Second Cause of Hidden Hearing Loss Identified

By Michigan Medicine - University of Michigan

Some people can pass a hearing test but have trouble understanding speech in a noisy environment. New research identifies a new mechanism for this condition just years after its discovery. Credit: Michigan Medicine

Patients who complain they can't hear their friends at a noisy restaurant, but pass a hearing test in their doctor's office, may be describing hidden hearing loss.

Now, less than six years since its initial description, scientists have made great strides in understanding what hidden hearing loss is and what causes it. In research published in Nature Communications, University of Michigan researchers report a new unexpected cause for this auditory neuropathy, a step toward the eventual work to identify treatments.

"If people can have hidden hearing loss for different reasons, having the ability to make the right diagnosis of the pathogenesis will be critical," says author Gabriel Corfas, Ph.D., director of the Kresge Hearing Research Institute at Michigan Medicine's Department of Otolaryngology -- Head and Neck Surgery.

Corfas published the research with co-author Guoqiang Wan, now with Nanjing University in China. They discovered using mice that disruption in the Schwann cells that make myelin, which insulates the neuronal axons in the ear, leads to hidden hearing loss. This means hidden hearing loss could be behind auditory deficits seen in acute demyelinating disorders such as Guillain-Barré syndrome, which can be caused by Zika virus.

Corfas and Wan used genetic tools to induce loss of myelin in the auditory nerve of mice, modeling Guillain-Barré. Although the myelin regenerated in a few weeks, the mice developed a permanent hidden hearing loss. Even after the myelin regenerated, damage to a nerve structure called the heminode remained.

Synapse loss versus myelin disruption

When the ear is exposed to loud noises over time, synapses connecting hair cells with the neurons in the inner ear are lost. This loss of synapses has previously been shown as a mechanism leading to hidden hearing loss.

In an audiologist's quiet testing room, only a few synapses are needed to pick up sounds. But in a noisy environment, the ear must activate specific synapses. If they aren't all there, it's difficult for people to make sense of the noise or words around them. That is hidden hearing loss, Corfas says.

"Exposure to noise is increasing in our society, and children are exposing themselves to high levels of noise very early in life," Corfas says. "It's clear that being exposed to high levels of sound might contribute to increases in hidden hearing loss."

The newly identified cause -- deficiency in Schwann cells -- could occur in individuals who have already had noise exposure-driven hidden hearing loss as well. "Both forms of hidden hearing loss, noise exposure and loss of myelin, can occur in the same individual for an additive effect," Corfas says.

Previously, Corfas' group succeeded in regenerating synapses in mice with hidden hearing loss, providing a path to explore for potential treatment.

While continuing this work, Corfas started to investigate other cells in the ear, which led to uncovering the new mechanism.

There are no current treatments for hidden hearing loss. But as understanding of the condition improves, the goal is for the research to lead to the development of drugs to treat it.

"Our findings should influence the way hidden hearing loss is diagnosed and drive the future of clinical trials searching for a treatment," Corfas says. "The first step is to know whether a person's hidden hearing loss is due to synapse loss or myelin/heminode damage."

Materials provided by Michigan Medicine - University of Michigan. Co-author Guoqiang Wan, Ph.D., was a 2014 Emerging Research Grants recipient funded by the Wes Bradley, M.D. Memorial Grant.

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Celebrating Hearing Innovations

By Frankie Huang

On Feb. 25, Hearing Health Foundation is celebrating International Cochlear Implant Day to raise awareness of this life-changing technology. Cochlear implants greatly enhance the lives of individuals with severe to profound hearing loss and individuals who don’t benefit from the use of hearing aids. Did you know that as of November 2012, there are 324,000 cochlear implants in use worldwide, and that number is growing daily!

Cochlear implants (CI) are electronic medical devices that are implanted via a surgical procedure. Although implants replace the function of the damaged inner ear, it is important to remember that CIs do not restore normal hearing but work by bypassing damaged structures in the inner ear and stimulating the auditory nerve. This sends signals to the brain, allowing the user to perceive sounds.

Researchers found that children 5 years or older with bilateral severe or profound hearing loss who are implanted with CIs have better speech perception and development over time than children treated with hearing aids. In addition, children with profound hearing loss who used CIs showed greater development of preverbal behavior than those using hearing aids.

Other researchers found that children receiving CIs before 24 months of age greatly benefit in terms of their overall language development. Levels of spoken language in children implanted before age 24 months were on par with their typical hearing peers by age 4.5, but those implanted after age 24 months did not “catch up” with hearing peers by age 4.5. It’s important to note the study didn’t evaluate language development or ongoing delays after age 4.5.

