Ask the Scientist: Gene Therapies and Hearing

By Peter G. Barr-Gillespie, Ph.D.

A DNA double helix

National Human Genome Research Institute

Recently, Hearing Health Foundation (HHF) has received several questions regarding the Reuters report on gene therapies for hearing. There are two separate but related topics raised in this article. As the scientific research director of HHF’s Hearing Restoration Project, which since 2011 has been uncovering concrete discoveries toward a biologic cure for hearing loss and tinnitus, I want talk about each individually, and then discuss what I interpret they mean together.

The article first presents the Science Translational Medicine paper from Jeffrey Holt’s lab. This is very much a proof-of-principle report, focused on an animal model and using a time for delivery of the corrected gene that is extremely early in development (equivalent to a 5-to-6-month-old human fetus). It is important to point out that their strategy will only correct one type of genetic hearing loss and genetic hearing loss from mutations in other genes will require related but different strategies. Nevertheless, this is an exciting example of modeling gene therapy in animals, and represents a logical progression toward that goal in humans.

The article then moves on to reference the Novartis trial. For this trial, they are using a similar technical strategy, viral delivery of a gene, but they are targeting people—those who have lost their hearing through non-genetic means, such as noise damage, aging, or infections. The gene they are delivering, known as ATOH1, may stimulate production of new hair cells; it is a gene that is essential for formation of hair cells during development, and in some experimental animal models, delivery of the gene can lead to production of a few hair cells in adult ears.

That said, many people who I have talked to in the field who work with experimental models of hair cell formation using ATOH1, including members of our Hearing Restoration Project consortium, believe that this trial is premature. By and large, the animal models do not support the trial; most suggest that there will be few hair cells formed and little hearing restored. While we can hope for a little bit of hearing recovery, we are concerned about toxic responses to the gene delivery using viruses. Personally, while I think it would be truly fantastic if the Novartis trial works, at this moment in time I don’t think the rewards yet outweigh the considerable risks being imposed on a human (include safety during the procedure and potential side effects afterward).

Still, the Novartis trial will tell us about the safety of viral delivery into the ears of humans, and knowing that is critically important. I think the most likely outcome is that we will learn whether the strategy the Novartis trial used to deliver the gene is safe. Unfortunately, if we don’t see improved hearing, we won’t know why—did the gene not get to the right place, or does it just not work?

Technical aspects of gene delivery are what ties together the Novartis work and the Holt lab work. Both use viruses for delivering genes, and together the results from these and others will let us know, from a procedural standpoint, how we can deliver genes to the ear. I think it is unlikely that delivering just ATOH1 will do the trick of restoring hearing; it may be that we need to deliver other genes or to use drugs to overcome the block we see to making new hair cells.

So while these are exciting reports to hear about, especially that Novartis is actually carrying out a trial in humans, it is still premature to think that this is going to be a viable strategy for restoring hearing. This is why Hearing Health Foundation's Hearing Restoration Project is doing everything possible to accelerate the pace of its research.

Hair cell regeneration is a plausible goal for the treatment of hearing and balance disorders. The question is not if we will regenerate hair cells in humans, but when. Your financial support will help to ensure we can continue this vital research and find a cure in our lifetime! Please help us accelerate the pace of hearing and balance research and donate today. Your HELP is OUR hope!

If you have any questions about this research or our progress toward a cure for hearing loss and tinnitus, please contact Hearing Health Foundation at info@hhf.org.

Taking Hair Cell Regeneration Down a Notch

By Andy Groves

Hearing Restoration Project (HRP) consortium scientists, Andy Groves and Stefan Heller had their research published in Frontiers in Cellular Neuroscience on March 31, 2015. Below is a summary of their research:

Sensorineural hearing loss is most commonly caused by the death of hair cells in the organ of Corti, and once lost, mammalian hair cells do not regenerate. In contrast, other vertebrates such as birds can regenerate hair cells by stimulating division and differentiation of neighboring supporting cells.

