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.
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:
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
Signs and symptoms of fatigue include:
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:
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 breath). 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:
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.
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.
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:
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.
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:
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:
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, 2002. (Personal communication)
The best advice is to not drive if you are tired. However, some tips include:
Fatigue is increased by:
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:
For more information on extended work days and shift work, please see the following OSH Answers documents:
Document last updated on February 17, 2012