Theoretical ReviewDistinguishing sleepiness and fatigue: focus on definition and measurement
Introduction
It is not an uncommon experience for a clinician, both in sleep medicine and other fields, to be faced with the patient presenting with a chief complaint of being ātiredā. Such patients, and often their physicians, are usually unaware of the heterogeneity of potential symptoms inherent in this general lay term, not the least of which are the entities of sleepiness and fatigue. As a result, sleepiness and fatigue are two terms often used interchangeably, in both clinical practice and in the research literature, despite the distinct implications each of them has in terms of diagnosis and treatment. In fact, these two symptoms can be difficult to separate. This paper will attempt to outline the nature of both sleepiness and fatigue, with the ultimate goal of providing a framework for defining and evaluating between these two complex phenomena.
Section snippets
Definition and mechanisms
Sleepiness is an ubiquitous phenomenon, experienced not only as a symptom in a number of medical, psychiatric and primary sleep disorders, but also as a normal physiological state by most individuals over any given 24Ā h period. Pathology is inferred both when its presence becomes pervasive (as in narcolepsy) or in its absence (as in insomnia). Alternatively, sleepiness can be considered abnormal when it occurs at inappropriate times, or does not occur when desired. Consequently, no clear
Scope of the problem
Fatigue, like sleepiness, is a highly prevalent phenomenon, associated with a significant level of physical and psychosocial morbidity. It is a commonly reported chief complaint in both primary and specialty medicine. Fatigue is the primary symptom of chronic fatigue syndrome (CFS), and is associated with a number of acute and chronic illnesses, such as rheumatoid arthritis, cancer and multiple sclerosis. It is also prevalent in certain medical treatments, such as radiation or chemotherapy. In
Conclusion
The distinction between fatigue and sleepiness remains somewhat obscure, despite the development of a number of objective and subjective tools for measuring sleepiness, and numerous fatigue scales. Neither sleepiness, nor fatigue is unitary phenomena, each in themselves being complex, heterogeneous phenomena. Sleepiness and fatigue often coexist as a consequence of sleep deprivation, and are often grouped together by such patients under the complaint of being ātiredā. On closer examination,
Glossary
- Cronbach's alpha
- A statistic that is used to estimate the reliability of a test.
- Chronic fatigue syndrome (CFS)
- A disorder with fatigue as its major symptom. CFS patients sometimes feel too fatigues to do normal activities or are easily exhausted with no apparent reason. This condition can be months or years.
- Electrooculogram (EOG)
- A study using electrodes placed around the eyes to detect electrical activities associated with eye movements.
- Functional magnetic resonance imaging (fMRI)
- An instrument
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