The effects of intensive speech treatment on intelligibility in Parkinson's disease: A randomised controlled trial

Abstract

Background: More than 6,000,000 individuals worldwide are diagnosed with Parkinson's disease (PD). Nearly 90% develop speech signs that may substantially impair their speech intelligibility, resulting in losses in their communication and quality of life. Benefits of intensive speech treatment have been documented for a range of speech signs. However, the critical question of whether speech is more intelligible after treatment has not been investigated in a randomised controlled trial (RCT). We hypothesised that intensive speech treatment would improve speech intelligibility in PD.

Method: Sixty-four patients with hypokinetic dysarthria secondary to PD participated in this single-centre, parallel arm, statistically-powered RCT. Reporting follows CONSORT guidelines for non-pharmacological treatment. Patients were recruited from US clinics and randomised using a statistician-derived minimisation algorithm, to intensive speech treatment (16 1-hour sessions/1 month) targeting voice (voice group) or targeting articulation (articulation group) or to an untreated group (no treatment group). Speech treatments were delivered by speech clinicians who specialised in treating patients with PD. Trial design minimised bias and supported equipoise. For intelligibility assessment, blinded listeners (n = 117) orthographically transcribed 57 patients' recorded, self-generated narrative speech samples, randomly presented in multi-talker babble noise. Listeners were American-English speakers, ages 18-35 years, with normal hearing. The primary outcome was baseline (pre-treatment) to post-treatment change in transcription accuracy (TA), recognised as the most objective measure of intelligibility. TA was defined as the percentage of words transcribed correctly. Listeners, data collectors, and data managers were blinded to treatment conditions and groups. Reliability was evaluated using intraclass correlation coefficients and differences amongst groups were evaluated by mixed-effects models, in accordance with the intention-to-treat approach.This trial was registered with ClinicalTrials.gov Identifier: NCT00123084.

Findings: Between June 23, 2016 and August 14, 2017, blinded listeners transcribed baseline and post-treatment speech samples for intelligibility assessment of 57 patients in the voice (n = 19), articulation (n = 19) and no treatment (n = 19) groups. Between-group differences (d) in changes from baseline to post-treatment in TA indicated significantly greater increases following treatment targeting voice than treatment targeting articulation (d = 26·2%, 95% CI 1·5 - 51·0; p = 0·04; ES=1·0). Differences between TA changes in the treatment targeting voice and in the no treatment group were significant (d = 42·8%, 95% CI 22·4 - 63·2; p = 0·0002; ES=1·8). Differences between TA changes in the treatment targeting articulation and in the no treatment group were not significant (d = 16·5%, 95% CI -6·1 - 39·2; p = 0·147; ES=0·9).

Interpretation: These findings provide the first RCT evidence that intensive speech treatment targeting voice improves speech intelligibility in PD. Thus, this evidence-based treatment may positively impact health-related quality of life for patients with PD globally when it is included in patient management.

Keywords: Dysarthria; Intelligibility; Parkinson's disease; RCT; Speech treatment.

Conflict of interest statement

EL, GMG, KFo, MB, and YMC declare no competing interests. KFr has been a paid consultant for LSVT Global, Inc. for many years. LR is employed as Chief Scientific Officer and has ownership interest in the for-profit company LSVT Global, Inc. She is in full compliance with Federal Statute 42 C.F.R. Part 50, Subpart F (see https://grants.nih.gov/grants/policy/coi/index.htm). She has fully disclosed any conflict of interest and her conflict of interest management plan has been approved by the Office of Conflict of Interest and Commitment at the University of Colorado, Boulder and she is in full compliance. LR reports grants from the National Institutes of Health during the conduct of the study.

© 2020 The Authors.

Figures

Fig. 1

Trial Profile. In this RCT, patients with PD generated speech samples. Subsequently, listeners performed intelligibility assessment of these speech samples. Data are summarized in the Results. Please see Ramig and colleagues’ previous work for details on patients with PD . PD=Parkinson's disease; BDI-II=Beck Depression Inventory-II; MMSE=Mini Mental Status Exam; ENT=Ear Nose Throat examination. *For details on PD patient enrolment, see Ramig and colleagues’ previous work .

Fig. 2

Transcription (TA) accuracy by treatment. Error bars denote standard errors. For treatment targeting voice (voice group), within group increases in TA from baseline to post-treatment were significant (p<0.0001). For treatment targeting articulation (articulation group), increases in TA from baseline to post-treatment were not significant (p = 0.18). For the no treatment group, decreases in TA were significant (p = 0.0115). Between-group comparisons of changes in TA from baseline to post-treatment indicated that increases in the voice group were significantly greater than those for both the articulation group (p = 0.04) and the no treatment group (p = 0.0002). Differences in TA changes between the articulation group and the no treatment group were not significant (p = 0.147).