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Notes from the hearing science frontier: The Good, the Bad, and the Ugly

I won’t claim that the title of this 1960s spaghetti western featuring the (at the time) mostly unknown Clint Eastwood is directly related to hearing research. But it’s a great title, and it has some relevance to hearing-loss issues—there really is good, bad, and even ugly stuff.

Where to start?

We will follow the title, but we will end up on a hopeful note; after all, Clint Eastwood’s career got a big lift from this movie, too. What’s good about hearing loss? In itself, nothing. In fact it’s bad, and for some it’s really ugly. But there really is science-based hope. Here’s why.

In the 1980s several international consortia started to decipher the human genome. By 2007 several efforts had yielded an initial picture—a stunning finding that we humans have more than 20,000 genes. Of course, just knowing that there are 20,000-plus genes is not the same as knowing what they do. But now that we presumably know what we are up against, numerous scientists at many research institutions and biotech companies are busy mining the data and trying to ferret out the functionality of genes. All of which has yielded many gene-based therapies for conditions such as hemophilia, blood diseases, fat metabolism disorders, and cancer, to name but a few.

With hearing loss, what is important is to discover the genes that have a role in hearing and to understand how they are involved in it and, especially, in hearing loss. To date scientists have discovered more than 200 genes involved in hearing. That is the good news. How so? We started with 20,000 unknown genes and now have 200 genes that we know have a role in hearing. The next (ongoing) step is to uncover their role and to develop gene-based therapies. This is vital because it turns out that age-related hearing loss has a genetic component, meaning that if we can learn the underlying genetic components that create hearing loss as we age, scientists can reverse-engineer a solution—the basis for genetic therapeutics. A relatively new science and technology developed as a result of the genome project.

Scientists at the University of Southern Florida have found a particular gene that is involved in age-related hearing loss. The gene, called GRM7, is essential in making proteins that help convert the sound entering the ear into biological signals sent to the brain for further processing. Scientists have found that over time, this gene can lose its effectiveness in producing the protein necessary for your ears to function optimally. Think of proteins as fuel for your body. If the fuel is diluted or unavailable, you will slow down or stop altogether—like a car without fuel or with the wrong fuel. What are the implications of this discovery? In time scientists will be able to create a substitute for the protein deficiency and either prevent or significantly slow down age-related hearing loss. You can watch this 4-minute video to learn more.

Unfortunately, this does not change your condition now; I told you to expect the good, the bad, and the ugly. In this case, you get the good with the bad. In maybe 10 years, your children and grandchildren will be able to avoid this problem altogether, but for you it’s bad; you still have hearing loss now. Is there any good news along genetic lines that might help you? A lot depends on your time horizon and on how optimistic you are about your longevity. I suggest that you be optimistic. No matter how old you are, if you are otherwise healthy, chances are you will continue to live. Most people develop the killing diseases—heart disease, diabetes, cancer, and Alzheimer’s—before they hit 70. If you are older and still have not developed these, chances are you will not develop them. You will probably go on living for a good while longer, so you may well benefit from future scientific developments.

Several lines of research suggest genetic opportunities to reverse age-related hearing loss. A number of serious efforts are focused on restoring hearing, as Dr. Robert Jackler explains here. He is very optimistic. According to him, “we have achieved sufficient level of maturity in regeneration of tissue.” As he further explains, when it comes to bone marrow cancer, for example, we can now regenerate the bone marrow because the architecture of the bone and the marrow remains basically intact. On the other hand, as he explains, we can’t regenerate the liver: once it’s gone, it can’t be rebuilt, because its architecture is not available. The key is biological retention of the architecture of the organ. If it is intact—and even a deaf person’s ear is intact—all we need to do is learn to fix what is broken. We don’t have to rebuild the ear itself.

Age-related hearing is mostly about the hairs inside the cochlea (inner ear) withering away over time. The little hairs in the cochlea are like the keys of a piano: they sense sound and transmit the vibrations to the nerve fibers that send signals to the brain area which processes sound. The best analogy is a piano with missing keys. Replace them and the piano works. The same will be true for the ear: replace the hairs that have withered away, and hearing will be restored. See here.

When will this happen? Good research takes time, but experts like Dr. Jackler give us cause for optimism. He believes that in 10 years we may see results from research on stem cells, gene therapy, molecular therapy, and neural stimulation. All of these approaches could lead to a reversal of hearing loss.

But here is the big ugly: Progressive untreated hearing loss leads to cognitive decline. You can read about it here. New research shows that “Older adults with hearing loss are more likely to develop problems thinking and remembering than older adults whose hearing is normal, according to a new study by hearing experts at Johns Hopkins.” Doesn’t sound good—I agree. So what about people who wear hearing aids? That study is going on now. What do you think?