Most people are well aware that our temperature should be about 98.6, a normal pulse rate hovers around 60 to 70 and a healthy blood pressure range is below 120/80. Yet when it comes to measuring how well we hear, the descriptors for hearing loss are mild, moderate and profound.
This frustrates to no end Dr. Frank Lin, director of the Cochlear Center for Hearing and Public Health at Johns Hopkins Bloomberg School of Public Health, and professor of Otolaryngology—otherwise known as ear nose and throat (ENT) surgery. The average public’s understanding level of hearing falls around 1 to 2 on a scale of 1 to 10, said Lin, a knowledge base that needs improving.
Lin is proposing wider adoption of the Pure Tone Average, an existing hearing metric that would be more readily understood by the public and the healthcare community. This metric would not only accurately reflect how much hearing someone has, but also would be easily comparable on a year to year basis.
Using such a metric could be critical not just for understanding hearing levels but also because hearing loss has been linked to dementia. Lin is studying whether using a hearing aid might prevent or slow down the onset of such a condition.
What Is the Pure Tone Average?
The Pure Tone Average indicates how loud speech sounds have to be for someone to hear them and generally ranges between 0 decibels (a unit of loudness) to 100 decibels. This number is calculated from the hearing test (audiogram) that is routinely done by audiologists and other hearing care providers.
Most audiologists and ENTs, pressed for time, don’t report this number to patients and instead just describe the results using categories of mild, moderate and severe hearing loss that is based on the Pure Tone Average. Hence a Pure Tone Average (PTA) between 0 and 25 decibels (with 25 decibels being roughly equivalent to a loud whisper) is considered a normal hearing range, 25 to 40 decibels is considered mild hearing loss, 40 to 60 decibels is considered a moderate loss, and so on.
Lin says providing patients with the PTA value rather than a somewhat arbitrary classification would be much more useful. Physicians could tell a patient their hearing level is now a 38, when last year it was a 31, and the patient can easily see how things are worsening, as opposed to telling them that their hearing loss is still in the mild range.
“It empowers people,” says Lin. “They then say, ‘Oh, that makes sense. I wonder what my husband’s is?’ ”
Lin is well aware of the stigma surrounding hearing loss and the willingness or lack thereof to use hearing aids. “No one wants to know they have hearing loss,” he said. “But when you’re given a metric you’re not labeling it, instead you’re alerting them to a change. It’s a metric about yourself you would know and could respond to. That number is meaningful and actionable,” he said.
Such measuring can only be performed by an audiologist, but Lin said iPad- and smart phone–based apps, if properly calibrated, can also be used and are remarkably accurate. And he’s convinced this sort of technology will only accelerate in the next few years. Patients could at least see a variance year to year and know that they need to be checked by a professional.
The PTA is universal, too. Currently speech tests are not standard worldwide, so there’s no equivalency between countries. Audiometry testing involves tones of sound, on the other hand, which would produce the same scores no matter where one lived.
‘Hearing loss was found to be the single largest modifiable risk factor for dementia.’
Lin says this method is clinically meaningful, too—already used routinely in clinical practice. And it’s scientifically important in that as more practices begin to think about hearing loss and its strong links to dementia, loneliness and hospitalization (proven in large epidemiological studies), those studies have all measured hearing loss in PTA.
Lin thinks general practitioners would welcome such a metric. With a summary saying this patient has a PTA of 50 in their right ear and 55 in left ear, the practitioner (after basic instruction in how to understand and use the PTA metric) would know to make a greater effort with face-to-face contact when speaking to this person, and that their patient needs to use hearing aids.
Link to Dementia Is Multifaceted
It’s easy to understand how hearing loss might cut people off from conversations and friend groups and limit one’s desire to socialize, thus isolating the person with hearing loss. And it’s well known that social isolation and loneliness are linked to dementia.
But there are physical realities to hearing loss that actively foster cognitive decline as well. Even when studies controlled for age, education level, health issues such as diabetes, heart disease and smoking, a correlation was found between hearing loss and dementia. In 2020 a Lancet commission analyzed all existing literature on the topic and found major risk factors for dementia. In their analysis, hearing loss was found to be the single largest modifiable risk factor for dementia, accounting for 8 to 9 percent of all dementia cases.
The hypothesis is that when someone has hearing loss and the ear is sending a more garbled message about speech to the brain, the brain works harder to process the sound. This constant toll on the brain, which is having to recruit other brain sections to hear better, impairs other thinking, said Lin.
Other studies have shown that hearing loss in and of itself leads to the brain atrophying at a faster rate. This is the sensory deprivation hypothesis, wherein reduced auditory stimulus to the brain allows faster atrophy. Areas of the brain that receive sound atrophy more quickly. Unfortunately, these are the same brain areas that handle memory and other thinking abilities.
Lin is running a large randomized controlled trial across the United States through the National Institutes on Health, which is investing $20 million. Half the subjects are treated for their hearing loss and half are given education about topics important for healthy aging. In 2022 the results will be in that will answer the question, 'Does treating hearing loss reduce the risk of dementia?' On a gut level, Lin said, “Hearing aids could conceptually improve social engagement and positively impact brain functioning, so we hope it will make a difference.”
The Otolaryngology professor is excited by the campaign that he and his colleagues are soon kicking off to publicize and convince practitioners to use the new, easier to understand and more meaningful metric of Pure Tone Average, and he’s actively seeking partners in the healthcare sector and elsewhere to help spread the message.
He’s also thrilled about the recently passed regulation allowing over-the-counter hearing aids to be sold. Knowing that Bose and other consumer technology companies are already actively planning to manufacture such devices, Lin hopes this type of hearing aid will cut down on the stigma that still surrounds hearing loss.
“It’s not that suddenly you will need to use hearing aids when you have hearing loss, but that you’ll be able to begin naturally using your over-the-counter AirPods or other types of consumer electronic hearable devices to customize the sounds around you that you’d like to hear.
“If I find these devices are helping me in a restaurant, why wouldn’t I use it? It’s not stigmatizing anymore,” said Lin.
Alison Biggar is ASA's Editorial Director. @biggar_a
