Efficacy of Resonant Voice Therapy in Individuals With Voice Disorders: Systematic Review and Meta-Analysis

To systematically evaluate the efficacy of resonant voice therapy (RVT) in individuals with voice disorders and to quantitatively examine its effects across auditory-perceptual, subjective, and acoustic outcome domains.

A systematic literature search was conducted across Web of Science, PubMed, Scopus, Embase, Cochrane Library, and CNKI databases to identify randomized controlled trials (RCTs) and quasi-RCTs investigating RVT in pediatric and adult populations with voice disorders. A meta-analysis was performed for outcomes deemed clinically and statistically comparable, using fixed- or random-effects models. Outcomes that could not be quantitatively synthesized were summarized narratively. Risk-of-bias (RoB) was assessed using the Cochrane RoB tool.

Eight eligible studies involving 321 participants were finally included. The meta-analysis showed that RVT significantly improved auditory-perceptual voice quality, as reflected by GRBAS (G) (mean difference [MD] = -0.52, 95% confidence interval [CI] [-0.75, -0.30], P < 0.00001). Significant decreases in subjective outcomes, particularly voice handicap index-30, were observed when RVT was compared with no-direct-voice intervention (MD = -9.64, 95% CI [-14.70, -4.58], P = 0.0002). Among acoustic parameters, RVT was associated with significant extensions in maximum phonation time (MD = 4.36, 95% CI [2.45, 6.28], P < 0.00001) and drops in Jitter (MD = -0.19, 95% CI [-0.26, -0.12], P < 0.00001). However, results for Shimmer (MD = -0.70, 95% CI [-1.85, 0.44], P = 0.23) and fundamental frequency (standardized mean difference = 0.02, 95% CI [-0.43, 0.47], P = 0.93) were inconsistent or nonsignificant.

RVT is an effective intervention for improving auditory-perceptual voice quality and patient-reported voice handicap in individuals with voice disorders, with selective benefits on acoustic measures. Although the evidence is limited by clinical and methodological heterogeneity and the small number of high-quality trials, the findings support the applicability of RVT and underscore the need for well-designed studies with standardized outcome measures to strengthen the evidence base.