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An observational study published in The Lancet Public Health looks at hearing aid use and all-cause and cause-specific dementia.
Prof Bart De Strooper, Director of the UK Dementia Research Institute, and Group Leader at the UK Dementia Research Institute at UCL, said:
“This is an interesting study but it should be stressed that correlation is not the same as causation. There are a lot of additional confounders which mean that this report should be interpreted with a lot of caution. There are many good reasons to take care of hearing, but that this will protect you from dementia is not proven. Furthermore UK Biobank data are based on self reports: ‘do you have any difficulty with your hearing’ (yes/no/completely deaf). Almost 100.000 people answer ‘yes’ and have no hearing aid , while ~15.000 have hearing loss and use a hearing aid. I am not sure what a complaint about hearing loss factually means, is it problems in hearing or is it problems in understanding other people? The latter could indicate beginning of neurodegeneration. I am always worried about reverse causation, although the authors mention this as unlikely: “Third, the association between hearing loss and dementia might be due to reverse causation through neurodegeneration or other shared mechanisms. However, the consistent findings after sensitivity analyses with 5-year and 10-year lag implied that the reverse causation was less likely”. How much “less likely” seems a rather subjective criterion.”
Dr Tracey Newman, Associate Professor of Neuroimmunology, University of Southampton, said:
“In short this is an important piece of work that supports and builds on the other findings in this area. A unique aspect is the size of the study population and the breadth of health measures that have been included, which have made a more nuanced analysis possible.
“This work adds to the evidence that losing your hearing increases your risk of dementia. The analysis of the data from more than 400,000 people in the UK biobank over a 12 year period found that people who had developed hearing loss and that used hearing aids were at a lower risk of dementia than people not using aids.
“The authors highlight the limitations of how hearing and hearing aid usage was assessed in the biobank population however, as they point out, this makes it likely that the protection they see, although small, is an underestimate.
“The study adds to our understanding that maintaining your hearing protects your brain. The work shows this is probably partially through being able to stay socially connected, and through direct effects on brain connectivity that are not fully understood.
“Dementia typically becomes evident years after hearing loss is first recognised by the person or people around them. This is an opportunity, but only if we think about hearing tests and hearing aids in the way we consider sight tests and glasses.”
Prof Tim Griffiths, Professor of Cognitive Neurology, Newcastle University, said:
“The numbers are impressive and have allowed authors to assess multiple factors that might affect dementia risk apart from hearing loss. But this observational study needs to be interpreted with caution. The best quality data on the relationship between hearing loss and dementia were the studies included in a model developed by the Lancet Commission based on hearing tests (audiograms) and follow up of the patients to see if they developed dementia. The UK biobank data do not include hearing tests: the hearing data are based on self-report which is not reliable. Hearing aid effects are difficult to interpret for two reasons: 1) people who have hearing aids often tend not to use them (although that would work against the effect of hearing-aid use shown here); 2) it is difficult to be certain if association of not using hearing aids reflects dementia causing lower hearing aid use as opposed to the reverse. So, the suggested effect is interesting but we really need are prospective studies of hearing aid use that measure deafness like the Lancet Commission studies and carefully evaluate device use and incident dementia. There is a large multisite US study funded by NIH currently doing just that.”
Dr Rebecca Dewey, Senior Research Fellow in Neuroimaging, University of Nottingham, said:
“The UK Biobank provides rich data for these sort of retrospective research questions. However it needs to be understood that they are just that: retrospective. The questions included in the Biobank questionnaire were not particularly well-designed for exactly this sort of analysis, but these sorts of studies can provide justification to do future well-designed research into areas that are likely to be of interest. For example, the question “do you have any difficulty with your hearing?” is problematic as respondents will interpret it differently.
“The choice to include everyone who responded “I am completely deaf” in with the people who responded that they did not use hearing aids is a massive assumption, and not one that I agree with. Some people who describe themselves as deaf do get great benefit from hearing aids, or may use another device, such as a cochlear implant. However, this is addressed by the authors as they re-analysed the data without including these individuals and found the same result, which shows that their result is good and robust.
“All the usual caveats around UK Biobank data also apply here – the resource represents a self-selecting sample of the population and may not reflect the health and socio-economic characteristics of the UK as a whole.
“Having said that, there are huge numbers of participants here (over 400,000, including nearly 6,000 with dementia) and many of those reservations I have expressed may well come out in the wash. The size of the difference between the two groups in terms of likelihood of developing dementia is huge. I don’t think they are likely to have found this result if there was not something there (i.e., the confidence intervals are sufficiently far away from zero difference between groups). The finding is also robust to varying the definitions of the groups, again a reassuring point.”
Prof Tom Dening, Professor of Dementia Research, University of Nottingham, said:
“This is a timely and important paper. There has been a lot of interest in hearing conditions and their possible contribution to the risk of developing dementia in recent years and it is estimated that hearing may account for about 8% of the potentially modifiable risk of developing dementia. This then raises the question as to whether treating hearing loss will actually make a difference to a person’s future risk of developing dementia.
