OSH Answers Fact Sheets
Easy-to-read, question-and-answer fact sheets covering a wide range of workplace health and safety topics, from hazards to diseases to ergonomics to workplace promotion. MORE ABOUT >
Search all fact sheets:
What is fatigue?
Fatigue is the state of feeling very tired, weary or sleepy resulting from 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.
Acute fatigue results from short-term sleep loss or from short periods of heavy physical or mental work. The effects of acute fatigue are of short duration and usually can be reversed by sleep and relaxation.
Chronic fatigue syndrome is the constant, severe state of tiredness that is not relieved by rest. The symptoms of chronic fatigue syndrome are similar to the flu, last longer than six months and interfere with certain activities. The exact cause of this syndrome is still unknown.
Is fatigue a workplace issue?
Fatigue levels are not easily measured or quantified; therefore, it is difficult to isolate the effect of fatigue on accident and injury rates.
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. WorkSafeBC reports the following:
- 17 hours awake is equivalent to a blood alcohol content of 0.05
- 21 hours awake is equivalent to a blood alcohol content of 0.08 (legal limit in Canada)
- 24-25 hours awake is equivalent to a blood alcohol content of .10
Fatigue is regarded as having an impact on work performance. Alberta Human Resources and Employment* reports that most accidents occur when people are more likely to want sleep - between midnight and 6 am, and between 1-3 pm. And, indeed, sleep deficit has been linked to large scale events such as the Exxon Valdez oil spill and the nuclear accident at Chernobyl.
*From: Alberta Human Resources and Employment. Fatigue, Extended Work Hours, and Safety in the Workplace in Workplace Health and Safety, June 2004, Reformated August 2010
What are the signs of fatigue?
Signs and symptoms of fatigue include:
- sleepiness, including falling asleep against your will ("micro" sleeps),
- loss of appetite,
- digestive problems, and
- increased susceptibility to illness.
What are the effects of fatigue and their relationship to work?
Because fatigue cannot be "measured", it is difficult to separate the effects of long working hours or lack of sleep to any changes in accident or injury rates.
However, studies report the effects of fatigue as:
- reduced decision making ability,
- reduced ability to do complex planning,
- reduced communication skills,
- reduced productivity / performance,
- reduced attention and vigilance,
- reduced ability to handle stress on the job,
- reduced reaction time - both in speed and thought,
- loss of memory or the ability to recall details,
- failure to respond to changes in surroundings or information provided,
- unable to stay awake (e.g., falling asleep while operating machinery or driving a vehicle),
- increased tendency for risk-taking,
- increased forgetfulness,
- increased errors in judgement,
- increased sick time, absenteeism, rate of turnover,
- increased medical costs, and
- increased accident rates.
What are some causes of fatigue?
There are many, many causes of fatigue.
Work-related factors may include long work hours, long hours of physical or mental activity, insufficient break time between shifts, inadequate rest, excessive stress or a combination of these factors.
Sometimes, a sleep disorder may cause fatigue. You should ask your doctor or health professional for more information. These conditions include:
People who suffer from insomnia often complain that they cannot fall asleep, or cannot stay asleep for a full night. They may frequently wake up during the night, wake up too early, not able to fall asleep at night, or have difficultly getting back to sleep if woken. Either way, they do not feel rested. Insomnia can be both short term (in response to a stressful event or change in environment) or long term.
Most cases of sleep apnea are caused by a condition called "Obstructive Sleep Apnea". Sleep apnea is a breathing disorder in which there are brief interruptions (lasting a minimum of 10 seconds) in breathing during sleep. This condition is caused by a narrowing (or collapse) of the throat or upper airway during sleep. This narrowing restricts or prevents breathing while you are sleeping (air cannot flow into or out of your nose and mouth even though your body continues to try to breathe). With sleep apnea, there are frequent interruptions to sleep making your sleep unrestful. People often complain of early morning headaches and excessive daytime sleepiness.
Symptoms of sleep apnea include:
- chronic, loud snoring,
- gasping or choking while sleeping,
- excessive daytime sleepiness, and
- personality changes or difficulties thinking.
