Your Patients' Brain Health Depends on Hearing

As a hearing-focused brain scientist who co-invented the cochlear implant decades ago, which has restored the hearing of literally hundreds of thousands of profoundly deaf people, and as someone who has a deep concern about the negative effects of acquired hearing loss on the quality of life and brain health of older individuals, I'd like you to listen to me.

Michael Merzenich, PhD

I was heartened by the US Food and Drug Administration (FDA) October ruling that hearing aids are now available over the counter (OTC), without a prescription, at an affordable price.

Although I'm not a great prognosticator, I can confidently predict that 2023 will allow many more patients in the United States to finally acquire that first, often long-delayed, hearing aid.

The National Council on Aging (NCOA) estimates that the new OTC hearing aids will save Americans an average of up to $3000 per pair compared with prescription devices.

Although the NCOA estimates a pair of OTC hearing aids will cost about $1600, it recommends hearing aids in six categories, including one pair that costs just $249. That kind of price reduction will allow many more people to benefit from hearing aids.

Of course, the OTC market also means that more people will acquire hearing aids without any assistance from a hearing expert — an audiologist or other hearing professional. Without that professional guidance, what is important for a consumer to understand about such products?

First, the FDA has limited approval of OTC hearing aid use for patients with "mild to moderate" hearing loss. If patients have difficulty following a conversation even in a quiet room, they should be assessed by an audiologist.

Second, hearing loss can signal underlying medical conditions that may not be helped by hearing aid use alone, so a visit to an otolaryngologist or other specialist may be indicated. For example, if a patient experiences hearing loss after an injury; if fluid is coming from one or both ears; or if hearing loss is sudden, fluctuates over time, or is associated with tinnitus, dizziness, or pain, a medical examination is called for before a hearing aid purchase.

If none of those apply, it is likely that mild to moderate hearing loss can be at least substantially addressed, to the benefit of patients' everyday life and brain health, by acquiring a hearing aid from an audiologist or an OTC device.

A 'Double Whammy'

The inner ear contains a spiral-shaped cavity called the cochlea. Within the cochlea are vibration-sensitive "hair cells" that sit atop a thin membrane that naturally vibrates at different sound frequencies. The highest sound frequencies vibrate the membrane to stimulate location-specific hair cells most strongly near the bottom of the spiral. Lower sound frequencies, most important for human speech and music, generate larger vibrations near the top of the spiral.

Like the strings of a piano, all frequencies in our human range of hearing are detected by this continuous array of frequency-specific hair cells. The hair cells translate their specific vibrations into electrical signals that are delivered to the brain, which "maps" those sound frequencies in a highly ordered low to high frequency manner in the brain's very complex central auditory system. The brain's job is to read those electric pulses and make sense of it all — which it accomplishes in a nearly miraculous manner when all is well.

Alas, two major problems commonly arise in older age.

First, those sensory hair cells in the inner ear are fragile. Historic or current exposure to loud sounds, some genetic factors, and a rich variety of other vicissitudes in life can result in their progressive loss. It is an extremely rare 75-year-old who has not endured a considerable loss of hair cells.

These losses most commonly result in progressive loss of hearing of higher frequency sounds, which eventually begin to degrade the accurate reception of speech — but hair cell losses can occur in a variety of different patterns. Hearing aids are designed to increase the loudness of the sounds that have been attenuated in the inner ear because of this degradation of hearing organ function.

Second, as we age, typically beginning in our late 20s and independent of any problems that might be arising in the ears, the brain's processing speed and accuracy begin to deteriorate. These changes occur slowly and are not usually noticeable at a younger age, but the degradation accumulates over the passing decades and in most people is ultimately substantial.

By age 75, the average individual is resolving what they hear at a rate of about eight sound events per second. By contrast, the average 20-year-old accurately resolves more than 20 sound events per second. This greater than twofold decrease in sound resolution has a significant impact on a person's listening ability and is a significant contributor to — and an index of — deteriorating brain health.

