Introduction: Asthenia: Definitions and Dimensions

Abstract

Abstract Patients with chronic medical diseases commonly report a distressing lack of vitality. This phenomenon is characterized by a range of descriptors, which together suggest both physical and mental aspects. The physical aspects may be characterized by weakness or tiredness, which suggests dysfunction in muscles, or by lethargy or sleepiness, which indicates difficulties in maintaining alertness. Other descriptors, such as apathy, lassitude, inattention, difficulty concentrating, or loss of motivation, recognize a prominent mental (usually cognitive) aspect. Two commonly used terms, asthenia and fatigue, capture these characteristics more broadly. Either can refer to a sense of diminished vitality in physical or mental functioning, or both, that occurs in the setting of medical disease. Although an asthenia-anorexia-cachexia syndrome has been appreciated in patients with far-advanced diseases, including cancer, the empirical data now available do not provide a basis for distinguishing the asthenia component of this syndrome from a constellation of symptoms generally described as fatigue. For now, progress in understanding and managing the lack of vitality that commonly afflicts the medically ill would be facilitated by considering fatigue and asthenia together. Asthenia, or fatigue, is a symptom. Like other symptoms, it is fundamentally subjective. This subjectivity implies that the “weakness” often reported as part of the symptomatology does not require an objective correlate. Although some patients who report fatigue have demonstrable muscle weakness, most do not. Some patients experience easy fatigability with physical activity, but this, too, does not require a correlate on physical examination or electrophysiologic testing. Although objective evidence of a physical problem can help the clinician understand the origins of the complaint and maybe choose a therapy, such evidence is not required to confirm or quantitate the patient’s report.