Electronic Thesis and Dissertation Repository

Thesis Format

Monograph

Degree

Master of Science

Program

Health and Rehabilitation Sciences

Abstract

Age-related changes in the auditory nerve and brainstem function were studied using electrocochleography (ECochG) and auditory brainstem responses (ABR) in young and old adult age groups. Isolating the effects of aging from lifetime ototoxic exposures such as noise is challenging. For this reason, only participants with normal audiograms were studied. Extended high frequency thresholds and distortion product otoacoustic emissions (DPOAEs) were also measured. Results reveal significant age-related differences. Older adults exhibit longer ECochG AP and ABR wave I and V latencies compared to younger adults, while the amplitude of these components, and the ECochG SP latency and amplitudes were unaffected by age. Additionally, elevated extended high frequency thresholds and lower DPOAE levels were found in older adults. Age-related changes in auditory nerve and brainstem function in adults with normal clinical hearing may impact speech understanding, particularly in noisy environments.

Summary for Lay Audience

Hearing loss is a common issue as people get older, but it can be hard to tell if it’s due to aging or other factors like exposure to loud noises over a lifetime. To better understand the impact of aging on hearing, this study focused on people who had normal hearing based on standard tests. The research looked at how the auditory nerve and brainstem—key components in the pathway that carries sound signals from the ear to the brain—change as people age.

To do this, the study used several specialized tests. Electrocochleography (ECochG) and auditory brainstem responses (ABR) measure how the auditory nerve and brainstem respond to sound, by recording electrical activity in these areas. Extended high-frequency hearing tests check a person's ability to hear high-pitched sounds, which are often the first to be lost with age. Distortion product otoacoustic emissions (DPOAEs) look at the health of the outer hair cells in the inner ear, which are crucial for hearing.

The findings showed that older adults, even those with normal hearing by standard tests, had differences in the way their auditory nerve and brainstem respond to sound. Specifically, certain response times were longer in older adults, indicating age-related changes in how quickly sound information travels through the auditory system. Additionally, older adults had problems hearing extended high frequency tones and worse outer hair cell activity, suggesting age-related decline in these areas. These results are important because they suggest that even if an older adult passes a regular hearing test, they might still experience difficulties with hearing, especially in noisy environments. This could affect their ability to understand speech or other important sounds in everyday life.

Overall, this study adds to our understanding of age-related changes in hearing. It underscores the importance of looking beyond conventional hearing tests to identify subtler signs of hearing decline that could impact the quality of life for older adults. By gaining a clearer picture of these changes, we can work toward better ways to diagnose and address age-related hearing issues.

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