Background: One third of patients with Parkinson's disease (PD) have mentioned "dysphonia" as their most debilitating communication deficit. Patient-based measurements, such as Voice Handicap Index (VHI) add necessary supplementary information to clinical and physiological assessment. There are a few studies about relation between VHI and disease severity in PD, although none of them showed any significant correlation. The goal of this study was to find correlation between these variables in Iranian PD patients.

Method: This cross-sectional, analytical and non-interventional study was done on 23 PD patients who reported a voice disorder related to their disease. They were selected from attendants of movement disorders clinic of Hazrat Rasool Akram Hospital. The relationship between disease severity (according to Hoehn and Yahr/H&Y and Unified Parkinson's Disease Rating Scale-part3 /UPDRS-III) and VHI questionnaire (and its 3 domains) was investigated based on patients' sex, UPDRS-III score H&Y and VHI.

Results: Total VHI and its 3 domains had no relationship with disease severity (H&Y) in all patients and by sex separation. However, there was a positive correlation between VHI and disease severity (UPDRS-III) (r = 0.485). There was also a relation between physical and functional domains of VHI and UPDRS (rP=0.530, rF=0.479) while no relationship observed regarding sex differences. 9 out of 18 UPDRS-III items had strong relationship with VHI (total and 3subscales).

Conclusion: Iranian PD patients feel handicap according to voice disorder caused by PD. Patient satisfaction of voice decreases with the disease severity and progression. A larger sample size is necessary to find relationship in genders. VHI is an important issue could be offered to be used in PD beside other assessments.