Of the fourteen modifiable risk factors for dementia identified by the Lancet Commission, one contributes more than any other, and almost nobody treats it as a brain issue.
It is hearing loss.
What the Commission found
The Lancet standing Commission on dementia prevention published its 2024 update, expanding its list from twelve modifiable risk factors to fourteen, with the addition of high LDL cholesterol and untreated vision loss.
The headline conclusion: around 45% of dementia cases worldwide are potentially preventable by addressing these fourteen factors across the life course.
The population attributable fractions — the share of cases that would be prevented if a factor were eliminated entirely — put hearing loss at 7%, tied with less education for the largest single contribution. High midlife LDL cholesterol also came in at 7%. Social isolation contributed 5%, physical inactivity 2%, and untreated vision loss 2%.
Seven percent of all dementia cases, attributable to something that is routinely treated as an inconvenience rather than a health risk.
Why hearing would affect the brain
Three mechanisms are proposed, and they are not mutually exclusive.
Cognitive load. When the auditory signal is degraded, the brain spends more resources decoding speech. Those resources come from somewhere — attention, working memory, the capacity that would otherwise go into remembering what was said. Over years, this reallocation may have consequences.
Reduced stimulation. Auditory input is one of the brain’s main sources of complexity. Diminished input has been linked to structural changes, including accelerated atrophy in regions involved in processing sound and language.
Social withdrawal. This is the most straightforward and probably the most important. Hearing loss makes conversation effortful, particularly in groups and background noise. People stop going to the pub, the family gathering, the club. And social isolation is itself on the Commission’s list at 5%.
That last chain matters: hearing loss produces isolation, isolation carries its own risk, and the person experiencing it describes the problem as “I don’t enjoy going out any more” rather than as a hearing problem at all.
Why it goes unaddressed for years
Hearing loss is unusual among health problems in how it presents.
It arrives slowly. Age-related hearing loss develops over decades, and there is no day on which anything changes. The brain compensates continuously, and adaptation is invisible from the inside.
It presents as other people’s fault. The universal first symptom is not “I can’t hear” but “people mumble.” Both are the same observation, and only one prompts action.
High frequencies go first. Consonants — s, t, f, th — carry most of the information in speech and sit at high frequencies. Vowels are lower and survive longer. The result is a characteristic complaint: I can hear that they’re talking, I just can’t make out the words. Volume is not the problem, clarity is, which is why turning the television up stops helping.
Noise is where it shows. Someone can hear well in a quiet room and struggle badly in a restaurant. If your social life happens in noisy places, the disability appears there first and is easy to blame on the venue.
And there is stigma. Hearing aids are associated with age in a way that glasses are not. People who would not think twice about a reading prescription resist a hearing test for years.
The average delay between noticing hearing difficulty and doing something about it is measured in years, not months.
Does treating it help?
This is where the evidence gets more careful, and honest coverage has to say so.
The association between hearing loss and dementia is well established across large cohorts. Whether treating hearing loss reduces dementia risk is a separate question, and the answer is not settled.
The ACHIEVE trial, the largest randomised test of this question, found no significant effect of hearing intervention on cognitive decline in its overall population over three years. However, in a prespecified subgroup at higher risk of decline, hearing intervention did slow cognitive change.
That is a mixed result and should be reported as one. A subgroup finding in a trial with a null primary outcome is a reason for continued investigation rather than a conclusion.
The Lancet Commission’s recommendation — that hearing aids and eye tests be made accessible to all — rests on the totality of evidence, not on one trial.
What is not in dispute: treating hearing loss improves communication, reduces the effort of conversation, and addresses the social withdrawal that follows. Those are worth having regardless of what the dementia question eventually resolves to.
What to do
Get tested if any of this is familiar. Asking people to repeat themselves. Turning the television up while others say it is loud. Struggling in restaurants and groups. Missing the phone or the doorbell. Tinnitus.
In the UK, ask your GP for a referral to audiology — NHS hearing aids are free, including batteries and repairs. High street providers offer free tests, but be aware they are also selling a product.
Do not wait for it to get bad. The brain adapts to reduced input over time, and the adaptation period after fitting a hearing aid is harder the longer you have gone without. Everything sounds strange at first, and that is worse after fifteen years of gradual loss than after three.
Protect what you have. Noise damage is cumulative and permanent. Power tools, concerts, and — most commonly now — headphones. If someone next to you can hear your music, it is too loud.
Treat it as one of several. The Commission’s list is fourteen items and most people who develop dementia have been exposed to several. The actionable cluster for anyone over forty is unglamorous and cheap: a hearing test, an eye test, blood pressure, LDL cholesterol, regular movement, treating depression, limiting alcohol, and taking social connection seriously.
The point worth holding onto
The reason to write about hearing rather than about supplements is that this is where the evidence actually sits, and it is not close.
A hearing test costs nothing on the NHS and takes half an hour. The factor it addresses is tied for the largest single contribution to preventable dementia in the most authoritative review of the field.
Meanwhile the longevity market sells compounds with no human outcome data at £40 a month, and the audiology waiting list is full of people who came ten years later than they should have — because the first symptom of the biggest modifiable risk factor for dementia is the belief that everyone around you has started mumbling.
This article is for general information and is not medical advice. If you have noticed changes in your hearing, speak to your GP or an audiologist.
Sources
- Livingston G, Huntley J, Liu KY, et al. Dementia prevention, intervention, and care: 2024 report of the Lancet standing Commission. The Lancet, 2024. https://www.thelancet.com/commissions-do/dementia-prevention-intervention-and-care
- Lancet Commission 2024 risk factor infographic with population attributable fractions. https://www.thelancet.com/pb/assets/raw/Lancet/infographics/dementia-2017/image-1721911723223.pdf
- Alzheimer Europe. 2024 Lancet Commission underscores the potential for dementia risk reduction, identifying 14 modifiable risk factors across the life course. https://www.alzheimer-europe.org/news/2024-lancet-commission-underscores-potential-dementia-risk-reduction-identifying-14-modifiable
- Dementias Platform UK. New modifiable risks included in Lancet report on dementia. https://www.dementiasplatform.uk/news-and-media/latest-news/new-modifiable-risks-included-in-lancet-report-on-dementia
- Lin FR, et al. 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.
This article is for general information and is not medical advice. If a health problem is affecting your daily life, speak to your GP.
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