Supplementary Material for: Ambulatory Activity Components Deteriorate Differently across Neurodegenerative Diseases: A Cross-Sectional Sensor-Based Study

Background and Purpose: Reduced ambulatory activity is a major burden in neurodegenerative disease (NDD), leading to severe restrictions in social participation and further deterioration of motor capacities. However, objective evidence on walking behavior patterns and components underlying this impairment and its decline with disease progression is scarce for many NDDs. We aimed to unravel the detailed metrics underlying the reduced ambulatory activity in selected NDDs, and their relation to disease duration. We hypothesized that progressively reduced ambulatory activity is a feature shared across different NDDs, characterized by changes in both common and distinct components. Methods: Sixty-five subjects with NDD (n = 34 degenerative ataxia; n = 15 progressive supranuclear palsy, and n = 16 Parkinson's disease) and 38 healthy older adults (total n = 103) wore a three-axial accelerometer (activPAL3™) for 7 consecutive days. Detailed metrics of ambulatory activity were calculated. Results: The average daily walking duration was significantly decreased in all three NDDs, yet characterized by a differential pattern of changes in number and length of walking bouts and sit-to-stand transfers. Decline in walking duration progressed with increased disease duration in all three NDDs, yet at a differing rate. This decline was associated with progressive reductions in walking bout length and walking behavior pattern diversity in all three NDDs. Conclusions: These findings provide objective evidence that reduced ambulatory activity is a shared feature across different NDDs. Moreover, they reveal that several underlying walking behavior components change with increasing disease duration, yet at a differing rate in different NDDs. This indicates that metric analysis of ambulatory activity might provide ecologically relevant and disease-specific progression and outcome markers in several NDDs.