Physical Activity, Dietary Sodium, and Smoking As Correlates of Walking Performance in Persons with MS

Background: There is increasing interest in studying the association between modifiable health behaviors and clinical outcomes in persons with multiple sclerosis (MS). Physical activity, dietary sodium intake, and smoking may be associated with walking performance as a clinical manifestation of MS. We are unaware of research analyzing the joint association of these three health behaviors with walking performance in MS. 

Objectives: This study examined the relationships of physical activity, dietary sodium intake, and smoking with walking performance after accounting for disability status as a covariate. 

Methods: Thirty-one community-dwelling participants with MS underwent neurological examinations for generation of EDSS scores, followed by breath carbon monoxide (BCO) evaluation using the Bedfont Micro+ Smokerlyzer for assessment of smoking status (ppm). Participants completed the Timed 25-Foot Walk (T25FW) recorded in speed (feet/second) and 6-minute walk (6MW) recorded in distance (feet), and wore an accelerometer during the waking hours of a 7-day period to objectively measure physical activity as minutes/day of moderate-to-vigorous physical activity (MVPA). Participants completed a 24-hour urine collection following the protocol developed by the National Center for Health Statistics for the National Health and Nutrition Examination Survey (NHANES) for a marker of dietary sodium intake (ppm). The data were analyzed using bivariate correlations and multiple linear regression (MLR) in SPSS Statistics 22.0.

Results: MVPA was moderately correlated with 6MW (r=.50), T25FW(r=.47), and EDSS (r=-.35). Dietary sodium intake was weakly correlated with 6MW (r=.16), T25FW(r=.17), and EDSS (r=-.13). There was a moderate correlation between smoking and 6MW (r= -.40), and a weak correlation with T25FW(r= -.29), and EDSS(r= .32). MLR indicated that only MVPA explained a significant portion of variance in 6MW (ΔR²= .20, β=.48) and T25FW (ΔR²=.18, β=.45), after controlling for EDSS scores; dietary sodium intake and smoking did not explain variance in 6MW or T25FW.  

Conclusions: Physical activity was independently associated with walking performance. This suggests that increasing MVPA levels might be of greater value than decreasing salt consumption or smoking for improving clinical outcomes such as walking in MS.