Digital motor and cognitive variability as early markers of the prodromal Parkinsons disease spectrum
- 1Centre for Preventive Neurology, Wolfson Institute of Population Health, Queen Mary University of London, London, United Kingdom.
Abstract
BackgroundIndividuals with isolated REM sleep behaviour disorder (iRBD) show motor and cognitive dysfunction prior to clinical -synucleinopathy. Performance instability may represent an earlier marker of neurodegeneration but remains underexplored using digital tests.
ObjectivesTo assess baseline and longitudinal differences in motor and cognitive performance and examine performance variability in iRBD and related phenotypes.
MethodsThree PD-risk-stratified prodromal cohorts (normosmic probable RBD (pRBD), hyposmic pRBD and polysomnography-confirmed iRBD (PSG-iRBD)) were compared with healthy controls. Participants completed the BRadykinesia Akinesia Incoordination (BRAIN) test, Distal Finger Tapping (DFT) test, and Trail Making Test (TMT) remotely. Motor outcomes included kinesia score (KS), akinesia time (AT), and incoordination score (IS); cognitive outcomes included TMT-A/B reaction times and executive function. Baseline differences were analysed using age- and sex-adjusted logistic regression, longitudinal change using linear mixed-effects models, and variability using the mean of squared successive differences (MSSD) and heteroscedastic modelling.
ResultsAt baseline, PSG-iRBD participants showed greater motor and cognitive impairment than controls, hyposmic pRBD demonstrated intermediate deficits and normosmic pRBD participants showed milder but significant impairments. Linear mixed-effects models showed no change in motor trajectories across all groups, while executive function declined significantly in PSG-iRBD (p=0.001). However, variance modelling showed widespread variability. Cognitive variability was elevated in PSG-iRBD and hyposmic pRBD participants (MSSD p<0.035), and heteroscedastic modelling captured significant visit-specific motor instability across all prodromal cohorts on the BRAIN test (all p<0.02).
ConclusionsPerformance variability precedes measurable linear decline across PD-risk stratified groups. Remote digital testing offers a scalable framework to capture this early instability.
Related
- Explainable machine learning identifies predictors for postural instability and cognitive impairment in early Parkinsons Disease
- Digital biomarkers derived from wearable and portable devices in prodromal Parkinson’s disease and at-risk populations: a scoping review
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- Cognitive Performance in Prodromal Neuronal α Synuclein Disease
- Vascular and neurodegenerative contributions to cognitive decline and multidomain progression in de novo Parkinsons disease
BibTeX
@misc{chohan2026digital,
title = {{Digital motor and cognitive variability as early markers of the prodromal Parkinsons disease spectrum}},
author = {H. Chohan and S. Waters and L. Perez-Carbonell and G. Leschziner and M. T. Perinan and B. Huxford and S. Eriksson and J. Bestwick and A. Schrag and A. Noyce and C. Simonet},
howpublished = {medRxiv},
year = {2026},
month = sep,
doi = {10.64898/2026.09.06.26358479},
url = {https://www.medrxiv.org/content/10.64898/2026.09.06.26358479v1},
note = {CC BY-NC-ND},
}
RIS
TY - UNPB
TI - Digital motor and cognitive variability as early markers of the prodromal Parkinsons disease spectrum
AU - H. Chohan
AU - S. Waters
AU - L. Perez-Carbonell
AU - G. Leschziner
AU - M. T. Perinan
AU - B. Huxford
AU - S. Eriksson
AU - J. Bestwick
AU - A. Schrag
AU - A. Noyce
AU - C. Simonet
PY - 2026
DA - 2026/09/06
PB - medRxiv
DO - 10.64898/2026.09.06.26358479
UR - https://www.medrxiv.org/content/10.64898/2026.09.06.26358479v1
AB - BackgroundIndividuals with isolated REM sleep behaviour disorder (iRBD) show motor and cognitive dysfunction prior to clinical -synucleinopathy. Performance instability may represent an earlier marker of neurodegeneration but remains underexplored using digital tests. ObjectivesTo assess baseline and longitudinal differences in motor and cognitive performance and examine performance variability in iRBD and related phenotypes. MethodsThree PD-risk-stratified prodromal cohorts (normosmic probable RBD (pRBD), hyposmic pRBD and polysomnography-confirmed iRBD (PSG-iRBD)) were compared with healthy controls. Participants completed the BRadykinesia Akinesia Incoordination (BRAIN) test, Distal Finger Tapping (DFT) test, and Trail Making Test (TMT) remotely. Motor outcomes included kinesia score (KS), akinesia time (AT), and incoordination score (IS); cognitive outcomes included TMT-A/B reaction times and executive function. Baseline differences were analysed using age- and sex-adjusted logistic regression, longitudinal change using linear mixed-effects models, and variability using the mean of squared successive differences (MSSD) and heteroscedastic modelling. ResultsAt baseline, PSG-iRBD participants showed greater motor and cognitive impairment than controls, hyposmic pRBD demonstrated intermediate deficits and normosmic pRBD participants showed milder but significant impairments. Linear mixed-effects models showed no change in motor trajectories across all groups, while executive function declined significantly in PSG-iRBD (p=0.001). However, variance modelling showed widespread variability. Cognitive variability was elevated in PSG-iRBD and hyposmic pRBD participants (MSSD p<0.035), and heteroscedastic modelling captured significant visit-specific motor instability across all prodromal cohorts on the BRAIN test (all p<0.02). ConclusionsPerformance variability precedes measurable linear decline across PD-risk stratified groups. Remote digital testing offers a scalable framework to capture this early instability.
ER -