Age-related hearing loss, then, is not just a matter of the inner ear hair cells slowly going to blazes. The brain's processing speed and accuracy also contribute to our age-related listening and associated cognitive struggles.

Of course, many of us, including yours truly, are challenged by the burden of this double whammy. I have a moderate to severe hearing loss and have had to work hard at exercises in the brain gym to keep my brain operating up to speed, and with high accuracy.

Tips and Tricks

It's important for any hearing aid user to understand that because the brain has slowed in the face of a now more limited hearing range (to make sense of the impoverished information delivered from the ears to the brain), when a patient first puts those hearing aids on, the brain isn't ready for them.

It's doing the best it can, using machinery that had adjusted to processing the old, more limited pattern of sound information. The brain must now readjust to using hearing aids so it can take full advantage of the now-restored sound inputs.

Picture an older man (like me) hectored by his family — who have been just a little bit exhausted by having to repeat themselves because they are not being heard — to finally get hearing aids. On the basis of my experience with glasses, which instantly corrected my vision, I might be led to expect similar instant results from my shiny new hearing aids — just as I experienced instant correction when I got my glasses at an earlier age. However, hearing and vision are not the same.

Hearing restoration requires both amplification of missing sounds and brain retraining to correctly interpret new sound reception and sort out what is said and where the sound is coming from. As a result, there can be a lot of disappointment for new users and a strong feeling that "these damn things just don't make much of a difference." Instead of being worn in the ear, those hearing aids often end up being worn in a pocket.

Here are a few tips to pass along to new hearing aid users (and those who do their laundry):

First, patients should be advised to check all pockets before putting anything in the wash. You might also want to suggest they consider purchasing insurance that covers washing machine accidents and hearing aid loss because they just forgot where they put the damn things.

Second, patients should be advised not to think of their new hearing aids as being equivalent to "glasses for the ears." It takes time and practice to get used to them and they need to persevere and be patient (and not wear their hearing aids in their pocket).

Third, patients should be encouraged to engage the brain's remarkable plastic ability to advance its sound processing abilities so that it can rapidly put their now-recovered hearing to good use. This can be accomplished via a combination of listening-heavy environmental experiences, and by training the brain to restore higher-fidelity listening abilities.

For example, in the auditory experiential realm, patients can be encouraged to develop a habit of sharply focused listening in normal conversation. Beyond conversation, learning a new language or a musical instrument, focusing on listening to music and other hearing-heavy hobbies can help augment the effect of new hearing aids.

The most direct approach to training the brain to be faster and more accurate, regardless of whether a patient is or is not a candidate for hearing aids, is through brain training exercises. Over the past several decades, my team and I have developed computerized brain training exercises to rapidly improve listening abilities.

In independent studies (here and here), these auditory exercises have been shown to improve hearing and have been recommended by many hearing professionals to help accelerate the brain's adjustment to restored hearing.

Finally, as many clinicians are aware, there is a strong correlation between hearing loss and serious cognitive decline, including dementia. In the face of a hearing loss, patients can, and should, take action. Thanks to the FDA, they are now able to do that at lower cost than ever before and, as a result, have an opportunity to substantially slow cognitive decline.

Michael Merzenich, PhD, is often credited with discovering lifelong plasticity, with being the first to harness plasticity for human benefit (in his co-invention of the cochlear implant), and for pioneering the field of plasticity-based computerized brain exercise. He is professor emeritus at UCSF and a Kavli Laureate in Neuroscience, and he has been honored by each of the US National Academies of Sciences, Engineering, and Medicine. He may be most widely known for a series of specials on the brain on public television.

Follow Medscape on Facebook, Twitter, Instagram, and YouTube

Comments

Commenting is limited to medical professionals. To comment please Log-in.

Comments on Medscape are moderated and should be professional in tone and on topic. You must declare any conflicts of interest related to your comments and responses. Please see our Commenting Guide for further information. We reserve the right to remove posts at our sole discretion.