Hearing loss and dementia: what the research does and doesn't show

The short answer

Three things are true at once:

• The link is real. Hearing loss is one of the biggest modifiable risk factors for dementia in the Lancet Commission's analysis ^[1][2].
• Cause and effect is not proven. The risk estimates assume hearing loss causes dementia. That assumption is plausible but untested at the scale needed.
• The best trial is mixed. ACHIEVE, the largest randomized trial so far, found no overall benefit of hearing aids on 3-year cognitive decline, but did find slower decline in a higher-risk subgroup ^[3][4].

If you or a parent has trouble hearing, the practical advice doesn't depend on settling the science: get a hearing test and treat what it finds.

What the Lancet Commission found

The Lancet Commission on dementia prevention is a panel of international researchers that pools evidence on what raises dementia risk. It has published reports in 2017, 2020 and 2024.

2020 report. The Commission named 12 modifiable risk factors that together account for around 40% of dementias worldwide, which "could theoretically be prevented or delayed" ^[1]. Hearing loss in midlife (ages 45 to 65) carried a relative risk of 1.9 and a weighted population attributable fraction of 8.2%, the largest of any single factor ^[1].

2024 report. The update added two factors, high LDL cholesterol in midlife and untreated vision loss in later life, for 14 in total. It estimates that addressing all 14 could prevent or delay about 45% of dementia cases ^[2]. Midlife hearing loss and high LDL cholesterol each account for 7%, tied for the largest share ^[2].

	2020 report	2024 report
Number of modifiable risk factors	12	14
Share of dementia potentially preventable or delayable	About 40%	About 45%
Share linked to midlife hearing loss	8.2%	7%
Hearing loss rank	Largest single factor	Tied for largest (with high LDL)

What those percentages mean. A population attributable fraction estimates how many cases across a whole population would not happen if a risk factor disappeared, assuming it actually causes the disease. It is not your personal risk, and the percentages for different factors overlap.

What the Commission recommends. The 2020 report says to "encourage use of hearing aids for hearing loss and reduce hearing loss by protection of ears from excessive noise exposure" ^[1]. It also cited studies in which people with hearing problems who used hearing aids did not show the same rise in dementia risk ^[1].

Why hearing loss might affect the brain

Researchers have several working theories. None is settled.

• Mental effort. One hypothesis is that straining to process sound uses up mental resources needed for other tasks ^[8].
• Brain changes. The 2020 Commission cites a study that followed adults with MRI scans for a mean of 19 years and found that midlife hearing loss measured on a hearing test was associated with faster shrinkage in the temporal lobe, including memory-related areas ^[1].
• Withdrawal. Hearing loss can make conversation exhausting, and people pull back. Social isolation in later life is itself on the Commission's list, accounting for 5% of cases in the 2024 estimate ^[2].

There is also a less hopeful possibility: hearing loss and dementia could share underlying causes, such as aging blood vessels. If so, treating hearing wouldn't change dementia risk much. Only randomized trials can sort this out, which is why ACHIEVE matters.

The ACHIEVE trial: what it tested

ACHIEVE (Aging and Cognitive Health Evaluation in Elders) was published in The Lancet in 2023 ^[3].

Feature	Details [3]
Who	977 adults aged 70 to 84 with untreated hearing loss and no substantial cognitive impairment
Where	Four U.S. sites
Two recruitment pools	238 people from a long-running heart-health study (ARIC) and 739 new community volunteers
Hearing group	Audiological counseling and hearing aids
Comparison group	Health education sessions on chronic disease prevention
Main outcome	3-year change in a global cognition score from a full battery of thinking and memory tests
Average age	76.8 years

The hearing group got three years of hearing aids, a self-management toolkit and ongoing counseling with an audiologist ^[4]. The ARIC participants were older, had more risk factors for cognitive decline and had lower thinking-test scores at the start than the volunteers ^[3].

What ACHIEVE showed, and what it didn't

The main result was a tie. Over 3 years, cognitive scores fell by 0.200 standard units in the hearing group and 0.202 in the comparison group, a difference of 0.002 that was not statistically significant (p = 0.96) ^[3].

The subgroup result was striking. A sensitivity analysis planned before the trial started found that the hearing intervention's effect differed between the two recruitment pools ^[3]. In the 238 higher-risk ARIC participants, the hearing intervention slowed cognitive decline by 48% ^[4]. The authors concluded that a hearing intervention "might reduce cognitive change over 3 years" in older adults at higher risk of cognitive decline, but not in lower-risk groups ^[3].

No safety concerns. No significant adverse events attributed to the study were reported in either group ^[3].

What ACHIEVE did not show:

• It did not test dementia prevention. The outcome was a change in test scores, not new dementia diagnoses ^[3].
• It did not show a benefit for everyone. The overall result was neutral. The 48% figure applies to one subgroup ^[3][4].
• It was not blinded. Participants knew which group they were in ^[3].
• It doesn't represent everyone. 88% of participants were White ^[3].
• Three years may be too short. A follow-up study is tracking the same participants for longer, looking at cognitive decline and new cases of mild cognitive impairment or dementia. Its registry lists data collection for the main outcome as finished in May 2026, with the study expected to wrap up in 2027. No results had been posted as of this guide's update ^[5].

What other studies add

Observational data lean positive. A 2023 meta-analysis in JAMA Neurology pooled 8 long-term studies with 126,903 participants followed for 2 to 25 years. Hearing aid users had a 19% lower risk of cognitive decline than people with uncorrected hearing loss (hazard ratio 0.81) ^[6]. Across 11 smaller studies, using hearing devices was linked to a 3% short-term improvement in thinking-test scores ^[6].

The catch: people who get hearing aids may differ from people who don't in income, health and social support. The meta-analysis authors called for randomized trials to test the benefit ^[6].

Hearing loss is common, and often untreated, in people who already have dementia. In a national sample of Medicare beneficiaries aged 71 and older, 79.4% of those living with dementia had hearing loss, and only 21.7% of them used hearing aids ^[7].

What this means for you and your family

• Get a baseline hearing test. The ACHIEVE lead investigator's advice for now is that older adults "have their hearing checked regularly" ^[4]. Not sure what to look for? Start with our list of early signs of hearing loss.
• Treat hearing loss for the reasons that are certain. Easier conversations, safety and staying involved with family are reason enough. Our guide to age-related hearing loss covers the options.
• Wear the devices. ACHIEVE's hearing group got regular audiologist support, not just a box of hearing aids ^[4]. The first 30 days with hearing aids are when most people decide whether to keep going.
• Don't skip parents who already have memory problems. Given how few people with dementia use hearing aids ^[7], a hearing check is a reasonable step to raise with their doctor.
• Be wary of "prevents dementia" claims. No trial supports that wording.

Ready to book a test? Find a hearing provider near you.