Associations of non-motor symptoms with perceptual speech impairments in Parkinson's disease

Communication impairments are common, multifaceted, and progressive symptoms of Parkinson's disease (PD), and have deleterious impacts on individual wellbeing. Self-awareness of communication impairments and the rate and extent of decline in speech skills vary substantially across individuals and are challenging to predict. To address these, we aimed to (1) evaluate associations between non-motor symptoms (NMS) and speech impairment at year seven and (2) compare the progression of self-perceived and examiner-rated speech impairment ratings scores across a seven-year follow-up period.

The study included 417 PD participants from the Parkinson's Progression Marker Initiative. NMS were assessed using validated instruments covering sleep, olfaction, neurobehavioral, autonomic, and neuropsychological domains. Speech severity was measured using the Movement Disorder Society-Unified Parkinson's Disease Rating Scale. Multivariate ordinal logistic regression examined associations between baseline NMS and speech severity at year seven. Changes in speech severity scores over seven years were analyzed using Friedman's test.

Several NMS were associated with self-perceived and examiner-rated speech severity at year seven. Baseline REM sleep behavior disorder and autonomic dysfunction were associated with significantly higher odds of speech impairment at year seven. For self-perceived speech, odds ratios (OR) and 95% confidence interval (CI) were 1.58 (1.18-2.12) for REM sleep behavior disorder and 1.71 (1.24-2.36) for autonomic dysfunction. For examiner-rated speech, ORs were 1.45 (1.06-1.98) and 1.71 (1.21-2.42), respectively. Daytime sleepiness was associated with worse examiner-rated speech scores at year seven (OR = 1.51, 95% CI 1.10-2.09). Both self-perceived and examiner-rated speech impairments worsened over seven years (p < 0.001), with no significant differences between the two assessments (p > 0.05).

Several NMS were associated with worse speech ratings at year seven. These simple and readily accessible instruments may help identify individuals at greater risk of worsening speech skills, with the goal of enabling timely and targeted speech and language therapy. The consistency between self-perceived and examiner-rated speech scores suggests individuals with PD maintain good insight into their speech impairments, despite a decline in communication abilities.