'We were surprised in a good way.' Hearing aids may cut dementia risk by half in older adults.

By Jessica Hall

For older adults at greater risk of dementia, the use of hearing aids may reduce cognitive decline by nearly half, according to a new study in The Lancet.

In the study, the use of hearing aids did not help everyone, but those who were at risk for dementia saw a 48% reduction in cognitive decline over three years compared with the control group, the study in the scientific journal said.

"We were surprised in a good way. Seeing the magnitude of the decrease was really impressive," Frank Lin, co-principal investigator of the study and professor at Johns Hopkins University School of Medicine and the Bloomberg School of Public Health, told MarketWatch.

Those considered at risk for dementia included those who were two to eight years older with lower baseline cognitive scores, were more often female, Black, had less education, lower income, and more often had diabetes, hypertension, smoked, and lived alone, the study said.

"In the group of volunteers who had a lower risk of decline, we didn't notice changes. But they didn't have cognitive decline and you can't slow down what's not in decline," Lin said.

Age-related hearing loss is extremely common, affecting two-thirds of adults aged over 60 globally. However, less than one in 10 individuals with hearing loss in low- and middle-income countries, and fewer than three in 10 in high-income countries, currently use hearing aids, the researchers said.

Read:'It democratizes what you get': Hearing aids are now available over the counter -- what you need to know

Untreated hearing loss is associated with greater cognitive decline and was estimated by the 2020 Lancet Commission on Dementia to contribute to around 8% of dementia cases worldwide -- equivalent to 800,000 of the nearly 10 million new cases of dementia diagnosed every year, researchers said.

"Hearing loss from midlife onwards is a potent and common risk for accelerated cognitive decline and dementia," the study said. "Hearing aids could really make a difference for populations at risk of dementia."

Untreated hearing loss may contribute to cognitive decline and dementia in several ways. Hearing loss can make the brain work harder, or cause the aging brain to shrink more quickly. A third possibility is that hearing loss leads people to be less socially engaged and the reduced stimulation may result in brain atrophy, the researchers said.

"The bitter pill of the trial is that in this government-supported study we found that hearing aids and support can reduce cognitive decline, but those services are not covered by Medicare," Lin said.

Lin called the over-the-counter hearing aid industry in flux because not all manufacturers have entered the market. It will still take time for that market to mature, he said.

Lin recommended hearingnumber.org as a website to help people measure their hearing themselves and learn ways to find necessary help.

Over-the-counter (OTC) hearing aid sales began last year nationwide, without a prescription. With the arrival of OTC options, hearing aids can now cost hundreds of dollars, rather than several thousands.

About 15% of American adults (37.5 million) aged 18 and over report some trouble hearing, according to the National Center for Health Statistics. The OTC devices are not meant for children or adults with severe hearing difficulties, according to the National Institutes of Health.

"It's fundamentally about awareness. People often don't realize they have hearing loss -- they just think 'My wife is mumbling at me,'" Lin said.

-Jessica Hall

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07-19-23 1430ET

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