During the development of the inner ear, newly-born hair cells send signals to their neighbors that instruct them to not become hair cells, but to become supporting cells instead. Hair cells are the mechanosensitive cells of the ear. Supporting cells surround them and as their name implies, physically support them and help regulate some of the properties of hair cells. One of these signals is an evolutionarily ancient pathway, the Notch signaling pathway. We and others have shown that if you block the Notch signaling pathway in the cochlea or balance organs of young mice, the supporting cells no longer get the message to stay as supporting cells, and instead they transform into hair cells. This process also happens during hair cell regeneration in birds - supporting cells transform into hair cells, which then send a Notch signal to their neighbors and prevent too many hair cells from being formed.

These observations suggest that it might be possible to block Notch signaling in mature, deafened animals as a means of getting new hair cells to form. We performed a simple experiment to test this in progressively older and older animals. To our surprise, we found that once mice are more than a week old, blocking Notch signaling has no effect on the cochlea any more, and no new hair cells are made.  We showed that this was due in part to components of the Notch signaling pathway being switched off in the ear as the animals get older. Viewed this way, the Notch signaling pathway can be thought of as a “Scaffold” - it is used to allow the cochlea to be built in the first place, but is then dismantled once the cochlea becomes functional.

What does this mean? It suggests that inhibiting Notch signaling alone is unlikely to be an effective means of hair cell regeneration in mammals. It is possible that other factors will be required, and some HRP members are busy testing these other pathways right now. It will also be of great interest to understand HOW the Notch pathway is dismantled with age, whether we can exploit this in future therapies.

Read more about this research proposal here: http://hearinghealthfoundation.org/hrp-consortium-projects-groves-segil-stone.

This work was supported by Department of Defense Grant DODW81XWH-11-2-004(AKG) and Hearing Restoration Project consortium grants from the Hearing Health Foundation (AKG and SH), NIH grant DC004563 (SH), NIH grant P30DC010363 (SH, JSO), and NIHR01DC014450 (JSO).

Hair cell regeneration is a plausible goal for the treatment of hearing and balance disorders. The question is not if we will regenerate hair cells in humans, but when. Your financial support will help to ensure we can continue this vital research and find a cure in our lifetime! Please help us accelerate the pace of hearing and balance research and donate today. Your HELP is OUR hope!

If you have any questions about this research or our progress toward a cure for hearing loss and tinnitus, please contact Hearing Health Foundation at info@hhf.org.

Gene Discoveries May Lead to Regeneration of Cells Needed for Hearing

By Jeffrey Norris

The researchers identified patterns of gene expression that may determine whether the ear’s inner pillar cells can give rise to new hair cells, which are key to hearing.

School of Medicine scientists have discovered biological mechanisms that appear to play a role in the regeneration of cells in the inner ear.

Over a lifetime, these cells often are damaged or die due to oxidative stress, excessive noise exposure or toxic drugs. The accumulated loss can significantly compromise hearing. Nearly one in four people ages 65-74, and half who are 75 or older, are candidates for hearing aids because of disabling hearing loss.

The discoveries could lead to new ways of evaluating, in animal models, experimental drug treatments intended to prevent hearing loss or restore hearing, and might even lead to methods for regenerating vital cells that have been lost, said Stefan Heller, PhD, professor of otolaryngology.

A paper describing the findings, as well as new methods to quickly link changes in cell function during development to molecular changes within cells, was published June 9 in Cell Reports. Heller is the senior author of the paper. Postdoctoral scholars Jöerg Waldhaus, PhD, and Robert Durruthy-Durruthy, PhD, share the lead authorship.

Discoveries by Stefan Heller and his colleagues could lead to new ways of evaluating, in animal models, experimental drug treatments intended to prevent hearing loss or restore hearing. - Steve Fisch

Sound waves striking the eardrum cause vibrations that are transmitted through tiny bones in the middle ear to fluid within the snail-shell-shaped cochlea of the inner ear. Specialized cochlear cells in a region called the organ of Corti use hairlike sensors to detect the vibrations in cochlear fluid and then trigger nerve signals that are sent to the brain.

