Placebo effects in hearing-aid trials are reliable

A recent study suggested that placebo effects are a source of bias in non-blinded hearing-aid trials. Given the potential impact of this finding on the interpretation of non-blinded trials and design of future research trials, the objective of the present study was to investigate the reliability of this effect.

Using the same procedure as an earlier study, participants were told that they were taking part in a trial of new hearing-aid technology. Participants compared two devices that were acoustically identical, except one was described as "new" and the other as "conventional". Participants completed a speech-in-noise test, sound quality ratings, and rated overall personal preference for both hearing aids.

Sixteen adult hearing-aid users.

Participants had significantly better mean speech-in-noise performance (70.9% versus 66.8%, Z = 2.30, p = 0.02, effect size Pearson's r = 0.15) and sound quality ratings for the "new" hearing aid (8.1 versus 7.4, Z = - 2.99, p = 0.003, r = 0.28). A significant proportion of participants (75%) expressed an overall preference for the "new" hearing aid (p = 0.001, effect size φc = 0.66).

Placebo effects reliably impact on hearing-aid trials. In order to control for placebo effects, double-blind methodology is optimal. However, when double-blinding is not possible other strategies may be appropriate.