Effects of Water-Resistance Therapy on Multidimensional Voice Outcomes in Older Patients with Presbyphonia.

OBJECTIVE: To evaluate the effect of a structured voice therapy program incorporating Water-Resistance Therapy (WRT), a Semi-Occluded Vocal Tract Exercise, on voice quality in patients with presbyphonia. METHODS: A total of 61 patients who underwent WRT were enrolled. Voice outcomes were assessed using the Acoustic Voice Quality Index (AVQI), Acoustic Breathiness Index (ABI), auditory-perceptual (A-P) ratings, and Voice Handicap Index-10 (VHI-10). Depending on normality, paired t tests or Wilcoxon signed-rank tests were used to compare pre-post differences. Correlation analysis examined inter-measure relationships, and ROC curve analysis identified AVQI and ABI cutoffs associated with clinically meaningful voice improvement. RESULTS: All parameters improved significantly with large effect sizes (Cohen's d = 1.03-1.60 for acoustic and self-reported measures; r = 0.80-0.81 for A-P ratings, P < 0.01), with over 80% of patients showing improvement. A-P ratings demonstrated high reliability (ICC = 0.78-0.86). Acoustic measures correlated strongly with A-P ratings (r = 0.76-0.82) and VHI-10 scores (r = 0.65-0.79). ROC analysis identified cutoff values of 5.3 and 5.8 for AVQI and ABI, respectively, as indicative of treatment-related improvement (AUC = 0.78 for both). CONCLUSION: A WRT-based treatment program produced clinically meaningful, multidimensional improvements in presbyphonia, supported by strong inter-measure correlations and comparable discriminative performance across acoustic indices in detecting treatment response. These findings support WRT-based intervention as an effective treatment for age-related voice changes.