“Compared to other senses, we know very little about how hearing works,” Heller said. “The cells are rare. We have to crack open a bone to get to them. They perish quickly, so we must work fast.” There are 120 million retinal cells in a mouse eye, Heller said, but only 3,200 hair cells in a mouse ear.

By using new techniques to rapidly and deeply probe individual cells, Heller’s team has begun to close the knowledge gap.

Molecular mysteries

Many of the biophysical properties of hair cells are understood. Different hair cells along the cochlear spiral are tuned to respond to distinct ranges of sound frequency based on differences in their electrical properties. Frequency is encoded by the place and the properties of the cells’ locations in the cochlea. This understanding has led to the development of cochlear implants to restore hearing in deaf people.

However, little is known about the molecular biology that determines how hair cells develop at specific locations and how different electrical properties arise among hair cells specialized to detect different frequencies. This makes it difficult for scientists to envision strategies to regenerate the specialized cells or to prevent their death, particularly in the high-frequency region of the cochlea, where cells are more susceptible to injury.

Once hair cells die in a mature mammal, they are not replaced. But scientists have recently determined that a supporting cell type, called the inner pillar cell, has the potential to regenerate hair cells in newborn mice.

In its new study of 2-day-old mice, Heller’s lab team measured the activity of 192 genes. The researchers determined which genes were turned on, or “expressed,” in each of 808 hair cells and supporting cells from either the apex or base of the organ of Corti. They quantified this gene expression by measuring the amount of RNA produced from each gene.

The researchers identified patterns of gene expression that may determine whether inner pillar cells can give rise to new hair cells. Similarly, they discovered gradual changes in the expression of specific genes across cells that span the organ of Corti from its base to its apex that may be crucial for the establishment and maintenance of a population of hair cells that responds to a range of sound frequencies.

Crunching the data

Using powerful number-crunching software to analyze the large amount of genetic data, Heller’s lab team accurately identified the two known types of hair cells and the seven known types of supporting cells and created a computer-generated map of their locations within the organ of Corti. They did this using only the genetic data, but then used other previously known DNA sequences to independently verify the accuracy of the cell identification and mapping.

The strategy the researchers used to predict the spatial location of cells within the organ of Corti from gene-expression data also should prove useful to biologists who study other types of cells in different organs, Heller said.

Rapid advances in single-cell gene-expression analysis are likely to supplant a standard technique called in-situ hybridization, according to Heller. The standard technique relies on labeled genetic probes to target individual genes one by one in order to identify specific cell types. The new approach of measuring hundreds of genes in parallel and reconstructing the organs in the computer appears to be more accurate and powerful.

“Molecular gradients play a key role in developmental biology, but in the past researchers depended on identifying gradients in one molecule at a time,” Heller said. “With these new techniques, we are identifying cells that, for example, have molecular characteristics of stem cells, by analyzing the expression of many genes all at once, and we know precisely where they are located.”

The research was funded by the National Institutes of Health (grants DC006167 and DC012250), the Stanford Initiative to Cure Hearing Loss and Hearing Health Foundation’s Hearing Restoration Project.

Stanford’s Department of Otolaryngology-Head & Neck Surgery also supported the work.

Republished with permission from the Stanford School of Medicine's Office of Communication & Public Affairs.

Men's Health and Hearing Health are Linked

By Laura Friedman

Hearing health affects so many aspects of a man’s life that routine hearing tests should be part of a healthy lifestyle. Hearing Health Foundation and Better Hearing Institute (BHI) which are encouraging hearing tests during Men’s Health Month in June and Men’s Health Week (June 15-21). Addressing hearing loss can help men safeguard their wellbeing and quality of life. And new research shows that people with hearing loss who use hearing aids enjoy a better overall quality of life and are more likely to be optimistic, have a strong social network, tackle problems actively, and feel engaged in life. At the same time, an increasing number of studies are showing a link between hearing loss and other health conditions.

