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.
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:
1. 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
2. Concurrently have four or more of the following symptoms:
-impaired memory or concentration
-multi-joint pain without redness or swelling
-tender cervical or axillary lymph nodes