Fatigue in patients with rheumatoid arthritis: what is known and what is needed.

Fatigue is, just like pain, a subjective symptom which may occur in patients with many different diseases and thereby also in patients with RA. In the literature, a consensus definition for fatigue is not presented. However, most authors define fatigue as: ‘an overwhelming, sustained sense of exhaustion and decreased capacity for physical and mental work’ [1]. For chronic fatigue, Piper’s definition is widely used in international studies and is as follows: ‘chronic fatigue is perceived as unpleasant, unusual, abnormal or excessive whole-body tiredness, disproportionate to or unrelated to activity or exertion and present for more than one month. Chronic fatigue is constant or recurrent, it is not dispelled easily by sleep or rest and it can have a profound negative impact on the person’s quality of life’ [2]. To distinguish between chronic fatigue and the chronic fatigue syndrome (CFS), the Centre for Disease Control and Prevention (CDC) has formulated special criteria for CFS [3]. In published studies, fatigue is mostly described as a multicausal, multidimensional and complex concept in which psychological, biochemical and physiological mechanisms play a role. As with pain, the definition is not the most important issue in clinical practice but the way fatigue can and should be assessed is, because quantifying fatigue enables us to study fatigue.