A Cochrane review [Abstract] 1 included 6 studies with a total of 553 patients with tinnitus. Studies were varied in design, precluding meta-analysis of the data. Most of trials applied combination therapies, sound therapy with masking/noise generators/sound enrichment was for most of the time combined with an element of counseling. There was no long-term follow up. In one study (n=35) users found sound therapy devices subjectively helpful and tinnitus annoyance being at a lower level but found no difference between sound therapy devices, hearing aids or combination instruments. Another study (n=123) found decreased scores on the Tinnitus Handicap Questionnaire at 6 months but this was less than the effect seen for Tinnitus Retraining Therapy. The third study (n=153) showed a general improvement in the Tinnitus Reaction Questionnaire (TRQ) after treatment, when both sound therapy and counselling were used. In the fourth trial (n=45) no method was found to be more efficacious than another. In the fifth trial (n=52) no significant benefit was seen for sound therapy. In the last trial (n=99) none of 3 treatments compared in this study (information, relaxation or sound therapy) were found to be more effective than the others in facilitating tinnitus. No side effects or significant morbidity were reported from the use of sound-creating devices.
Comment: The quality of the evidence is downgraded by study quality (inadequate allocation concealment, short follow-up time), inconsistency (heterogeneity in patients, treatments and outcomes) and imprecise results (few studies for each comparison).
Another Cochrane review [Abstract] 2 included 8 studies with a total of 590 patients. Seven studies investigated the effects of hearing aids, 4 combination hearing aids and 3 sound generators. No data for the outcomes were available for any of the 3 main comparisons (comparing hearing aids, sound generators and combination devices with a waiting list control group, placebo or education/information only). Data for the additional comparisons (comparing these devices with each other) were also few, with limited potential for data pooling.
Hearing aid only vs. sound generator device only: There was no difference in their effects on the primary outcome, tinnitus symptom severity measured with the Tinnitus Handicap Inventory (THI) at 3, 6 or 12 months (1 study, n=91). The use of both types of device was associated with a clinically significant reduction in tinnitus symptom severity.
Combination hearing aid vs. hearing aid only: When tinnitus symptom severity was measured using the THI or Tinnitus Functional Index, there was no difference between them (SMD -0.15, 95% CI -0.52 to 0.22; 3 studies, n=114). The use of both types of device was again associated with a clinically significant reduction in tinnitus symptom severity. None of the studies measured depressive symptoms or depression, anxiety symptoms or generalised anxiety, or health-related quality of life as measured by a validated instrument.
Comment: The quality of the evidence is downgraded by study quality (unclear allocation concealment, short follow-up time), inconsistency (heterogeneity in treatments) and indirectness (differences in outcomes).
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