Cancer patients, especially those who have had severe cancers of the blood, often report extreme fatigue that keeps them from daily activities months after the end of their treatment. Doctors have speculated that a variety of things might cause fatigue, including depression, anemia (low numbers of red blood cells), skewed levels of some regulating hormones in the body, low levels of proteins, and stress on the immune system. A team of researchers from Berlin, Germany, attempted to give scientific backing to those theories.

What the researchers wanted to know: What causes extreme fatigue in recovering cancer patients?

What they did: Seventy-one adults who had been treated for hematological (blood-related) cancer but who had not undergone treatment for at least three months were recruited for the study. They were given a couple of questionnaires that asked them about depression, general level of activity, and whether they could perform specific tasks that varied in their physical intensity. Blood samples were also taken to measure hormone levels, red blood-cell count, and proteins.

What they found: No correlation was found between any blood or immune system measures (hormones, red blood cells, and proteins) and fatigue level. People who were more fatigued were less likely to be physically active and more likely to be depressed than other patients.

What it means to you: The researchers are not sure if fatigue made people depressed and inactive, inactivity made them depressed and tired, or depression just knocked them out entirely. Or, it could be that all three are caused by a separate, yet unmeasured, factor. In previous studies, endurance and weight resistance training programs have helped cancer survivors feel less tired, and the researchers say those programs hold a lot of promise.

Caveats: First, the researchers relied solely on patient's reporting of their own fatigue levels, as well as their own depression and the amount of activity they could do. So, some patients could have a tendency to over-report all three, leading to a false correlation. Second, the researchers measured fatigue and its potential causes at only one point in time (when the subjects were given the study) whereas a longitudinal study that tracked patient's health over a period of time might be able to figure out the causes of fatigue rather than just correlations.

Find out more: The National Cancer Institute has a page that deals with dealing with cancer, including information about fatigue.

The Cancer Recovery Foundation of America also has a good site, especially for people who are trying to deal with the effects of cancer themselves.

Read the article: Dimeo, F., Schmittel, A., Fietz, T., Kohler, P., Boning, D., Thiel, E. "Physical Performance, Depression, Immune Status, and Fatigue in Patients With Hematological Malignancies After Treatment." Annals of Oncology. July 19 2004, Vol. 15, No. 8 pp. 1237-1242.

Abstract online: http://annonc.oupjournals.org