A pooled analysis of 61,000-plus older adults across 33 countries links hearing aid use and lower dementia risk. But the benefit only showed up when the devices actually improved hearing. Two more studies published this year add context. One supports cause and effect for hearing loss and dementia. The other offers early trial evidence for a biological mechanism.
Hearing loss and the aging brain
Hearing loss grows more common with age. Nearly half of people over 75 have trouble hearing. It’s more common in men. Hearing loss also ranks among the largest modifiable dementia risk factors, contributing to an estimated 7% to 8% of cases worldwide.
Researchers propose several reasons why hearing loss is related to dementia. Straining to hear can drain mental resources the brain would otherwise use for memory. Hearing loss can also drive social withdrawal, which independently raises dementia risk. It has even been linked to faster brain shrinkage in some studies. For more background details, see our webpage on hearing, hearing aids, and dementia.
Early research on hearing aids and dementia risk reduction
Hearing aids are the standard treatment for presbycusis, the medical term for age-related hearing loss. But whether they actually protect the brain, not just the ears, has been surprisingly hard to pin down. While earlier observational studies gave mixed results, others reported a protective effect of treating hearing loss on dementia. For example, a 2015 French study found that self-reported hearing loss was associated with increased cognitive decline in older adults, but hearing aid use reduced this risk. A 2022 meta-analysis of more than 30 studies found that hearing aids were associated with a 19% decrease in the risk for long-term cognitive decline.
Even the field’s most rigorous trial had nuanced results. The Aging and Cognitive Health Evaluation in Elders (ACHIEVE) trial randomly assigned 977 older adults to hearing aids or a health-education program and tracked them for three years. Overall, hearing aids didn’t slow cognitive decline any more than the control program did. But among older participants already at higher risk for decline, hearing aids cut the rate of decline by nearly half. That split result hinted that hearing aids might matter most for people who use them well, and for people most vulnerable to begin with. The three new studies below dig into exactly that idea.
Hearing aid effectiveness across 33 countries
A team led by researchers at the School of Public Health at the LKS Faculty of Medicine, University of Hong Kong tackled the effectiveness question with the largest study yet. Their May 2026 paper appeared in Cell Reports Medicine. The team pooled data from seven aging studies spanning 33 countries, including the US, UK, China, Korea, Mexico, and Ireland.
The study details
The researchers worked to reduce measurement error and assessed hearing improvement.
- 61,089 hearing-impaired adults aged 55 and older were followed for 6.5 years on average.
- The groups were statistically weighted to balance age, education, and other factors.
- The definition of probable dementia used a combination of cognitive testing, functional assessment, and reports from close informants.
- The study split hearing aid users into those who reported good hearing improvement and those who reported poor improvement.
The study results
A total of 8,911 developed probable dementia. Overall, hearing aid users had a 9% lower dementia risk than non-users. Hearing aid effectiveness mattered a lot, though. People who reported good hearing improvement had a 14% lower risk. Those with poor improvement saw no meaningful benefit. The authors argue that blending effective and ineffective users together in past research likely diluted true effects and helped explain the field’s inconsistent results.
The protective effect of hearing aids varied by national income: about 24% lower risk in middle-income countries versus 8% in high-income ones. Adoption differed sharply too, at 2.6% in middle-income countries versus 20% in high-income countries. The benefit also looked stronger among women, unmarried people, and those with less education. The authors called for improving access to hearing aids and hearing rehabilitation, especially for socially vulnerable groups.
Study co-leader Professor Chen Shanquan of the School of Public Health, HKUMed said in a university statement, “…the benefit is not simply about wearing a device, but whether the device meaningfully improves hearing in daily life.”
Even with these strengths, two open questions remain. The study relied on self-reported effectiveness, not a validated instrument, which the authors themselves flag as a limitation. And observational data can’t fully rule out “reverse causation,” where early cognitive decline drives both hearing aid use and reported benefit.
“Our study suggests that the benefit is not simply about wearing a device, but whether the device meaningfully improves hearing in daily life.”
— Professor Chen Shanquan
The School of Public Health
LKS Faculty of Medicine
The University of Hong Kong
A test of cause and effect
Reverse causation worries researchers for a specific reason. Most hearing loss is sensorineural, meaning it involves nerve damage. Early brain disease like dementia could itself help cause nerve damage, resulting in hearing loss. A study in The Laryngoscope sidesteps this problem. It focuses only on conductive hearing loss, a type caused by outer or middle ear problems, not the nerves.
The researchers used cross-sectional data from over 338,000 adults in the All of Us Research Program. Only 363 (0.3%) participants had bilateral conductive hearing loss, and 6,597 (1.9%) participants had dementia.
When controlling for age, sex, race, ethnicity, education, and smoking history, people with conductive hearing loss had roughly twice the odds of dementia. This hearing loss type has no direct neural link to the brain. So, the finding argues against reverse causation as the full story, since a purely mechanical ear problem is unlikely to be caused by dementia itself.
Definitions:
Sensorineural hearing loss:
Damage to the inner ear or the nerve pathways that send sound signals to the brain.
Conductive hearing loss:
Sound waves cannot reach the inner ear because of a blockage or damage in the outer or middle ear.
Treating conductive hearing loss, surgically or otherwise, only modestly lowered dementia odds in the same study. However, interpretation is hampered because the total number of treated individuals was low.
A possible brain mechanism on hearing aids and dementia risk
Another recent study offers different evidence: a biological mechanism. A secondary analysis of the ACHIEVE trial appeared in eClinicalMedicine in September 2026. It examined blood markers of neuroinflammation and neurodegeneration in people already enrolled in that hearing aid trial.
The two markers measure different things. GFAP reflects activation of the brain’s support cells, a sign of neuroinflammation. NfL reflects damage to nerve fibers, a sign of neurodegeneration. Both tend to rise with age and with progression toward dementia.
Among 164 participants with blood drawn at the trial’s start, those randomized to hearing aids showed a significantly slower rise in GFAP than a health-education control group. NfL also showed the same trend but fell short of significance. The authors concluded that hearing interventions may reduce the rate of change in biomarkers associated with brain health and dementia progression.
This sample came from the same ACHIEVE participants who already showed slower cognitive decline in the original trial, so the biomarker findings extend that earlier result, rather than confirm it independently. Even so, it’s an encouraging clue about a biological pathway linking hearing correction to brain health. The small sample means it needs replication, ideally in a larger and more diverse group, before anyone treats it as settled.
Where the science stands, and what you can do
Together, these three studies paint a consistent, still-cautious picture. Along with other research, hearing aids and dementia risk appear genuinely connected. But the benefit seems to depend on how well the device restores hearing, not simply on wearing one. None of the studies can fully prove causation. Each carries its own limitations, from self-reported outcomes to small sample sizes, and none should be read as a guarantee for any one person.
Still, correcting hearing loss carries little downside and real potential upside. Here’s what the evidence suggests for taking action:
- Get evaluated if you notice signs of hearing loss, such as trouble following conversations, frequently asking people to repeat themselves, or turning up the TV so loud it bothers others.
- Insist on a proper fitting, ideally through an audiologist, and follow up if the device still doesn’t feel like it’s helping. A poorly working hearing aid may offer little protection at all, according to the largest study.
- Reassess periodically, since hearing needs and device performance can drift over time.
- Pay extra attention if you’re socially isolated, unmarried, or have less access to health care, since the protective association looked strongest in exactly these groups.
For more background and practical guidance, including a downloadable hearing aid care guide, see the Parsemus Foundation’s full review of hearing, hearing aids, and dementia.
