The connection between Hearing Loss and the Brain

Senior citizens are often afflicted by loss of hearing and a new study concluded it's the brain, not the ears that may be the cause of the hearing difficulties.

The study -- from researchers at the University of Maryland -- revealed that trouble processing conversations in a loud setting may indicate that the brain's ability to quickly and easily process speech is diminished.

The findings demonstrate that "separately from any typical hearing loss that might occur as we age, our brains also get worse at processing the sound of talking when there are other sounds at the same time," said study co-author Jonathan Simon. He's an associate professor at the University of Maryland's Institute for Systems Research.

But "the implication is that typical older adults need to exert more effort, and take more time, in order to understand what someone is saying to them when there's also noise, even only moderate noise, around them," Simon explained in the study.

Hearing about the problem

About one in three Americans aged 65 to 74 has some degree of hearing loss, according to the U.S. National Institute on Deafness and Other Communication Disorders and nearly half of those older than 75 have difficulty hearing.

Age is the strongest predictor of hearing loss among adults with 91 percent of adults with hearing loss aged 50 and older Those older than 80 have the greatest amount of hearing loss Adult men in their 50s are three times as likely to have hearing loss than women of the same age, but as they age, hearing loss rates become similar among the sexes. As women age, they may have more difficulty hearing at lower frequencies than do men.

The new study included 17 young adults (aged 18 to 27) and 15 older adults (aged 61 to 73). All had normal hearing and were dementia-free.

All had a series of hearing tests, some of which included background noise. All also underwent brain scans focused on two regions of the brain: the midbrain, which controls basic sound processing; and the cortex, which is critical to speech comprehension.

Younger adults performed significantly better than seniors in both quiet and noisy settings. But the researchers found that noisy settings were more challenging for seniors.

The scans suggested the reason why the performance difference.

Midbrain scans revealed that neurological signaling related to hearing was weaker among the older study participants. And cortex scans suggested that auditory information took longer to process among seniors than young adults.

The study concluded that seniors often have to expend more effort to hear, and often end up with worse results. The study found that a more effective solution to combat hearing loss for seniors may be a kind of physical therapy for hearing and speech recognition instead of just a hearing aid.

How is the brain affected

In recent years, research on hearing loss have focused on how age-related hearing loss and brain function and especially cognition are connected. This new research has generated some interesting theories, including one theory that hearing loss leads to a decreased input to the brain, so there is less processing that occurs, which contributes to cognitive decline (a “bottom-up” approach).

Another theory is that early cognitive deficits may impact a person’s ability to process sound, and thus contribute to hearing loss (a “top-down” approach). Both theories connect the dots between hearing and cognition.

This new research concludes that much more testing is needed, as is more immediacy in treating hearing loss.

An article in the JAMA Otolaryngology highlights this need. In this article, researchers reviewed two large population databases of 6,451 people who had had hearing and cognitive testing. The research showed that those who were 50 or older had cognitive scores that seemingly declined even before they reached clinically defined hearing loss (subclinical hearing loss).

The research also noted that the association between hearing and cognition is stronger among subjects with normal hearing compared to those with hearing loss. For example, in the population they analyzed, cognition scores dropped in the normal hearing population faster than in the population with hearing loss. This surprising result suggests that maybe what we currently define as normal hearing may in fact include some people with hearing deficits. The research also challenges what clinicians have accepted as basic measures for hearing loss on hearing tests.

The bottom line

A number of qualitative studies have examined the impact of hearing loss on intimate relationships. Seamless communication may breakdown, however, and may manifest as reduced understanding, frequency or depth of conversation. Individuals who are hard of hearing and their partners may both report increased effort, fatigue, stress, anxiety, depression, isolation, negative self-image and difficulties in family relationships resulting from communication difficulties.

The onset of hearing loss is typically subtle and insidious and many people may be unaware they have a hearing problem until they start violating basic social rules, such as talking too loudly, asking others to repeat themselves, or turning up the TV. Family and friends dealing with people who have undiagnosed hearing loss Others may misinterpret that behavior as a sign of inattention, boredom, stupidity or dementia, rather than hearing loss. Moreover, the stigma associated with hearing loss may threaten self-image and it’s often true that many people would rather pretend to understand a conversation than disclose a hearing problem.

While new research demonstrates a link between hearing loss and cognitive issues, it does not suggest that hearing loss is going to lead to cognitive decline. In this case, association does not mean they are causally related.

However, this research does show how important it is for people (especially as they get older) to have their hearing tested if they notice problems such as challenges hearing when in social settings, requiring the TV or earbuds at higher volumes, or constantly requiring people to repeat themselves.

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