Does treating hearing loss protect the ageing brain? The big trial complicates it
Observational studies tie hearing loss to faster mental decline. But the first large randomised trial found no overall benefit from hearing aids over three years — with a signal of help only in higher-risk older adults.
| Group | Value (%) |
|---|---|
| Global function (3MS) | 41 |
| Executive function (Digit Symbol) | 32 |
Hearing loss is one of the most talked-about modifiable risk factors for dementia, and the pitch is seductive: a common, treatable problem that might protect the brain if caught early. The honest summary is more guarded. The link between poor hearing and faster cognitive decline is real and consistent in observational data — but the first large trial built to test whether treating it slows decline found no overall benefit, with a possible effect confined to older adults already at high risk [s1]. Hearing aids are worth having for hearing. Whether they buy cognitive protection is not settled.
What the observational data show
The association is well documented. In the Health ABC study, 1,984 older adults with a mean age of 77.4 years were followed for six years with repeated cognitive testing [s2]. Those with baseline hearing loss — a pure-tone average worse than 25 decibels — declined faster: annual rates of decline on a test of global function and a test of executive function were 41% and 32% greater, respectively, than in people with normal hearing [s2]. On the strength of findings like these, the 2020 Lancet Commission on dementia named hearing loss among the leading potentially modifiable risk factors across the life course [s3].
That is a strong prior, but it is the kind of evidence that traps the unwary. Hearing loss travels with age, vascular disease, social isolation and reduced activity, any of which can independently drag cognition down. Observational studies adjust for what they can measure, but they cannot randomise, so they cannot prove that the hearing loss itself is doing the damage rather than simply marking a person whose brain is ageing faster for other reasons.
What the trial found
That is what makes the ACHIEVE trial important. It randomly assigned 977 adults aged 70 to 84 with untreated hearing loss and no substantial cognitive impairment to either a hearing intervention — audiological counselling and hearing aids — or a health-education control, and followed them for three years [s1]. The cohort had a mean age of 76.8 years and 523 participants (54%) were female [s1]. The primary outcome was three-year change in a global cognition score.
The headline result was flatly null. Cognitive change was almost identical in the two groups: −0.200 standard-deviation units in the hearing group and −0.202 in the control group, a difference of 0.002 (95% confidence interval −0.077 to 0.081; p=0.96) [s1]. On its face, treating hearing loss did nothing to slow three-year cognitive decline.
The nuance sits in the design. ACHIEVE recruited from two populations: participants from a long-running cardiovascular cohort (ARIC), who were older and carried more risk factors, and healthier de-novo volunteers who answered adverts. A prespecified analysis found the intervention's effect differed significantly between the two groups (interaction p=0.010), with a benefit appearing in the higher-risk ARIC participants but not the low-risk volunteers [s1]. The authors' careful reading: a hearing intervention "might" slow cognitive change in older adults at increased risk, but not in those at low risk [s1].
How to read a null with a subgroup
Subgroup findings are where trials go to be over-interpreted, and this one deserves caution. The overall result was negative; the encouraging signal comes from one prespecified split, in a trial not powered to prove benefit within a subgroup. That is hypothesis-generating, not confirmatory — exactly the sort of result that looks convincing in a press release and fails to replicate. It would be wrong to treat "hearing aids prevent dementia" as an established fact on this evidence.
It would also be wrong to dismiss the idea. A biologically plausible mechanism, a consistent observational signal and a positive subgroup in a rigorous trial together make a reasonable case that treating hearing loss in higher-risk older people might help — enough to justify the larger, longer trials now needed to settle it.
The honest use
None of this argues against getting hearing loss treated. Restored hearing improves communication, mood and social participation, and those are reasons enough; the Lancet Commission's framing stands on public-health grounds independent of any single trial [s3]. What the evidence does not yet support is the stronger, tidier claim sold in some marketing — that a hearing aid is a proven dementia preventive. Treat hearing because hearing matters. Regard the brain benefit as promising and unproven, strongest in those who already have the most to lose [s1].
This article is informational and is not medical advice.
Sources
- [s1] Hearing intervention versus health education control to reduce cognitive decline in older adults with hearing loss in the USA (ACHIEVE): a multicentre, randomised controlled trial. The Lancet, 2023. https://doi.org/10.1016/S0140-6736(23)01406-X
- [s2] Hearing Loss and Cognitive Decline in Older Adults. JAMA Internal Medicine, 2013. https://doi.org/10.1001/jamainternmed.2013.1868
- [s3] Dementia prevention, intervention, and care: 2020 report of the Lancet Commission. The Lancet, 2020. https://doi.org/10.1016/S0140-6736(20)30367-6
Sources
- Hearing intervention versus health education control to reduce cognitive decline in older adults with hearing loss in the USA (ACHIEVE): a multicentre, randomised controlled trial — The Lancet , September 1, 2023
- Hearing Loss and Cognitive Decline in Older Adults — JAMA Internal Medicine , February 25, 2013
- Dementia prevention, intervention, and care: 2020 report of the Lancet Commission — The Lancet , August 1, 2020
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