The Effectiveness of Vocal Health Programs in the Prevention of Voice Disorders in Teachers: A Systematic Review and Meta-Analysis.

PURPOSE: To assess the effectiveness of voice disorder prevention programs and to verify the effectiveness of direct and indirect voice training on the Voice Handicap Index (VHI), Voice-Related Quality of Life (V-RQOL), maximum phonation time (MPT), fundamental frequency and shimmer, for the prevention of voice disorders in regular-school teachers. METHODS: This is a literature review with meta-analysis, carried out through an electronic search in PubMed, Cochrane Central, Embase, Web of Science, Scopus and BVS, and Google Scholar, as well as ClinicalTrials.gov databases for gray literature. SELECTION CRITERIA: Randomized clinical trials and quasi-experimental studies were selected. The population consisted of regular schoolteachers, adults, with no vocal complaints submitted to a vocal health education and prevention program of voice disorders classified as direct (direct vocal tract training) and indirect (vocal hygiene guidelines that influence voice production). The outcomes vocal self-assessment: fundamental frequency, aerodynamic measurements (maximum phonation time), acoustic measures (shimmer) was analyzed in comparison with other vocal interventions or no vocal intervention. DATA ANALYSIS: Studies were independently assessed using the Cochrane Risk of bias and ROBINS-I tools. Effect sizes were calculated only at post-treatment. GRADE criteria were used to assess the quality of evidence. RESULTS: Twenty-six studies were included but, only 12 studies were included in the meta-analysis and investigated for direct and/or indirect intervention compared to no intervention. No studies were judged to be at low risk of bias, and the quality of evidence was considered high only for the Voice Handicap Index. No evidence was found that suggested effectiveness of direct and indirect voice training for any of the outcomes: VHI -1.87 (95% CI -7.03, 3.30), maximum phonation time -1.11 (95% CI -3.40, 1.17), fundamental frequency 0.87 (-1.06, 2.79) and shimmer 0, 28 (-1.50, 2.05). CONCLUSION: Results of this study were not considered significant to conclude on the effectiveness of voice training for preventing dysphonia in teachers.