The hearing aid that lowers dementia risk

The 2024 update of the Lancet Commission on dementia identified hearing loss as the single largest modifiable risk factor for the condition. Of all the things we could do to lower dementia risk across a population, treating hearing loss has the highest potential effect.

This was already plausible. It is now, after the ACHIEVE trial, also well supported.

What the trial showed

The ACHIEVE trial enrolled nearly 1,000 older adults with hearing loss, all without dementia at baseline. Half received hearing aids and ongoing audiology support. The other half received a control programme focused on healthy ageing.

The headline result, in the subset of participants at higher dementia risk: a 48 percent reduction in cognitive decline over three years in the hearing-aid group.

The effect was specific to higher-risk participants. Healthy older adults at low baseline risk did not show a measurable cognitive benefit.

Why hearing loss matters for the brain

Three plausible mechanisms, possibly all contributing:

Cognitive load. Hearing loss makes listening effortful. Resources that would otherwise go to memory and reasoning are spent decoding speech. Over years, this depletes cognitive reserve.

Reduced auditory input to the brain. Sensory deprivation produces measurable changes in cortical structure. Older adults with hearing loss show accelerated atrophy in auditory regions, and the changes spread beyond the auditory cortex.

Social withdrawal. People who cannot hear well in conversation often disengage from social settings. Social engagement is one of the most protective factors against cognitive decline.

Why it has been underused

Despite the evidence, hearing aid adoption is low. In high-income countries, only about 20 percent of adults who would benefit actually wear one. In low and middle-income countries, the rate is closer to 3 percent.

Reasons include:

• Cost. Most hearing aids are not covered by insurance.
• Stigma. Hearing aids are read as an ageing signal.
• Mild hearing loss is often dismissed or unrecognised.
• The fitting process can be off-putting.

The rise of over-the-counter hearing aids in some countries, prescribing hearing screens at routine adult checkups, and emerging earbuds with hearing assistance built in may all help shift this.

Practical implications

If you are over 60, or someone you care about is:

• Get a baseline hearing test. The cost and effort are low.
• Treat mild-to-moderate hearing loss promptly. The longer hearing loss is uncorrected, the more entrenched the cognitive effects appear to become.
• Pair hearing aids with social engagement. The protection comes from continued participation in conversation, not the device itself.

Mild cognitive impairment and dementia have few interventions that move the needle this much. Hearing care is one of them.