Fatigue. Measures and relation to pain

Fatigue describes reduced capacity to sustain force or power output, reduce d capacity to perform multiple tasks over time and simply a subjective expe rience of feeling exhausted, tired, weak or having lack of energy. Pain and fatigue have several components in common, such as being subjective, preva lent in most patients with cancer and caused by multiple factors of both a physical and psychological nature. In order to explore the relationship bet ween fatigue and pain, data from five studies were used: two random samples from the Norwegian population (n=2323 and n=1965), Hodgkin's disease survi vors (n=459), palliative care patients (n=434) and patients with bone metas tases (n=94). All patients had completed one or more of the following instr uments: EORTC QLQ-C30, SF-36 and/or Fatigue Questionnaire. The level of fat igue was much higher in the two palliative care populations (54.4 and 63.2) as compared to the normal population samples (25.0). Patients with bone me tastases had significantly more pain (72.0) than the patients in the pallia tive care trial (47.4) and norms (20.5). In the two palliative care and bon e metastases populations fatigue was almost unchanged over time, while pain was reduced. In the palliative care population a high level of fatigue (80 .3) and pain (57.8) was reported 0-1 month before death. The relationship b etween pain, fatigue and the health-related quality of life domains should be explored in more detail, especially in follow-up studies in order to ass ess possible changes over time. In addition, the validity of the existing i nstruments measuring fatigue should be investigated for use in patients wit h advanced disease and short life expectancy.