Men are more likely to suffer from hearing loss than women. But luckily, the vast majority of people with hearing loss can benefit from hearing aids. In fact, most people who currently wear hearing aids say it not only helps their overall ability to communicate effectively in most situations, but it also has a positive effect on their relationships. Most hearing aid users in the workforce even say it has helped their performance on the job.

Other research shows that addressing hearing loss can help protect your earnings. One study showed that the use of hearing aids reduced the risk of income loss dramatically—by 90-100% for those with milder hearing loss, and from 65 -77% for those whose hearing loss was severe to moderate.

What’s more, people with hearing difficulty who use hearing aids get more pleasure in doing things and are even more likely to exercise and meet up with friends to socialize!

Men who want to maintain a healthy, fulfilling lifestyle should know that new technological advances have revolutionized hearing aids in recent years. Today’s hearing aids can automatically adjust to all kinds of sound environments and filter out noise. Many are virtually invisible, sitting discreetly and comfortably inside the ear canal. Some are even waterproof, and others are rechargeable. Best of all, many are wireless, so you can stream sound from smartphones, home entertainment systems and other electronics directly into your hearing aid(s) at volumes just right for you.

5 Men’s Health Motivators for Getting a Hearing Test:

1. Your hearing may say something about your heart. Cardiovascular and hearing health are linked. Some experts say the inner ear is so sensitive to blood flow that it’s possible that abnormalities in the cardiovascular system could be noted here earlier than in other less sensitive parts of the body.
   

2. Hearing loss is about twice as common in people with diabetes. Studies show that people with diabetes are about twice as likely to have hearing loss. When broken down by age, one study showed that those 60 and younger are at greater risk.
   

3. Addressing hearing loss may benefit cognitive function. Research shows a link between hearing loss and dementia, leading experts to believe that interventions, like hearing aids, could potentially delay or prevent dementia. Research is ongoing.
   

4. Hearing loss is tied to sleep apnea. Research shows that sleep apnea is significantly associated with hearing loss at both high and low frequencies. Findings suggest that sleep apnea is a systemic disease and is associated with an increased risk of hearing loss, along with a number of diseases like diabetes, high blood pressure, heart disease, and stroke.
   

5. Hearing loss is tied to depression. Studies show that hearing loss is associated with an increased risk of depression in adults of all ages, but is most pronounced in 18 to 69 year olds. Research also shows that the use of hearing aids reduces depressive symptoms.

BHI and HHF are encouraging men of all ages to take a free, quick, and confidential online hearing check at BetterHearing.org to help determine if they need a comprehensive hearing test by a hearing healthcare professional.

The content for this blog post originated in a press release issued by The Better Hearing Institute on June 3, 2015. 

The Path to a Cure for Hearing Loss and Tinnitus

By Laura Friedman

On May 21, 2015, Hearing Health Foundation hosted its first live-video research briefing as part of our effort to provide regular updates on our research programs and progress. Through these briefings, our goal is for our attendees to obtain new information and understanding about hearing loss, prevention and research toward a cure.

During this inaugural research briefing, Dr. Peter Barr-Gillespie, Scientific Director, Hearing Restoration Project presented the Hearing Restoration Project (HRP). The HRP was founded in 2011 and is the first and only international research consortium focused on investigating hair cell regeneration as a cure for hearing loss and tinnitus. The overarching principle of the consortium is collaboration: open sharing of data and ideas. The HRP consortium consists of 14 of the top investigators in the audiological space, as well as a scientific director, Dr. Barr-Gillespie.

We wanted to share with you highlights from the presentation, which is available to watch with live captioning or to read with notes summarizing each slide. 

1. History of Hearing Health Foundation

   • Founded in 1958, established reputation for pioneering breakthroughs in hearing and balance research.

