Fatigue definition and facts
- Fatigue (either physical, mental or both) is a symptom that may be difficult for the patient to describe and words like lethargic, exhausted and tired may be used.
- Taking a careful and complete history is the key to help making the underlying diagnosis of the cause for the symptom of fatigue. However, in about a third of patients the cause is not found and the diagnosis is not known.
- There are numerous causes of fatigue symptoms. Examples of some treatable causes of fatigue include anemia, diabetes,thyroid disease, heart disease, COPD and sleep disorders (Table).
- Long lasting complaints of fatigue do not equate to chronic fatigue syndrome. Specific criteria as set by the CDC need to be met to make that particular diagnosis.
What is fatigue? What does it feel like?
Fatigue can be described as the lack of energy and motivation (both physical and mental). This is different than drowsiness, a term that describes the need to sleep. Often a person complains of feeling tired and it is up to the health care professional to distinguish between fatigue and drowsiness, though both can occur at the same time. Aside from drowsiness, other symptoms can be confused with fatigue including shortness of breath with activity and muscle weakness. Again, all these symptoms can occur at the same time. Also, fatigue can be a normal response to physical and mental activity; in most normal individuals it is quickly relieved (usually in hours to about a day, depending on the intensity of the activity) by reducing the activity.
Fatigue is a very common complaint and it is important to remember that it is a symptom and not a disease. Many illnesses can result in the complaint of fatigue and they can be physical, psychological, or a combination of the two.
Often, the symptom of fatigue has a gradual onset and the person may not be aware of how much energy they have lost until they try to compare their ability to complete tasks from one time frame to another. They may presume that their fatigue is due to aging and ignore the symptom. This may lead to a delay in seeking care.
While it is true that depression and other psychiatric issues may be the reason for fatigue, it is reasonable to make certain that there is not an underlying physical illness that is the root cause.
Individuals with fatigue may have three primary complaints; however, it can vary in each person.
- There may be lack of motivation or the ability to begin an activity;
- the person tires easily once the activity has begun; and
- the person has mental fatigue or difficulty with concentration and memory to start or complete an activity.
While fatigue can last for a prolonged period of time, the presence of chronic fatigue is different than chronic fatigue syndrome, which has specific set of two criteria set for by the Centers for Disease Control and Prevention as follows:
- Have severe chronic fatigue for at least six months or longer with other known medical conditions (whose manifestation includes fatigue) excluded by clinical diagnosis; and
- Concurrently have four or more of the following symptoms:
- post-exertional malaise
- impaired memory or concentration
- unrefreshing sleep
- muscle pain
- multi-joint pain without redness or swelling
- tender cervical or axillary lymph nodes
- sore throat
Other words that a person might use to describe fatigue may include:
- lack of energy,
- worn out,
- malaise, or
- feeling run down.
What causes fatigue?
There are numerous potential causes of fatigue as a major complaint. They range from those that cause poor blood supply to the body's tissues to illnesses that affect metabolism, from infections and inflammatory diseases to those that cause sleep disturbances. Fatigue is a common side effect of many medications. While numerous patients with psychological conditions often complain of fatigue (physical and mental), there are also a group of patients where the cause of fatigue is never diagnosed.
The following table summarizes some common causes of fatigue but is not meant to be comprehensive:
|Common Causes of Fatigue|
|anemia; hypothyroidism; diabetes; electrolyte abnormalities; kidney disease; liver disease; Cushing's disease|
|Infectious||infectious mononucleosis; hepatitis; tuberculosis; cytomegalovirus; HIV infection; influenza (flu); malaria and many other infectious diseases|
|Cardiac (heart) and Pulmonary (lungs)||congestive heart failure; coronary artery disease; valvular heart disease; COPD; asthma; arrythmias; pneumonia|
|Medications||antidepressants; anti-anxiety medications; sedative medications; medication and drug withdrawal; antihistamines; steroids; some blood pressure medications; some antidepressants|
|Psychiatric (Mental Health)||depression; anxiety; drug abuse; alcohol abuse; Eating disorders (for example; bulimia; anorexia); grief and bereavement|
|Sleep Problems||sleep apnea; reflux esophagitis; insomnia; narcolepsy; shift work or work shift changes; pregnancy; Extra night hours at "work"|
|Vitamin Deficiencies||vitamin B12 deficiency, vitamin D deficiency, folic acid deficiency, iron deficiency|
|Other||cancer; rheumatology illnesses such as rheumatoid arthritis and systemic lupus; fibromyalgia; chronic fatigue syndrome; normal muscle exertion; obesity; chemotherapy and radiation therapy|
What are the signs and symptoms of fatigue?
