Digital Outcomes as Biomarkers of Disease Progression in Early Parkinson's Disease: A Systematic Review

Outcomes derived from digital health technologies (DHTs) are promising candidate markers for monitoring Parkinson's disease (PD) progression. They have the potential to represent a significant shift in clinical research and therapeutic development in PD. However, their ability to track disease progression is yet to be established. This systematic review aimed to identify digital biomarkers capable of tracking early PD progression (disease duration <5 years) by reviewing longitudinal studies (minimum follow-up of 6 months). We evaluated study design and quality, population features, reported DHTs and their performance to track progression. Of 1507 records screened, 15 studies were selected, published between 2009 and 2023, with the majority coming from the last 5 years. Of the 15, 11 were observational and four were interventional trials (follow-up range: 6–60 months). Twelve different DHTs were used (8 required active tests, 8 in-hospital use), capturing features related to motor function and daily activities, including five DHTs focused on gait/posture. Rating scales were used as comparators in all but one study. Three DHTs detected longitudinal changes when scales did not, with one study showing larger effect sizes for change over time of selected DHT features compared to rating scales. Four studies showed longitudinal correlations among DHT features and rating scales. Preliminary promising data suggest that DHT-derived outcomes may help reduce sample sizes in disease-modifying trials. There is a need to standardize study methodologies and facilitate data sharing to confirm these results and further validate the sensitivity of DHTs to track disease progression in PD. © 2024 The Author(s). Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.