Speech intelligibility of Parkinson's disease patients evaluated by different groups of healthcare professionals and naïve listeners.

Introduction: Speech intelligibility, how well a listener comprehends the speaker's message, is related to the listener' expertise and type of the message conveyed. There is no evidence about speech intelligibility in different groups of healthcare professionals and naïve listeners.

Objectives: This study is the first to understand if there were differences in the speech intelligibility of Parkinson's Disease (PD) patients by different experienced and naïve listeners, according to the speech stimuli and dysarthria severity.

Materials and methods: Randomly digitised audio-files (50 words and 50 sentences) of 10 PD patients, one without dysarthria and 9 with different dysarthria severities (3 each: mild, moderate and severe dysarthria), were collected from a database of 60 PD patients' audio-files. A jury panel was formed by five different listeners groups including 10 speech and language therapists, 10 neurologists, 10 PD relatives, 12 PD patients, and 10 people from the general population. The jury panel transcribed single words and sentences from the audio recordings, the percentage correctly understood was calculated and the results were compared between the groups.

Results: Multiple comparisons showed significant speech intelligibility differences between healthcare professionals and naïve listerners in words (highest effect size, η² = 0.7) and sentences (the highest effect size: η² = 0.6). Pairwise comparisons revealed that those significant differences were specifically in words with moderate and severe dysarthria and sentences with all severity levels of dysarthria.

Conclusion: The groups of healthcare professionals who work with dysarthria are more likely to understand the PD patients' speech than the groups of naïve listeners.