WRONG! According to ScienceDaily (Sep. 20, 2011), mild hearing loss has now been linked to brain atrophy in older adults. Anecdotally, over the course of my 30+ years in private practice as a board certified audiologist, I’ve observed this to be true. But now, more and more research is indicating strong correlation between failure to obtain or use hearing devices and increased problems with understanding speech and cognition.
We have all heard (or perhaps experienced) the complaint that despite the fact that speech is audible, it’s not understandable. “I hear, but I can’t understand,” is probably the most commonly voiced concern in my office. So, if someone has hearing loss, and if their hearing aids make sounds louder, why doesn’t that solve all hearing related issues? Well, like lots of things in life, it’s just not that simple.
A person’s audiogram (or those little blue X’s and red O’s on the graph of your responses to the beeps) tells us a lot, but it does not yield the whole story. Hearing thresholds (or the point at which someone is just barely able to detect sound across the frequency range) are certainly important, but they don’t give much information regarding how well someone will understand when speech sounds are made sufficiently loud. Word recognition testing, with and without noise, provides additional information regarding this capability, and as a by-product, an indirect measure of the distortional component inherent to sensorineural hearing loss.
We now have mounting evidence that those who have hearing loss, but who fail to get and/or use hearing devices, run the risk of depriving their auditory system of sufficient loudness, which in turn results in degradation of the mechanisms responsible for understanding speech. A new study by researchers from the Perelman School of Medicine at the University of Pennsylvania shows that declines in hearing ability may accelerate gray matter atrophy in auditory areas of the brain and increase the listening effort necessary for older adults to successfully comprehend speech. When any one of our senses (smell, taste, sight, hearing, or touch) is changed in some way, the brain reorganizes and adjusts. In the case of those with hearing loss, researchers found that the gray matter density of brain in areas specific to hearing was lower in people with decreased hearing ability, suggesting a link between hearing ability and brain volume.
So, “use it or lose it” may be the prevailing philosophy. Take heart (and USE those instruments that you have!). According to this study, early intervention for hearing loss with the consistent use of amplification can slow the progression of speech comprehension difficulty. “As hearing ability declines with age, interventions such as hearing aids should be considered not only to improve hearing but to preserve the brain,” said lead author Jonathan Peelle, Ph.D., research associate in the Department of Neurology. “People hear differently, and those with even moderate hearing loss may have to work harder to understand complex sentences.”
In two recent research studies, researchers measured the relationship of hearing acuity to the brain, first measuring the brain’s response to increasingly complex sentences and then measuring cortical brain volume in auditory cortex. Results indicate that older adults (60–77 years of age) with normal hearing for their age were evaluated to determine whether normal variations in hearing ability impacted the structure or function of the network of areas in the brain supporting speech comprehension.
The studies found that people with hearing loss showed less brain activity on functional MRI scans when listening to complex sentences. Poorer hearers also had less gray matter in the auditory cortex, suggesting that areas of the brain related to auditory processing may show accelerated atrophy when hearing ability declines.
In general, research suggests that hearing sensitivity has important consequences for neural processes supporting both speech perception and cognition. Although most of the research has been conducted in older adults, the findings also have implications for younger adults, including those concerned about listening to music at loud volumes. “Your hearing ability directly affects how the brain processes sounds, including speech,” says Dr. Peelle. “Preserving your hearing doesn’t only protect your ears, but also helps your brain perform at its best.”
Physicians should monitor hearing in patients as they age, and everyone should have a baseline audiogram performed by a board certified audiologist, looking specifically at speech recognition abilities even in the presence of normal hearing. Patients should talk to their physician or audiologist if they are experiencing any difficulty hearing or understanding speech. If your physician has not referred you for hearing evaluation, take action!