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July 18, 2023

Results of trial looking at the use of hearing aids for cognitive decline has been published in The Lancet.

Dr Thomas Littlejohns, Senior Epidemiologist, Nuffield Department of Population Health, University of Oxford, said:

Does the press release accurately reflect the science?

Yes.

Is this good quality research? Are the conclusions backed up by solid data?

Overall, this research is of high quality. I expand upon the study in the following bullet points.

How does this work fit with the existing evidence?

This is a very timely study as in the last few years there has been a lot of scientific interest and speculation on whether hearing problems could represent a key target for reducing the risk of dementia. This interest has largely been driven by an influential Lancet review article, which identified hearing problems as potentially the strongest risk factor for preventing dementia. This means that treating hearing, if causal, would have the biggest impact on reducing the number of dementia cases compared to any other factor. However, the findings in the Lancet review were based on very limited observational evidence, which are prone to various sources of bias. Therefore, the results from this trial are very welcome. It provides the first direct evidence on whether treating hearing problems could slow the decline in cognitive function which precedes the clinical onset of dementia.

Have the authors accounted for confounders? Are there important limitations to be aware of?

The greatest limitation of previous observational studies is the inability to account for confounding factors. So whilst hearing problems have been associated with dementia risk in these studies, the associations could be driven by some different factors, such as lifestyle or other health problems. Trials, such as the current study, address the issue of confounding by randomly assigning individuals to either control or intervention, resulting in equally balanced groups in each arm. In the current study, the sociodemographic characteristics, lifestyle factors and health history are identical in the control and intervention groups. An unavoidable limitation of this trial is that participants were not blinded to the treatment. However, the authors compensate for this by providing a different form of intervention to the control arm to account for any placebo effect. As the authors note, the lack of effect for the primary outcome might be because participants who are fairly healthy dont experience cognitive decline over three years to enable a difference be detected. This is a difficulty of conducting dementia trials, because the underlying pathology of dementia can occur over many years, before dementia is clinically diagnosed. Longer follow-up could eventually address this, whilst the effect of hearing aid use on the other outcomes collected, in particular from brain scans, will be informative once published by the study team.

What are the implications in the real world? Is there any overspeculation?

The researchers present their findings clearly without overspeculation and applying the appropriate caveats. Whilst it is disappointing that the findings showed no effect for the whole population, the slower rates of cognitive decline in the unhealthier population is promising. The reasons for this are unclear. It should be emphasised that hearing problems are highly common world wide, especially at older ages. Improving the access and uptake of treatments for hearing problems remains an important public health goal, and if this leads to improved cognition and a reduced risk of dementia, then that is a very welcome bonus.

Tara Spires-Jones, President of the British Neuroscience Association and Professor at the UK Dementia Research Institute at the University of Edinburgh, said:

This study by Lin and colleagues found that providing hearing aids to older adults with hearing loss did not protect against changes in cognition in a general population. However, in a population at higher risk of dementia, there was protection against cognitive decline over 3 years when people were given hearing aids compared to a control group. This study adds to evidence that keeping your brain engaged including through treating hearing loss may protect against degeneration during ageing.

Dr Susan Kohlhaas, Executive Director of Research & Partnerships at Alzheimers Research UK, said:

Hearing loss is a well-established risk factor for dementia, but we currently dont understand whether treating hearing loss will reduce this risk in the long-term. This is an important question to answer for the 1 in 3 of us who will develop dementia one day.

This large-scale trial tested whether interventions for hearing loss, such as hearing aids, reduced cognitive decline over a three-year period in two different groups of people. One group had a higher risk of developing dementia as they were older and had a history of cardiovascular disease, compared with the other group.

Although there were no benefits seen when both groups of people were analysed together, the group who were at a great risk of developing dementia appeared to have less cognitive decline over a three-year period compared to people who werent given a hearing intervention.

We know that dementia is not an inevitable part of ageing and while we work towards a cure it is important to understand what we can do to protect our brain health. People who are concerned about hearing loss should speak to a healthcare professional options to preserve hearing may have additional benefits of protecting their brain health.

Beyond this, weve asked the government to include a hearing check in the existing NHS Health Check, which is freely available to those over 40. Were also actively encouraging people to sign up to Alzheimers Research UKs free, evidence-based Think Brain Health Check-In to find out ways to look after their brain health. This can be accessed at https://www.alzheimersresearchuk.org/brain-health/check-in/

Dr Charles Marshall, Clinical Senior Lecturer, Queen Mary University of London, said:

These findings show us that there might be a small benefit of hearing aid use in reducing cognitive decline in an otherwise healthy population with hearing loss, but they dont yet tell us whether hearing aids are actually preventing dementia or just improving peoples ability to perform cognitive testing. It will be very interesting to see the longer term follow up data in years to come so that we can start to understand whether hearing aids truly have a role in dementia prevention. In the meantime, it seems that for those who are able to use them, hearing aids might have some benefit on brain function and should continue to be recommended for those with hearing difficulty.

Prof Tom Dening, Professor of Dementia Research, University of Nottingham, said:

The results of the ACHIEVE trial of hearing interventions aimed at helping cognition in older people are very welcome. This is a really important piece of research and will have implications for patients, clinicians and researchers. As a hearing aid user myself, I am personally very interested in this topic.

The background is that hearing loss from midlife is recognised as a major independent risk factor for developing dementia in later years, so the big question is whether hearing interventions, that is, supporting people to wear hearing aids, help to slow down cognitive decline and prevent dementia. If so, up to 8% of cases of dementia might be prevented, which would be a massive benefit.

