labour
Signs and symptoms of fatigue can vary, and include:
Consequences of fatigue can include mental and physical performance,
Studies report the effects of fatigue as:
Work-related factors may include long work hours, long hours of physical or mental activity, insufficient break time between shifts, changes to jobs or shift rotations, inadequate rest, excessive stress, having multiple jobs, or a combination of these factors.
Fatigue is increased by:
Sometimes, a sleep disorder such as those disorders that may affect length or effectiveness of sleep, cause extended wakefulness, or cause disruptions to our circadian rhythms may result in fatigue. You should ask your doctor or health professional for more information. These conditions include:
Illness, medical conditions, and pharmaceutical products (including over-the-counter medications) can also affect sleep length and sleep quality.
For example, substances such as nicotine, caffeine, and alcohol can affect the quality of sleep. Caffeine can remain in the body for about 3 to 7 hours. Alcohol may shorten the time to fall asleep, but it disrupts sleep later in the night. Nicotine also can disrupt sleep and reduce total sleep time.
Fatigue can be addressed through the workplace’s safety management system, or as a separate fatigue management program. Creation of a program that addresses both workplace and personal factors may include to:
For more information, please see the following OSH Answers documents:
It varies, but on average studies say we need at least 7 to 9 hours every day. Studies have reported that most night shift workers get about 5 to 7 hours less sleep per week than the day shift. (You can accumulate a sleep "debt", but not a surplus.)
Humans follow an "internal" or "biological clock" cycle of sleep, wakefulness, and alertness. Although these circadian rhythms are influenced by external clues such as the sun setting and rising, it is the brain that sets your pattern. Most cycles are 23-25 hours long and there are natural dips or periods when you feel tired or less alert - even for those who are well-rested.
If you suspect you may have a medical condition that interferes with your sleep, go to your doctor and have any concerns investigated.
There is no one way to get a good sleep - what works for one person may not work for another. In general, suggestions include:
The Dietitians of Canada have made the following recommendations:
Establish Regular Eating Times
Our bodies need energy provided by food to be able to perform our daily activities. Having meals at regular times is important to function at our best. If you tend to skip meals or eat at irregular times, you may experience fatigue, food cravings or increased eating at the next meal. Aim to have at least three meals a day including a variety of foods as described in Canada's Food Guide.
If working night shifts, try to have your “main meal” before going to work. A heavy meal during the night may cause heartburn, gas or constipation, as well as make you feel sleepy or sluggish.
Snack Ideas for Your Work Break(s)
Having snacks in between meals is a great way to keep us nourished and give us the energy we need to complete our work shifts. At breaks, opt for healthy snacks that include combinations from a variety of foods from the four food groups. Here are some ideas:
Check your Caffeine Intake
Excessive intake of caffeine can cause insomnia, headaches, irritability and nervousness. It is recommended that foods containing caffeine should not be consumed up to 8 hours before sleeping.
Common caffeine sources include:
Snacks for sleeping well
Going to bed with an empty stomach or immediately after a heavy meal can interfere with sleep. If you get home hungry, have a snack that is low in fat and easy to digest. A light snack before going to bed helps in getting a good restful sleep. Examples include:
From: The Dietitians of Canada, 2017