A Prospective Multi-Centre Study of the Benefits of Bilateral Hearing Aids

In Brief Objectives: In this prospective study the benefits of a second hearing aid were evaluated objectively (functional tests) and subjectively (questionnaires). In addition, a battery of diagnostic tests (by headphones) was applied to determine whether the bilateral benefit could be predicted from a priori tests. Design: Diagnostic tests by headphones (binaural masking level difference, interaural time difference, and speech reception thresholds per ear) were conducted to focus on binaural functioning, and free-field tests were used for unilateral and bilateral hearing aids in the same participants to analyze differences in speech intelligibility and horizontal localization. The participants were recruited from the regular patients for hearing aid fitting in eight Audiological Centers. Eventually, 214 participants participated in this study. Each of these participants was fitted with two new hearing aids and started a trial period. Before the trial period the headphone tests were conducted, after the trial period the free-field tests were conducted with one and two hearing aids, and the participants completed a questionnaire. Results and Conclusions: In a number of respects bilaterally fitted hearing aids offered a benefit relative to unilaterally fitted hearing aids (the so-called bilateral benefit), both subjectively (questionnaire) and objectively (speech perception in noise and localization). However, we found large interindividual differences and not all differences were clinically relevant. The results of the diagnostic tests showed that it was not possible to predict the bilateral benefit from a priori information based on headphone tests. At the end of the trial period 93% of the participants preferred a bilateral fitting. The benefits of a second hearing aid were evaluated objectively and subjectively in 214 participants. Diagnostic tests were applied to determine whether this bilateral benefit could be predicted. Diagnostic tests were focused on binaural functioning (binaural masking level difference, interaural time difference, asymmetry in speech reception thresholds). After a trial period free-field tests were conducted with a unilateral and a bilateral hearing aid fit to analyze differences in speech intelligibility and localization. Also, the participants completed a questionnaire. This study showed bilateral benefits (both subjectively and objectively), but it turned out to be impossible to predict bilateral benefit from a-priori audiologic information.