Association of Daily Physical Activity with Cervical Spinal Cord Areas in Multiple Sclerosis

Background and purpose Remote activity monitoring has the potential to evaluate real-world motor function and disability outside of the clinic. The relationships of daily physical activity with spinal cord white matter and grey matter areas, MS disability, and leg function are unknown. Our purpose was to evaluate the association of remotely captured ambulatory activity with structural central nervous system pathology via quantitative magnetic imaging, in people with multiple sclerosis (MS). Methods Fifty adults with progressive or relapsing MS with motor disability who could walk at least 2 minutes, were assessed using clinical, patient-reported, and quantitative brain and spinal cord MRI measures. Fitbit Flex2, worn on the non-dominant wrist, remotely assessed activity over 30 consecutive days. Univariate and multivariate analyses were performed to assess correlations between remote physical activity and other disability metrics. Results The mean age of the cohort was 53.3 years and the median EDSS was 4.0. Average daily step counts (STEPS) were highly correlated with EDSS and walking measures (i.e., Timed 25-foot Walk, Timed up and Go tests, and subjective 12- item MS Walking Scale). Greater STEPS correlated with greater C2-C3 spinal cord grey matter areas (rho=0.39, p=0.04), total cord area (rho=0.35, p=0.04), and brain volume (rho=0.32, p=0.04). Discussion These results provide preliminary evidence that spinal cord grey matter area is a neuroanatomical substrate associated with STEPS. STEPS could serve as a proxy to alert clinicians and researchers to possible changes in structural nervous system pathology. Longitudinal observations are needed to determine directionality and 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. Remote activity monitoring has the potential to evaluate real-world motor function and disability outside of the clinic. The relationships of daily physical activity with spinal cord white matter and grey matter areas, MS disability, and leg function are unknown. Our purpose was to evaluate the association of remotely captured ambulatory activity with structural central nervous system pathology via quantitative magnetic imaging, in people with multiple sclerosis (MS). Fifty adults with progressive or relapsing MS with motor disability who could walk at least 2 minutes, were assessed using clinical, patient-reported, and quantitative brain and spinal cord MRI measures. Fitbit Flex2, worn on the non-dominant wrist, remotely assessed activity over 30 consecutive days. Univariate and multivariate analyses were performed to assess correlations between remote physical activity and other disability metrics. The mean age of the cohort was 53.3 years and the median EDSS was 4.0. Average daily step counts (STEPS) were highly correlated with EDSS and walking measures (i.e., Timed 25-foot Walk, Timed up and Go tests, and subjective 12- item MS Walking Scale). Greater STEPS correlated with greater C2-C3 spinal cord grey matter areas (rho=0.39, p=0.04), total cord area (rho=0.35, p=0.04), and brain volume (rho=0.32, p=0.04). These results provide preliminary evidence that spinal cord grey matter area is a neuroanatomical substrate associated with STEPS. STEPS could serve as a proxy to alert clinicians and researchers to possible changes in structural nervous system pathology. Longitudinal observations are needed to determine directionality and 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.