Fatigue is a symptom of an underlying disease and is described in many ways from feeling weak to being constantly tired or lacking energy.
There may be other associated symptoms depending upon the underlying cause.
- Individuals with heart disease, lung disease, or anemia may complain of associated shortness of breath or tiring easily with minimal activity.
- Persons with diabetes may complain of polyuria (excess urination), polydypsia (excess thirst), or change of vision.
- Those who have hypothyroidism may also have symptoms of feeling cold, dry skin and brittle hair.
It is important that the health care professional consider the complaint of fatigue in the context of the whole patient to try to come to an accurate causative diagnosis.
Is there a test to diagnose fatigue?
The key to finding the cause of fatigue in a patient is the care the health care professional takes in compiling a medical history. It is important to ask questions not only about the loss of energy but also about other potential problems that the patient may be experiencing such as shortness of breath, sleep patterns, hair loss, color of the stools, or any of the myriad of questions that might provide information as to what organ system may be involved.
Usually, a history is taken by the health care professional asking questions about the quality and quantity of fatigue. Examples of some of the questions the health care professional may ask include:
- Does the patient feel well in the morning when they wake?
- Does the fatigue progress through the day?
- Does the person nap unexpectedly or take excessive amounts of stimulants such as caffeine to complete daily activities?
- Does the fatigue come on gradually or abruptly?
- Is it a daily occurrence or intermittent/periodic?
- What makes it better and what makes it worse?
- How has the patient's life changed because of the fatigue?
- Is the fatigue more mental than physical?
Other associated symptoms with fatigue include:
- weight loss,
- chest pain and shortness of breath,
- vomiting and diarrhea,
- fevers and chills,
- muscle weakness or pain, and/or
- anxiety and depression.
It is also appropriate for the health care professional to ask questions about the patient's social situation and to also ask about their psychologic state of mind. Alcohol and drug abuse screening questions should be expected as routine.
Because fatigue is such a non-specific symptom, each answer may direct the health care professional to explore a different potential cause.
A full physical examination is important to look for underlying signs of illness. The general appearance of the patient is important looking for hygiene, vital signs, and evidence of anxiety or agitation. Examination and evaluation of the different systems of the body (heart, lungs, abdomen, neurological system, etc.) and combining any abnormal findings with the clues found in the history taking may help make the diagnosis.
Special attention may be taken to palpate (feel) for an abnormal thyroid gland, swollen lymph nodes, listen for abnormal heart sounds including murmurs and to check for normal muscle tone and reflexes.
Depending on the findings in the history and physical examination, blood tests and other imaging studies may be ordered. Initial screening blood tests may include:
- CBC (complete blood count that includes a red blood cell, white blood cell and platelet count);
- electrolytes (sodium potassium, chloride, carbon dioxide, and sometimes calcium and magnesium);
- glucose (blood sugar);
- BUN/creatinine (to measure kidney function);
- TSH or thyroid stimulating hormone;
- tests for deficiencies in vitamins B12, D, folic acid, and iron;
- CPK (elevated in illnesses that cause muscle inflammation); and/or
- ESR or erythrocyte sedimentation rate (non specific blood marker for inflammation in the body).
CPK and ESR screening tests are rarely done initially. The decision to obtain X-rays, CT scans, electrocardiogram (ECG, EKG) and other imaging or testing will depend upon the individual patient's circumstances and what the health care practitioner suspects may be the underlying cause of the fatigue.
What is the treatment for fatigue?
Since fatigue is a symptom of an underlying condition, the treatment depends upon the condition that is causing the fatigue, regardless of whether it is physical, psychological or a combination of the two.
There may be a lag time between when the illness has been treated and the intensity of fatigue symptoms; some symptoms may resolve as soon as the underlying condition is treated. For example, individuals who are anemic feel much better as soon as their red blood cell count increases, while those recovering from infectious mononucleosis may require weeks to have their energy levels return to normal.
Can fatigue be prevented?
Fatigue as a symptom can occur as the result of many causes and therefore, prevention is not an issue. More importantly, the early recognition of fatigue will allow a person to seek medical care and potentially have an earlier diagnosis of the underlying cause made.
Sometimes, symptoms like fatigue arise gradually and it is difficult for the person to realize that there is a problem. It may take an outside perspective from a friend or family member to appreciate a difference in function. Self-awareness of gradual decline in body performance is often difficult as a person makes repeated small accommodations to complete daily activities.
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Centers for Disease Control and Prevention. Chronic Fatigue Syndrome.
Davis, Mp., Walsh, D. Mechanisms of fatigue, J. Support. Oncol., 8:164-174, 2010
Holley, AB, MD. The Evaluation and Management of Fatigue. Medscape. Updated: Oct 14, 2015.