Abstract
Cognitive fatigue and cognitive fatigability are distinct constructs. Cognitive fatigue reflects perception of cognitive fatigue outside of the context of activity level and duration and can be reliably assessed via established instruments such as the Fatigue Severity Scale (FSS) and the Modified Fatigue Impact Scale (MFIS). In contrast, cognitive fatigability reflects change in fatigue levels quantified within the context of the level and duration of cognitive activity, and currently there are no reliable measures of cognitive fatigability. A recently published scale, the Pittsburgh Fatigability Scale (PFS), attempts to remedy this problem with a focus on the aged population. While the physical fatigability subscore of PFS has been validated using physical activity derived measures, the mental fatigability subscore of PFS remains to be tested against equivalent measures derived from cognitive activities. To this end, we recruited 35 older, healthy adult participants (mean age 73.77 ± 5.9) to complete the PFS as well as a prolonged continuous performance of a Stroop task (>2 h). Task-based assessments included time-on-task changes in self-reported fatigue scores (every 20 min), reaction time, and pupil diameter. Defining subjective fatigability, behavioral fatigability, and physiologic/autonomic fatigability to be the slope of change over time-on-task in the above three assessed variables, we found that the PFS mental subscore was not correlated with any of the three task-based fatigability measures. Instead, the PFS mental subscore was correlated with trait level fatigue measures FSS (ρ = 0.63, p < 0.001), and MFIS cognitive subsection (ρ = 0.36, p = 0.03). This finding suggested that the PFS mental fatigability subscore may not be an adequate measure of how fatigued one becomes after a given amount of mental work. Further development efforts are needed to create a self-report scale that reliably captures cognitive fatigability in older adults.
Highlights
Fatigue is a common complaint in older adults and is associated with poor quality of life, functional disability, and increased mortality (Cathébras et al, 1992; Gill et al, 2001; Hardy and Studenski, 2008a,b)
Recent work has suggested a unified taxonomy for more precisely communicating and describing the construct of fatigue (Kluger et al, 2013). Important aspects of this taxonomy include: (1) Distinguishing subjective fatigue from objective performance fatigability; (2) distinguishing fatigue from related phenomena; (3) specifying what domains of performance are affected by fatigue; and (4) describing what physiologic factors are associated with fatigue
Participants were eligible for the study if they were free from diagnoses of either neurological disorders or non-neurological disorders that might contribute to fatigability, including the following: cardiac, respiratory, endocrine disorders; currently receiving treatment for cancer; severe depression; attention deficit disorder; or sleep disorders
Summary
Fatigue is a common complaint in older adults and is associated with poor quality of life, functional disability, and increased mortality (Cathébras et al, 1992; Gill et al, 2001; Hardy and Studenski, 2008a,b). Despite the apparent importance of fatigue as a public health concern, research in this area has long been hampered by problems associated with definition and measurement (Muscio, 1921). To address this issue, recent work has suggested a unified taxonomy for more precisely communicating and describing the construct of fatigue (Kluger et al, 2013). Given the well-documented adverse consequences of limiting one’s activities, there is a great need to develop and validate measures of both performance and subjective fatigability, which are essential for diagnosis and treatment
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