Hearing Loss and Dementia

The mystery of hearing occurs at the connection between the ear and the brain.

Ear anatomy is better understood than the complex inner workings of the brain while it processes the web of sonic stimuli coming from the ear. More seems to be known about technical aspects of neural signal processing than how we derive complex meanings from these impulses. One way that scientists have advanced their knowledge of the connection between the ear and the brain is to study the relationship between hearing loss and cognitive disorders, such as dementia.
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Research that Links Hearing Loss & Dementia

Dementia has been linked to hearing loss in a number of clinical studies. A study by Dr. Frank Lin at Johns Hopkins University found that brain tissue loss was accelerated in those who had suffered from hearing loss. Although all brains shrink in mass over time, those who had hearing loss experienced even greater shrinkage of the brain tissue. The Baltimore Longitudinal Study of Aging engaged 126 participants in magnetic resonance imaging (MRI) over a ten-year period. This longitudinal study was able to compare the outcomes of participants with different hearing experiences ranging from no loss to serious impairment. The accelerated brain tissue loss was statistically significant among those with hearing loss.

Understanding Dementia

Dementia is linked not only with brain tissue loss but also with cognitive and memory problems, as well. Studies have reported that not only is the overall likelihood of dementia increased among those with hearing loss, but also the rate of cognitive decline. These relationships may seem like an even greater puzzle, given how much we do not know about the link between hearing and understanding. Though we don’t know exactly how those tiny impulses of air particles against the eardrum and the hairs of the inner ear translate into electrical impulses that can be understood in the brain as language or music, we do know that hearing problems are connected to cognitive disorders such as dementia.

Scientists have sought to understand this connection between hearing loss and dementia by imagining a causal mechanism. We know that language is essential to the way that our brains process information and remember our experiences. It is even hard to imagine what brain processes would be like without the assistance of language to categorize and code the sensory stimuli we encounter in the world. One possible explanation for the link between hearing loss and dementia is that our brains rely on hearing language to keep a clear link between words and thoughts. Imagine a person who is able to hear clearly. When carrying on a conversation, the links between words, phrases, sentences, and ideas are clear and stable. An entire chain of words is heard and translated into an idea in the mind.

However, a person who has trouble hearing would not have the same experience. Only a few words might break through to the mind out of a long string of sounds. The mind has to scramble within the conversation to put together complete ideas out of the fragments of sounds and words that are heard and understood. With such a jumble of syllables, phonemes, and words assaulting the mind, it can easily become confused. In some cases, the mind simply shuts down and stops listening to the sounds it encounters. In other cases, it may form bizarre meanings out of the sounds, adding to the confusion. We have all had the experience of hearing the wrong word in a song, sometimes with a comical effect! But just imagine how much the mind would struggle if it encountered these mistaken phrases over and over again.


Seeking Treatment for Hearing Loss

Scientists think that the link between hearing loss and dementia might happen in this way. When the mind has to scramble to create meaning out of a jumble of sounds, it may start to fail. Memory can be affected, as can other cognitive abilities to understand language.

The good news is that hearing loss can be greatly assisted through hearing aid technology. By making hearing clear and loud in later life, the risk of dementia may decrease, as well.  The first step to treating hearing loss is taking a hearing test. It is recommended for people over the age of 50 to schedule an annual hearing test, to keep track of their hearing abilities.


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