Tiredness happens to everyone -- it is an expected feeling after certain activities or at the end of the day. Usually, you know why you are tired and a good night's sleep solves the problem.
Fatigue, in contrast to tiredness, is a daily lack of energy, an unusual or excessive whole-body tiredness not relieved by sleep. It can be acute (lasting a month or less) or chronic (lasting from one month to six months or longer). Fatigue can prevent a person from functioning normally and impacts a person's quality of life.
For more information, U.S. residents may call the National Cancer Institute's (NCI's) Cancer Information Service toll-free at 1-800-4-CANCER (1-800-422-6237) Monday through Friday from 8:00 a.m. to 8:00 p.m., Eastern Time. A trained Cancer Information Specialist is available to answer your questions.
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Fatigue is one of the most common side effects of cancer and its treatment. It is not predictable by tumor type, treatment, or stage of illness. Usually, it comes on suddenly, does not result from activity or exertion, and is not relieved by rest or sleep. It often is described as "paralyzing." It may continue even after treatment is complete.
What Causes Cancer-Related Fatigue?
The exact reason is unknown. Cancer-related fatigue may be related to the disease process or its treatments.
Cancer treatments commonly associated with fatigue include:
Chemotherapy. Any chemotherapy drug may cause fatigue. Patients frequently experience fatigue after several weeks of chemotherapy, but this varies among patients. In some patients, fatigue lasts a few days, while in others, it persists throughout and after the treatment is complete.
Radiation therapy.Radiation therapy can cause cumulative fatigue (fatigue that increases over time). This can occur regardless of the treatment site. Fatigue usually lasts from three to four weeks after treatment stops, but can continue for up to two to three months.
Biological therapy. Interferons and interleukins are cytokines, natural cell proteins that are normally released by white blood cells in response to infection. These cytokines carry messages that regulate other elements of the immune and endocrine systems. In high amounts, these cytokines can be toxic and lead to persistent fatigue.
Combination or sequential therapy. More than one cancer treatment at the same time or one after the other increases the chances of developing fatigue.
Other factors that may contribute to cancer-related fatigue include:
Tumor-induced hypermetabolic state. Cancer cells compete with normal cells for nutrients, often at the expense of the normal cells' growth. In addition to fatigue, weight loss and decreased appetite are common effects of this condition.
Decreased nutrition from the side effects of treatments (such as nausea, vomiting, mouth sores, taste changes, heartburn, or diarrhea) can cause fatigue.
Anemia. Cancer treatments can cause reduced blood counts, which may lead to anemia, a blood disorder that occurs when there is not enough hemoglobin in the blood. Hemoglobin is a substance in the red blood cells that enables the blood to transport oxygen through the body. When the blood can't transport enough oxygen to the body, fatigue can result.
Hypothyroidism. If the thyroid gland is under-active (hypothyroidism), metabolism may slow down so that the body does not burn food fast enough to provide adequate energy. This is a common condition in general, but may happen after radiation therapy to the lymph nodes in the neck. Symptoms include feeling cold and unexplained weight gain, in addition to severe fatigue.
Medications. Medications used to treat side effects such as nausea, pain, depression, anxiety, and seizures, can cause fatigue.
Pain. Research shows that chronic, severe pain increases fatigue.
Stress. Stress can worsen feelings of fatigue. Stress can result from dealing with the disease and the "unknowns," as well as from worrying about daily accomplishments or trying to meet the expectations of others.
Overworking yourself. Fatigue may result when patients try to maintain their normal daily routines and activities during treatments. Modification may be necessary in order to conserve energy.
Depression. Depression and fatigue often go hand-in-hand. It may not be clear which started first. One way to sort this out is to try to understand your depressed feelings and how they affect your life. If you are depressed all the time, were depressed before your cancer diagnosis, are preoccupied with feeling worthless and useless, then you may need treatment for depression.
Immobility can reduce endurance and decondition muscles.
Hormonal changes, a side effect of cancer treatment or pain medication, can cause fatigue.
Medications for other illnesses, and the illnesses themselves, may cause fatigue. A classic example are blood pressure medications.