Hearing aids are now available over the counter without a prescription, a potential game changer for hearing and brain health.
Dementia is one of the biggest health obstacles to aging well. It is irreversible, but we can reduce our risk of getting it. One important, and historically underappreciated, way of preventing it is addressing hearing loss. By taking care of our hearing, we can also take care of our brains.
More than 50 million people were living with dementia worldwide in 2019. This number is expected to grow with an aging population: More than 130 million people are forecast to be living with dementia in 2050.
Hearing loss in middle age — ages 45 to 65 — is the most significant risk factor for dementia, accounting for more than 8 percent of all dementia cases, research suggests. A 2020 Lancet report calculated that hearing loss approximately doubles the risk of dementia, akin to the increased risk caused by a traumatic brain injury. In addition, because hearing ability exists on a continuum, even subclinical hearing loss can mean a greater risk for dementia.
As a way of reducing the occurrence of dementia, addressing hearing loss is a win-win, said Frank Lin, the director of the Cochlear Center for Hearing and Public Health at Johns Hopkins Bloomberg School of Public Health. “It’s really common, it’s treatable, and there are interventions that come at no risk” that are underutilized, he said.
Preserving our ability to hear is foundational to public health “strategies that can best optimize the health of older adult populations, so older adults are living a long and full life till the very, very end,” Lin said.
Why degraded hearing may degrade cognition
There are several overlapping hypotheses for why hearing loss in middle age is associated with a higher risk of dementia.
One hypothesis suggests that poor hearing increases the cognitive load on the brain, which needs to work harder, at the expense of other mental faculties, to decipher the garbled signals the ears send.
This may not be the best explanation, however, because those with hearing loss and declining cognition also struggle on tests that do not depend on hearing, said Tim Griffiths, a professor of cognitive neurology at Newcastle University in England.
Research on animals and humans has found that with the loss of hearing, the brain atrophies faster, especially in the temporal lobe — where key auditory and memory functions occur — potentially because of diminished use and stimulation.
Hearing loss may also cause aberrant activity in the temporal lobe, making it more susceptible to damage and pathologies associated with Alzheimer’s disease, Griffiths said.
Hearing loss can make connecting with others difficult, leading to social isolation, loneliness and depression, which are known risk factors for dementia. As the deaf and blind author and activist Helen Keller reportedly said, “Blindness cuts us off from things, but deafness cuts us off from people.”
How we can take care of our ears and brain
The cochlea’s sensory cells in our inner ear allow us to hear. These sensory cells, called hair cells, translate the vibrations of sound waves hitting our eardrums into electrical signals that are sent to auditory regions of the brain, which decode them into what we perceive as sound.
When these hair cells become degraded or die, the signals sent to the brain also become garbled. These hair cells are not regenerated.
Prolonged exposure to loud noise is one way we can permanently damage our cochlear hair cells and, consequently, our hearing. Avoiding loud noises or wearing earplugs in settings where you know you will be subject to potentially harmful sounds is vital to protecting your hearing.
We also lose hearing as we age, a process that is not completely understood.
“It’s not inevitable,” Griffiths said. “There is a population out there of elderly folk who don’t have any hearing deficit.”
But many people will experience a muffling, which is a gradual loss of hearing, with age. According to the National Institute on Deafness and Other Communication Disorders, 1 in 3 people between the ages of 65 and 74 and nearly half of those older than 75 have clinical hearing loss.
Knowing our own hearing ability, or hearing number, by going to resource websites such as hearingnumber.org is crucial to understanding how we can address any deficits, Lin said. Like daily step count, cholesterol level, or weight, “it’s another metric that you would know about a dimension of your own health,” he said.
Most people who can benefit from hearing aids do not use them. For hard-of-hearing adults 70 and older, only 30 percent report using the devices; for younger adults who are hard of hearing, only 16 percent use hearing aids.
If you have hearing loss, hearing aids can help and may also preserve mental capabilities. Preliminary studies appear to promise that using hearing aids protects against dementia. One review of 30 studies found that while people with hearing loss had poorer cognition than those with normal hearing, those who used hearing aids fared cognitively better than those who did not use hearing aids.
Lin is leading a large, randomized controlled trial with nearly 1,000 older adults to answer more definitively whether treating hearing loss with hearing aids reduces the risk of cognitive decline. After three years and $20 million from the National Institutes of Health, the trial will wrap up in 2023. Another $20 million has been funded to follow all trial participants until 2027.
We have a lot of control over how well we age. About 40 percent of dementias are thought to be potentially preventable by addressing risk factors such as hypertension, sleep problems, alcohol use, smoking, social isolation and obesity.
And taking care of our hearing is one of the biggest gifts we can give to our present and future selves.
To reap the benefits of better hearing and preserved cognition, “I think the main thing is getting properly fitted hearing aids, and actually wearing them,” Griffiths said.
Do you have a question about human behavior or neuroscience? Email BrainMatters@washpost.com and we may answer it in a future column.
correction
A previous version of this article incorrectly stated that Frank Lin's clinical trial has $40 million in funding through 2023. It has $20 million in funding through 2023, and another $20 million in funding to follow participants until 2027. This version has been corrected.