HHF is proud to have supported research in the 1970s that led to the development of cochlear implants. Since then the technology has continued to evolve and improve in order to increase the benefits yielded from having a cochlear implant and to reduce risks associated with an invasive surgical procedure. By further improving the design and the function of CIs, researchers may find a way to maximize all the possible benefits for the patient, to preserve residual hearing, and to improve the health of the inner ear.

If you’re interested in funding research related to hearing loss technology,
please consider donating today at hhf.org/donate or contact us at development@hhf.org.

A Healthy Heart Could Mean Better Hearing Health

By Frankie Huang

In honor of American Heart Month in February, Hearing Health Foundation wants to shine light on the link between heart disease and hearing loss. According to the Centers for Disease Control and Prevention, 610,000 Americans die from heart disease each year, making it the leading cause of death for men and women in the U.S.

Heart disease is linked to or causes numerous health issues, including hearing loss. One study suggests that low-frequency hearing loss may be able to predict cardiovascular health. Using an audiogram, researchers were able to determine the probability of cardiovascular disease in men and women. The study found that there was a correlation of heart attacks in men, and a correlation of claudication (pain caused by too little blood flow) in women.

High blood pressure can also be a contributing factor to developing hearing loss, since the inner ear is sensitive to blood flow. High blood pressure damages blood vessels and increases the risk of plaque buildup in the arteries, making it harder for blood to flow throughout the body. In other words, inadequate blood flow and nerve damage in the inner ear may lead to irreversible hearing loss.

A common cause of heart disease and hearing loss is smoking. Smoking increases blood pressure and plaque buildup, and causes hardening of the arteries, all of which decreases blood flow to the organs and other parts of the body. The effects of smoking damages the cardiovascular system, boosting the risk of hearing loss. Additionally, cigarettes contains nicotine, disrupting the neurotransmitters in the auditory nerve (which tell the brain which sound you are hearing) and preventing the brain to accurately interpret sound. Cigarette smoke contains many harmful chemicals that are believed to be ototoxic (toxic to the ear) that may damage hair cells.

There are a variety of ways to prevent heart disease and cut your risk for hearing loss. Eating healthy and incorporating moderate exercise into your daily life can drastically improve your health. Include more fish in your diet: Salmon, mackerel, and herring are high in the omega-3 fatty acids that help reduce high blood pressure and prevent plaque buildup, so you can decrease your overall risk of hearing loss.

Remember, a healthy heart leads to better hearing health.

HHF Welcomes Two New Board Members

By Nadine Dehgan

Hearing Health Foundation (HHF) is thrilled to welcome two new board members, Jason Frank and Sophia Boccard. Their unwavering dedication to furthering research and awareness of hearing loss and its associated disorders make Jason and Sophia the perfect addition to our leadership team.

Jason Frank is a Vice President/Assistant General Counsel of JPMorgan & Co. in New York City. Jason and his wife Jenny delved into the world of hearing loss after their son was diagnosed with bilateral, mild to moderate sensorineural hearing loss. When looking for resources, Jason says, “We found HHF and the Hearing Restoration Project and knew we wanted to to get involved…. It has been over five years and, while our son is doing wonderfully thanks to early intervention and access to hearing aids since he was 8 weeks old, we remain committed to spreading awareness for hearing loss and finding a cure. I am extremely excited about joining the National Board and becoming more intimately involved with HHF and its cause.”

Sophia Boccard is a digital marketing strategist in the hospitality industry with over a decade of marketing experience in the entertainment industry. “As someone who was born with moderate to severe hearing loss, I've always accepted the loss of hearing as a part of who I am. After being diagnosed with Usher syndrome type 2a in 2012, I realized that a cure for both hearing and vision was something I needed to fight for,” Sophia says. HHF looks forward to working with Sophia to share her experience living with Usher syndrome to raise awareness and find better therapies and cures.

HHF is excited to have Jason and Sophia as new board members and we look forward to their contributions to HHF’s mission. Please join us in giving them both a warm welcome!

When It's Not Just Hearing Loss

By Morgan Leppla & Laura Friedman

This year Autism Sunday, an international day to raise awareness of autism spectrum disorder (ASD), is on Feb. 12.

Did you know that one third or more of pediatric hearing loss cases overlap with another condition? This may sometimes be ASD, making treatment and management of co-occurring conditions a challenge.

In a 2007 report in the Journal of Deaf Studies and Deaf Education, British researcher Lindsay Edwards, Ph.D., cites an estimate that 30 to 40 percent of children with hearing loss have co-occurring conditions that could prohibit them from forming language, speech, and sociocognitive skills. But despite this large percentage, there is little research on hearing loss that occurs with other disorders. What research there is has shown the benefit of cochlear implantation for children with additional needs (such as physical or learning disabilities), and the difficulties of language acquisition and development for 3-year-olds with developmentally related conditions such as ASD, cerebral palsy, or Down syndrome.

