Could Hearing Impairment be an Indicator of Alzheimer’s?

Do you have hearing loss? If yes, do you occasionally find that it feels like work just to understand what the people around you are saying? This experience of having to work to understand people is normal even among people who use hearing aids, because the aids need to be fitted and tuned correctly to work well, and people need to become acclimated to using them.

As though that wasn’t bad enough, it may not be just your hearing that is affected, but also cognitive abilities. In the latest studies, scientists have found that hearing loss drastically increases your chances of developing dementia and Alzheimer’s.

One of these studies, from the Johns Hopkins School of Medicine, analyzed 639 volunteers ages 36 to 90, for a period of 16 years. At the conclusion of the research, scientists found that 58 people (9%) had been identified as having dementia, and that 37 of them (5.8 percent) had developed Alzheimer’s. The degree of hearing loss was positively correlated with the probability of developing either condition. For every 10 decibel further hearing loss, the risk of developing dementia increased 20%.

A separate study of 1,984 people, also 16 years long, showed similar results connecting dementia and hearing loss. In this second research study, investigators also found decline of cognitive functions among the hearing-impaired over the course of the study. The hearing-impaired individuals showed memory loss and reduced thinking capacity 40% faster than participants with normal hearing. An even more astonishing conclusion in both studies was that the connection between dementia and hearing loss held true even if the participants used hearing aids.

A number of hypotheses have been suggested to explain this seeming link between hearing loss and loss of cognitive ability. One of these explanations relates to the question that began this article, about having to work harder to hear; this has been called cognitive overload. The cognitive overload theory states that the hearing-impaired individual expends so much brain power trying to hear, that the brain tires itself out and has a reduced capacity to comprehend and assimilate verbal information. Maintaining a two-way dialogue requires understanding. A lack of understanding causes interactions to break down and might bring about social isolation. Another idea is that neither dementia nor hearing loss cause the other, but that they are both linked to an as-yet-undiscovered disease mechanism – possibly vascular, possibly genetic, possibly environmental – that causes both.

However dismal these study results may sound, there are lessons to be learned from them. For those of us who wear hearing aids, these outcomes serve as a reminder to see our audiologists on a regular basis to keep the aids properly adjusted and tuned, so that we’re not constantly straining to hear. The less you have to strain, the more cognitive power your brain has in reserve to comprehend what is said, and remember it. Also, if loss of hearing is related to dementia, knowing this might bring about interventional methods that can postpone its development.