Hearing Loss and Dementia

Understanding the Auditory Process

Did you know that hearing happens in the brain? While our ears play a very important role in the auditory process, the brain is central to how we hear. In the past decades, researchers have found convincing information linking the potential risk for developing dementia with untreated hearing loss. Here, we take a look at the process of hearing and how untreated hearing loss affects your cognitive ability, possibly increasing the risk for dementia.

Believe it or not, hearing is the fastest sense that you have. Sight comes second, because it takes longer for information from your eyes to get to your brain. Meanwhile, it only takes your brain 0.05 seconds to recognize a sound wave, once it reaches your ear.

Your outer ear is responsible for conducting sound. This means the outer ear picks up sound in your environment. Sound waves travel through to the middle ear, where they are amplified and turned into vibrations by the ear drum. These vibrations travel to the inner ear, where they are translated into neural signals by your inner ear hair cells. These neural signals then travel to the brain, where they are processed as sounds.

There are a number of different causes for hearing loss. One of the most common causes is sensorineural hearing loss, caused by the loss of inner ear hair cells. Exposure to loud noises or certain classes of medication can damage these inner ear hair cells; once they are gone, they do not regenerate. As a result, sensorineural hearing loss affects the way our brains process sound.

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Studies Linking Hearing Loss and Dementia

A 2015 study from the University of Colorado, conducted by Anu Sharma of the Department of Speech Language and Hearing Science, looked at the brain’s neuroplasticity. Neuroplasticity is “the ability of the brain to forge new connections, to determine the ways it adapts to hearing loss, as well as the consequences of those changes.” Sharma’s study first recorded the way brain waves responded to sound stimulus amongst adults and children who experienced hearing loss or deafness. They found that “the areas of the brain responsible for processing vision or touch can recruit, or take over, areas in which hearing is normally processed, but which receive little or no stimulation in deafness” and that “cross-modal cortical organization” meant that the brain was siphoning energy to overcompensate for hearing loss. According to Sharma, “These compensatory changes increase the overall load on the brains of aging adults, which may be a factor in explaining recent reports in the literature that show age-related hearing loss is significantly correlated with dementia.”

Researchers at Johns Hopkins University in Baltimore have led the charge on studies around hearing loss and the risk for dementia. In one notable study, Dr. Frank Lin and his team tracked 2,000 older adults (average age 77) over the course of six years. They found that 24% of test subjects (who experienced untreated hearing loss) were more likely to experience diminished cognitive decline, compared to those with normal hearing.

In another study from 2011, Dr. Lin and his team tracked 639 test subjects over the course of 12-18 years. At the beginning of the study, all test subjects had normal, healthy cognitive ability. Over the course of the study, test subjects had annual hearing exams. At the end of the study, analysis of data revealed that “study participants with hearing loss at the beginning of the study were significantly more likely to develop dementia by the end. Compared with volunteers with normal hearing, those with mild, moderate, or severe hearing loss had twofold, threefold, and fivefold, respectively, the risk of developing dementia over time.”

In both studies, Dr. Lin and his team reached a common conclusion: untreated hearing loss places a heavy cognitive strain on the brain, which detracts energy from other processes (such as memory, speech, etc.) and could potentially increase the risk for dementia.

It’s not all bad news. A 2011 Japanese study found that participants who experienced hearing loss – who were prescribed hearing aids early on in the study – had higher cognitive abilities compared to participants with untreated hearing loss.

Hearing loss is a common and highly treatable medical condition. There is no reason to live with hearing loss. Contact us at Professional Hearing Services today to schedule a consultation.