Objective: To explore baseline predictors of improvement in voice intensity following group-based speech intervention in PD.

Background: Speech and voice impairments are common in PD and may improve with behavioral speech interventions. However, predictors of individual treatment response remain poorly understood. Identifying clinically accessible predictors could support screening and individualized treatment planning.

Method: This secondary analysis included intervention completers from a randomized controlled trial of a 10-week group-based speech and communication intervention (HiCommunication) and an active control intervention. Responders were defined as participants with an increase in voice intensity of ≥2 dB during standardized text reading, reflecting a difference previously reported between individuals with PD and healthy controls. Nineteen baseline variables representing demographic, clinical, motor, cognitive, perceptual, and acoustic domains were entered into Random Forest classification models. To reduce circularity, primary models excluded baseline voice sound level. Model performance was evaluated using Cohen’s kappa, precision, recall, and specificity. Variable importance and partial dependence analyses were used to explore predictors of treatment response.

Results: In the HiCommunication group (n=35), 21 participants were classified as responders and 14 as non-responders. The voice intensity model showed moderate agreement beyond chance (kappa=0.57; precision=0.79; recall=0.90; specificity=0.64). Higher baseline auditory-perceptual ratings of reduced loudness and overall speech deviation were associated with higher predicted probability of improvement in voice intensity. Higher Acoustic Voice Quality Index values were also associated with higher response probability, whereas higher levodopa equivalent daily dose was associated with lower response probability. Models in the active control group showed low predictive performance.

Conclusion: Clinician-rated auditory-perceptual speech measures predicted improvement in voice intensity following HiCommunication with moderate accuracy. These clinically accessible measures may support screening, expectation-setting, and individualized planning of speech intervention in PD, but findings require replication.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/baseline-auditory-perceptual-speech-ratings-predict-improvement-in-voice-intensity-after-group-based-speech-intervention-in-parkinsons-disease/