Restless Legs Syndrome
With restless legs syndrome, people report sensations of creeping, crawling, pulling, or tingling which cause an irresistible urge to move their legs. This phenomenon usually happens as a person is trying to fall asleep, making sleep difficult. Movements may also occur during sleep, partially waking the person (even though they might not "notice") and disrupting sleep patterns.
Narcolepsy is a rare condition associated with sudden sleep "attacks" where a person will have an uncontrollable urge to sleep many times in one day.
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 and may affect sleep. Alcohol may shorten the time to fall asleep, but it disrupts later in the night. Nicotine also can disrupt sleep and reduce total sleep time.
Other substances such as over-the-counter medications or prescriptions may also affect sleep. For example, long-acting benzodiazepines (drugs used to relieve anxiety or insomnia) may contribute to daytime sleepiness.
How much sleep do people need?
It varies, but on average studies say we need at least 7.5 to 8.5 hours everyday. Studies have reported that most night 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.
How can I get a "better" sleep?
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:
- Go to bed and get up at the same time every day.
- Exercise regularly.
- Eat at regular intervals and consume a balanced diet of fruits, vegetables, whole grains, healthy fats and protein.
- Use your bed primarily just for sleeping (e.g., do not watch television, read or do work in bed).
- If you are not sleepy, do not try to go to bed. Get up and read or do something quiet instead.
- Avoid caffeine, tobacco or alcohol - especially before bed time.
- Turn off the telephone ringer and answering machine speaker.
- Ask family members to be respectful if one person is sleeping. Family members can use headphones for the TV and radio if necessary.
- Make the room as dark and quiet as possible. Use heavy, dark curtains, blinds, or a sleeping eye mask. Soundproof the room where possible or use ear plugs.
- Most people sleep better when the room is cool. Consider using an air conditioner or fan in the summer months.
What are some tips for "good" eating habits that help encourage sleep?
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 from the four food groups of Canada's Food Guide.
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:
- crackers and cheese,
- social tea cookies and milk,
- yogurt and a small low fat muffin,
- celery sticks with peanut butter,
- baby carrots with low fat cream cheese dip,
- cut up fresh fruit mixed with plain yogurt.
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 five hours before sleeping.
Common caffeine sources include:
- iced tea,
- cola drinks,
- headache relievers.
- decaffeinated coffee or tea,
- non-cola beverages,
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:
- cereal with milk,
- fresh fruit and yogurt,
- oatmeal with raisins,
- digestive cookies and milk,
- piece of toast with a small banana,
- multigrain bagel, toasted and lightly buttered.
From: The Dietitians of Canada, 2002. (Personal communication)
What are some tips if driving?
The best advice is to not drive if you are tired. However, some tips include:
- Keep vehicle well ventilated.
- Avoid caffeine or other drugs to keep you awake (you will feel very tired when they wear off).
- Listen to the radio (especially "talk" radio).
- Eat lightly and avoid heavy fatty foods.
- Stop often (about every two hours). Take a walk and get some fresh air.
- Change drivers if you are travelling with others.
How can a workplace help keep workers "alert"?
Fatigue is increased by:
- dim lighting,
- limited visual acuity (i.e., due to weather),
- high temperatures,
- high noise,
- high comfort,
- tasks which must be sustained for long periods of time, and
- work tasks which are long, repetitive, paced, difficult, boring and monotonous.
Workplaces can help by providing environments which have good lighting, comfortable temperatures, and reasonable noise levels. Work tasks should provide a variety of interest and tasks should change throughout the shift.
If extended hours/overtime are common, remember to consider the time required to commute home, meal preparation, eating, socializing with family, etc. Workplaces may wish to consider providing:
- on-site accommodations,
- prepared meals for workers, and
- facilities where employees can take a nap before they drive home.
For more information on extended work days and shift work, please see the following OSH Answers documents:
Although every effort is made to ensure the accuracy, currency and completeness of the information, CCOHS does not guarantee, warrant, represent or undertake that the information provided is correct, accurate or current. CCOHS is not liable for any loss, claim, or demand arising directly or indirectly from any use or reliance upon the information.