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Updated: May 22, 2025
The Multiple Sclerosis Performance Test MSPT: An iPad-Based Disability Assessment Tool
Published on: June 30, 2014
Trait fatigue impacts Symbol Digit Modalities Test (SDMT) performance in multiple sclerosis: The role of working
Christopher J Cagna1, Ekaterina Dobryakova1, Erica Weber1
1Center for Traumatic Brain Injury Research, Kessler Foundation, 120 Eagle Rock Avenue, Suite 100, East Hanover, NJ 07936, USA; Department of Physical Medicine & Rehabilitation, Rutgers - New Jersey Medical School, 183 South Orange Avenue, Suite F-1560, Newark, NJ 07101, USA.
Background:
Cognitive impairment and fatigue are two prevalent symptoms of multiple sclerosis (MS). Fatigue is often thought to be associated with slower processing speed. The Symbol Digit Modalities Test (SDMT) is a widely used assessment of processing speed in MS, but it has also been shown to tap into working memory as well. Investigation into fatigue's influence on SDMT performance in MS and potential mechanisms for this relationship are lacking. The present study examined the effect of trait fatigue on SDMT performance and its associated mechanisms in MS and healthy control (HC) participants. Working memory performance was specifically examined as a potential mechanism, given its frequent association with processing speed in MS.
Methods:
In a secondary data analysis, performance on the SDMT and other neuropsychological assessments, as well as self-reported trait fatigue, were examined in 80 MS and 45 HC participants. Trait fatigue was measured via self-report on the Modified Fatigue Impact Scale (MFIS).
Results:
Higher MFIS ratings were significantly associated with worse SDMT performance in MS (r = -0.33, p = .002), but not HC (r= 0.06, p = .71), participants. A mediation analysis further revealed that for MS participants, working memory performance (WAIS-IV Digit Span Backward condition) partially mediated the relationship between trait fatigue and SDMT performance. Higher MFIS scores significantly predicted lower Digit Span Backward scores (b = -0.04, 95 % CI: [-0.08, -0.002], p = .04], which in turn, significantly predicted lower SDMT response accuracy (b = 0.23, 95 % CI: [0.10, 0.35], p = .001). No such relationship was observed in HC participants.
Conclusions:
Elevated trait fatigue may reduce SDMT performance via its negative impact on working memory performance in people with MS. Future research should focus on additional factors that may also contribute to this relationship.
