July 21, 2021

expert reaction to study looking at hearing difficulties and risk of dementia

A study published in Alzheimer’s & Dementia: The Journal of the Alzheimer’s Association looks at speech-in-noise hearing impairment and risk of dementia.

Prof Tom Dening, Professor of Dementia Research and Head of the Centre for Dementia at the Institute of Mental Health, University of Nottingham, said:

“This is an important and well-conducted study. It uses a hearing test called speech-in-noise, which is probably a more realistic way of testing hearing than alternatives, like pure tone audiometry. In other words, what does it matter if you cannot hear a high-pitched tone compared with the frustration of not being able to follow a conversation in a social situation.

“The study results are consistent with other research that has shown that people with hearing loss do have an increased risk of developing dementia over the following period, in this case up to 10 years.

“There are two big questions about hearing loss and dementia. One is, how does hearing loss contribute to dementia? One suggestion is that the mechanism is a social one – that is, if a person can’t participate in social conversations, they may simply give up and restrict their social activity, placing themselves at risk of loneliness and depression. The study reported here tested for this possibility and found no effect from depression and isolation on the risk of dementia. That’s an important finding so we still don’t know the mechanism, even though this study weighs against a social explanation. Perhaps the cause lies in the brain and some common mechanism by which brain changes contribute to a higher risk of both problems.

“The second big question is whether the dementia risk due to hearing loss is modifiable, for example by the use of hearing aids. The authors of the paper found some evidence that hearing aids may be helpful but they were not able to be very confident about this. It would be wonderful if hearing assessment and assistance for hearing loss was able to help people reduce their risk of dementia. We know that hearing loss is a big risk factor but we need further evidence before we can be confident that its effects can be prevented by assistance for people’s hearing.”

Prof Bart De Strooper, Director, UK Dementia Research Institute, said:

“This interesting study suggests a relationship between difficulty hearing speech and dementia, using the unique BIOBANK resource. However it should be stressed that correlation does not mean causation: both dementia and hearing loss are correlated with aging so further scientific study is needed to determine if hearing problems truly influence the development of dementia. 

“The brain is complex and hearing speech in a noisy environment depends on complex processing events in the brain to filter the signal from the background. We know that dementia is a slow process and can affect different brain functions. Therefore it could be that in these people the hearing problem is an early sign and not a cause of dementia. This can only be clarified by more discovery science looking at mechanisms so we can find conclusive answers and ultimately treatments that tackle the cause of the problem.”

Dr Helen Brooker, Senior Research Fellow at the University of Exeter, said:

“Hearing loss is emerging as a potentially important risk factor for dementia, and could be an area where we could make a real difference, through treating hearing loss at an early stage. This research contributes to a  growing body of work to find out whether hearing loss has a relationship to cognitive decline and to what extent it presents a risk factor for dementia. Importantly this work adds to the area of Speech-in-noise hearing impairment that has little published work.

“The study uses a large and diverse cohort for analysis (UK Biobank), with a clearly defined methodology and has performed a robust analysis with appropriate controls.  

“This study aligns with the findings of our research from our PROTECT study at Exeter, where hearing was found to be a modifiable risk factor, in that those who self-reported hearing impairment and did not wear hearing aids performed poorer on core aspects of cognitive function compared to those who wore hearing aids, and also showed a steeper decline. The authors of this research have been very honest about its limitations (e.g. short study follow up given area of detection and use of death certificates to confirm dementia), but this does not detract from this important contribution to the field.

“This study further adds to the growing evidence that shows we can all contribute to reducing our own risk of dementia if we take action to look after our brain health from mid-life. There are many benefits to wearing a hearing aid if you are experiencing hearing loss – increasing evidence shows that protecting your brain in later life could be one of them.”

Prof Jason Warren, Professor of Neurology and Consultant Neurologist, Dementia Research Centre, UCL Queen Square Institute of Neurology, University College London, said:

“The apparent link between hearing loss and dementia is both worrying and puzzling. This timely new study contributes an important piece to the puzzle. Evidence from one of the largest cohorts of older people yet assembled now suggests that reduced ability to understand speech in background noise carries a substantially increased risk of developing dementia. In focussing on a crucial aspect of everyday communication, this work raises far-reaching implications for how we assess and manage hearing impairment and dementia risk. We hear with or brains no less than our ears. Does reduced noisy listening promote dementia or is it an early warning ‘stress test’ for the ageing brain? What is actually happening in the brain as hearing loss occurs? And what should we recommend to older people worried about their hearing and wishing to protect their memory? Stay tuned.”

Prof David Curtis, Honorary Professor, UCL Genetics Institute, said:

“There is a well-established association between hearing problems and dementia. However what is not at all clear is whether hearing problems themselves cause or exacerbate dementia or whether they reflect an early sign of impaired cognitive ability which may be manifest before a formal diagnosis is made. The authors themselves state that if hearing problems are a feature of early, preclinical dementia then one might observe an increased risk of dementia within three years of hearing problems being present but less so after nine years. In fact, this is exactly what we do see. Although the numbers involved are small they are consistent with the notion that hearing problems can be a symptom of early dementia but do not cause dementia. If this is the case, then providing people with hearing aids or similar interventions would not be expected to reduce their dementia risk.

“It is very plausible that discerning speech in a noisy environment could be an early symptom of dementia because this task requires extraordinary computational abilities within the brain. (Though it should be said that such problems are very common as people age for a variety of reasons and should not in themselves be taken as a worrying sign that dementia is imminent.) On the other hand, it is quite difficult to see how hearing problems could impact on the mechanisms of neuronal degeneration and cell loss which can ultimately manifest in a diagnosis of dementia. Thus, while this study confirms that the conditions are associated with each other I am not convinced that it establishes a causal relationship from hearing problems to dementia.”

(also in the press release from Oxford, Alzheimer’s Research UK were not funders of this study) Dr Katy Stubbs from Alzheimer’s Research UK, said:
“While most people think of memory problems when we hear the word dementia, this is far from the whole story. Many people with dementia will experience difficultly following speech in a noisy environment – a symptom sometimes called the ‘cocktail party problem’.

“This study suggests that these hearing changes may not just be a symptom of dementia, but a risk factor that could potentially be treated.

“Large studies like the UK Biobank are powerful tools for identifying genetic, health and lifestyle factors linked to conditions like dementia, but it is always difficult to tease apart cause and effect in this type of research.

“Anyone who has concerns about their hearing should speak to their GP.”

‘Speech-in-noise hearing impairment is associated with an increased risk of incident dementia in 82,039 UK Biobank participants’ by Jonathan S. Stevenson et al. was published in Alzheimer’s & Dementia: The Journal of the Alzheimer’s Association on Wednesday 21 July

DOI: 10.1002/alz.12416

Declared interests

Prof Tom Dening: “I have no interests to declare.”

Prof Jason Warren: “I have no relevant conflicts.”

Prof David Curtis: “No conflicts of interest.”

None others received.