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Investigating the Relationship Between the Dysphonia Severity Index and the Speech and Voice Severity of Parkinson Disease Patients

Objectives: This study aims to investigate the relationship between dysphonia severity index (DSI), speech disease and voice severity of Parkinson disease (PD) patients. Methods: This was a cross-sectional study, carried out on 45 randomly selected PD patients with the age range of 50 to 75 years. The Hoehn and Yahr scale (H.Y scale) was employed to measure the severity of PD. To measure the DSI, we required detecting the acoustic features of the voice, such as shimmer (dB), vital capacity (VC), semitone range (STR), and voice onset time (VOT); therefore, the 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 the Praat software (version 6.0.23). F0 and F2 were utilized to calculate the STR. The VOT was assessed by analyzing the spectrograph of the syllable /pa/. The Kruskal-Wallis test was used to understand the correlation between DSI scores and the stage of PD (Y.H scale); the P value of less than 0.05 was considered significant. Results: A significant relationship was detected between severe DSI and the stage of PD. Meanwhile, the DSI score was statistically significant compared to the scores of the other four groups (P<0.05). Discussion: There was a significant relationship between the severity of voice changes in PD patients by DSI and the stage of their disease. Further studies in this field are needed considering that such information may be of cardinal importance for voice professionals to take early interventions, appropriate to the stage of PD.