Review articleMeasurements of sleepiness and fatigue
Introduction
Sleepiness and fatigue are terms commonly used in both clinical practice and research literature. Both sleepiness and fatigue are ubiquitous phenomena. Sleepiness and fatigue negatively effect daily functioning, and patients who have these feelings are distressed.
Although sleepiness and fatigue are two different and distinct entities, many patients and unfortunately many medical practitioners are unaware of the complexity and heterogeneity of these symptoms. This may be because that some patients use the terms tired, sleepy and fatigued interchangeably and it is difficult to tease apart whether the primary issue is fatigue or sleepiness. The two complaints have distinct implications for clinical diagnosis and treatment. These two symptoms are particularly common in the psychosomatic field. It is beyond the scope of this primarily methodological review to discuss the implications of the distinctions but the interested reader is referred to the following references [1], [2], [3].
Currently, there are objective methods measuring sleepiness. A number of rating scales are being used to subjectively assess sleepiness and fatigue. The objective of this review is to assess the psychometric properties of the objective and subjective measurements available on the topic of sleepiness and fatigue. A broader compilation of scales relevant to sleep medicine will be published in the book titled “One Hundred Sleep Related Scales” [4].
Section snippets
Sleepiness
Generally, sleepiness means an increased propensity to doze off or fall asleep; it may be related to a low arousal level [5]. Sleepiness is also defined as a tendency to fall asleep.
Sleepiness may be affected by different conditions, such as medical problems, psychiatric diseases and primary sleep disorders. When sleepiness occurs at an inappropriate time or an atypical situation, it becomes pathological. For example, excessive daytime sleepiness (EDS) is an important feature of narcolepsy.
Fatigue
Fatigue is common in physical and psychiatric disorders [46]. Symptoms of fatigue are commonly reported in patients with depression, chronic fatigue syndrome, HIV, cancer. Fatigue may be a side effect of a number of medication treatments [47]. Generally, fatigue is not specific in its presentation and symptomatology. Fatigue may be induced by physical, physiological and psychological causes; it often presents as a feeling of tiredness and exhaustion [48].
Fatigue is the most common symptom
Conclusion
Sleepiness and fatigue are commonly seen in clinical settings, as well as in the general population. Accurately assessing sleepiness and fatigue is crucial for clinical understanding of patients and for research. There are objective and subjective instruments to measure sleepiness. However, only rating scales are available for measuring fatigue. In the listed 11 scales measuring fatigue, the top three commonly used are the FSS, CFS and FIS. During any assessment (clinical purposes or for
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