THE EFFECTS OF NOISE EXPOSURE AND AGEING ON PHYSIOLOGICAL AND BEHAVIOURAL MEASURES OF PERIPHERAL AUDITORY FUNCTION

Abstract

Noise exposure and ageing may damage cochlear hair cells and the synapses connecting inner hair cells with auditory nerve fibres (ANFs). Cochlear synaptopathy (CS), which can occur before outer hair cells are widely lost, is associated with the loss of low- and medium-spontaneous rate high threshold ANFs that could code suprathreshold speech information as well as mediate the middle ear muscle reflex (MEMR). These pathophysiological changes may lead to poorer speech-perception-in-noise (SPiN) ability, tinnitus, and hyperacusis. In this project, the evidence on the relative and combined effects of noise exposure and ageing in the context of CS was critically discussed and evaluated. The effects of lifetime noise exposure, occupational noise exposure, and age on SPiN, self-reported hearing function, tinnitus, and hyperacusis in individuals with no past diagnosis of hearing loss were examined through two online studies. In the first online study, lifetime noise exposure in UK adults was not associated with behavioral nor self-report measures except for tinnitus which had a higher prevalence with greater lifetime noise exposure in young but not older adults. In the second online study, Palestinian workers with higher exposure to occupational noise had poorer SPiN performance, poorer self-reported hearing ability, higher risk of tinnitus, and greater severity of hyperacusis. In both online studies, age was consistently significantly associated with poorer SPiN ability. Finally, the relation between MEMR thresholds and a measure of binaural temporal coding in audiometrically normal young adults was evaluated. No significant associations were found. However, greater lifetime noise exposure was linked to higher MEMR thresholds. In conclusion, the results of the current project suggest that occupational noise exposure and ageing have hearing-related perceptual and self-reported implications in adults with no past diagnosis of hearing impairment. In addition, behavioural measures may not be optimally sensitive in detecting the subclinical effects of CS in audiometrically normal young adults. However, our data present some evidence that the MEMR thresholds could be sensitive to subclinical noise-induced peripheral auditory neural pathology.

Date of Award	1 Aug 2023
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Chris Plack (Supervisor) & Garreth Prendergast (Supervisor)