Speech Rhythm in Parkinson's Disease: A Study on Italian

Experimental studies on different languages have shown that neurogenetic disorders connected with Parkinson’s disease (PD) determine a series of variations in the speech rhythm. This study aims at verifying whether the speech of PD patients presents rhythmic abnormalities compared to healthy speakers also in Italian. The read speech of 15 healthy speakers and of 11 patients with mild PD was segmented in consonantal and vocalic portions. After extracting the durations of all segments, the vowel percentage (%V) and the interval between two consecutive vowel onset points (VtoV) were calculated. The results show that %V has significantly different values in mildly affected patients as compared to controls. For Italian, %V spans between 44% and 50% for healthy subjects and between 51% and 58% for PD subjects. A positive correlation was found between %V and the number of years of PD since its insurgence. The correlation with the age at which the disease insurges is weak. With regard to VtoV, PD subjects do not speak at a significantly slower rate than healthy controls, though a trend in this direction was found. The data suggest that %V could be used as a more reliable parameter for the early diagnosis of PD than speech rate.