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Hearing and Dementia: From Ears to Brain

Writer's picture: Emma RiceEmma Rice


Hearing is one of our most valued senses and like all of our senses, tends to dull as we age. In recent decades, research has also found a possible connection between hearing loss and cognitive decline, with hopes of using hearing as a potential warning sign of early dementia on the research horizon. In a 2020 article, researcher Jeremy Johnson and his team at the University College London set out to explore how the two are related. In their paper, they find that hearing loss does seem to relate to several forms of dementia. However, interpreting their findings first requires defining what exactly they mean by “hearing” and “hearing loss.”


When we talk about hearing, we refer to peripheral hearing, which includes the process of picking up sounds with your ears and turning those sounds into signals that can be relayed from one neuron to the next. Central hearing refers to the brain’s ability to interpret these signals in the context of your environment, often filling in gaps in our peripheral hearing. This auditory processing allows you to hear what your friend is telling you in a noisy room at a party. Most of this central hearing processing is done in the cortex of the brain, which is also largely affected by Alzheimer’s Disease (AD).


The current accepted model of AD progression explains that buildup of abnormally folded proteins (amyloid and tau) damages neurons and causes inflammation in the brain, which causes neuronal death and eventual atrophy of the brain’s memory centers (the hippocampi) and the brain cortex, which is responsible for higher level function and thinking. Research on Alzheimer’s Disease has found that the same neurodegeneration that causes memory loss causes destruction of the processing centers involved in central hearing. And, as Johnson et al. mention in their article, this deficit in auditory processing seems to happen before memory problems start to show, sometimes long before someone is diagnosed with Alzheimer’s Disease. Identifying early signs of AD, like hearing loss, can allow us to diagnose and treat the disease early on with the hopes of slowing progression and prolonging memory. However, to complicate the picture, our peripheral hearing naturally decreases as we age. Adding AD-related degradation of central hearing only amplifies the deficits we may have, as we may have trouble interpreting sounds in our environment or filling in gaps in our auditory processing. This makes our hearing seem much worse than it is.


Because of this complicated relationship between peripheral and central hearing and dementia, there is much research to be done to establish how these are related. With more research, it may be possible to develop targeted tests of auditory processing that allow us to determine auditory effects of Alzheimer’s Disease even before memory is affected at all.


Article of Interest:

Johnson JCS, Marshall CR, Weil RS, Bamiou DE, Hardy CJD, Warren JD. Hearing and dementia: from ears to brain. Brain. 2021 Mar 3;144(2):391-401. doi: 10.1093/brain/awaa429. PMID: 33351095; PMCID: PMC7940169.

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