Many hearing aid (HA) users receive limited benefit from amplification, especially when trying to understand speech in noise, and they often report hearing-related residual activity limitations. Current HA fitting strategies are typically based on pure-tone hearing thresholds only, even though suprathreshold factors have been linked to aided outcomes. Furthermore, clinical measures of speech perception such as word recognition scores (WRSs) are performed without frequency-specific amplification, likely resulting in suboptimal speech audibility and thus inaccurate estimates of suprathreshold hearing abilities. Corresponding measures with frequency-specific amplification (“aided”) would likely improve such estimates and enable more accurate aided outcome prediction. Here, we investigated potential links between either unaided WRSs or aided WRSs measured at several above-conversational levels and two established HA outcome measures: The Hearing-In-Noise Test (HINT) and the International Outcome Inventory for Hearing Aids (IOI-HA).
Thirty-seven older individuals with bilateral hearing impairments participated. Two conditions were tested: unaided and aided, with all stimuli presented over headphones. In the unaided condition, the most comfortable level (MCL) for the presented speech stimuli, WRS at MCL+10 dB as well as uncomfortable levels (UCLs) for narrowband noise stimuli were measured. In the aided condition, all stimuli were individually amplified according to the “National Acoustic Laboratories—Revised, Profound” fitting rule. Aided WRSs were then measured using an Interacoustics Affinity system at three above-conversational levels, allowing for the maximum aided WRS as well as the presence of “rollover” in the performance-intensity function to be estimated. Multivariate data analyses were performed to examine the relations between the HINT (measured using a simulated HA with the NAL-RP amplification) or IOI-HA scores (for the participants’ own HAs) and various potential predictors (age, pure-tone average hearing loss, unaided WRS, aided WRS, rollover presence [ROp], and UCL).
Aided WRSs predicted the HINT scores better than any other predictor and were also the only significant predictor of the IOI-HA scores. In addition, UCL and ROp in the aided WRSs were significant predictors of the HINT scores and competed for variance in the statistical models. Neither age nor pure-tone average hearing loss could predict the two aided outcomes.
Aided WRSs can predict HA outcome more effectively than unaided WRSs, age or pure-tone audiometry and could be relatively easily implemented in clinical settings. More research is necessary to better understand the relations between ROp, UCL and speech recognition at above-conversational levels.