Objective: To describe the stability and reliability of acoustic measures of speech in Parkinson’s Disease (PD) at 3 and 12 months.

Background: Speech biomarkers hold promise as viable proxies for disease progression and treatment response in PD. Speech changes as a function of disease progression, but little is known about its stability over medium and longer inter-recording intervals. We need to know how stable a measure is before we can make assumptions about its sensitivity and viability as a marker of change.

Method: Seventy-two individuals (71.3 years, 27 M 45 F, years since diagnosis 8.7 ± 6.1 years) with idiopathic Parkinson’s Disease were assessed at baseline, 3-months and 12-months. Participants completed a speech protocol at these time points including a reading task, a sustained vowel and producing a monologue. A variety of timing, vocal control and voice quality measures were derived from these stimuli. Disease severity was also assessed at baseline and 12-months using the MDS – Unified Parkinson’s Disease Rating Scale.

Results: Preliminary analyses indicate good stability (r >0.70) and reliability (Cronbach α > 0.7) for 7 timing acoustic variables extracted from the reading speech task at 3- and 12-month timepoints. Measures included derivatives of pause length and speech time. In contrast, 6 timing acoustic variables for extemporaneous speech task failed to display adequate stability with limited reliability over both 3- and 12-month timepoints. A similar distribution of stable and dynamic measures of voice quality are reported. Measures of stability include within subject standard deviation, ICC and correlations.

Conclusion: Acoustic analysis is known to be sensitive to variations in vocal output. Our data highlight the insidious decline in speech function over a 12 month period. Other measures appear to be adversely affected by noise in the signal rendering them unsuitable for monitoring change over time.

References: 1. Tsanas, A., et al., Nonlinear speech analysis algorithms mapped to a standard metric achieve clinically useful quantification of average Parkinson’s disease symptom severity. J R Soc Interface, 2011. 8(59): p. 842-55. 2. Vogel, A.P., et al., Reliability, stability, and sensitivity to change and impairment in acoustic measures of timing and frequency. J Voice, 2011. 25(2): p. 137-49. 3. Awan, S.N., et al., Quantifying dysphonia severity using a spectral/cepstral-based acoustic index: Comparisons with auditory-perceptual judgements from the CAPE-V. Clin Linguist Phon, 2010. 24(9): p. 742-58.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/stability-and-reliability-of-objective-measures-of-speech-in-parkinsons-disease-over-12-months/