Speech rate and rhythm in Parkinson's disease

Articulatory rate and pause time in a standardized reading task in Parkinson's disease (PD) patients in correlation to disease duration and severity as compared to healthy controls were analyzed. In 121 PD patients and 70 healthy controls, an acoustical analysis was performed on the first and last sentence of a standardized 170-syllabic text, using a commercial audio software. Articulatory rate and speech to pause ratios were calculated by measuring the length of each syllable and each pause both at the end of words and within polysyllabic words. No significant difference in overall articulatory rate was found between PD patients and controls. Both groups showed an accelerated speech rate in the last sentence compared to the first; however, PD patients had a higher speech acceleration than did controls. PD patients exhibited a significantly reduced percental pause duration in relation to total speech time in the first sentence and a reduced percental pause time within polysyllabic words. PD patients made significantly less but longer pauses at the end of words and less pauses within polysyllabic words. UPDRS III showed an inverse relation to number and rate of intraword pauses, and disease duration was negatively correlated with articulatory rate. The characteristics of parkinsonian speech feature was not only a stronger acceleration of articulation rate in the course of speaking but also a significant reduction of the total numbers of pauses, indicating an impaired speech rhythm and timing organization.