Development and Validation of a Brief Version of the Vanderbilt Fatigue Scale for Adults: The VFS-A-10.

OBJECTIVES

Listening-related fatigue can be a significant problem for adults who struggle to hear and understand, particularly adults with hearing loss. However, valid, sensitive, and clinically useful measures for listening-related fatigue do not currently exist. The purpose of this study was to develop and validate a brief clinical tool for measuring listening-related fatigue in adults.

DESIGN

The clinical scale was derived from the 40-item version of the Vanderbilt Fatigue Scale for Adults (VFS-A-40), an existing, reliable, and valid research tool for measuring listening-related fatigue. The study consisted of two phases. Phase 1 ( N = 580) and Phase 2 ( N = 607) participants consisted of convenience samples of adults recruited via online advertisements, clinical records review, and a pool of prior research participants. In Phase 1, results from item response theory (IRT) analyses of VFS-A-40 items were used to identify high-quality items for the brief (10-item) clinical scale: the VFS-A-10. In Phase 2, the characteristics and quality of the VFS-A-10 were evaluated in a separate sample of respondents. Dimensionality was evaluated using exploratory factor analyses (EFAs) and item quality and characteristics were evaluated using IRT. VFS-A-10 reliability and validity were assessed in multiple ways. IRT reliability analysis was used to examine VFS-A-10 measurement fidelity. In addition, test-retest reliability was assessed in a subset of Phase 2 participants ( n = 145) who completed the VFS-A-10 a second time approximately one month after their initial measure (range 5 to 90 days). IRT differential item functioning (DIF) was used to assess item bias across different age, gender, and hearing loss subgroups. Convergent construct validity was evaluated by comparing VFS-A-10 responses to two other generic fatigue scales and a measure of hearing disability. Known-groups validity was assessed by comparing VFS-A-10 scores between adults with and without self-reported hearing loss.

RESULTS

EFA suggested a unidimensional structure for the VFS-A-10. IRT analyses confirmed all test items were high quality. IRT reliability analysis revealed good measurement fidelity over a wide range of fatigue severities. Test-retest reliability was excellent ( rs = 0.88, collapsed across participants). IRT DIF analyses confirmed the VFS-A-10 provided a valid measure of listening-related fatigue regardless of respondent age, gender, or hearing status. An examination of associations between VFS-A-10 scores and generic fatigue/vigor measures revealed only weak-to-moderate correlations (Spearman's correlation coefficient, rs = -0.36 to 0.57). Stronger associations were seen between VFS-A-10 scores and a measure of perceived hearing difficulties ( rs = 0.79 to 0.81) providing evidence of convergent construct validity. In addition, the VFS-A-10 was more sensitive to fatigue associated with self-reported hearing difficulties than generic measures. It was also more sensitive than generic measures to variations in fatigue as a function of degree of hearing impairment.

CONCLUSIONS

These findings suggest that the VFS-A-10 is a reliable, valid, and sensitive tool for measuring listening-related fatigue in adults. Its brevity, high sensitivity, and good reliability make it appropriate for clinical use. The scale will be useful for identifying those most affected by listening-related fatigue and for assessing benefits of interventions designed to reduce its negative effects.