Cognitive fatigability is a quantifiable distinct phenomenon in multiple sclerosis

Abstract

Cognitive fatigability in multiple sclerosis represents the decrease in cognitive performance over time. It is a frequent symptom that negatively affects quality of life and ability to work. There are no objective measures of cognitive fatigability. This study aimed at quantifying cognitive fatigability despite the learning effect and to clarify whether cognitive fatigability represents a free‐standing phenomenon rather than an aspect of cognitive impairment. We measured information processing speed with the Symbol Digit Modalities Test, and the number of right answers was recorded every 30 s for 180 s. We approximated the number of right answers as function of time with two logarithmic models, one including a first‐order term alone and the other adding also a second‐order term. The coefficient of the latter (B) may quantify performance deflection and may represent cognitive fatigability. We tested 173 patients with multiple sclerosis, including 119 cognitively impaired and 54 cognitively preserved patients, and 35 healthy subjects. The performance of cognitively preserved patients showed a deflection at the end of task that was detected neither in controls nor in cognitively impaired patients and needed a second‐order term to be approximated (p < .03, F = 14.02). B was explained neither by depression nor fatigue. We proposed for the first time a method to quantify cognitive fatigue via a second‐order least square fit model, easily usable in the clinical practice. By using this novel approach, cognitive fatigability results to be a free‐standing phenomenon that is more evident in cognitively preserved than in cognitive impaired patients.

Effects of a 6-Min Treadmill Walking Test on Dual-Task Gait Performance and Prefrontal Hemodynamics in People With Multiple Sclerosis

“…In the MS context, fatigue is often defined as a subjective lack of physical and/or mental energy that is perceived by the affected person or caregiver interfering with usual and desired activities ( 2 ). However, this definition does not cover the different dimensions of fatigue comprising perceptual and performance aspects that were investigated separately in the past ( 3 – 6 ). To resolve this, Enoka and Duchateau ( 3 ) provided a fatigue definition and framework, which were recently adapted to describe the dimensions and mechanisms contributing to fatigue in pwMS ( 7 ).…”

“…In contrast, activity-induced state fatigue describes the temporary decline in motor and/or cognitive performance (performance fatigability) and/or the increase in the perception of fatigue (perceived fatigability) in response to a motor or cognitive task. Thereby, motor performance fatigability is determined by the activation characteristics as well as the contractile function of muscles ( 3 ) and cognitive performance fatigability by the integrity of the central nervous system (e.g., neural excitability, metabolites, and neurotransmitter) ( 6 , 8 ). Perceived fatigability strongly depends on the psychophysiological state of the individual ( 9 ).…”

Fatigue and Human Performance: An Updated Framework

“…Cognitive performance fatigue (traditionally termed objective cognitive fatigue) induced by sustained and/or intense cognitive tasks can be quantified as a decline in an objective cognitive performance measure during as well as after a cognitive task (e.g., change in reaction time, its variability, and/or accuracy) [4,10,111,112]. The occurrence and extent of cognitive performance fatigue seem to depend on various modulating factors, for instance, subjects-specific factors (e.g., age, sex, diseases) and the characteristics of the cognitive task (e.g., type of task, duration, cognitive load) [113][114][115][116][117][118] (Fig.…”

“…The multitude of psychophysiological processes that inevitably accompany motor or cognitive activity above a certain intensity or duration can become a limiting factor for motor as well as cognitive performance and are typically summarized under the umbrella term fatigue. In the past, a variety of disciplines (e.g., psychology, exercise physiology, neuroscience, medical fields) have specialized on selected aspects investigating either the subjective perception of fatigue or changes in motor or cognitive performance [1][2][3][4][5]. Due to this fragmentation, a multitude of fatigue definitions emerged leading to an inconsistent use of the term and neglecting the dynamic interactions between the taskinduced psychophysiological adjustments and the resulting perceptual, affective, and cognitive responses.…”

Development of a behavioural intervention for cognitive fatigability in multiple sclerosis: Protocol for a pilot and feasibility study

“…While CF can be evaluated in a number of different ways ( 34 ), our group has used the Paced Auditory Serial Addition Test (PASAT) as a measurement tool. Its sensitivity to CF differs depending on how it is scored ( 23 , 26 ).…”