Acoustic analysis of voice in Parkinson’s disease: A systematic review of voice disability and meta-analysis of studies

Aim. To systematically review all the literature, focusing on instrumental quantitative assessment of voice in patients with Parkinson’s disease (PD). Furthermore, a meta-analysis was performed to identify the main characteristics of voice disturbances in PD. Patients and methods. Literature searches with the keywords ‘Parkinson’ and ‘voice’ were conducted in PubMed, EMBASE, Cochrane Library and Web of Science. Main inclusion criteria were: clinically confirmed PD and instrumented measurement of voice parameters with acoustic analysis of voice. Results. Fourteen publications met the inclusion criteria and were included in the meta-analysis. The data within the meta-analysis revealed that several voice parameters including jitter, shimmer and fundamental frequency variation presented significant variations between patients with EP and healthy controls. Significant variations of fundamental frequency, maximum phonation time, harmonic to noise ratio, standard deviation of fundamental frequency were observed, but with a high heterogeneity between the studies. On the other hand, significant variations of noise to harmonic ratio, s/z ratio, variation of amplitude were not observed. Conclusion. Acoustic analysis of voice, using an electronic system, allows the identification of changes in voice parameters for predicting the worsening of disease and for targeting specific intervention. Among the voice parameters, jitter and shimmer significantly increased in patients with PD.