(PP1409) Tinnitus and Hyperacusis in Young Adults: Audiometric Measures and Risk Factors

Young adults do not proactively complain about tinnitus and hyperacusis, but when they are questioned, they can describe them. This study evaluated 140 young adults aged 18-35 years (70 with tinnitus) with normal conventional audiograms. The study evaluated extended high-frequency hearing thresholds and speech-in-noise perception. Hyperacusis was evaluated with the questionnaires and loudness discomfort level. Individuals with tinnitus and hyperacusis showed significantly elevated hearing thresholds at the extended high frequency. We documented high heterogeneity in the extended high-frequency range. We concluded that young adults with tinnitus and hyperacusis might exhibit cochlear dysfunction in the far basal end of the cochlea.     

Summary: 

Purpose:

Young adults do not proactively report tinnitus, but they can describe tinnitus and hyperacusis when they are questioned (Bhatt, 2018). Tinnitus and hyperacusis are often associated with cochlear hearing loss (Tyler et al., 2014; Henry et al., 2014). However, many young adults with tinnitus and hyperacusis exhibit normal hearing sensitivity in the conventional frequency range (Savastano, 2008). The neurophysiological mechanism underlying tinnitus and hyperacusis in young adults with normal audiograms remains elusive.

Recent studies suggest that noise levels typically encountered at the occupational and recreational settings might cause damage to the auditory nerve terminals without causing significant cochlear hair cell lesions (e.g., Kujawa & Liberman, 2009). The animal studies showed that auditory nerve damage could be observed in the cochlear partitions with no hair-cell loss (Kujawa & Liberman, 2015). The auditory nerve terminals in the mid-to-apical cochlear sections show more vulnerability to noise than cochlear cells in the far basal cochlear end (Liberman et al., 2014). It has been argued that nerve terminal loss is likely to be present in mid-to-low frequency regions of the cochlea when hair cell damage is present at the extended high-frequency regions (Kujawa & Liberman, 2015). We hypothesized that young adults with tinnitus and hyperacusis exhibit cochlear dysfunction at the extended high-frequency regions.

Methods:

This study evaluated 140 young adults aged 18-35 years (70 with tinnitus) with normal conventional audiograms (250-8000 Hz). The study evaluated extended high-frequency hearing thresholds (9000-16000 Hz) and speech-in-noise perception (word-in-noise task). The participants filled out a questionnaire inquiring about the following: (1) Demographic details and general health history (e.g., age, sex, ethnicity). (2) Noise exposure background (NEB): assessed with Megerson’s Noise Exposure Questionnaire (Johnson et al., 2017). (3) Tinnitus: We used Tinnitus Handicap Inventory (THI) and Tinnitus Functional Index (TFI) to document tinnitus-related distress in daily living. (4) Quality of Hearing: Speech, Spatial, and Quality of Hearing Scale – 12 item version (SSQ12) (Nobel et al., 2013). (5) Hyperacusis: Hyperacusis was measured using two methods – Inventory of Hyperacusis Symptoms (IHS) and loudness discomfort levels. Participants were categorized into three groups based on their IHS scores: low (low-risk for hyperacusis), mid, high (high-risk for hyperacusis).

Results:

The linear mixed model utilized age, sex, ethnicity, tinnitus, IHS category, NEB as covariates and hearing thresholds as dependent variables. Individuals with tinnitus showed significantly elevated hearing thresholds (F=21.18, p< 10^-5) than those with no tinnitus. Individuals with high IHS scores (high-risk for hyperacusis) showed significantly elevated hearing thresholds (F=7.09, p = 0.001) than those with low IHS scores. The interaction between hyperacusis and tinnitus was statistically significant (F = 19.23, p< 10^-8).

Conclusions:  The results support that cochlear deafferentation and elevated central gain might be potential mechanisms underlying tinnitus and hyperacusis in young adults. We documented high heterogeneity in the extended high-frequency range.

Importance and Innovation: The present study hypothesized that cochlear dysfunction in the far basal end of the cochlea could predict tinnitus and hyperacusis. The present study provides novel mechanistic insight into tinnitus and hyperacusis in young adults.