Effect of clear speech intervention program on speech intelligibility in persons with idiopathic Parkinson's disease: A pilot study

Purpose: This preliminary study was designed to assess the feasibility of Clear Speech Intervention Program (CSIP) on improving speech intelligibility of persons with idiopathic Parkinson's disease (PD). Clear Speech is a behavioural approach which focuses on improving speech intelligibility of persons with PD within a relatively short frame of time. Method: A single group pretest-posttest design was used to assess the effectiveness of CSIP. Fifteen adults diagnosed with PD participated in 8 sessions of CSIP with each session lasting 45-50 minutes over a period of 4 weeks in South Korea. All the data were collected in a quiet room with an ambient noise level of equal to or less than 40 dB SPL. Data on acoustical/aerodynamic, auditory-perceptual, and self-perceptual measures were obtained pre- and post-intervention. The Phonatory Aerodynamic System (PAS) was used to analyse acoustical/aerodynamic data. Result: The acoustical/aerodynamic assessment revealed statistically significant (p < 0.01) improvements in habitual pitch, pitch range, speaking rate, and number of respirations. In the auditory-perceptual assessment, statistically significant (p < 0.01) improvements were observed in overall speech intelligibility, tone, intonation, intensity, and articulation. Medium to large effect sizes were observed for significant results. The Pearson correlation analysis showed significant (p < 0.01) and strong correlation between articulation and speech intelligibility. Conclusion: The preliminary data has provided promising results and warrants future large-scale studies with suitable controls. Additionally, future research must focus on investigating long term effects of the intervention.