Factors Related to Fatigue

It is not always possible to determine the factors that cause fatigue in patients with cancer. Possible factors include the following:

• Cancer treatment.
• Anemia.
• Medications.
• Weight loss and loss of appetite.
• Changes in metabolism.
• Hormone levels that are too low or too high.
• Emotional distress.
• Decline in physical condition.
• Trouble sleeping.
• Inactivity.
• Trouble breathing.
• Loss of strength and muscle coordination.
• Pain and other symptoms.
• High levels of inflammation-causing cytokines.
• Poor nutrition.
• Dehydration.
• Infection.
• Heart trouble.
• Having other medical conditions in addition to cancer.

Cancer treatment

Fatigue is a common symptom following radiation therapy or chemotherapy. Fatigue may also be a side effect of biologic response modifier therapy, a type of treatment to boost or restore the ability of the immune system to fight cancer, infections, and other diseases. It may be caused by anemia, or the collection of toxic substances produced by cells. In the case of radiation, it may be caused by the increased energy needed to repair damaged skin tissue.

Several factors have been linked with fatigue caused by chemotherapy. Some people may respond to the diagnosis and treatment of cancer with mood changes and disrupted sleep patterns. Nausea, vomiting, chronic pain, and weight loss can also cause fatigue.

Studies have reported that patients have the most severe fatigue around mid-way through all the cycles of chemotherapy. Fatigue decreases after chemotherapy is finished, but patients often don't feel back to normal even 30 days after the last treatment.

Fatigue during cancer treatment may be increased by the following factors:

• Pain.
• Depression.
• Anxiety.
• Anemia. Some types of chemotherapy keep the bone marrow from making enough new red blood cells, causing anemia (too few red blood cells to carry oxygen to the body).
• Lack of sleep caused by certain anticancer drugs.

Many patients undergoing radiation therapy report fatigue that keeps them from being as active as they want to be. After radiation therapy begins, fatigue usually increases until mid-way through the course of treatments and then stays about the same until treatments end. Fatigue usually lessens after the therapy is completed, but some fatigue may last for months or years following treatment. Patients who are older, have advanced disease, or receive combination therapy (for example, chemotherapy plus radiation therapy) are at a higher risk for developing long-term fatigue.

In men with prostate cancer, fatigue was increased by having the following symptoms before radiation therapy started:

• Poor sleep.
• Depression.
• Anxiety.
• Pain.

In women with breast cancer, fatigue was increased by the following:

• Working while undergoing radiation therapy.
• Having children at home.
• Depression.
• Anxiety.
• Poor sleep.
• Younger age.
• Being underweight.
• Having advanced cancer or other medical conditions.

Biological therapy frequently causes fatigue. In this setting, fatigue is one of a group of side effects known as flu-like syndrome. This syndrome also includes fever, chills, muscle pain, headache, and a sense of generally not feeling well. Some patients may also experience problems with their ability to think clearly. The type of biological therapy used may determine the type and pattern of fatigue experienced.

Many people with cancer undergo surgery for diagnosis or treatment. Fatigue is a problem following surgery, but fatigue from surgery improves with time. It can be made worse, however, when combined with the fatigue caused by other cancer treatments.

Anemia

Anemia may be a major factor in cancer-related fatigue and quality of life in people with cancer. Anemia may be caused by the cancer, cancer treatment, or may be related to other medical causes.

Nutrition factors

Fatigue often occurs when the body needs more energy than the amount being supplied from the patient's diet. In people with cancer, 3 major factors may be involved: a change in the body's ability to process food normally, an increased need by the body for energy (due to tumor growth, infection, fever, or problems with breathing), and a decrease in the amount of food eaten (due to lack of appetite, nausea, vomiting, diarrhea, or bowelobstruction).

Psychological factors

The moods, beliefs, attitudes, and reactions to stress of people with cancer can also contribute to the development of fatigue. Anxiety and depression are the most common psychologicaldisorders that cause fatigue.

Depression may be a disabling illness that affects approximately 15% to 25% of people who have cancer. When patients experience depression (loss of interest, difficulty concentrating, mental and physical tiredness, and feelings of hopelessness), the fatigue from physical causes can become worse and last longer than usual, even after the physical causes are gone. Anxiety and fear associated with a cancer diagnosis, as well as its impact on a person's physical, mental, social, and financial well-being are sources of emotional stress. Distress from being diagnosed with cancer may be all that is needed to trigger fatigue. Some patients report having more fatigue after cancer treatments than others do. Studies have found that patients who worry about or expect fatigue before, during, or after treatment may be more likely to report having fatigue. (Refer to the PDQ summaries on Depression and Adjustment to Cancer: Anxiety and Distress for more information.)

Mental ability factors

Decreased attention span and difficulty understanding and thinking are often associated with fatigue. Attention problems are common during and after cancer treatment. Attention may be restored by activities that encourage rest. Sleep is also necessary for relieving attention problems but it is not always enough.

Sleep disorders and inactivity

Disrupted sleep, poor sleep habits, less sleep at night, sleeping a lot during the day, or no activity during the day may contribute to cancer-related fatigue. Patients who are less active during the daytime and awaken frequently during the night report higher levels of cancer-related fatigue.

Poor sleep affects people in different ways. For example, the time of day that fatigue is worse may be different. Some patients who have trouble sleeping may feel more fatigue in the morning. Others may have periods of severe fatigue in both the morning and the evening.

Even in patients who have poor sleep, correcting sleep problems does not always decrease fatigue. A lack of sleep may not be what is causing the fatigue.

Medications

Medications other than those used in chemotherapy may also contribute to fatigue. Opioids used in treating cancer-related pain often cause drowsiness, the extent of which may vary depending on the individual. Taking opioids over time may lower the amount of sex hormones made in the testes in men and the ovaries in women. This can lead to fatigue as well as sexualdysfunction and depression. Other types of medications such as tricyclic antidepressants and antihistamines may also produce the side effect of drowsiness. Taking several medications may compound fatigue symptoms.