Gene shows who will have early hearing losses

By Irene Maher
Tampa Bay Times

So, maybe there were a few loud concerts over the years. You’ve always loved big fireworks shows. And you don’t always protect your ears when using the leaf blower. But you’re just in your 40s or 50s, way too young for significant hearing loss.

Still, conversations are getting harder to follow and you feel awkward asking people to keep repeating themselves. What’s going on? Can you be losing your hearing decades before Medicare age?

Yes, say researchers at the University of South Florida’s Global Center for Hearing & Speech Research. They have identified a gene — known as GRM7 — responsible for age-related hearing loss that is more severe and occurs earlier than expected.

“Everyone has the gene and everyone will have some age-related hearing loss,” said Robert Frisina Jr., director of the center and professor of chemical and biomedical engineering at the university “But in some people the abnormal sequence of proteins in that gene causes these people to have worse age-related hearing loss than others their age.”

The study, conducted by Frisina and researchers in New York and California, represents the first time a genetic biomarker has been identified for age-related hearing loss. Frisina talked with the Tampa Bay Times about the research and what it may mean to those of us who want to hear everything possible as we age.

Q: What does your research tell us about hearing loss that we didn’t know before?

A: Previous studies have suggested that age-related hearing loss is familial, that your hearing will be similar to your parents’. But, until our study, there hadn’t been any genes definitively identified that were associated with age-related hearing loss. The people with the abnormal gene sequence make a slightly different protein in the inner ear, which reduces the normal functioning of the inner ear, which worsens age-related hearing loss. In our study, people in their 60s who had the genetic variation had hearing that was more like someone in their 70s who didn’t have the variation.

Q: What should people do with this information?

A: First, if you have the gene you know it will be especially important to protect the hearing you have. But also, if you are in your 40s and are having trouble hearing you should be evaluated because hearing loss can be caused by a number of things, including a tumor or even medication. As part of that evaluation you can be tested for this gene. If you have the gene you know to be careful with medications that can affect hearing, you will be more careful with using hearing protection when mowing the lawn, hunting, listening to loud music. And you can look into prevention intervention or, in the future, reversal treatment.

Q: Treatment to prevent or reverse hearing loss?

A: We’re on the horizon of being able to treat genetic disorders right now. So, in the next 10 to 15 years, we’ll be able to compensate for genes that are abnormal and possibly make the protein in that gene right, correct the protein. That’s the most exciting part of this development. Ideally, we will be able to intervene in middle age, before the hearing loss develops and prevent it from happening. Hearing loss is caused by cells that die in the inner ear. They don’t grow back, like your skin heals after a cut. Reversing hearing loss is a lot harder (than preventing it). That could come, too, but later.

Q: How many people have this genetic configuration?

A: That we don’t know yet. Our study was the largest of its kind and included 687 people. But that’s not enough to know the prevalence of the condition in the general population. Also, we will probably find that more genes and more variations of those genes are responsible for early and more severe age-related hearing loss.

Q: Does everyone lose their hearing as they age?

A: Almost everyone has diminished hearing as they age but it doesn’t become troublesome until about the 60s. But take someone with the genetic variation, add all the environmental factors, such as chronic exposure to loud sounds, and the normal aging process and these people will have significant hearing loss, perhaps as early as their 40s or 50s.

Q: What about gender differences? Women often swear their husbands are deaf and men are sure their wife has the hearing problem.

A: Generally, regardless of age, women tend to have better hearing than men. In the present study, we found an interesting difference in the genetic variation of the GRM7 gene, where for a couple variations, women had better hearing than men. This may be related to the hormonal differences between men and women, something we found in our previous studies.