Differential effects of aging on motor and cognitive functioning in multiple sclerosis

Background: Multiple sclerosis (MS) patients are impaired in motor and cognitive performance, but the extent to which these deficits are magnified by aging is unknown. In one prior study, differences in cognitive processing speed between MS patients and healthy individuals were of similar magnitude across the lifespan. Here, we have improved on this work by expanding assessment to multiple cognitive domains and motor functioning. Objective: To determine whether the degree of cognitive and motor dysfunction in MS is magnified with increasing age. Methods: In all, 698 MS patients (aged 29–71 years) and 226 healthy controls (HCs; aged 18–72 years) completed neuroperformance tests covering ambulation, upper extremity function, information processing speed, and memory. Results: Linear regression models predicting cognitive and motor function revealed main effects of MS/HC diagnosis, age, and education across all measures. There was also an interaction between age and diagnosis on measures of motor function, but not on cognitive outcomes. Conclusion: The progression of motor decline is amplified by aging in MS. However, the degree of cognitive impairment does not vary across the lifespan. Thus, evidence of accelerated cognitive impairment in older adults with MS may signal the presence of other age-related cognitive pathologies.