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Research Recent Research by Hearing Health Foundation Scientists, Explained.
Recent Research by Hearing Health Foundation Scientists, Explained
Major Federal Funding to Continue Hidden Hearing Loss Research
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A team of Mass Eye and Ear researchers in the Eaton-Peabody Laboratories has been awarded a five-year, $12.5 million P50 Clinical Research Center Grant from the National Institute on Deafness and Other Communicable Disorders (NIDCD) of the National Institute of Health (NIH) to continue their research on cochlear synaptopathy, or hidden hearing loss, a type of hearing damage first discovered at Mass Eye and Ear in 2009.
Funding from the grant extends support of four projects that aim to clarify the prevalence, nature, and functional consequences of hidden hearing loss in humans. The work promises to inform cellular-based diagnosis and development of future therapies. Each of the related projects is led by a separate principal investigator.
The collaborating Mass Eye and Ear principal investigators on the projects are Sharon Kujawa, Ph.D., the Sheldon and Dorothea Buckler Chair of Otolaryngology at Mass Eye and Ear and professor of otolaryngology–head and neck surgery at Harvard Medical School; Charles Liberman, Ph.D., professor of otolaryngology–head and neck surgery at Harvard Medical School; Stéphane Maison, Au.D., Ph.D., CCC-A, associate professor of otolaryngology–head and neck surgery at Harvard Medical School; and Daniel Polley, Ph.D., professor of otolaryngology–head and neck surgery at Harvard Medical School and interim director of the EatonPeabody Laboratories.
Kujawa is the program director overseeing the entirety of the grant. She is a member of Hearing Health Foundation’s Board of Directors and its Council of Scientific Trustees, which oversees HHF’s Emerging Research Grants program, from which Kujawa received a grant in 1999.
Under the initial NIH grant, the research team focused on detecting and characterizing hidden hearing loss in humans and animals with typical hearing thresholds. With the new grant, their focus will expand to detecting this hearing damage in the presence of hearing loss as traditionally defined by a clinical audiogram, as well as to better understanding the consequences of this damage in hearing function.
“The discovery of hidden hearing loss has forever changed the way clinicians think about hearing loss, from its diagnosis to its treatment,” says Mark A. Varvares, M.D., FACS, the chief of the departments of otolaryngology–head and neck surgery at Mass Eye and Ear and Massachusetts General Hospital. “The continuation of this P50 grant is another example of our commitment to pioneering life-changing diagnostics and cures at Mass Eye and Ear.”
Hidden Hearing Loss
The audiogram has long been used by clinicians as the gold standard for hearing tests. The test reflects the health of sensory cells in the inner ear, called hair cells, which convert sound into electrical signals. While the health of these cells can determine a person’s hearing threshold, or how loud a sound needs to be in order for a person to hear it, the thresholds do not reveal how clearly sounds are heard. A healthy auditory nerve, able to faithfully transmit sound information to the brain, plays a crucial role.
In 2009, Kujawa and Liberman discovered that exposure to noise destroys the synapses connecting hair cells to the auditory nerve well before the noise-damaged hair cells, which meant hearing damage could exist before it was revealed by the audiogram.
“We used to think that if thresholds recovered to normal after exposure to noise, then there was no lasting ear damage, which we’ve come to find out isn’t the case,” Kujawa says. “Rather, it’s as if the loss was ‘hidden’ in the normal audiogram.”
This prompted the researchers to evaluate widespread neural degeneration in patients who had hearing difficulties, but also had typical audiogram measurements.
Under the NIH initial grant, the research team focused on detecting and characterizing hidden hearing loss in humans and animals with typical hearing thresholds. With the new grant, their focus will expand to detecting this hearing damage in the presence of hearing loss as traditionally defined by a clinical audiogram, as well as to better understanding the consequences of this damage in hearing function.
