Health Impacts of Untreated Hearing Loss

A common complaint for people who have hearing loss is that they feel they can hear, but there is the perception that everyone is ‘mumbling’ or people are not speaking clearly. The reason for this is that when there is a loss of hearing, high frequencies are typically more impacted than low frequencies. High frequencies provide speech with a lot of its meaning, so when those high frequency sounds are missing, there is a loss in the clarity of speech. The job of a hearing aid is to help increase the frequencies of speech that are more difficult to hear due to hearing loss. Hearing aids in the past did not enhance high frequencies as well as current technology, and noise management technology has also dramatically improved which is increasing patients perceived benefit with over 80% of users expressing satisfaction with their hearing aids⁽¹²⁾ The question on how hearing loss and cognitive decline are associated still remains.

Normal Hearing: The cow jumped over the moon.

Hearing Loss: _ _e _ow _um_ _ _ over _ _e moon.

Listen to hearing loss

There is an abundance of research which links accelerated cognitive decline and untreated hearing loss. Studies have shown that individuals with a mild, moderate and severe untreated hearing loss are twice, three times and five times as likely to develop dementia or exhibit accelerated cognitive decline as compared to their normal hearing peers, and that untreated hearing loss is linked to mild cognitive impairments not exhibited in those with hearing loss who opted treatment with hearing aids^(2,8). Untreated hearing loss has also been linked to accelerated reduction in brain volume. Individuals with untreated hearing loss had an additional cubic centimeter of brain tissue atrophy as compared to their normal hearing counterparts when studied over a 10-year period⁽⁷⁾ Hearing and the brain have a clear connection in that the ear functions to convert sound from the outside world into an electrical signal so the brain can interpret and process those signals into something meaningful. When an individual has hearing loss, there are gaps in the speech signal that are left open for interpretation, and this means the brain has to work harder to fill in the gaps, causing fatigue. Research has shown that individuals with untreated hearing loss show a reorganization of the brain and use of the frontal lobe which is unusual for hearing⁽³⁾. The frontal lobe, amongst many other functions, is the region of the brain used for planning, executive function, problem solving, our personality and more. Researchers have theorized the frontal lobe is being accessed when there is untreated hearing loss because it is the problem-solving region of the brain, and with a hearing loss, there is an element of problem solving since the entire speech signal is not being heard, while the brain fills in the gaps. In addition to frontal lobe recruitment, studies have also shown that poorer cognition, ability to identify speech and more severe hearing loss was associated with greater cross-modal recruitment of the auditory cortex in the right hemisphere⁽⁶⁾. This brain reorganization is possibly where the dementia link is made, although more research needs to be completed to substantiate these claims^(3,4,5). Studies have shown that with a binaural hearing aid fitting, a decrease in cross-modal recruitment was identified in the auditory cortex, which corresponded with improvements in cognitive function and speech perception⁽⁶⁾. Several studies also seem to indicate that treating hearing loss attenuates the accelerated cognitive decline exhibited in those with untreated hearing loss^(1,4,6).