The time course of hearing aid benefit

The present study sought to determine whether benefit derived from hearing aid use increases with hearing aid experience. This question is of considerable interest to both researchers and clinicians. Several previous investigations recently published have obtained mixed results.

Control conditions were provided to address the potential influences of practice effects and changes in preferred hearing aid gain. The experimental group consisted of 13 hearing-impaired listeners about to be fit with their first hearing-aid. The control group consisted of 13 hearing aid users with at least 1 yr's experience with their hearing aids. The control group permitted examination of practice effects that may have confounded previous results showing increases in benefit with experience. Hearing aid benefit was defined as aided speech recognition ability minus unaided speech recognition ability and was assessed repeatedly over 18 wk. Two measures of hearing aid benefit were employed: an objective syllable recognition task and a subjective questionnaire. For the objective measure, hearing aid benefit was assessed for the condition of fixed hearing aid gain and also for the condition of subject-adjusted hearing aid gain to examine effects of changes in audibility that may have influenced benefit and confounded previous results.

The objective measure of group mean hearing aid benefit increased significantly over time for both gain conditions for the new hearing aid users, but did not increase for the long-standing control group. Subjective benefit increased over time, but without statistical significance for the new hearing aid users, and was essentially unchanged for the long-standing control group.

Results suggest that the observed improvements in speech recognition are not due to increases in audibility nor to simple practice effects. The overall improvements in benefit over time were of statistical significance and also practical importance for studies of group differences. However, the improvements are too small to be observed consistently for individual hearing aid users.