Hearing & dementia (hearing care)

The figure that was revised

A commission of the journal The Lancet compiles which risk factors for dementia can be modified. In the 2020 version, hearing loss stood at the top with 8 %. This figure went around the world and still appears in countless texts today.

In 2024 the calculation was redone, with 14 factors instead of 12. Hearing loss is now at 7 % and thus still at the top, level with high LDL cholesterol. They are followed by low education and social isolation with 5 % each; high blood pressure is at 2 %. So the statement about the largest modifiable risk factor still holds in the new version.

The more remarkable figure gets lost in the process: all 14 factors together explain around 45 % of dementia cases — mathematically, almost half would be preventable or at least postponable.

What a population share says — and what it does not

The percentages on this list do not describe the risk of an individual person. Behind them is the question: how many dementia cases would disappear if a factor could be eliminated in the entire population? So 7 % means: 7 % less dementia if no one had untreated hearing loss any more.

That is something different from saying that your own risk drops by 7 %. The figure also depends on how widespread a factor is: a very dangerous but rare factor gets a small share, a moderately dangerous but common one a large share. For a personal decision, such a share says little; for the question of where a society should intervene, it says a lot.

Why poor hearing could harm the brain

Three explanations are discussed. First, listening effort: anyone who hears poorly has to guess constantly. The brain puts computing power into mere understanding, which is then missing elsewhere. Second, withdrawal: conversations become tiring, invitations rarer — and social isolation is itself on the list of 14 factors. Third, remodeling in the brain: auditory pathways that no longer have anything to do regress, and this is measurable.

All three pathways are plausible. Alongside them, however, there is a fourth explanation that is not a cause: perhaps the incipient dementia process also damages hearing. Hearing loss would then be an early sign and not the trigger. Observational data alone cannot separate the two.

ACHIEVE: one trial with two results

ACHIEVE, published in The Lancet, followed 977 older people with hearing loss for 3 years at several centers in the US. One half received hearing care consisting of hearing aids and counseling, the other a health education program on healthy aging — so both groups received the same amount of attention.

The design is decisive: 238 participants came from a long-running cardiovascular cohort, so they were older and had more risk factors. 739 were healthy volunteers who had newly signed up.

In the overall analysis nothing happened: hearing care was no better than the control program, and the primary endpoint was missed. In the group from the cardiovascular cohort, by contrast, cognitive decline over 3 years slowed by 48 % — almost half.

Why this subgroup is different from the usual ones

Subgroups are the classic way to turn a failed trial into a success story after all. Anyone who searches long enough will always find a subgroup in which something shows up. Two things make this case different. First, the groups were not assembled after the fact: the trial recruited from two sources from the outset, and the analysis by origin was part of the plan. Second, there was an explanation known beforehand — in the control group, the healthy volunteers declined much more slowly (the risk group 2.7 times as fast), so in 3 years there was hardly anything to slow down in them. You cannot measure a brake if the car is almost standing still anyway.

The difference between an explanation and an excuse lies in whether it was there beforehand. Here it was. It nonetheless remains a subgroup result, and the honest wording is: nothing was shown in the overall group.

Why the trade-off is clear here anyway

A hearing aid is not a substance that is swallowed, and that it helps with hearing needs no study. The only open question is whether it also protects the brain. This puts the topic in a different position from most: elsewhere it is about substances with unclear benefit, unclear risk and ongoing costs; here it is about a device with a certain benefit and a possible additional benefit. Even if the dementia effect is not confirmed, nothing is lost.

What matters most in practice is the time until care. Between noticing hearing loss and the first hearing aid, years pass on average — out of vanity, out of habit, out of denial. These are exactly the years in which ACHIEVE measured cognitive decline.

What the studies show

ACHIEVE, Lancet 2023

977 older people with hearing loss, 3 years, several US centers, randomized to hearing care versus a health education program on healthy aging. Primary endpoint missed: in the overall group, cognitive decline did not differ. In the prespecified subgroup from a cardiovascular cohort (238 people) it was slowed by 48 %; in the control group, the risk group declined 2.7 times as fast as the 739 healthy volunteers.

Lancet Commission on dementia prevention, 2024 version

Recalculation with 14 factors instead of 12. Hearing loss and high LDL cholesterol lead with 7 % of cases each, followed by low education and social isolation with 5 % each and high blood pressure with 2 %. All 14 together explain around 45 % of cases — population-based shares, not individual risks.

Lancet Commission on dementia prevention, 2020 version

The previous version with 12 factors, together 40 % of cases, in which hearing loss ranked first with 8 %.

Where the data stop

It has not been shown that hearing aids prevent dementia. The primary endpoint of the only large randomized trial was missed, and the 48 % comes from a subgroup — prespecified or not, it remains an analysis following a missed primary result. For healthy older people without additional risk, this trial provides no evidence of a protective effect.

Status, approval and legal

Hearing aids are medical devices and are routinely available in Germany through ENT physicians and hearing aid acousticians; a hearing test is part of normal diagnostics. There is no approval for dementia prevention — the shares of the Lancet Commission are epidemiological calculations, not an indication. There is no doping relevance. Anyone who suspects a hearing problem should have it clarified by a physician rather than by self-assessment.

Safety

Hearing care is not a pharmacological intervention: no active substance, no metabolic pathway, none of the typical adverse effects. In ACHIEVE it was followed in a controlled way over 3 years. The real risk lies elsewhere — in waiting.

Sources

• ACHIEVE trial, Lancet 2023
• Lancet Commission on dementia prevention (Livingston et al.), Lancet 2024
• Lancet Commission on dementia prevention (Livingston et al.), Lancet 2020
• ARIC cohort (Am J Epidemiol 1989) — origin of the risk group in ACHIEVE