Speech Perception Ability in Noise is Correlated with Auditory Brainstem Response Wave I Amplitude

Background: Difficulty understanding speech in background noise is a common complaint of individuals with sensorineural hearing loss. Recent animal studies suggest this difficulty may be due, in part, to spiral ganglion cell degeneration related to aging or noise exposure. Although auditory brainstem response (ABR) thresholds and standard clinical audiometric tests are minimally affected by neuronal degeneration, the amplitude of wave I of the ABR is correlated to spiral ganglion cell density. Purpose: This study hypothesized that wave I amplitude was correlated to speech-in-noise performance. To test this, the relationships between wave I amplitude, age, and speech perception ability were analyzed in human participants. Research Design: This is a correlational study. Study Sample: A total of 101 ears from 57 adults ranging in age from 19 to 90 yr with a pure-tone average of 45 dB HL or better were examined in this study. Only individuals with no history of neurological disease and ears without any evidence of conductive involvement were included. Data Collection and Analysis: Speech perception was measured in quiet using NU-6 word lists and in background noise using the QuickSIN. Ear canal electrodes were used to obtain ABR waveforms from each ear and the amplitude of wave I was measured as the absolute difference in voltage between the peak of the wave and the following trough. Speech perception performance in quiet and in background noise were both modeled using a linear mixed model with the covariates age, four-frequency pure-tone average ((4f)PTA), wave I amplitude, and the interaction between (4f)PTA and wave I amplitude. ABR wave I amplitudes were modeled using a linear mixed model with age and (4f)PTA as the covariates. The correlation between the right and left ears of the same participant were modeled using random effects. Results: The results indicate that reduced ABR wave I amplitudes are (1) related to increased age, (2) associated with decreased speech-in-noise performance, with the greatest effects in individuals with poorer pure-tone thresholds, and (3) not correlated to speech perception in quiet. Conclusions: Reduced ABR wave I amplitude, an indicator of cochlear neuronal degeneration, is associated with decreased speech perception ability in noise, with a more pronounced effect in ears with poorer pure-tone thresholds, but does not appear to contribute to decreased speech perception in quiet.