One silver lining is that the fact that 30 to 40 percent of pediatric hearing loss may occur with other conditions may prove helpful in predicting future disorders. A July 2016 Autism Research paper suggests that a noninvasive measure of otoacoustic emissions in the inner ear—a common hearing test for infants, who are preverbal—may help identify the risk of ASD at an early age, accelerating treatment. Study author Anne Luebke, Ph.D., of University of Rochester Medical School, found that children with ASD often have trouble hearing a frequency range (1–2 kHz) that is important for understanding speech. The range includes sounds for the meaning-conveying consonants S-, H-, and F-.

Scientific conclusions can help shape future research, but cannot illustrate daily life for families with children with co-occurring conditions. Dual diagnoses make unlocking any child’s learning style challenging, but reviving research and upgrading professional training are essential tools in order to advocate for and successfully educate children with co-occurring conditions.

If you’re interested in funding research related to diagnosing and treating co-occuring disorders, such as hearing loss and autism, please consider donating today: hhf.org/donate or contact us at development@hhf.org.

This blog was adapted from an article original appearing in Hearing Health magazine’s Fall 2016 issue. For references in this story, see hhf.org/fall2016_references.

Noise-Induced Hearing Loss Affects More Than 50% Not in Noisy Jobs

By Yishane Lee

The Centers for Disease Control and Prevention (CDC) made an announcement Feb. 7 on the dangers of noise-induced hearing loss (NIHL). Among the many statistics cited, the CDC says:

• 40 million U.S. adults ages 20 to 79 have NIHL

• More than half (21 million) with hearing damage do not have noisy jobs

• One in four U.S. adults who say they have good or excellent hearing actually show hearing damage

• Hearing loss is the third most common chronic health condition in the U.S.

• People report hearing loss at a rate nearly double of those reporting diabetes or cancer

The CDC says its latest Vital Signs report, using data from more than 3,500 hearing tests in the 2012 National Health and Nutrition Examination Survey (NHANES), shows “much of this [hearing] damage is from loud sounds encountered during everyday activities at home and in the community,” such as using a leaf blower or going to a loud concert without hearing protection. Nearly three-quarters of those who are exposed to loud noises never or rarely use hearing protection, the report says.

According to the press release, CDC researchers “found that 20 percent of people who reported no job-related noise exposure had hearing damage in a pattern usually caused by noise. This damage—shown by a distinctive drop in the ability to hear high-pitched sounds—appeared as early as age 20.” But it added that while a few studies have linked noise exposure among young people to the use of portable devices and entertainment venues, more research is needed to determine the relationship between this type of early noise exposure and hearing loss in older age.

Untreated hearing loss is linked with anxiety, depression, loneliness, and stress, the CDC says. In addition to causing hearing loss, chronic noise exposure can worsen heart disease and increase blood pressure, among other adverse health effects.

But don’t forget, noise is the only fully preventable cause of hearing loss.

Please see HHF’s resources on NIHL here, as well as our Summer 2015 cover story about NIHL. Taking care of your hearing should always be part of your overall health. If you suspect a hearing loss, get your hearing checked, and if you do have a hearing loss, get it treated. Avoid noisy areas, and wear protective earplugs or stronger when you need them in noisy environments. Download the CDC’s fact sheet here.

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A Fight Against Cancer Is a Fight Against Hearing Loss

By Frankie Huang

In honor of World Cancer Day on February 4, Hearing Health Foundation (HHF) wants to raise awareness of the connection between cancer and hearing loss. Every year, 8.2 million people worldwide die from cancer, a disease that is responsible for 13% of all deaths globally.

Depending on the type of cancer, patients that undergo chemotherapy are sometimes required to take certain drugs that could cause many side effects, including hearing loss. Cisplatin is a chemotherapy drug that is often used to treat testicular, bladder, ovarian and lung cancers. However, an excessive dose of cisplatin can be ototoxic (toxic to the ear), which could lead to temporary or permanent hearing loss.

One study suggested that cisplatin-induced hearing loss is generally bilateral (both ears) and irreversible. The study also found that cisplatin accumulates in cochlear tissue, preventing the cochlea from flushing out toxins. The same researchers found that patients receiving doses of cisplatin between 150-225 mg/m2 showed some degree of hearing loss. For testicular cancer patients, more than 50% of the patients that took cisplatin in doses greater than 400 mg/m2 had permanent hearing loss. Hearing loss may occur within hours or days after the treatment, or hearing may gradually decline after completion of therapy. After following up more than two years later, the study authors found that 44% of patients who took cisplatin had significant hearing loss.

In another recent study, researchers found that the WFS1 gene is associated with cisplatin-related ototoxicity; the heavier the dose, the more severe the hearing loss. Also, a mutation of the WFS1 gene results in Wolfram syndrome, a disorder with deafness as a major symptom.

