Relationship between acoustic voice characteristics and the duration and severity of Parkinson's disease

Parkinson’s disease (PD) is the second most common neurodegenerative disease. It affects the voice sooner and more severely than the other speech subsystems. This study investigated the relationship between disease duration (DD) and disease severity (DS) using acoustic voice characteristics (AVC) in Iranian patients with PD. This study was carried out on 23 PD subjects (12 male, 11 female) and 23 healthy subjects. DS was evaluated according to the unified Parkinson’s disease rating scale (UPDRS-III) and Hoehn and Yahr (H&Y) evaluation during medication treatment by a neurologist. AVC consisted of average fundamental frequency (F0), standard deviation of F0 (sdF0), minimum and maximum F0 (minF0, maxF0), mean percentage of jitter, shimmer, and harmonic to noise ratio (HNR) was evaluated for /a/ prolongation. Disease duration was related for all patients for F0, sdF0, minF0, maxF0, and female F0 and shimmer. There was no correlation between DD and DS (UPDRS-III) for all patients of both sexes. There was a positive correlation between H&Y and DD for all PD subjects (r = 0.557, p = 0.003) and females (r = 0.606, p = 0.037). H&Y correlated with F0, minF0, and maxF0, but no relationship was found between UPDRS-III and AVC. There is an increased influence on laryngeal signs by PD for F0 and its variations. The duration of the disease is related to disease severity but its relationship with motor disabilities needs more investigation.