Cognitive fatigue in traumatic brain injury: a pilot study comparing state and trait fatigue.

Cognitive fatigue is a common and disabling symptom following a traumatic brain injury (TBI). Literature on cognitive fatigue has distinguished between two types of fatigue: "state" fatigue refers to the acute experience of fatigue, whereas "trait" fatigue refers to the susceptibility to fatigue over an extended period. However, it is not clear whether state and trait fatigue are distinguishable constructs. Here, we examine the relationship between state and trait fatigue in individuals with TBI, hypothesizing that trait and state measures assess different constructs. Twenty-one participants with moderate-severe TBI were recruited. Participants underwent a cognitively fatiguing task while in an MRI scanner and completed self-report measures examining trait and state fatigue. No correlation was found between state and trait fatigue. However, the two measures of trait fatigue, Fatigue Severity Scale (FSS) and the Modified Fatigue Impact Scale (MFIS), correlated with one another; additionally only trait fatigue correlated with depression scores, consistent with the literature. These findings suggest that trait and state fatigue may not be interdependent and that it is important to carefully define the type of fatigue under consideration when assessing fatigue in individuals with TBI.