Investigating the relationship between the Dysphonia Severity Index (DSI) and the speech and voice severity of Parkinson disease patients

   Objectives: The present study aimed at investigating the relationship between Dysphonia Severity Index (DSI) and disease speech and voice severity of Parkinson disease (PD) patients. Method. This study was a cross-sectional ones, carried out on 45 PD patients with the age range of 50 to 75 years, who were randomly selected. The Hoehn and Yahr Scale (H.Y Scale) was employed to measure the level of severity of PD. To measure the DSI, the detection of acoustic features of voice such as shimmer (dB), vital capacity (VC), semitone range (STR) and voice onset time (VOT) was needed. Therefore, participants were asked to produce the vowel /a/ three times for calculating the variables, i.e. STR, VOT, Fundamental frequency (f0), second formant (F2) and shimmer (dB). Their voices were analyzed by Praat software (version 6.0.23). F0 and F2 were utilized to calculate STR. The VOT was assessed by analyzing the spectrograph of syllable /pa/. Kruskal-Wallis test was used to find out the correlation between DSI scores and stage of PD (Y.H scale) and P-value of less than 0.05 was considered as significant. Results. A significant relationship between severe DSI and stage of PD was found and the DSI score was statistically significant compared to that of the other four groups (p-value<0.05). Conclusion. There was a significant relationship between the severity of voice changes in PD patients by DSI and the stage of their disease. Also, further studies in this field are needed in view of the fact that such information may be of cardinal importance for voice professionals to take early interventions, appropriate to the stage of PD.