Building on Earlier Projects
Since Kujawa and Liberman’s 2009 discovery, investigators have made it a priority to understand what hidden hearing loss is, what causes it, and how to identify it. In 2017, the NIH awarded Kujawa, Liberman, Maison, and Polley a P50 grant to research this new type of hearing damage from multiple angles. Through four separate projects, including one studying donated human temporal bones, one focusing on animal models of human hearing loss, and two working with human subjects, the team of researchers has found widespread evidence of neural degeneration hidden behind typical audiogram measurements.
Their research also unveiled several new clues about this new type of hearing damage. Growing evidence has suggested that perceptual disorders, some as mild as difficulty hearing in a noisy environment, or as potentially debilitating as tinnitus and hyperacusis, could share a common tie to neural degeneration. Additionally, studies found that sound deprivation—not just aging, loud noises, or ototoxic drugs—can lead to neural degeneration.
According to Kujawa, evaluating human and animal subjects with overt hearing loss under the new P50 grant will bring investigators a step closer to devising sensitive diagnostic tools, thereby making it possible to apply future therapeutics to prevent, limit, or reverse cochlear neural degeneration.
“Right now, we have therapeutics on the horizon that have shown the potential to repair or reconnect these nerve fibers in the inner ear,” she says. “If we can improve our tests so they show us who has neural degeneration and who doesn’t, then we can test the efficacy of these therapeutics, which would be a big advance for hearing loss research and clinical treatment.” —Mass Eye and Ear
This is adapted from a press release by Mass Eye and Ear. Research reported above was supported by the National Institute on Deafness And Other Communication Disorders of the National Institutes of Health under Award Number P50DC015857. A 1999 Emerging Research Grants (ERG) scientist, Sharon Kujawa, Ph.D., is a member of HHF’s Board of Directors and Council of Scientific Trustees. She presented her research on hidden hearing loss for HHF’s Hearing Health Hour webinar, at hhf.org/webinar.
Support our research: hhf.org/donate.
How Pharmacists Can Help Bridge the Gap in Hearing Care for Seniors
One third of people between 65 and 74 years of age and one half of those 75 years of age and older have some degree of hearing loss, according to the National Institute on Deafness and Other Communication Disorders. The number of people with hearing loss is expected to continue to rise because of the aging population of the United States.
The World Health Organization says hearing loss is associated with impaired cognition, communication, and balance, as well as an increased risk of dementia, falls, hospitalization, and early mortality. The risk of dementia is up to five times greater and the risk of falling up to three times greater in people with hearing loss left untreated.
To mitigate these risks, it is crucial for older people with hearing loss to be identified in order to treat their hearing. Historically, collaboration between otologists, audiologists, and pharmacists has been limited, but pharmacy graduate students and their advisers at the University of Maryland in Baltimore and College Park recognized that as frontline health care providers, pharmacists have the potential to expand knowledge and facilitate hearing care for patients.
After reviewing the literature on pharmacy, audiology, and their integration, their paper in The Senior Care Pharmacist in July 2022 aims to provide pharmacists with education on hearing loss that colleagues in audiology believe is most critical for pharmacists.
Access to Care
Hearing care is delivered through a clinic-based model by a hearing care professional such as an audiologist or otologist. This model limits access to care for individuals living in remote areas and often leaves the responsibility with the patient to prioritize and seek out their own hearing care. The need for a separate specialized office visit creates a barrier for patients with financial struggles.
Recent changes in legislation led to the approval of over-the-counter (OTC) hearing aids for patients with mild to moderate hearing loss. These hearing aids will be offered, like reading glasses, in pharmacies and other consumer shops. As a result, pharmacists may not only be the most accessible frontline providers, but also be best positioned to promote hearing health and provide on-site consultation.
Geographically, more than 90 percent of people in the United States live within 2 to 5 miles of a community pharmacy. In the United States, 66 percent of adults older than 65 years of age use at least five prescription medications; as a result, most older people interact with a pharmacist multiple times per year. In collaboration with audiologists and otologists, pharmacists can bridge the gap for patients in need of hearing assistance.