     • Early supporters of the revolutionary cochlear implant. Today, over 220,000 children and adults benefit.

     • Advocated for the passage of Universal Newborn Hearing Screening legislation in the 1990s. Today, 97% of newborns are tested for hearing loss at birth.

     • The Emerging Research Grants Program provides seed funding for researchers in hearing and balance science such as discoveries in hair cell regeneration, tinnitus, hyperacusis, and Ménière’s research. 

2. The Challenge

   • In the past century, the primary treatment for hearing loss has been hearing aids and cochlear implants. While these have been very successful treatments, they have limitations.

   • For this century, we have a number of different avenues for more effective therapy. 

     • Preventing the damage to the hair cells to preserve hearing. By generating greater awareness of the effects of hearing loss, we aim encourage people of all ages to protect their ears.

     • Gene therapy, targeting those who have lost hearing due to genetic disorders.

     • The majority of people who have lost hearing have done so through noise damage or aging, and may be candidates for hair cell regeneration/restoration.

3. HRP Consortium History & Model

   • One of the key facets of the HRP’s approach is that we use three different animal models for studying hair cell regeneration

     • Two of those models, the chick and the zebrafish, show robust hair cell regeneration.

       • f you damage the hair cells of a chick or a fish, within a short time—only a day or two for the fish, a few weeks for the chick—the hair cells come back; new hair cells are formed.

         • So, that's spectacular, because it tells us that animals are capable of regenerating hair cells.

     • y contrast, the mouse is our other experimental model. Like in the human, the mouse shows no hair cell regeneration after a few days following birth.

       • You can damage the hair cells in the mouse and as far as we can tell, nothing much happens in terms of restoring hair cells. So, if we can figure out how to regenerate hair cells in the mouse, then we will be able to regenerate hair cells in people.

4. HRP Strategic Research Plan

   • Our strategic plan consists of three separate phases. We have already made a lot of progress on Phase 1 and we have initiated Phase 2:

     • Phase 1 – Discovery research:  Compare the fish, chick, and mouse to discover pro- or anti-regeneration pathways and determine supporting cell fates.

     • Phase 2 – Pathway validation: Verify pathways using fish, chick, and mouse models and describe regeneration strategies.

     • Phase 3 – Develop therapies and treatment options: Identify drugs that trigger hair cell regeneration in the mouse model.

5. Progress To-Date

   • Progress on Phase 1: We've identified a variety of candidates for hair cell regeneration and the pathways that are necessary. 

     • We have too many, so we really are continuing to use bioinformatics methods to winnow down and determine which are most important.

     • We have definitively shown, at least in the mouse, the specialized supporting cells remain.

     • We know now what our target cells are for triggering hair cell regeneration. 

   • Phase 2 has begun, but we haven’t stopped Phase 1: 

     • We've got multiple approaches to try and see whether or not we can block regeneration in the fish and chick or stimulate regeneration in the mouse.

   • Phase 3 is in sight:

     • Experimental models from Phase 2 will be used to screen for drugs—using the mouse first

6. The Next Five Years

   • With your help, we can continue to quicken the pace towards a cure. Here’s our plan for the next five years: 

     • Phase 1 will continue: more candidate generation for Phase 2

     • Phase 2 (pathway verification) already initiated in zebrafish, mouse, chick (low throughput)

     • Phase 2 must be scaled up: many more genes, combinatorial approaches; cell lines for screening

     • Phase 3 (drug screening) requires the right screening model, which will come out of Phase 2.

The Future is Very Bright – But we need your support!

Hair cell regeneration is a plausible goal for eventual treatment of hearing and balance disorders. The question is not if we will regenerate hair cells in humans, but when.  However, we need your support to continue this vital research and find a cure! Please make your gift today.  

What Animals Can Tell Us About Humans

By Yishane Lee

Recent findings in mice by University at Buffalo scientists may one day help us better understand human hearing loss. Mice have an inner ear structure and auditory system organization similar to humans, and they also progressively lose their hearing as they age. As published in the Journal of the Acoustical Society of America in October 2014, the researchers found that mice process and understand their “ultrasonic vocalizations” (USVs), which the human ear cannot perceive, in the same way humans make sense of our own vocalizations.

