Setting Hearing Aids for Older Adults

Abstract

"Normal" ageing is defined as that without pathological cognitive impairment, such as dementia or mild cognitive impairment. It is associated with a decline in auditory processing and some other domains of cognition that support speech perception, which particularly affects listening in challenging situations such as speech in noise. This might be important to the way in which hearing aids are set for older adults, not least because they form the majority of patients to whom we fit hearing aids. Three papers in publishable journal format are presented in this thesis. The first paper is a literature review that describes the changes to auditory processing and other elements of cognition associated with normal ageing. It highlights that an important consequence of ageing is the decline in sensitivity to temporal fine structure in speech and greater dependence on modulations in the speech signal. Some hearing aid processing strategies, such as fast-acting compression with a high compression ratio, increase the distortion to the speech envelope that could negatively impact speech perception for those with reduced degrees of cognition and increase listening effort. There is evidence to support this argument, but it is variable and does not confirm whether there is a clinically significant effect. Based on the literature, audiologists should consider these factors in hearing aid fittings, but it may be best to validate which setting is best for each individual. A survey of current practices amongst UK audiologists, described in the second paper, demonstrated that many audiologists do not explicitly consider distortion, although this has been suggested by others in the past. Awareness of compression speed settings in hearing aids was low, likely a result of the variable evidence and a lack of information provided by hearing aid manufacturers. A randomised control trial was designed to assess whether compression speed settings resulted in a clinically meaningful difference amongst older adults, described in the third paper. Most normally-ageing older adults expressed a preference for fast or slow-acting compression, but the degree of cognition had no influence on this, nor on the reported or objective benefit of either setting. However, the preference was determined, to some extent, by the degree of hearing loss, which suggested that those with lower degrees of hearing loss (below 35 dB HL four-frequency threshold average) could be given fast compression as a default, and those with greater degrees of hearing loss given slow-acting compression. This rule would be counter to a user's preference in about one in five cases, so it remained preferable to validate the best setting for each individual. However, there were some confounding factors in the study, not least a strong order effect, suggesting that non-audiological factors may have a stronger influence on user preference. An Innovation Proposal was developed to consider how further research could address these issues by enabling self-fitting hearing aids, whilst also challenging some of the service issues in the UK.

Date of Award	31 Dec 2024
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Antje Heinrich (Supervisor)