Vocal Fatigue Index in Finnish-Speaking Population

Abstract

Vocal fatigue is an important complaint that may indicate a voice disorder or a risk thereof. There is a need for a reliable tool to detect and quantify vocal fatigue and distinguish dysphonic and vocally healthy speakers. The Vocal Fatigue Index (VFI) questionnaire has been found valid and reliable among speakers of different languages. This study aims to validate it for speakers of Finnish. Experimental comparative study. The VFI questionnaire was translated from English to Finnish according to the WHO recommendations. Next, it was subjected to the validation procedure. In total, 160 Finnish speakers volunteered to participate in the study. Hundred-and-eight were voice patients (83 males, 25 females) and 52 were vocally healthy controls (37 females, 15 males). As a comparison, the Voice Handicap Index (VHI) questionnaire was completed and voice samples were recorded to enable Acoustic Voice Quality Index (AVQI03.01FIN) analysis. Results from the first and second completions of the VFI(F) questionnaire correlated strongly (Spearman's rho 0.901, P=0.01). Answers to the individual questions the VFI(F) also correlated strongly, showing high internal consistency. Factor 1 (Tiredness of voice and avoidance of voice use) of the VFI correlated strongly with the VHI, and the two other factors (Physical discomfort associated with voicing and Improvement of symptoms) correlated moderately with the VHI. Factor one of the VFI(F) correlated moderately with AVQI03.01FIN and its sub-parameters, CPPS, HNR, and shimmer. The VFI(F) showed good construct validity, differentiating voice patients and controls at cut-off 13.5, with sensitivity of 0.963 and specificity of 0.885. Discriminatory power was strong for all factors: F1 AROC=0.985, F2 AROC=0.864, and F3 AROC=0.821. The VFI(F) correlates with the VHI and with AVQI01.01FIN and it is a valid and reliable tool for detecting vocal fatigue in Finnish speakers.