Predictors of Tinnitus Symptom Relief With Hearing Aids in a European Multicenter Study.

Objectives: Hearing aids (HAs) are a widely accepted first-line treatment option for individuals suffering from both hearing loss and chronic tinnitus. Though HAs are highly effective at improving speech understanding, their effectiveness in ameliorating tinnitus symptoms is less clear. In recent years, several investigators have reported on attempts to predict HAs effectiveness on tinnitus symptoms using an array of variables. These included tinnitus attributes (e.g., frequency, loudness, character), audiological characteristics (e.g., degree and configuration of hearing loss), or HA signal processing parameters (e.g., gain, noise reduction processing). The aims of this study were to determine whether (1) HA usage improves tinnitus-related distress and subjective tinnitus loudness and, if so, whether (2) tinnitus frequency, degree of hearing loss, HA-use time, and the accuracy of the HA fitting influence this effect.

Design: Participants were recruited as part of the "Unification of Treatments and Interventions for Tinnitus Patients (UNITI)" study, a large multicenter randomized controlled trial conducted across five European study sites. Here, we report on the 60 participants with chronic tinnitus and mild-to-moderate hearing loss that were randomized to the HAs-only treatment arm of UNITI. HAs were programmed according to the National Acoustic Laboratories-Nonlinear 2 or Desired Sensation Level ((i/o) v.5) prescriptive formulas and the fitting was verified using in-situ verification. Subsequently, participants underwent a 12-week treatment phase. Improvements in tinnitus-related distress measured with the Tinnitus Handicap Inventory (THI) and the Tinnitus Functional Index (TFI), as well as subjective tinnitus loudness (dB HL), were assessed after 6 and 12 weeks of treatment. Accuracy of the HA fitting was operationalized as the deviation of in-situ measured real ear-aided response from target real ear-aided response parameters, as specified by the respective prescriptive formula.

Results: Participants' HA-use time averaged 4.8 hr/d (SD 2.4 hr/d) over the 12-week treatment phase. Multilevel regression analyses revealed significant reductions of tinnitus distress scores after 6 and 12 weeks (THI: F(2,156) = 7.80, p < 0.01; TFI: F(2,155) = 8.79, p < 0.01) of treatment, as compared with baseline. After 6 weeks of HA usage, THI scores were decreased by 11.64 points and TFI scores by 12.80 points, on average. There was no further statistically significant reduction in tinnitus distress between 6 and 12 weeks of HA usage (THI: M = 1.75, p = 0.89; TFI: M = -1.58, p = 0.91). Contrary to expectations, none of the included factors predicted these effects. Subjective tinnitus loudness remained unchanged with treatment (M = 1.90; F(1,105) = 0.40, p = 0.53).

Conclusions: HA usage is associated with reductions in tinnitus-related distress-irrespective of tinnitus attributes, degree of hearing loss, or HA fitting characteristics. Future research designs that include additional predictors, control groups and larger, more heterogeneous samples are needed to further clarify mechanisms of change with hearing amplification in individuals with hearing loss and chronic tinnitus.