Hearing Aids and Dementia. The Trial Result Is More Interesting Than the Headline

Ask a room of people in their sixties what they worry about most as they age and memory usually comes up first. Hearing rarely does. Yet among the risk factors for dementia that researchers consider changeable, hearing loss sits at the very top of the list.

The 2024 report of the Lancet Commission² on dementia, an international panel that periodically reviews the evidence, estimated that nearly half of dementia cases worldwide could in theory be prevented or delayed by addressing 14 risk factors across a lifetime. Hearing loss and high LDL cholesterol were tied for the largest share, each linked to about 7 percent of cases. The Commission also concluded that the evidence for treating hearing loss had grown stronger since its previous report.

That conclusion leans heavily on one trial. Understanding what it found, and what it did not, is the best way to decide whether a hearing test belongs on your list.

What ACHIEVE tested

The Aging and Cognitive Health Evaluation in Elders study, known as ACHIEVE, was the first large randomized trial designed to ask whether treating hearing loss slows cognitive decline. Researchers enrolled 977 adults ages 70 to 84 with untreated hearing loss, mostly in the mild to moderate range, and without substantial cognitive impairment.

Half received a hearing intervention that went well beyond handing out a device. It included fitted hearing aids, a self-management toolkit and ongoing sessions with an audiologist. The other half received a health education program on aging well, a deliberate choice so that both groups got similar time and attention from the study team.

Participants came from two sources. About a quarter were already enrolled in a long-running heart study known as ARIC. The rest were healthy volunteers recruited from the community.

The headline and the subgroup

The main result, published in The Lancet¹ in July 2023, was negative. Across all 977 participants, the hearing intervention did not reduce cognitive decline over three years compared with health education.

The researchers had planned in advance to look at the two recruitment groups separately, and there the picture split. Among the 238 participants from the heart study, the hearing intervention slowed three-year cognitive decline by 48 percent. Among the healthy volunteers, it had no measurable effect.

The heart study participants differed in ways that matter. They had more risk factors such as diabetes and high blood pressure, and started with slightly lower cognitive scores. Most importantly, their thinking declined about three times faster during the study than the volunteers' did. The investigators argue that a faster background decline made it possible to see a benefit within three years. In the healthier group, there may simply not have been enough decline to slow.

That explanation is plausible. It is also exactly the kind of reasoning that should make readers cautious. A subgroup result, even a prespecified one, is a hypothesis rather than a verdict. The study team itself⁴ has said more follow-up is needed, and ACHIEVE participants are being tracked longer to see whether differences emerge in the healthier group over time.

Why hearing might matter to the brain

Researchers have proposed a few ways hearing loss could raise dementia risk. Straining to decode muffled speech may pull mental resources away from memory and other thinking. Reduced sound input over years may change brain structure. And people who cannot follow conversation often withdraw from social life, which is itself a dementia risk factor and a theme we covered in our story on loneliness as a health metric.

None of these mechanisms has been proven. All of them point in the same practical direction, which is that hearing well keeps people engaged.

Getting tested is easier than it used to be

Hearing loss creeps in gradually, and many people underestimate their own. Family members often notice first, through a television volume that keeps climbing or a habit of answering a slightly different question than the one asked. A formal hearing test from an audiologist takes under an hour and tells you the type and degree of loss.

Cost has long been the barrier. In August 2022 the FDA finalized a rule³ creating a category of over-the-counter hearing aids for adults 18 and older with perceived mild to moderate hearing loss. Since that October, these devices have been sold in pharmacies and online without a prescription, exam or professional fitting. The agency estimated close to 30 million American adults could benefit from hearing aids.

Over-the-counter devices are a reasonable start for many people with mild loss. They are not a fit for everyone. Sudden hearing loss, loss in only one ear, ear pain, drainage or dizziness all call for a medical evaluation rather than a store purchase. And the ACHIEVE intervention was a full audiology program with counseling and follow-up, which an off-the-shelf device does not replicate.

The practical read

Treating hearing loss improves communication and quality of life whether or not it protects memory, which makes it an easy recommendation even with the dementia question unsettled. For people who already carry other risks, such as diabetes, high blood pressure or a family history of dementia, the ACHIEVE subgroup gives one more reason not to wait.

Medicare's annual wellness visit is one natural place to ask for a hearing screen. Coverage for the devices themselves varies widely, so it pays to ask your plan directly what it includes before you shop.