Walking and cognitive performance in adults with multiple sclerosis: Do age and fatigability matter?

•Ambulation and cognition worsen with age in adults with multiple sclerosis (MS).•Fatigability might influence such age-related worsening of ambulation and cognition.•This study tested possible age-group differences in fatigability in adults with MS.•There were no significant age-group differences in walking/cognitive fatigability.•Fatigability may not explain age-related declines in walking and cognition in MS. Co-occurring walking and cognitive performance deficits are debilitating consequences of multiple sclerosis (MS) that worsen with age. However, it is unknown if fatigability influences such age-related worsening of walking and cognitive performance. This cross-sectional study examined possible age-related differences in walking-related motor fatigability (incremental six-minute-walk (6MW) performance) and cognitive fatigability (incremental Symbol Digit Modalities Test (SDMT) performance) in adults with MS. 196 adults with MS were categorized into age-groups: younger (20–39 years; n = 53), middle-aged (40–59 years; n = 89), and older (60–79 years; n = 54), and completed the 6MW and SDMT. Age-group differences in incremental 6MW and SDMT performance, controlling for disability status, were examined using separate, mixed-factor ANCOVAs. There were no statistically significant age-group-by-time interactions on walking-related motor or cognitive fatigability when controlling for disability. However, there were significant main effects of time on incremental 6MW (p = 0.01) and SDMT (p