The German Restructured Vocal Fatigue Index and Characteristics of Dysphonic and Vocally Healthy Populations

Abstract

The Vocal Fatigue Index (VFI), a 19-item psychometric self-report questionnaire, enables individuals with vocal fatigue (VF) to be identified and their complaints to be characterized. The purpose of this study was to improve the German-language version (VFI-G) and to evaluate further vocal fatigue-related characteristics of dysphonic and control populations. The VFI-G was restructured by replacing the three factors that structured the original: (1) tiredness of voice and voice avoidance; (2) physical discomfort; and (3) improvement of symptoms with rest, with two clusters developed on the basis of the results of a factor analysis by Nanjundeswaran etal. (2019). The two new clusters are: (1) tiredness and avoidance plus physical discomfort; and (2) symptom improvement through rest. One hundred one (101) individuals with voice disorders and 100 vocally healthy controls from a previous study that cross-validated the VFI-G participated in this study. In order to assess the validity of our newly adjusted VFI-G, independent samples t test, receiver operating characteristic curve, likelihood ratios and the Youden Index were calculated. The association of the two VF clusters with subject characteristics such as age, sex, type of voice disorder, and level of vocal usage was also analyzed using either a Pearson correlation or a one-way ANOVA for each of the two populations. Significantly higher scores were obtained in voice-disordered subjects in both clusters (all P values < 0.001) than in healthy-voice subjects. The threshold for cluster 1 of the VFI-G was determined as ≥17.5 (74.3% sensitivity and 88.0% specificity). The results of cluster 2 are identical to that of factor 3 of the previous cross-validation study of the VFI-G. Most subject characteristics show no significant association with cluster 1 of the VFI-G, but cluster 2 seems to be moderately associated with age, type of voice disorder and level of vocal usage in the dysphonic population. The restructured VFI-G showed improved validity and can be recommended for use in the assessment of VF. Cluster 2 is also moderately associated with several vocal fatigue-related subject characteristics of the dysphonic population.