Progression of dysprosody in Parkinson's disease over time--a longitudinal study.

Parkinsonian speech or hypokinetic dysarthria results from a multidimensional impairment of phonation, articulation, and prosody. Although the dysprosody in Parkinson's disease (PD) is well described (alterations in speech rate and pause time, speech intensity and pitch variation), little is known about alterations of these single prosodic parameters over a longer time course. The objective of this study is to analyze changes of speech rate and pitch variation in patients with PD over time and to compare these findings with healthy controls. Patients with PD (N = 50; 27 male and 23 female) and n = 50 age-matched healthy controls (25 male, 25 female) were tested and retested after at least 7 months (mean: 25.02; median: 21; SD: 17.44; range: 7-79 months). In the PD group, motor impairment according to UPDRS motor score was similar at first and second visit. The participants had to accomplish a standardized four sentence reading task. The acoustical analysis was performed using a standard head-worn microphone for voice recordings and commercial audio software (WaveLab). For the determination of intonation based upon fundamental frequency (F(0)) variation, we used a computer analysis program (Praat). Articulatory velocity was determined by measurement of syllable rate and pause ratios. In the PD group, total speech rate (syllables per second related to total speech time/TSR) and net speech rate declined from first to second examination, especially in the male patients, but showed no significant differences to the control group. The course of pitch variation revealed some gender particularities. Whereas female patients' pitch variability declined over time, male patients' intonation variability remained relatively stable. F(0) variation in male and female patients with PD were significantly reduced compared with the control group in the first examination and the follow up as well. Progression of prosodic impairment over time showed no correlation to disease duration or UPDRS motor score. Some aspects of dysprosody in PD show characteristic changes over time, but show no clear correlation with general motor impairment as assessed by UPDRS motor score. Therefore, we suspect that the underlying mechanism could be independent from dopaminergic deficits.