Abstract
Early features of Parkinson's disease (PD) include both motor and cognitive changes, suggesting shared common pathways. A common motor dysfunction is postural instability, a known predictor of falls, which have a major impact on quality of life. Understanding mechanisms of postural dynamics in PD and specifically how they relate to cognitive changes is essential for developing effective interventions. The aims of this study were to examine the changes that occur in postural metrics over time and explore the relationship between postural and cognitive dysfunction. The study group consisted of 35 people (66 ± 8years, 12 female, UPDRS III: 22.5 ± 9.6) diagnosed with PD who were recruited as part of the Incidence of Cognitive Impairment in Cohorts with Longitudinal Evaluation—PD Gait (ICICLE-GAIT) study. Postural and cognitive assessments were performed at 18, 36, and 54 months after enrolment. Participants stood still for 120 s, eyes open and arms by their side. Postural dynamics were measured using metrics derived from a single tri-axial accelerometer (Axivity AX3, York, UK) on the lower back. Accelerometry metrics included jerk (derivative of acceleration), root mean square, frequency, and ellipsis (acceleration area). Cognition was evaluated by neuropsychological tests including the Montreal Cognitive Assessment (MoCA) and digit span. There was a significant decrease in accelerometry parameters, greater in the anteroposterior direction, and a decline in cognitive function over time. Accelerometry metrics were positively correlated with lower cognitive function and increased geriatric depression score and negatively associated with a qualitative measure of balance confidence. In conclusion, people with PD showed reduced postural dynamics that may represent a postural safety strategy. Associations with cognitive function and depression, both symptoms that may pre-empt motor symptoms, suggest shared neural pathways. Further studies, involving neuroimaging, may determine how these postural parameters relate to underlying neural and clinical correlates.
Highlights
Parkinson’s disease (PD) is a common progressive neurodegenerative disease with a UK incidence of 84 per 100,000 in adults over 50 years [1]
There was a significant effect of time for Levodopa equivalent daily dose (LEDD), Hoehn, and Yahr stage and MDS-UPDRS III [X2(3) = 78.0, p < 0.001; X2(3) = 18.1, p < 0.001; X2(3) = 41.0, p < 0.001, respectively]
The MDS-UPDRS III score was significantly greater at baseline compared to 18 months (Z = −4.7, p < 0.001), 36 months compared to 18 months (Z = −4.0, p < 0.001) and 54 months compared to baseline (Z = −4.8, p < 0.001)
Summary
Parkinson’s disease (PD) is a common progressive neurodegenerative disease with a UK incidence of 84 per 100,000 in adults over 50 years [1]. Clinical characterizations include both motor and non-motor manifestations, indicative of a multisystem neurodegenerative disease [2]. Common motor symptoms include resting tremor, bradykinesia, rigidity, and postural instability [3]. Postural instability is clinically important as it is a predictor of falls, which impact on quality of life [4]. Falls may result in injury, leading to possible loss of functional independence, institutionalization and a poor quality of life [5, 6]. Previous studies indicate that 38–68% of people with PD are subject to falls, 25% of which have two or more falls every 6 months [7,8,9,10]
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