Oct 29, 2021

Examining the link between hearing loss and dementia

Examining the link between hearing loss and dementia

Many natural parts of aging can be difficult to admit, particularly hearing loss. Medical experts are encouraging us to be open about this change due to its possible link with Dementia. 

Dr Alexander Chern, based out of New York-Presbyterian Hospital is a specialist ear, nose and throat doctor. Speaking on the research that is building, he explains that the greater a person’s loss of hearing, the greater the likelihood of the onset of dementia. 

In the U.S there is a large disparity between the number of those losing hearing and those seeking treatment for it. 2 in 3 adults over 70 have lost a degree of hearing but less than 20% seek treatment.

A 2020 report from the Lancet Commission on Dementia prevention and care found that age- connected loss of hearing remains the most significant adjustable risk factor for dementia, with a loss of hearing in midlife relating to an assessed 9% of overall dementia diagnoses. 

Specialists and researchers continue to strive to understand this causal link 

Professor Timothy Griffiths, a specialist in cognitive neurology at Newcastle University in the UK, explains the complexities of factors present in understanding this link. As dementia has been found to have multiple causes, so too are there multiple possible connectors linking loss of hearing to a degradation in brain health, as well as the likelihood that multiple factors are occurring simultaneously. 

Griffiths, who was a co-author in a 2020 study in the medical journal, Neuron, explains that there is the possibility that the same disease process contributing to the deterioration of hearing may also be degrading cognition. He outlines that the minor strokes that bring about vascular dementia may be impacting the inner ear. Additionally the research pointed to the likelihood of loss of hearing reducing activity in core regions of the brain that fuel thinking, resulting in an accelerated neurodegeneration. 

Griffiths continues, “It could be [that] there’s a boosting effect on the brain from being able to hear, which allows you to better process auditory signals and experience speech and communication and emotional communication,” he said. “Impoverished input leads to impoverished brain reserve, so that leads to a higher risk for dementia.”

Cognitive Resources

Delving further into their work, Griffiths explains a third potential causal factor, the loss of hearing may trigger a person to divert cognitive resources away from other parts of the brain. He comments that a significant collection of studies suggest listening through challenging conditions can result in increased difficulty in executing other tasks that demand attention. In straining to hear, more brain capacity is being utilized to listen to sounds and that brain capacity is diverting away from the brain resources otherwise directed to other tasks. 

He further explains it may be the demand on the part of the brain committed to listening under challenging conditions, that actually fuels the speed of the disease process in the segment of the brain utilised for cognitive function. 

Research and solutions to continue but strong indicators present

Medical research is yet to conclude if treating loss of hearing would resist or impede the progression of dementia, Dr. Chern of New York states that the medical community cannot definitely conclude either way yet and that the data is mixed.

Having co-authored a 2021 review in The Laryngoscope looking at the proficiency of hearing aids in reducing dementia risk, they found that while there was partial evidence hearing aids could shield persons with hearing loss and mild cognitive impairment from further degrading, this could not be extrapolated for all cases and causal links. 

However, Chern and his colleagues did state that the adoption of hearing aids should be encouraged, as there was only the potential for help and not harm for those with loss of hearing.

This position was also seconded by Professor Griffith’s partnered Lancet Commission report, as hearing aids could potentially lower dementia risk without any risk of harm. 

Examining the mixed results, Griffiths reasons that many possible pathways are present. 

“If you restore hearing, you are no longer listening under difficult conditions, so if that’s the problem, the dementia risk might be removed,” he said. But, if difficult listening is triggering the disease process responsible for dementia, “it could already be too late.”

Hearing loss very likely a cause of dementia

While definitive conclusions are being worked towards in regards to the whys, hows and the exact routes to reduction, researchers are confident of the present evidential link between loss of hearing and dementia.

Additionally, Griffiths and his co-authors have specifically called for lines of inquiry at the molecular, neonatal and systems levels to “pin this down”. 

Chern contributes that many longitudinal projects have displayed that hearing loss is the first factor, and other studies have also expressed that with the increased severity of hearing loss comes the greater likelihood of dementia. 

Further studies have shown that loss of hearing can be a significant obstacle in people socialising, with the consequence of social isolation resulting in a 50% elevated risk for the onset of dementia. 

Chern continues to advocate for the use of hearing aids. While there may be concern over the wearing of a hearing aid, from a perceived stigma of disability or age,  he says, not being able to hear anyone may contribute to being seen as old anyway. Far better to have a hearing aid to hear well, and position yourself to be in the best place to limit the likelihood of dementia.

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