Trait fatigue impacts Symbol Digit Modalities Test (SDMT) performance in multiple sclerosis: The role of working...

Area of Science:

• Neuroscience
• Clinical Psychology
• Rehabilitation Medicine

Background:

• Multiple sclerosis (MS) frequently causes cognitive impairment and fatigue.
• Fatigue is often linked to slower processing speed, a key cognitive function assessed by the Symbol Digit Modalities Test (SDMT).
• The precise mechanisms linking fatigue to cognitive performance, particularly SDMT, in MS remain under-investigated.

Purpose of the Study:

• To investigate the effect of trait fatigue on SDMT performance in individuals with MS.
• To examine working memory as a potential mediating mechanism in the relationship between fatigue and SDMT performance.
• To compare these effects in MS participants and healthy controls (HC).

Main Methods:

• Secondary data analysis of 80 MS and 45 HC participants.
• Assessment of SDMT performance and other neuropsychological tests.
• Measurement of self-reported trait fatigue using the Modified Fatigue Impact Scale (MFIS).

Main Results:

• Higher trait fatigue (MFIS scores) correlated with worse SDMT performance in MS patients (r = -0.33, p = .002), but not in HC.
• Working memory (Digit Span Backward) partially mediated this relationship in MS.
• Increased fatigue predicted lower working memory, which in turn predicted lower SDMT accuracy in MS.

Conclusions:

• Elevated trait fatigue may impair SDMT performance in MS by negatively affecting working memory.
• Working memory is a significant mechanism linking fatigue and cognitive processing speed in MS.
• Further research is needed to explore other contributing factors to this relationship.