Hearing Screenings
According to the U.S. Census population prediction, by 2034 patients older than 65 years of age will outnumber children in the United States. As the population ages, increasing access to screening has never been more relevant. Early identification of hearing loss is key to effective management. Screening is recommended every 10 years for adults and every three years for adults 50 years of age or older and those with risk factors for hearing loss—but compliance with this practice is low.
In the community, pharmacists can informally screen patients for hearing loss, by identifying older patients who ask them to repeat statements or respond with short, noncommittal answers. A more formal screening is possible when the pharmacist is providing annual wellness visits or medication therapy management.
Enhanced Communication
Apart from screening, there are other ways senior care pharmacists can tailor their practices to better serve older patients with hearing loss. Studies have demonstrated inconsistent knowledge of common health issues among older patients with communication difficulties. Hearing loss can lower the quality of care delivered and lead to negative health outcomes.
Considering the prevalence of hearing loss, pharmacists should anticipate the need for auditory accommodation and have these services readily available to ensure effective communication. Auditory accommodations can include assistive listening devices, written information to supplement verbal communication, and ensuring that the environment is conducive to communication, such as through face-to-face communication in a quiet, well-lit area.
Geographically, more than 90 percent of people in the United States live within 2 to 5 miles of a community pharmacy. In the United States, 66 percent of adults older than 65 years of age use at least five prescription medications; as a result, most older people interact with a pharmacist multiple times per year. In collaboration with audiologists and otologists, pharmacists can bridge the gap for patients in need of hearing assistance.
Over-the-Counter Hearing Aids
The U.S. Food and Drug Administration (FDA) has recommended implementing a new device category for OTC wearable hearing devices for adults with no greater than moderate hearing loss. To date, the FDA approval process is not complete, so the following recommendations come from what the authors predict the technology of the approved OTC hearing aids will include.
It is estimated that 28.8 million adults in the United States could benefit from hearing aids, and less than 30 percent have ever used them. OTC devices are intended to address issues with the accessibility and affordability of amplification devices by reducing the regulatory burden of bringing hearing aids to the market.
With OTC devices available for sale in community pharmacies, pharmacists have the potential to provide vital education and counseling to older patients seeking hearing health care, helping to determine if they are a suitable candidate for an OTC hearing aid or if they should be referred to an audiologist or an otologist.
Signs a patient may be a good OTC candidate
» Hearing loss falls within the mild to moderate range » Patient has accurate and consistent perception of his or her hearing ability
Signs a patient may not be a good OTC candidate (prompting a referral)
» Signs of cognitive impairment » Inappropriate expectations about hearing aid benefit » Poor dexterity
Pharmacists should be aware of criteria for immediate medical referral which include dizziness, sudden hearing loss, pain or discomfort, discharge, or excessive earwax. Consulting with a medical professional can rule out an infectious disease or other trauma, or the ability to medically treat (e.g., steroid administration for sudden hearing loss).
Senior care pharmacists are well positioned to help but must be aware of the prevalence of hearing loss in their communities and be actively engaged in screening and person-centered interventions. Collaboration with audiologists and otologists will allow for referrals to be made by pharmacists when an older patient’s hearing loss needs further care.
When OTC hearing aids are made available, pharmacists will need to be able to make recommendations regarding hearing aids but also identify patients who require referral or are otherwise not good candidates for an OTC device. By working with audiologists and otologists, pharmacists have the potential to help mitigate the widespread problem of untreated hearing loss by helping older patients overcome the barriers of access and affordability in hearing healthcare. —Ronna Hertzano, M.D., Ph.D.
