Physical Activity and Cognitive Processing Speed In Multiple Sclerosis

Background: There is increasing recognition of the possible association between physical activity and cognitive processing speed (CPS) in neurological diseases, including multiple sclerosis (MS). To date, the evidence in MS is based on a limited number of cross-sectional studies with small samples. There further are unresolved methodological issues such as the lack of control for confounders, focus on fitness rather than physical activity, and variation and uncertainty in modes of cognitive assessment (i.e., written or oral administration).

Objectives: This study prospective examined the association of physical activity with both oral and written cognitive performance in 82 persons with MS and controlled for possible confounders of age, sex, education and disability.

Methods: Participants wore an accelerometer during the waking hours over 7 days for measuring physical activity as steps/day, and six-months later completed a demographics questionnaire, the self-reported EDSS (SR-EDSS), two versions of the Symbol Digit Modalities Test (SDMT) and the Paced Auditory Serial Addition Test (PASAT).

Results: Steps/day was significantly, moderately, and similarly associated with oral (r=.47, p<.01) and written (r=.52, p<.01) SDMT performance but weakly associated with scores on the PASAT (r=.20, p=.05). Age and disability status were identified as covariates based on joint associations with physical activity and CPS. After controlling for age and disability status, steps/day was still significantly associated with both oral (pr=.27, p=.01) and written (pr=.28, p=.01) SDMT performance, but not PASAT performance (pr=.13, p=.14).

Conclusions: The results of this prospective study support future examinations of physical activity behavior changes and its influence on cognitive processing speed using either oral or written administrations of the SDMT in persons with MS.