Physical activity and information processing speed in persons with multiple sclerosis: A prospective study

Objective There is increasing recognition of the possible association between physical activity and information processing speed (IPS) in multiple sclerosis (MS), but this is based on a limited number of cross-sectional studies with small samples. There further are unresolved methodological issues such as the appropriate mode (i.e., written or oral administration) and measure (e.g., Symbol Digit Modalities Test (SDMT) & the Paced Auditory Serial Addition Test (PASAT)) of cognitive assessment. This prospective study further examined methodological issues influencing the association between physical activity and IPS in 82 persons with MS. Methods Participants wore an accelerometer during the waking hours over 7 days for measuring physical activity as steps/day and six-months later completed two versions of the SDMT and the PASAT. Results Steps/day was significantly, moderately, and similarly associated with oral (r_s =.45, p <.01) and written (r_s =.51, p <.01) SDMT performance, but weakly associated with scores on the PASAT (r_s =.23, p =.02). After controlling for age and disability status as covariates of IPS, the associations among steps/day and oral (pr_s =.25, p =.02) and written (pr_s =.29, p =.01) SDMT performance were attenuated, but statistically significant, whereas after controlling for age and disability status, the association between steps/day and PASAT performance was not statistically significant (pr_s =.12, p =.34). Conclusions These results support inclusion of either oral or written administrations of the SDMT, rather than the PASAT, as measures of IPS in future physical activity interventions.