Fatigue and depression

What is fatigue - Causes of fatigue - Fatigue and cancer treatment - Fatigue and nutrition factors

What is fatigue

Cancer treatments may go on for weeks or months and may even cause more illness or discomfort than the initial disease. Many patients say they feel exhausted and depressed and unable to concentrate. Fatigue can be described as a condition that causes distress and decreased ability to function due to a lack of energy. Fatigue occurs in 14% to 96% of people with cancer, especially those receiving treatment for their cancer and, although depression and fatigue isn't a nutritional side effect in itself, it can affect your interest in food and your ability to shop and prepare healthy meals.

Fatigue is difficult to describe and people with cancer may express it in different ways, such as saying they feel tired, weak, exhausted, weary, worn-out, heavy or slow. Health professionals may use many terms to describe fatigue including: lassitude, exercise intolerance, lack of energy, and weakness.

Fatigue may be acute or chronic:

  • acute fatigue is normal tiredness with occasional symptoms that begin quickly and last for a short time; rest may alleviate fatigue and allow a return to a normal level of functioning in a healthy individual, but this ability is diminished in people who have cancer;
  • chronic fatigue is long lasting: the chronic fatigue syndrome describes prolonged debilitating fatigue that may persist or relapse and may not resolve with the rest. Chronic fatigue is sometimes diagnosed in people who do not have cancer. Although many treatment- and disease-related factors may cause fatigue, the exact process of fatigue in people with cancer is not known.

Fatigue can have a very profound effect on the life of a person with cancer and consequently people around them. It may affect how the person feels about him- or herself, his or her daily activities and relationships with others, and whether he or she continues with cancer treatment. Patients receiving some cancer treatments may miss work, withdraw from friends, need more sleep, and, in some cases, may not be able to perform any physical activities because of fatigue. Finances can become difficult if people with fatigue need to take disability leave or stop working completely. Understanding fatigue and its causes is important in determining effective treatment and in helping people with cancer cope with fatigue. Tests that measure the level of fatigue have been developed.

Specific fatigue symptoms may be physical, psychological, or emotional. It is complex, and has biological, psychological and behavioural causes.

Fatigue during cancer treatment can be related to a number of causes: not eating, inactivity, low blood counts, depression, poor sleep, and side effects of medicine.

To be treated effectively, fatigue related to cancer and cancer treatment needs to be distinguished from other kinds of fatigue.

Causes of fatigue

The causes of fatigue in people with cancer are not known. Fatigue commonly is an indicator of disease progression and is frequently one of the first symptoms of cancer in both children and adults. For example, parents of a child diagnosed with acute lymphocytic leukaemia or non-Hodgkin's lymphoma frequently seek medical care because of the child's extreme fatigue.

Tumours can cause fatigue directly or indirectly, by spreading to the bone marrow and causing anaemia, and by forming toxic substances in the body that interfere with normal cell functions. People who are having problems breathing, another symptom of some cancers, may also experience fatigue.

Fatigue can also occur for complex reasons: the extreme stress that people with cancer experience over a long period of time can cause them to use more energy, leading to fatigue.

However, there are also many chemical, physical, and behavioural factors that are thought to cause fatigue, as:

  • the central nervous system (the brain and spinal cord) may be affected by the cancer or the cancer therapy (especially biological therapy) and cause fatigue;
  • medication to treat pain, depression, vomiting, seizures, and other problems related to cancer may also cause fatigue;
  • tumour necrosis factor (TNF), a protein made mainly by white blood cells, can cause necrosis (death) of some types of tumour cells and may be given to a patient as a cancer treatment. TNF may cause the loss of protein stores in muscles, making the body work harder to perform normal functions and causing fatigue.

Fatigue and cancer treatment

Fatigue is a common symptom following cancer therapies.

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. Other chemotherapy side effects, as nausea, vomiting, chronic pain and weight loss, can also cause fatigue. Fatigue may be caused by anaemia or the collection of toxic substances produced by cells.

Fatigue has long been associated with radiotherapy although the connection between them is not well understood. In the case of radiation, fatigue may be caused by the increased energy needed to repair damaged skin tissue. Fatigue usually lessens after the therapy is completed, although not all patients return to their normal level of energy. Patients who are older, have advanced disease, or receive combination therapy (for example, chemotherapy plus radiotherapy) are at a higher risk for developing long-term fatigue.

In biological therapy, fatigue is one of a group of side effects known as flu like syndrome. This syndrome 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.

Fatigue is also 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.

Fatigue and 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, three 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 tumour growth, infection, fever, or problems with breathing),
  • a decrease in the amount of food eaten (due to lack of appetite, nausea, vomiting, diarrhoea, or bowel obstruction).

If you are worried about fatigue, talk to your healthcare professional. They will be able to help you understand why you are fatigued and how best to cope.

Source: National Cancer Institute