Perceived Mobility Challenges in Rare Bone Diseases: How Real-world Gait Data Aligns

Abstract

Rare bone diseases (RBD) are highly diverse and complex, and there is a lack of understanding of the correlation between perceived mobility challenges during everyday life and the physical abilities of people with RBD. This work aimed to elucidate perceived mobility challenges among people with RBDs and examine relationships with quantitative gait metrics captured in free-living environments to draw a link between physical abilities and everyday life challenges, which can be tracked with a smartphone. This study used a comprehensive approach involving a questionnaire including 70 daily mobility challenges across different areas of daily living and semi-supervised walks in an open-world setting using a smartphone on the thigh carried in the left jeans pocket. Gait analysis is conducted using standard (cadence, variance, covariance) and nonlinear variability calculations (Lyaopnov exponent and entropy) to assess stride characteristics and walking patterns, aligning with established methodologies for gait assessment in similar contexts. In summary, nine people with RBD and nine healthy controls completed the questionnaire and provided the smartphone data. People with RBD rated balance and walking-related mobility challenges significantly higher than healthy controls. Statistical analysis indicates a strong association between the sum score of relevant challenges and the dynamic gait stability (largest Lyapunov exponent), suggesting that gait irregularity correlates with perceived mobility challenges in people with RBD. Overall, the study draws a link between physical abilities and perceived mobility challenges using a smartphone and thus presents a way to track the progress of a disease remotely using a smartphone.