There are now quite a few good observational studies showing that people with untreated hearing loss do have an increased risk of cognitive decline and dementia compared to those who wear hearing aids. The problem with these studies is they dont account for other differences between hearing aid users and non-users, e.g. non-users may have other health and social issues that also contribute to dementia risk. So the only way to address this is by means of a clinical trial that randomly allocates people to active hearing support treatment versus a control condition where they get something else.

The ACHIEVE trial is the first major trial of this kind to report its findings. It included over 900 participants and followed them up for 3 years to measure various aspects of cognition. Interestingly, they were recruited from two different sources. One was simply advertising to the public for eligible volunteers. The other group came from an ongoing study (called ARIC) recruited to study cardiovascular disease in the population. The main finding was that overall there was no difference between the group receiving hearing intervention compared to the controls, who received a health education programme instead. The only difference was seen in the ARIC group, where the intervention group did better than the controls.

Why the difference between the ARIC group and the newly recruited volunteers? The latter were slightly younger, more affluent and in better general health, with fewer other risk factors for dementia (like high blood pressure or diabetes). Thus, maybe people in this group were just at very low risk of developing dementia during the study period and whether they had hearing aids or not made little or no difference to them. In contrast, the ARIC group had several risk factors for dementia and so were more likely to benefit from hearing aids at this stage in their health pathway.

Overall, maybe the results are a little disappointing that there wasnt a bigger effect for everyone taking part, but they do suggest that supporting people who at higher risk of dementia with interventions like hearing aids is important and likely to be effective.

However, I would stress that anyone with hearing loss should bear in mind that wearing hearing aids has many benefits besides potentially reducing your risk of dementia. You can hear better, function better socially, do your work in more comfort, and use the aids as cool Bluetooth devices to stay connected. All of which is great for well-being.

Prof Gill Livingston, Professor of Psychiatry of Older People, University College London (UCL), said:

This is an important and unique study. Hearing loss from midlife onwards is a potent and common risk for accelerated cognitive decline and dementia and is the most important risk at a population level. Observational studies have shown that those people who have hearing loss and wear hearing aids do not have this excess risk. The question has remained whether it is because people who wear hearing aids are those who would not develop dementia anyway as they have more coping and financial resources.

Randomised controlled trials mean that the intervention groups are expected to be the same as the control groups. Before this study (ACHIEVE) there had been no large randomised controlled trials of hearing aids to reduce cognitive decline and ultimately dementia. ACHIEVE randomised 977 participants to a hearing aids intervention or an educational intervention for successful ageing. ACHIEVE study participants were either healthy volunteers recruited from advertisements (N=739), or older adult from the Atherosclerosis Risk in Communities (ARIC, N=238) randomly recruited and followed since 1989. This one showed no effect in the healthy volunteers, possibly because neither the controls or the intervention group deteriorated very much. The prespecified analysis showed a large effect in the ARIC participants who were healthy volunteers in 1989 but now had deteriorated The outcome of incident cognitive impairment: a composite measure of newly diagnosed dementia, mild cognitive impairment or substantial decline in cognitive testing, was nearly three times higher in the ARIC group (24%) than in people who answered adverts (8%) at 3 years follow-up

The ARIC participants had many more risk factors for dementia than those who responded to adverts; they were 2.8 years older, with lower cognitive scores on tests at the beginning of the trial, were more often female, Black, had less education, lower income, and more often had diabetes, high blood pressure, smoked and lived alone. In addition, 19% of the control group who answered adverts started to use hearing aids compared to 8% of ARIC controls, thus reducing differences between randomised arms in healthy volunteers.

We need more trials in other settings, using the lessons learnt about the need to focus on people at high risk of cognitive decline and dementia.

Overall, the findings from this study are huge and hopeful results. Hearing aid treatment could really make a difference for populations at risk of dementia. These are for short term dementia trials but interestingly, it looks like even super-healthy people, which may include those recruited to ARIC forty years before, eventually become people at risk of dementia. Interventions to prevent dementia should recruit those at risk for timely results, but healthy people may develop risk over time.

Dr Sarah Bauermeister, Associate Professor and Senior Scientist & Senior Data Manager, Dementias Platform UK, University of Oxford, said:

Although important work, including our own, suggests the link between hearing aid use and mild cognitive impairment (MCI) /dementia progression, there is a need to understand difficulties wearing hearing aid. This paper suggest that intervention work did not significantly impact cognitive decline, suggesting an alternative strategy is required. Our current work investigates hearing aid use difficulties in people with cognitive impairment and dementia, and we hope that understanding these difficulties will lead to applied intervention work in hearing aid fitting, design and adherence.

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 by Frank R Lin et al. was published in The Lancet at 7:00 UK time on Tuesday 18 July.

DOI: https://doi.org/10.1016/ S0140-6736(23)01406-X

Declared interests

Dr Charles Marshall: I have no relevant conflicts to declare.

Prof Tom Dening: The only interest I have to declare is that I wear hearing aids myself, and I have written several blogs on my experiences. This makes me a bit of an advocate for wider hearing aid use, though I do so in terms of their immediate benefits, less so as a preventive measure against dementia, where I think that am able objectively to consider the evidence.

Prof Gill Livingston: Referred this paper and has written a linked comment. No other conflicts of interest

Dr Sarah Bauermeister: No conflicting interests.

For all other experts, no reply to our request for DOIs was received.

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