Abstract Purpose Investigate the association between levodopa therapy and vocal characteristics in Parkinson’s disease patients. Search strategy Studies published at MEDLINE, LILACS, and SciELO, from 1960 to December 2016. A systematic review and meta-analysis was performed using the following keywords: Parkinson’s disease; levodopa; L-dopa; voice; speech disorders; dysphonia; dysarthria. After analyzing titles and abstracts, two independent reviewers selected all clinical trials that met the eligibility criteria and selected the articles and the data recorded in a previously standardized table. Selection criteria Trials published in English between 1960 and December 2016 individuals with clinical diagnosis of Parkinson’s disease; use of levodopa therapy in stable doses; acoustic analysis combined or not with auditory-perceptual analysis to evaluate the vocal parameters under investigation. Data analysis The following vocal parameters were analyzed: fundamental frequency (F 0), jitter, and vocal intensity. Standardized mean differences (SMD) were calculated using the Comprehensive Meta-analysis V2 software. Results Nine articles met the eligibility criteria and were selected, with a total of 119 individuals. From these, six articles with 83 individuals were included in the meta-analysis. During the levodopa therapy “on” state, modifications in F 0 (SMD=0.39; 95% CI - 0.21-0.57) and jitter (SMD=0.23; 95% CI - 0.02-0.45) were observed. Vocal intensity was not affected (SMD=0.09; 95% CI - 0.22-0.39) by levodopa ingestion. Data of the included studies were controversial in the auditory-perceptual analysis of voice. Conclusion Levodopa therapy modifies F0 and jitter. No changes in vocal intensity were observed in either the “on” or “off” states of levodopa therapy.
Impact of levodopa treatment in the voice pattern of Parkinson’s disease patients: a systematic review and meta-analysis