“It is difficult to do convincing studies to explore this question as you need large samples and long enough periods of follow-up. However, the evidence is beginning to emerge to support the notion that the humble hearing aid can do much to fight the giant Dementia. This paper is an important contribution. Using data from nearly half a million participants in the UK Biobank, an international team of researchers found that people with untreated hearing loss had a 42% increased risk of developing dementia compared to people without hearing problems. However, for people with hearing impairment but who used hearing aids, their risk of dementia was almost the same as for people with normal hearing.
“The paper also explores some of the possible reasons as to how hearing aids may work, tending to favour the idea that they are effective because they reduce the cognitive effort involved in hearing and/or they reduce the effects of sensory deprivation if you can’t hear. The data provided less support or the idea that hearing loss-related dementia risk is mediated by social withdrawal and isolation.
“As someone has recently started to use hearing aids myself, I am greatly encouraged by these findings, and as a clinical researcher I appreciate having better data on which to base my advice to patients. We need to use studies like this to encourage the public not to be embarrassed by hearing problems and to seek assessment and treatment sooner rather than later.”
Prof David Curtis, Honorary Professor, UCL Genetics Institute, said:
“This observational study confirms previous findings that people who report difficulty with their hearing are more likely to be subsequently diagnosed with dementia, in particular if they do not use a hearing aid. The authors imply that wearing a hearing aid could protect against developing dementia but I am not convinced that this is a valid conclusion. It is hard to think of plausible mechanisms whereby having trouble hearing could lead to the kinds of damage to brain cells which are observed in the different types of dementia studied. On the other hand, we are already aware that struggling to understand conversations can be an early sign of dementia and it may be people with this kind of hearing difficulty are less likely to be prescribed a hearing aid and/or are less likely to wear one. The relationship between hearing loss and dementia needs to be investigated further before we advocate widespread usage of hearing aids as a preventative strategy.”
Prof Robert Howard, Professor of Old Age Psychiatry, UCL, said:
“This is a large and well-conducted study, but we should always remember that association is not the same as causation. As the authors acknowledge, dementia may have a prodrome of more than 20 years, during which subtle neuropsychological changes affect motivation and behaviour. Anyone who has observed an older relative without dementia, as they use (or fail to use) their hearing aid, will understand just how important any subtle cognitive or motivational impairment would be in this. I’m sceptical that use of hearing aids can be considered to prevent dementia. It seems more plausible to me that the association reflects that individuals on their way to developing dementia struggle to take up or use hearing aids.
“But hearing aids are important in reducing isolation and increasing quality of life, so we should encourage their use anyway.”
Dr Charles Marshall, Clinical Senior Lecturer in Neurology, Preventive Neurology Unit, Queen Mary University of London (QMUL), said:
“This study provides high quality evidence that those with hearing loss who use hearing aids are at lower risk of dementia than those with hearing loss who do not use hearing aids. This raises the possibility that a proportion of dementia cases could be prevented by using hearing aids to correct hearing loss. However, the observational nature of this study makes it difficult to be sure that hearing aids are actually causing the reduced risk of dementia.
“Hearing aids produce slightly distorted sound, and the brain has to adapt to this in order for hearing aids to be helpful. People who are at risk of developing dementia in the future may have early changes in their brain that impair this adaptation, and this may lead to them choosing to not use hearing aids. This would confound the association, creating the appearance that hearing aids were reducing dementia risk, when actually their use was just identifying people with relatively healthy brains.
“Hopefully the evidence from this paper will lead to randomised trials of hearing aid use that will provide a stronger foundation for public health advice about whether correcting hearing loss might help to prevent dementia.”
Prof Tara Spires-Jones, Professor of Neurodegeneration and deputy director of the Centre for Discovery Brain Sciences at the University of Edinburgh, and BNA President-Elect, said:
“In this study by Jiang and colleagues, scientists examined data from over 400,000 people to look at whether there is a relationship between hearing loss, hearing aid use, and dementia risk. They observed that people with hearing loss who did not use hearing aids had an increased risk of developing dementia. People with hearing loss who used hearing aids did not have an increased risk compared to people without hearing loss. The study is well-conducted and confirms previous similar studies showing an association between hearing loss and dementia risk. This type of study cannot prove conclusively that hearing loss causes dementia. For example, it is possible that people who are already in the very early stages of disease are less likely to seek help for hearing loss. However, on balance, this study and the rest of the data in the field indicate that keeping your brain heathy and engaged reduces dementia risk. I agree with the conclusions of the paper that it is important to help people with hearing loss to get effective hearing aids to help keep their brains engaged through allowing richer social interactions.”
‘Association between hearing aid use and all-cause and cause-specific dementia: an analysis of the UK Biobank cohort’ by Fan Jiang et al. was published in The Lancet Public Health at 23:30 UK time on Thursday 13th April.
DOI: https://doi.org/10.1016/S2468-2667(23)00048-8
Declared interests
Dr Tracey Newman: “I do not have any conflicts of interest.”
Prof Tim Griffiths: “No conflicts.”
Dr Rebecca Dewey: “No relevant conflicts of interest.”
Prof Tom Dening: “No conflicts.”
Prof David Curtis: “No conflicts of interest.”
Prof Robert Howard: “No conflicts.”
Dr Charles Marshall: “I have no relevant conflicts.”
Prof Tara Spires-Jones: “I have no conflicts with the study.”
For all other experts, no reply to our request for DOIs was received.