The Dysphonia Severity Index as a Mediator for the Relationship Between the Vocal Fatigue Index and the Voice-Related Quality of Life Among Elementary Teachers with Voice Complaint

Introduction. The multi-causal nature of voice disorders is required to be evaluated systematically and in different ways to determine the exact nature of the disorder. Given the importance of voice for teachers, the present study was designed to investigate the causal relationship between vocal fatigue index (VFI) and the voice-related quality of life (VRQOL) with the mediating role of the dysphonia severity index (DSI) among teach-ers with voice complaints. Method. This analytical and non-interventional study examined 57 male and 122 female teachers with voice complaint. The study used DSI, VRQOL and VFI. Acoustic data were extracted using Praat software, and statis-tical analysis was performed using SPSS. Direct and indirect path testing of the proposed research model was per-formed using path analysis and bootstrapping, respectively. Results. Model fit indices showed that the proposed model is data fit (CFI = 0.998, GFI = 0.996, RMSEA = 0.072). Moreover, all subtests of the VFI had a significant direct relationship with VRQOL. The DSI, measured using the proposed model, does not have a significant relationship with VRQOL. Therefore, the indi-rect path of the present model (including tiredness of voice to VRQOL through DSI, physical discomfort to VRQOL through DSI and the improvement of symptoms with rest to VRQOL through DSI) did not show a sig-nificant relationship. Conclusion. The vocal fatigue directly affects VRQOL. However, it does not affect it indirectly through DSI. Therefore, it can be concluded that although DSI and VRQOL are correlated, they do not have a causal relation-ship and DSI, as an acoustic parameter, cannot be an appropriate mediator for the relationship between the VFI and VRQOL.