Hearing loss affects about one-third of people aged 60–69, and two-thirds of those age 70 and up. Despite how commonly people experience hearing loss as we age, the problem is sorely undertreated. Only about one out of five people who need hearing aids is currently wearing them. On average, it takes a person seven years from the time they start to notice a hearing problem to the time they make an appointment for a hearing test and seek treatment.
Seven years—or even one year—is a long time to live with a hearing deficiency, and unfortunately, hearing loss is not an isolated problem. Hearing loss engenders changes in the brain that make it harder to concentrate, listen, and even understand speech—even after we start wearing hearing aids.
Hearing and the Brain
We don’t just hear with our ears! Our ears collect sound information, but the auditory cortex in our brain is where that information is constructed into something meaningful. The tens of thousands of tiny, hair-like cells in our inner ears—called stereocilia—each send bits of information about particular frequencies (pitches) of sound they encounter. Inside the brain, it’s all assembled into an idea of what is happening around us.
Auditory Deprivation
Auditory deprivation is what happens when we can’t hear well. It refers to the changes that occur in the brain when it stops receiving signals from the ears.
Neuroplasticity
When we talk about “changes in the brain,” we’re invoking the concept of “neuroplasticity.” This concept simply means that the brain has the capability to change—to reallocate resources from one part to another. A child’s brain exhibits incredible neuroplasticity, which we might imagine. We watch children easily pick up a language and sound like the other people who speak it in their region, while an adult is unlikely to master a new language and will probably always speak it with a “foreign” accent.
Still, adults’ brains do change over time in meaningful ways, though not always positive ones.
Auditory Cortex Atrophy
Auditory deprivation inspires the brain to reallocate resources. When sound isn’t coming into the auditory cortex, the brain notices that that area isn’t being used. It starts to shrink, and reallocate resources to the visual cortex. It’s not that the brain cells die, but the grey matter between them starts to dissipate, and the structure collapses.
Once the auditory cortex atrophies, speech comprehension is no longer a matter of simply amplifying sound with hearing aids. Even when hearing aids are worn, the brain won’t be able to make sense of sound. This is why hearing care practitioners offer hearing aid training classes. If a patient’s brain is no longer able to interpret sound, then hearing loss treatment needs to involve a process of retraining the brain. Over time and with effort, these training sessions can help people to hear again, and even reverse mild cognitive decline.
Hearing Loss and Cognitive Decline
Researchers have established a strong link between untreated hearing loss and an earlier onset of cognitive decline and dementia. The World Health Organization (WHO) puts hearing loss at the top of its list of twelve modifiable risk factors in developing Alzheimer’s disease. A number of studies have shown that hearing loss promotes cognitive decline and dementia, with the severity of hearing loss increasing the likelihood of poorer brain health. Mild hearing loss makes us twice as likely to develop dementia. Moderate hearing loss triples the risk, and severe hearing loss makes us five times as likely to develop dementia.
Researchers note that even a five-fold risk is not a guarantee. It may be that our risk factor for dementia is already very low. For example, say your risk of developing dementia without hearing loss is 0.4%. Even with severe hearing loss, then, your risk would be only 2%. However, if your risk factor is higher, then a five-fold increase could be very significant, indeed.
Hearing Aids Have Wide-Ranging Benefits
It’s also important to remember that treating hearing loss is about quality of life as much as it is about health. While cognitive decline is certainly an outcome we would all wish to avoid, the positive aspects of wearing hearing aids may be just as compelling. Those who wear hearing aids tend to report greater optimism, independence, and self-confidence than those with untreated hearing loss. They tend to get more exercise and spend more time out of doors. That’s really what treating hearing loss is all about: giving us the freedom and confidence to live life the way we choose, rather than having to avoid certain activities because our hearing may cause problems.
