Individuals with age-related hearing loss should not be treated with “standard” hearing aids, but fitted to their personal needs, while avoiding settings that add distortion.
New research published in Frontiers studied the peripheral changes and how that contributes to the auditory processing and cognitive decline through ‘normal aging.’
According to the study, normal aging is defined as nonpathological changes in cognition and hearing with age. The researchers said hearing aids should ideally match the peripheral changes that connect with normal aging to improve individuals’ reported hearing loss.
“We believe it is particularly important to address normally aging older adults because they represent the vast majority of patients attending audiology clinics. In the UK National Health Service (NHS), older adults (over 55 years of age) represent 78% of adult audiology attendances and 87% of those fitted with hearing aids; and reported hearing problems appear more strongly associated with age than the degree of peripheral hearing loss, which suggests that processes other than peripheral hearing play a role,” the study authors wrote.
The study defined peripheral changes as restrictions to the outer, middle, and inner ear, and the auditory nerve. Central changes are restrictions within the central auditory nervous system. This comes from the level of the cochlear nucleus to the cortex that connects to cognition.
One of the findings from the study that could have real-world impacts is the importance of hearing aid fittings that benefit individuals with differing levels of cognition and auditory processing.
“The ‘optimum’ hearing aid fitting should not solely consider peripheral hearing loss, but should aim to deliver maximum benefit over time, considering hearing loss, auditory processing, cognition, and non-auditory factors that affect an individual, their perception of treatment, and ability or intention to comply with it,” said the study authors.
The study confirmed that the primary reason for hearing aid fitting should be to ensure that the speech is audible but has minimal distortion to speech envelope cues (ENV). When introducing distortion to ENV, there is a chance to increase listening effort in speech and reduce the volume for listening.
“Hearing aid processing should aim to minimize cognitive load and listening effort by avoiding unnecessary distortion to the speech signal, loudness discomfort or other perceptual sound difficulties. Noise reduction settings should be considered,” said the study authors.
According to the study, compression speed is another tool to reduce the dynamic range of sound to match that of a hearing-impaired person.
“Hearing aids filter sound into frequency bands, or frequency channels, such that different degrees of compression, and other types of processing, can be differently applied within each channel. Wide-dynamic range compression (WDRC) with short time constants, or fast-acting compression (FAC), was employed to enable exaggeration of quieter syllables or phonemes within words by quickly applying greater gain, so is often referred to as “syllabic compression,” said the study authors.
The study confirmed that this type of compression could be useful for those who are unable to hear high frequencies—typically high-pitched fricatives. The FAC is used to rebuild normal loudness, as slow-acting compression (SAC) can enhance different high-frequency sounds.
Compression ratios also are an important implication to the study as they define the variety of improvement applied within a hearing aid channel. According to the study, the higher the compression ratio, the more likely it is to increase the range of input levels. This controls the noise levels, so the audio is not unpleasantly loud but reduces background noise.
There are various studies that compare FAC and SAC, although the researchers concluded that SAC could be more useful in most older adults with other cautious settings for compression ratios and noise reduction.
The findings suggest that there are objective benefits to each use for the hearing aids, but it is unclear whether the benefit will connect to the individual’s preference. The results concluded that ENV are useful for older adults to understand speech. Although most individuals who use hearing aids prefer SAC, they noted that FAC is better for quiet conditions with those who have good cognitive processes, and the compression ratio should be reduced. However, SAC could be useful for older adults in nosier environments.
“One should recognize that any recommendation regarding hearing aid parameters cannot be prescriptive given the current state of knowledge and considering the wide variability in individual needs. This implies that there must be some process of ensuring that hearing aid settings are optimal, or at least acceptable, for each individual. Overall, we believe that a full consideration of hearing aid parameters needs to be combined with the overriding principles of patient centered care,” said the study authors.
The findings suggest that individuals with age-related hearing loss should not be treated with “standard” hearing aids, but rather these devices should be fitted to their personal needs while avoiding settings that add distortion.
A review of auditory processing and cognitive change during normal ageing, and the implications for setting hearing aids for older adults. Frontiers. Study article. June 20, 2023. Accessed July 19, 2023. https://www.frontiersin.org/articles/10.3389/fneur.2023.1122420/full.