“Two-thirds of adults older than 70 have a clinically significant hearing loss,” says Jennifer Deal, assistant professor of epidemiology at the Johns Hopkins Bloomberg School of Public Health.

And people with hearing loss are twice as likely to be diagnosed with dementia.

So how might hearing loss harm memory? Scientists have suggested three possibilities:

Hearing loss adds to your cognitive load

“When sound comes in, it’s encoded into a neural signal in the inner ear,” explains Deal. “That signal is sent to the brain, where it’s decoded.”

But if the inner ear is damaged, it doesn’t encode the signal as well.

“So instead of being a clear signal, it’s a garbled signal,” says Deal. “It’s not an audibility issue so much as a clarity issue.” It sounds like people are mumbling.

“When that garbled signal goes to the brain,” adds Deal, “the brain has to work harder to decode it. And that comes at the expense of doing other things, like encoding a signal into a memory.”

Hearing loss might lead to brain atrophy

“People with hearing loss have faster rates of atrophy, particularly in the temporal lobe of the brain, than people without it,” explains Deal.

If hearing loss causes that withering, treating it could protect the brain.

Hearing loss can lead to social isolation

“When people have difficulty hearing in noisy situations, they may avoid those situations,” says Deal. “So they may go out less, be less involved in the community and in other areas.” And isolated people have a higher risk of memory loss.

But whatever causes hearing loss may also cause memory loss.

What a new trial is testing

So the question, says Deal, is “can we prevent cognitive decline by treating hearing loss?” That’s what the ACHIEVE (Aging and Cognitive Health Evaluation in Elders) trial aims to find out.

“We’ve enrolled nearly 1,000 people,” says Deal. All are aged 70 to 84 and have mild-to-moderate hearing loss. They’ll be randomly assigned to one-on-one sessions to get a hearing aid or to learn about lowering their risk of disease.

Results are due in 2022. Until then, if you have trouble hearing, try a hearing aid or a personal sound amplification product, or PSAP.

“Many people consider hearing loss to be part of normal aging, but it’s not,” says Deal. Even if treating hearing loss doesn’t protect the brain, “it has the potential to have a huge impact on somebody’s life.”

Photo: Sound World Solutions.