Abstract
Background: Unexplained prolonged fatigue (UPF) is one of the most common complaints in primary care. UPF is difficult to manage because of its nonspecific nature and unknown mechanism. UPF frequently frustrates health care professionals and has negative impacts on the physician-patient relationship. Although it is nonfatal, fatigue-associated functional impairments and economic consequences are substantial, negatively impacting patients' quality of life.
Objectives: To evaluate current knowledge development of UPF and to help focus the direction of future investigations.
Methods: A literature review was undertaken with the MEDLINE databases chosen as the primary electronic resources to retrieve the literature.
Results: Current understanding of UPF is limited. Lack of consistent scientific language is a major problem. There is no consensus about the case definition of UPF even for the most widely studied chronic fatigue syndrome (CFS). Various sets of classification have been developed, each with similar but not identical criteria. Clinicians are dubious about perceiving fatigue as a clinical entity and ignore the diagnosis criteria. Many more patients are excluded than included from the current classifications and lack appropriate evaluation and treatment. The predisposing factors are not well established with the exception of being female and relatively young. Laboratory testing and immune and endocrine abnormalities are inconsistent in determining the causes. Psychological and social factors play an important but inconclusive role in mediating fatigue status.
Conclusions: The high prevalence, persistence, and disability-associated consequences of UPF warrant more attention. Further investigations of the symptoms, psychosocial-based symptom experiences, and a search for effective management are needed.