One of the biggest pieces of news in healthcare in the last few years has been the strong correlation between hearing loss and cognitive decline. Hearing loss, independent of other factors, appears to promote an earlier onset of cognitive decline and dementia in seniors, with the increased risk corresponding to the degree of hearing loss.
Mild hearing loss (-25–40 decibels hearing level) doubles the risk of cognitive decline and dementia, while moderate hearing loss (-40–60 dBHL) increases it threefold. Severe or greater hearing loss (-60 dBHL or more) puts us at five times the risk of cognitive decline and dementia as a person with normal hearing.
Even a very mild hearing loss (no greater than -15 dBHL), sometimes called “minor” hearing loss, appears to result in measurable cognitive decline, as well. Hearing aids are not usually recommended for those with less than -25 dBHL of loss, so those with -15 dBHL would be considered to have something in the range of “normal” hearing. They would not typically recognize themselves as having hearing loss, though even this slight hearing loss appears to tax the brain significantly.
Why Does Slight Hearing Loss Contribute to Cognitive Decline?
There is no conclusive answer as to why there is such a strong link between hearing loss and cognitive decline, but several theories are under investigation.
Social Isolation
Those with a decreased hearing ability tend to start to avoid social occasions. In a short amount of time, it is very possible for a person with untreated hearing loss to become socially isolated. At the same time, spending time with other people is one of the best ways to exercise our brains. We are social animals, and our brains are highly tuned for interacting with others. This lack of social connection experienced by those with hearing loss may contribute to an overall decline in cognitive ability, as the brain does not get used as rigorously.
However, some research has attempted to correct for the already-known connection between social isolation and dementia, and has found that hearing loss still contributes, independently, to an increased risk of cognitive decline and dementia.
Brain Atrophy
As the brain stops receiving information from the ears, the auditory cortex begins to atrophy. The brain reallocates these resources to the visual cortex. While this may sound like an efficient use of resources, in practice this particular type of neuroplasticity may lead to a decline in cognitive functioning.
It’s not that brain cells in the auditory cortex “die,” but the grey matter that supports the structure begins to dissipate. This causes the structure to shrink in size. It may be possible to regrow the auditory cortex, once hearing aids start to be worn, though this takes a significant amount of time and effort. The best thing to do is to start wearing hearing aids as soon as they are recommended following the results of a hearing test.
Cognitive Load
This theory also seems likely to be a factor in the link between hearing loss and dementia. When hearing is less than optimal, we often have to pay more attention to speech. We need to draw resources from elsewhere in the brain to determine what we are hearing—a task normally designated entirely to the auditory cortex. When we employ more of the rest of our brain, we miss out on using it for the more rewarding aspects of conversation, like considering what we’ve just heard, creatively thinking about it, and formulating a response.
Using our frontal cortex less for creative thinking and more for the quotidian task of hearing may mean that our brain works harder, while somehow getting less actual exercise. Thinking tends to be an open-ended process, whereas simply confirming what we are hearing is something of a “dead end,” in terms of intellectual stimulation.
Hearing Aids May Help
While the link is still being studied, there is some research indicating that hearing aids can help decrease the risk of cognitive decline and dementia. It’s not yet clear what might be done about the very minor hearing loss (-15 dBHL) that also increases the risk of cognitive decline, but one thing is certain: those whose hearing tests indicate that they should wear hearing aids should wear them.
Hearing aids aren’t just about preventing illness, but are about increasing the quality of life, which in turn helps to prevent all kinds of chronic health issues. If you or a loved one may have a hearing loss, make an appointment for a hearing test today and find out whether hearing aids are right for you!