Do physical activity, cardiorespiratory fitness, and subcortical brain structures explain reduced walking performance in older adults with multiple sclerosis?

BACKGROUND

As adults with multiple sclerosis (MS) age, walking speed and endurance progressively decline, yet there is limited understanding of factors that explain such age-related declines. The current study examined subcortical brain structures, cardiorespiratory fitness, and moderate-to-vigorous physical activity (MVPA) as explanations for reduced walking performance in older adults with MS.

METHODS

Older adults with MS (n = 29, 62.8 ± 5.8 years) and age-and-sex matched controls (n = 28, 63.8 ± 5.5 years) completed measures of walking speed (Timed-25 ft Walk) and walking endurance (Six-minute Walk), cardiorespiratory fitness, device-measured MVPA, and underwent an MRI to provide composite volumes of the thalamus, caudate, putamen, and pallidum. We used a mediator variable framework to describe group differences, determine correlations in the overall sample, and identify variables that explain reduced walking performance.

RESULTS

Compared to controls, older adults with MS had worse walking speed (p<0.001) and endurance (p<0.001), lower fitness (p = 0.04), lower levels of MVPA (p = 0.001), and smaller composite volumes of the thalamus (p=<0.001), putamen (p = 0.04), and pallidum (p = 0.007). In the overall sample, both measures of walking performance were significantly correlated with fitness, MVPA, and volumes of the thalamus and putamen (r range 0.34-0.65). Regression analyses indicated that MVPA (β=0.007094) partially explained the group differences in walking speed, and fitness (β=7.7640) and MVPA (β=17.5797) partially explained the group differences in walking endurance.

CONCLUSIONS

Collectively, these results suggest that cardiorespiratory fitness and MVPA, but not subcortical brain structures, may be modifiable targets of future interventions for improving walking in older adults with MS.