This is adapted from the paper “Senior Care Pharmacists, Audiologists, and Otologists: Improving Hearing Health for Older Patients Through Interprofessional Collaboration” in The Senior Care Pharmacist, July 2022. The paper’s coauthor Ronna Hertzano, M.D., Ph.D., is a 2009–2010 ERG scientist and a member of HHF’s Hearing Restoration Project and Council of Scientific Trustees. She is a professor in the department of otorhinolaryngology–head and neck surgery at the University of Maryland School of Medicine.
Support our research: hhf.org/donate.
In this graph modified from Karawani et al., in Frontiers in Aging Neuroscience, 2022, the average changes in cortical response amplitudes to a speech syllable in 17 new hearing aid users are displayed for six sessions. A significant increase in N1 amplitude was noted in session 2 (two weeks after hearing aid fitting) but the increase in P2 amplitude did not consistently occur until session 4 (12 weeks after hearing aid fitting).
Hearing Aid Use Improves Brain Processing Over Time
New hearing aid users often report significant improvements in quality of life as they connect once again to the hearing world around them. Yet, first-time hearing aid users may find that newly amplified sounds are overwhelming.
The onset of hearing loss usually occurs slowly, and individuals may wait seven or more years before deciding to pursue treatment for hearing loss. During this time, the brain adjusts to the lack of sound input by increasing the firing rate of auditory neurons, making them more excitable. This increased excitability can make newly amplified sounds seem uncomfortably loud.
Fortunately, the brain can readjust to an increase in auditory input through the use of hearing aids. This adjustment period takes time, however, and knowledge of the time course of neural adaptation may be useful when counseling patients fit with hearing aids for the first time.
In 2014, my colleagues at the University of Maryland and I were awarded an Emerging Research Grant to evaluate neural plasticity associated with hearing aid use. We recruited listeners with mild-to-moderate sensorineural hearing loss who had never worn hearing aids and randomly assigned them to two groups.
The first group of 17 individuals was fit with hearing aids and wore them for at least eight hours a day for six months. The second group of 14 individuals was fit and tested with hearing aids but did not wear them during the six-month period. Both groups were tested with a battery of behavioral, electrophysiological, and cognitive tests.
Our initial studies demonstrated plasticity in the hearing aid use group through improved brain processing, speech-in-noise performance, and working memory scores (Neuropsychologia, 2018; Clinical Neurophysiology, 2018). These changes were not observed in the no hearing aid use group.
Our group recently published a follow-up study in Frontiers in Aging Neuroscience in May 2022 that determined the time course of changes in brain processing over the course of six months. We measured cortical speech processing while wearing hearing aids at six time points: initial fitting, two weeks, six weeks, 12 weeks, 18 weeks, and six months post-hearing aid fitting.
We found that early stages of brain processing changed rapidly. Peak N1 of the cortical response signals the brain’s orientation to an auditory stimulus.
The amplitude of N1 increased after just two weeks. Later stages of brain processing required more time to observe a consistent change. Peak P2 of the cortical response signals the brain’s early identification of an auditory stimulus. For example, if one hears the sound of a toilet flushing, the brain forms an auditory image of a toilet at an unconscious level. Increases in P2 amplitude were observed after six weeks of hearing aid use. Figure 1 displays changes in these amplitudes over the course of six sessions.
So, what does this mean for the new hearing aid user? The brain adjusts quickly to amplified sound—that’s a good thing. But the brain’s ability to fully interpret amplified signals in a meaningful way requires a longer period of time. The typical hearing aid trial period is 30 days, so the hearing aid user may not be experiencing the full benefits of amplification at the end of that period.
Audiologists may wish to use this information to counsel the patient that hearing through amplification should continue to improve, especially with respect to clarity. Our paper also found that electrophysiology testing on the first day of hearing aid fitting predicted later improvements. Perhaps in the future we will see an increase in the use of electrophysiology to manage hearing loss and to counsel patients regarding appropriate expectations. —Samira Anderson, Au.D., Ph.D.
A 2014 ERG scientist generously funded by Royal Arch Research Assistance, Samira Anderson, Au.D., Ph.D., is an associate professor and the director of graduate studies in the department of hearing and speech sciences at the University of Maryland.