As of now, there are no safe and protective agents against cisplatin, but scientists are hard at work to find a protective agent that would eliminate the negative side effects of cisplatin. Currently there’s a solution for children that are receiving cisplatin-based chemotherapy: The use of sodium thiosulfate may minimize or protect children and adolescents against cisplatin-induced hearing loss. HHF hopes more preventative therapies and cures for hearing loss can be discovered for all cisplatin-treated patients.

Interested in funding research in this area? Email us at development@hhf.org.

Real-Time Text: The FCC Makes It Official

By Kathi Mestayer

This will be the standard symbol for real-time text, from the RTT website.

Have you ever been on a phone call, slowly spelling out the word you just used? And finding out how very similar fifteen and fifty sound? Or how tough it is to communicate a word such as “impingement,” even if you do spell it?

The good news is that the FCC has now enacted the long-awaited transition to providing real-time text (RTT) by cellphone providers. "Real-time text allows characters to be sent as they are created without hitting ‘send,’” according to the Dec. 15, 2016, FCC press release. “This allows text to be sent at the same time as voice communications, permitting a more conversation-friendly service.”

People with hearing loss will now be able to clarify (or receive clarification) of spoken content by quickly texting the word(s) to the other party, without interrupting the ongoing conversation (or hitting “send”).

This action is discussed briefly in Hearing Health’s Winter 2017 issue here (before the official adoption of the rules by FCC had been completed).  

The new FCC rules require large phone carriers to make RTT available by the end of this year. The first phase would require users to download an app, but RTT would eventually be built into phones.  

According to Christian Vogler, the director of Gallaudet University’s Technology Access Program, AT&T worked closely with Gallaudet at various stages of planning for RTT. In one case the testing made it possible to show “how well it held up under network conditions that can be too poor even for voice calls.”

“Too poor for voice calls”—who hasn’t been there? Very soon we’ll have another option. For more information, see the RTT website.

Music-Induced Hearing Loss: What Do College Students Know?

By Frankie Huang

Music-induced hearing loss (MIHL) is a result from listening to music that exceeds 85 decibels for prolonged periods of time. A decibel, or dB, is a unit to measure sound intensity, and 85 dB is roughly equivalent to the sound of heavy city traffic. Our listening devices and preferred listening levels are the leading cause for MIHL. For example, when you’re working out at the gym and you up the volume of your music to 100% to drown out the music the gym is broadcasting, you are putting yourself at risk for permanent hearing loss.

The frequent use of these devices to listen to music and watch videos typically requires the use of headphones, increasing the risk of MIHL. Portnuff, Figor, and Arehart (2011) found that a person should only use their listening devices for no more than 4 hours per day at 70% volume, or 90 minutes per day at 80% volume.

In a recent study, researchers measured college students’ knowledge on the proper use of listening devices and the effects of listening to music at high volumes. It was found that prolonged use of these devices coupled with loud preferred listening levels is higher in males than in females, with males being less aware of safe listening habits and were more likely to exceed the recommended daily limit. The study also found that female students were more conscious of these limits and more knowledgeable about the maximum listening levels per day, compared with their male counterparts. Furthermore, younger students (freshmen) were less aware of safe listening levels compared with older students who were sophomores.

The use of certain headphones can also increase the risk of MIHL. Among college students, in-ear headphones (e.g., earbuds) are more commonly used than over-the-ear, noise-canceling headphones, and in-ear headphones are associated with a higher risk of MIHL. The biggest difference between in-ear and over-the-ear headphone users was the individual’s listening levels: The study found that in-ear headphone users preferred to listen at a higher volume, while over-the-ear headphone users favored a lower volume because the noise-canceling features meant ambient noise was less of an issue.

Headphone users tend to increase the volume if they can’t block out environmental noises. New York City, for example, is usually noisy so individuals are more likely to listen to their music at a higher volume, which is putting individuals at a greater risk of MIHL. There’s also a greater preference for in-ear headphones between males and females. According to the studies, 52.8% of males believed that in-ear headphones delivered better sound than over-the-ear headphones, compared with 46.4% of females.

Overall, the study suggested that individuals should refrain from listening to music and watching videos at the maximum volume for an extensive amount of time. However, if there’s too much background noise, and it's a distraction, the individual should only increase the volume to 80% of the maximum for no more than 90 minutes daily. In addition, education about the risks of hearing loss and how to prevent it is important, including how noise-canceling headphones drown out environmental noises so the wearer can enjoy music on their personal devices at safer levels.

Hearing loss is irreversible, so investing in a quality headphone that can reduce the risk of MIHL is priceless.

References

Berg, Abbey L. et al. Music-Induced Hearing Loss:What Do College Students Know?. 43rd ed. 2016. Web. 12 Dec. 2016.

http://www.asha.org/uploadedFiles/ASHA/Publications/cicsd/2016F-Music-Induced-Hearing-Loss.pdf

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