Auditory Profiles in Tinnitus are Age-Dependent: Electrophysiological and Behavioral Evidence

Abstract

Tinnitus is commonly associated with hearing loss, yet it can also occur in individuals with clinically normal audiometric thresholds. This dissociation has led to the hypothesis that hidden sensorineural hearing loss underlies tinnitus in audiometrically normal-hearing individuals. However, identifying such subclinical deficits non-invasively is challenging because audiometric measures are influenced by age-related changes and interactions among sensorineural processes. In this study, we disentangled the contributions of tinnitus, age, and hearing status to sensorineural encoding and speech perception. We included 113 participants, divided into age- and hearing-status-matched groups with and without tinnitus, and assessed them using otoacoustic emissions, auditory evoked potentials, auditory reflex measurements, and behavioral tasks of speech perception. This design enabled a rigorous evaluation of whether hidden sensorineural deficits underlie tinnitus. Age and hearing status had substantial effects on objective measures of sensorineural function, whereas tinnitus-related effects were subtle and age specific. Young adults with tinnitus and normal audiometric thresholds exhibited enhanced auditory brainstem responses, elevated envelope following responses, and better vowel discrimination. In contrast, middle-aged adults with tinnitus showed no such enhancements and demonstrated poorer speech-in-noise performance. Correlation analyses revealed a tinnitus-related shift toward greater reliance on central auditory processing, compared with the predominantly peripheral associations observed in controls. The middle ear muscle reflex was unaffected by tinnitus but was correlated with hyperacusis-related parameters. Together, these findings suggest distinct tinnitus-related auditory profiles across the lifespan: neural enhancement and improved vowel discrimination in young adults, versus degraded sensorineural encoding and reduced speech intelligibility in middle-aged adults. Significance StatementTinnitus affects a significant portion of the population, yet its underlying origins are still unclear. While hearing loss is a common cause, individuals with tinnitus may also have normal hearing thresholds. This suggests that subtle sensorineural damage may also play a role. This study critically investigates tinnitus-, age-, and hearing-related sensorineural encoding using non-invasive electrophysiological measures, auditory reflexes, and speech perception tasks in carefully matched participant groups. The study reveals distinct tinnitus-related auditory profiles throughout the lifespan; including enhanced sensorineural processing in young adults and degraded encoding with impaired speech perception in middle-aged adults. These findings provide critical insight into the mechanisms underlying tinnitus and offer objective markers for future research on tinnitus diagnosis and treatment