Like humans (and birds), it appears that mice can distinguish a vocalization when just the beginning part is heard, versus when the end part is heard. This helps strengthen the usefulness of mice as good models for understanding human communication and hearing loss.

Dogs also have a language comprehension ability similar to humans. According to recent British study, dogs process speech in a similar way to humans: They listen to our words, not just our intonation.

According to the report, published in the journal Current Biology in November, dogs use different parts of the brain—both the left and right hemispheres—to process the verbal components of a familiar sentence and the emotion or intonation of the speaker. The study suggests that dogs pay attention to the verbal content of human speech and perceive it in a way that broadly parallels human perception. The reseachers concluded, “Dogs may share ancestral or convergent hemispheric specializations for processing the different functional communicative components of speech with human listeners.”

Learn about the amazing chick discovery and HHF’s path to curing hearing loss and tinnitus.

The Link Between Your Kidneys and Your Hearing

By Judy Huch, AuD and Laura Friedman

March is National Kidney Month and today, March 12th, is World Kidney Day. Why is this important? For years we have been aware of rare syndromes involving renal disorder and hearing loss, such as Alport, MYHIIA, Muckle-Wells, Brescheck, and Bartter syndromes.1 But in October 2010, a study done in Australia showed a link between chronic kidney disease (CKD) and hearing loss, which was published in the American Journal of Kidney Diseases.

This study examined the “medical records of 2,564 people aged 50 and over, 513 of whom had moderate chronic kidney disease. Some 54.4% of all the patients with chronic kidney disease had some degree of hearing loss, as compared to only 28.3% of those who had no kidney problems.” Even more interesting, 30% of the CKD patients had a severe hearing loss compared to just 10% in those patients without CKD.

So what is the correlation between the CKD and hearing loss? According to researchers, "The link can be explained by structural and functional similarities between tissues in the inner ear and in the kidney. Additionally, toxins that accumulate in kidney failure can damage nerves, including those in the inner ear." Also, some treatments for kidney ailments are ototoxic, meaning they cause hearing loss. 

In the U.S., there are 31 million adults living with kidney disease, 7.5 million of whom have moderate forms of CKD.  Based on the recent findings it is important that these patients be aware that their hearing is also at risk. If you have patients or know anyone with chronic kidney disorder, please urge them to have their hearing tested annually to monitor any changes to their hearing status.

______

1Toriello, H. V., Reardon, W., & Gorlin, R. J. (2004). Hereditary hearing loss and its syndromes. (Second ed., pp. 267-289). New York, NY: Oxford University Press.

A portion of this post originally written by Judy Huch, AuD, Editor of Hearing Health @ Hearing Health & Technology Matters.Other content was contributed by Healthy Hearing, The American Speech-Language-Hearing Association, and Oregon's Deaf and Hard of Hearing Services.

Hearing Restoration Project (HRP) Special Research Update

By Peter G. Barr-Gillespie, PhD

We always seek ways to deepen the research collaboration between the consortium members. Since its creation more than three years ago, the HRP consortium has gathered twice each year for scientific meetings; these interactions have proven to produce meaningful research outcomes. The following is a recent example:

At the meeting held in Seattle last fall, 15 researchers convened to compare and discuss data from the past year, as well as to plan for the coming year’s projects. During the discussions, five of the investigators were surprised to find that they independently had the same observation, one that was so surprising that they each initially dismissed it as an experimental artifact. They had each separately found this result: in an adult mouse cochlea that had previously lost its hair cells due to damage from sound or drugs, weeks later, a few cells remaining in the cochlea began to display molecular markers related to hair cells.

