Findings showed that greater average daily step count was significantly correlated with greater C2-C3 spinal cord gray matter areas, total cord area, and cortical gray matter volume.
Using a cohort of adults with progressive or relapsing multiple sclerosis (MS), researchers provided the first demonstration that spinal cord gray matter (GM) is a neuroanatomical substrate associated with physical activity (STEPS). STEPS could serve as a proxy to alert clinicians and researchers to possible changes in the structural nervous system pathology.
In the prospective, observational cohort study, 52 individuals with MS, ranging from 24 to 77 years old, were recruited from the University of California, San Francisco (UCSF) EPIC study or Neuronal Determinants of Motor Disability in MS (MOTOR) study. Participants wore a Fitbit Flex2 device on their non-dominant wrist as much as possible for 30 days, with step count data collected using the Eureka Research Platform. The median disease duration was 17.5 years, with 30% of the patients untreated at the time of initial evaluation.
Led by Valeria Block, PT, adjunct instructor, UCSF Weill Institute for Neurosciences, patients had a median Expanded Disability Status Scale (EDSS) score of 4.0 and averaged 5408 steps per day (SD, 3350) over the 30-day window. At the conclusion of the analysis, remotely monitored physical activity was found to be highly correlated with disability (EDSS; ρ = −0.60, P < 0.01), and pyramidal (ρ = −0.57, P < 0.01), cerebellar (ρ = −0.40, P < 0.01) and bowel and bladder (ρ = −0.57, P < 0.01) functional scale scores. Lower STEPS were associated with longer timed up-and-go (TUG)(ρ = –0.52; P <.01) and timed 25-foot walk (T25FW)(ρ = –0.569; P <.01) times.
More STEPS were correlated with greater endurance (ρ = 0.61; P <.01), better patient-reported perception of walking impairment (MSWS-12: ρ = –0.70; P <.01), and better quality of life (WHO Disability Assessment Schedule: ρ = –0.51; P <.01). Additionally, this group showed less issues with bladder (BLCS: ρ = –0.47; P <.01) and bowel (Bowel Control Scale: ρ = –0.39; P = .02) control.
Block et al wrote, "This study supports the potential value of STEPS as an indicator of dysfunction in systems other than ambulation. MS-specific symptoms (e.g. bowel and bladder disturbances, fatigue, pain) strongly correlated with STEPS, suggesting that remote physical activity monitoring provides additional information about overall MS disability and function beyond ambulatory volumetrics (ie, the number/volume of steps taken per day)."
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Greater fatigue (MFIS-5: ρ = –0.40; P <.01) and MS-related pain (Pain Effects Scale: ρ = –0.30; P = .02) were correlated with lower STEPS, while no correaltions were observed for self-reported mental health (ρ = –0.05; P = .69) and body mass index (ρ = 0.18; P = .39). Of note, there was a larger variance in STEPS for people with lower BMI (3450 steps vs 3019 steps for higher BMI) that was not statistically significant (P = .70).
On quantitative MRI measures, higher STEPS were significantly associated with greater spinal cord GM areas (C2-C3: ρ = 0.39; P = .04), greater GM volume fraction (ρ = 0.32; P = .04) and greater TCA (ρ = 0.35; P = .04). In addition, investigators observed positive, nonsignificant, trends toward greater STEPS and cortical GM volume fraction (ρ = 0.37; P = .06) and brain volume (ρ = 0.31; P = .21) using univariate analysis.
The study investigators concluded that, “Longitudinal observations are needed to determine directionality and examine the value of STEPS as a proxy for generalized brain and cord volume loss. These results have potential implications for structural and functional modification of disease progression via therapeutic interventions aimed at altering STEPS.”