Support our research: hhf.org/donate.
As shown in this University of Florida image by Hillary Carter and Shena Hays, by combining electromagnetic articulography and electroglottography, researchers can simultaneously record lip, tongue, jaw, and glottal motion during speech production without electromagnetic interference.
Improving How to Assess Speech Production
When we talk, we have the impression that we don’t have to do much. We have an idea, our mouth starts to move, and the sound comes out, and we don’t have a sense of the steps involved in the process. Yet anyone who has ever attempted to produce speech in a foreign language can readily attest that the ability to produce the sound sequences in a fluent, natural, and coordinated way is a far from trivial skill. Moreover, the challenges encountered in learning to speak by individuals born with profound sensorineural hearing loss also hint at the complexity involved.
During typical conversational interactions, humans use over 100 different muscles in the vocal tract to produce up to 6 to 9 syllables per second, which is one of the fastest types of motor behavior. More complicated still, the various articulators of the vocal tract—the lips, tongue, jaw, and glottis—do not move in an isolated, independent manner. Rather, their movement patterns are lawfully orchestrated with one another in space and time. Unfortunately, though, no single instrument is capable of concurrently measuring the complex motion patterns of all the articulators involved in speech production.
Recently, my team and I demonstrated that two different instruments with complementary strengths—electromagnetic articulography (EMA) and electroglottography (EGG)—can be combined to concurrently measure laryngeal and supralaryngeal speech movements. EMA uses diffuse magnetic fields to track the positions of sensors fixated on the lips, tongue, and jaw during speaking, and EGG measures electrical impedance across the larnyx during the production of voice.
We plan to use these instruments to better characterize how congenitally deaf talkers who received cochlear implants (CIs) and their typical-hearing peers control and coordinate laryngeal and supralaryngeal movements. As published in JASA (Journal of the Acoustical Society of America) Express Letters in September 2022, this approach is novel because most clinical interventions for children with CIs focus on listening to speech. In our well-intentioned efforts to promote listening experiences we may be overlooking the importance of practice in producing speech.
We hypothesize that providing CI wearers with orofacial somatosensory inputs associated with speech production may “prime” motor and sensory brain areas involved in the sensorimotor control of speech, thereby facilitating perception of the degraded acoustic signal experienced through their processors. —Matthew Masapollo, Ph.D.
During typical conversational interactions, humans use over 100 different muscles in the vocal tract to produce up to 6 to 9 syllables per second, which is one of the fastest types of motor behavior. More complicated still, the various articulators of the vocal tract—the lips, tongue, jaw, and glottis—do not move in an isolated, independent manner. Rather, their movement patterns are lawfully orchestrated with one another in space and time.
A 2022–2023 ERG scientist, Matthew Masapollo, Ph.D., is an assistant professor in the department of speech, language, and hearing sciences, and the director of the University of Florida Speech Communication Lab.
For references, see hhf.org/fall2022-references.
YOU CAN MAKE A DIFFERENCE NOW
announcing a planned giving matching challenge
Ann Pruitt has named HHF in her estate plans.
Planned giving, also called estate or legacy giving, means a gift that your favorite charity receives upon your passing. It is a gift for the future. A generous, anonymous donor has launched a challenge that will match your planned gift now. This enables Hearing Health Foundation to continue funding the life-changing science that benefits the millions of people who live with hearing and balance challenges. Your planned gift will be matched when you make a bequest to HHF or name us as a partial beneficiary of a retirement fund or life insurance policy. Here’s how the matching challenge works: » For any planned gift of up to $10,000,
HHF receives a match of $1,000.
» For any planned gift of $10,000 or more,
HHF receives a match of $10,000.
» For larger planned gifts,
HHF receives a match of $100,000.
Please email Harriet Hessam at hhessam@hhf.org to let us know about your planned gift or for more information.
