Retrospective evaluation of secondary effects of hearing aids for tinnitus therapy in patients with hearing loss

Abstract Objective Acoustic therapies including hearing aids and tinnitus control instruments are widely used in Japan but without high levels of evidence. The outpatient hearing aid clinic at our institution fits patients with hearing aids and instructs patients on how to use them to control tinnitus if present. In this study, we examined the effects of this approach on tinnitus. Methods One hundred and eleven of 138 patients who visited our hearing aid clinic from April 2016 to September 2018 purchased hearing aids after fitting. Sixty-six of these patients (31 men, 35 women; mean age 78.0 ± 8.0 years) had both hearing loss and tinnitus and were enrolled. The tinnitus was bilateral in 41 patients and unilateral in 25 (poor hearing ear, n = 16, good hearing ear, n = 9). Hearing aids were worn bilaterally by 23 patients and unilaterally by 43 (89 devices). Seventeen of the 23 patients wearing bilateral hearing aids had bilateral tinnitus and 6 had unilateral tinnitus, i.e., in 40 ears, the tinnitus side matched the hearing aid side (40 devices) and in 6 ears did not (6 devices). Twenty-four of 43 patients wearing unilateral hearing aids had bilateral tinnitus, meaning that in 24 ears the tinnitus side matched the hearing aid side (24 devices). In six of the remaining 19 cases with unilateral tinnitus, the hearing aid and tinnitus were on the same side (6 devices) and in 13 were on opposite sides (13 devices). Changes in the Tinnitus Handicap Inventory (THI), visual analog scale (VAS, for tinnitus discomfort, severity, and persistence), and Hospital Anxiety and Depression Scale scores were measured immediately before using a hearing aid and 12 months later. Results Significant effects of hearing aids on tinnitus were observed in all subjects (THI, p = 0.0000030), VAS (severity, p = 0.000000066; discomfort, p = 0.0000013). Significant effects were observed with bilateral hearing aids (THI, p = 0.0012; VAS for severity, p = 0.00069; VAS for discomfort, p = 0.00052) and with unilateral hearing aids (THI, p = 0.00055; VAS for severity, p = 0.000034; VAS for discomfort, p = 0.00007). Spearman's rank correlation coefficient showed a significant positive correlation between the THI and VAS scores (p = 0.0033). In cases of bilateral tinnitus, significant differences were observed with bilateral hearing aids (THI, p = 0.011; VAS for severity, p = 0.0019; VAS for discomfort; p = 0.020) and with unilateral hearing aids (THI, p = 0.00069; VAS for severity, p = 0.00071; VAS for discomfort, p = 0.000093). Conclusion Acoustic therapy using hearing aids was effective for tinnitus. Even when bilateral, a unilateral hearing aid is able to improve tinnitus. When unilateral, the ipsilateral hearing aid is able to improve tinnitus.