Acquired Stuttering in Parkinson's Disease

Abstract

Background: Parkinson's disease frequently causes communication impairments, but knowledge about the occurrence of new-onset stuttering is limited.

Objectives: To determine the presence of acquired neurogenic stuttering and its relationship with cognitive and motor functioning in individuals with Parkinson's disease.

Method: Conversation, picture description, and reading samples were collected from 100 people with Parkinson's disease and 25 controls to identify the presence of stuttered disfluencies (SD) and their association with neuropsychological test performance and motor function.

Results: Participants with Parkinson's disease presented with twice as many stuttered disfluencies during conversation (2.2% ± 1.8%SD) compared to control participants (1.2% ± 1.2%SD; P < 0.01). 21% of people with Parkinson's disease (n = 20/94) met the diagnostic criterion for stuttering, compared with 1/25 controls. Stuttered disfluencies also differed significantly across speech tasks, with more disfluencies during conversation compared to reading (P < 0.01). Stuttered disfluencies in those with Parkinson's disease were associated with longer time since disease onset (P < 0.01), higher levodopa equivalent dosage (P < 0.01), and lower cognitive (P < 0.01) and motor scores (P < 0.01).

Conclusion: One in five participants with Parkinson's disease presented with acquired neurogenic stuttering, suggesting that speech disfluency assessment, monitoring and intervention should be part of standard care. Conversation was the most informative task for identifying stuttered disfluencies. The frequency of stuttered disfluencies was higher in participants with worse motor functioning, and lower cognitive functioning. This challenges previous suggestions that the development of stuttered disfluencies in Parkinson's disease has purely a motoric basis.

Keywords: Parkinson's disease; cognition; motor functioning; speech; speech disfluencies; stuttering.

Figure 1

Frequency of stuttered disfluencies in each task by group, divided into subgroups based on cognitive status; colored boxes represent lower quartile, median and upper quartile; PDD, PD dementia; PD–MCI, PD mild cognitive impairment; PD–N, PD normal cognition; *P < 0.05, **P < 0.01.

Figure 2

Relationship between frequency of stuttered disfluencies (%SD) during conversation and observed global Z cognitive scores in participants with PD. Each data point represents measured values, with colors indicating cognitive status. Blue line represents predicted output of multiple linear regression model with age and sex included as covariates: %SD in conversation ~ Global_Z + age + sex. PDD, PD dementia; PD–MCI, PD mild cognitive impairment; PD–N, PD normal cognition.

Figure 3

Relationship between frequency of stuttered disfluencies (%SD) during conversation and observed UPDRS Part III motor scores in participants with PD. Each data point represents measured values, with colors indicating cognitive status. Blue line represents predicted output of multiple linear regression model with age and sex included as covariates: %SD in conversation ~ UPDRS Part_III + age + sex. PDD, PD dementia; PD–MCI, PD mild cognitive impairment; PD–N, PD normal cognition.