These results may suggest that the supporting cells in the cochlea are more responsive to damage than we thought, and that they were trying to convert into new hair cells. The five different groups had the same observation using very different methods added considerable weight to the findings, and emphasize the value of the collaborative, data-sharing approach to science utilized by the HRP.

These observations were talked about among the 15 HRP investigators, and a new project was born to further investigate what were provisionally labeled “X-cells.” Given the flexibility of the HRP’s funding process, we were able to fast-track the proposal. The investigators wrote the proposal in a few weeks and vetted it with the rest of their HRP colleagues; the proposal was then evaluated and approved by the Scientific Advisory Board of the HRP and the project is now moving forward.

We hope to see exciting results from this project, which should establish whether these “X-cells” are real. If so, the HRP will determine how to push these cells further along their molecular differentiation pathway to become full-fledged hair cells, which might restore hearing in damaged ears. 

HHF understands the value of the consortium and has enabled the group to meet regularly for these important discussions. When the consortium members agree that an area of research deserves further exploration, a proposal is written and put forth for review and approval. Once approved, the fact that HHF can release the funds quickly helps to accelerate the pace of research.  

This helps us get closer to our goal of a cure!

Peter G. Barr-Gillespie, PhD

Director, Hearing Restoration Project

Advances in Brain Training

By Kathi Mestayer

Because the brain is an integral component of the hearing process, it sometimes needs help adjusting to new types of sound. The brain needs to fill in some of the blanks when hearing is impaired or when adjusting to a new hearing aid or cochlear implant. “Aural rehabilitation is so much more than speechreading [lipreading],” says Kathleen Cienkowski, Ph.D., an associate professor and the program director of audiology in the University of Connecticut’s Speech, Language, and Hearing Sciences Department. “It’s basically retraining the brain.” She adds, “Cochlear implants, hearing aids, and listening systems can do wonders, but no assistive device is as smart as your brain. Our brains know what we want— and don’t want—to hear; integrate the other senses; and interpret body language, tone, pacing, and context.” Getting used to new sounds is a big adjustment. That’s when aural or auditory rehabilitation comes in. Cienkowski, who also coordinates the Aural Rehabilitation Interest Group for the American Speech-Language- Hearing Association (ASHA), defines it as “improving the quality of life and communication for those with hearing loss.”

To read the full article please read Fall issue of Hearing Health Magazine by clicking here. 

Eating Sushi for Better Hearing Health

By Pallavi Bharadwaj

I recently became a pescatarian (mostly) and adore sushi. I am glad that after being a vegetarian all my life I finally added fish to my diet because according to a study published recently in the American Journal of Clinical Nutrition, women who eat fish regularly have a lower risk of developing hearing loss than those who rarely or never eat fish.

The authors of the study used data that were collected as part of the Nurses’ Health Study II, a prospective cohort study. On the basis of the data, they examined independent associations between consumption of fish and long-chain omega-3 polyunsaturated fatty acids (PUFAs) and self-reported hearing loss in 65,215 women who were followed from 1991 to 2009. Participants were asked to fill out questionnaires every two years.

The women who consumed fish at least twice a week were found to have a 20 percent lower risk of hearing loss versus those who consumed fish less often (less than once a month). This protective action was found irrespective of the type of fish consumed. A higher intake of omega-3s, particularly EPA (ecosapentaenoic acid) and DHA (docosahexaenoic acid), was also associated with a lower risk of hearing loss. However, no association was found for consumption of omega-6 fatty acids.

“Omega-3 antioxidants, polyunsaturated fatty acids, and vitamin C have been the focus of a growing body of evidence showing potential hearing benefits,” says Gordon Hughes, M.D., the program director for clinical trials at the National Institute on Deafness and Other Communication Disorders, which provided funding for the study.

Other studies had already established a link between eating fish—the omega-3s they contain in particular—and a lower risk of cardiac and cerebrovascular diseases. It is thought that a diet rich in these foods helps to maintain blood flow to the cochlea through similar mechanisms, thus providing oxygen and nutrients that the cochlea needs to function properly.