Speech and communication in Parkinson's disease: a cross-sectional exploratory study in the UK.

Objective: To assess associations between cognitive status, intelligibility, acoustics and functional communication in PD.

Design: Cross-sectional exploratory study of functional communication, including a within-participants experimental design for listener assessment.

Setting: A major academic medical centre in the East of England, UK.

Participants: Questionnaire data were assessed for 45 people with Parkinson's disease (PD), who had self-reported speech or communication difficulties and did not have clinical dementia. Acoustic and listener analyses were conducted on read and conversational speech for 20 people with PD and 20 familiar conversation partner controls without speech, language or cognitive difficulties.

Main Outcome Measures: Functional communication assessed by the Communicative Participation Item Bank (CPIB) and Communicative Effectiveness Survey (CES).

Results: People with PD had lower intelligibility than controls for both the read (mean difference 13.7%, p=0.009) and conversational (mean difference 16.2%, p=0.04) sentences. Intensity and pause were statistically significant predictors of intelligibility in read sentences. Listeners were less accurate identifying the intended emotion in the speech of people with PD (14.8% point difference across conditions, p=0.02) and this was associated with worse speaker cognitive status (16.7% point difference, p=0.04). Cognitive status was a significant predictor of functional communication using CPIB (F=8.99, p=0.005, η = 0.15) but not CES. Intelligibility in conversation sentences was a statistically significant predictor of CPIB (F=4.96, p=0.04, η = 0.19) and CES (F=13.65, p=0.002, η = 0.43). Read sentence intelligibility was not a significant predictor of either outcome.

Conclusions: Cognitive status was an important predictor of functional communication-the role of intelligibility was modest and limited to conversational and not read speech. Our results highlight the importance of focusing on functional communication as well as physical speech impairment in speech and language therapy (SLT) for PD. Our results could inform future trials of SLT techniques for PD.