The Acoustic Voice Quality Index (AVQI) in People with Parkinson's Disease Before and After Intensive Voice and Articulation Therapies: Secondary Outcome of a Randomized Controlled Trial

Objectives: The majority of individuals with Parkinson's disease (PD) experience voice and speech problems during the course of the disease. Despite the importance of voice quality in communication and the documented disordered voice quality in PD, few studies have explored the effects of speech treatment on this variable.

Study design/methods: A parallel arm, unblinded randomized controlled trial (RCT) was conducted with two active comparators, LSVT LOUD (n = 23) and LSVT ARTIC (n = 20), and an inactive comparator group of untreated individuals with PD (n = 22). A group of 20 healthy adults was also included for pre-treatment analysis. Voice recordings were obtained pre-treatment, immediately post-treatment and at 6-month follow-up. The acoustic voice quality index (AVQI) is reported here as a secondary outcome measure of the RCT. Linear mixed-effects regression analysis was performed with AVQI and sound pressure level (SPL) as dependent variables. Pearson correlation coefficient analysis was also conducted to explore the relationship between voice quality and SPL.

Results: Statistically significant improvements in AVQI and SPL from pre-treatment to post-treatment and follow-up were only observed in the LSVT LOUD group. Voice quality significantly improved only from pre-treatment to follow-up in the LSVT ARTIC group, whilst significant improvements in SPL were observed during maximum phonation only immediately post-treatment. No significant changes were observed in the untreated group.

Discussion: This study investigated the effects of intensive speech treatment targeting voice or targeting articulation on voice quality, as measured by the AVQI, in individuals with PD. Findings indicate that voice-focused treatment leads to greater improvements in voice quality in this population.