Body of Evidence: Hearing loss and brain health - what is the science telling us?

BY THE TIME Ludwig van Beethoven had turned 30, the celebrated virtuoso pianist had composed a couple of piano concertos, six string quartets and his first symphony. The prospect of a long, successful career as a composer and performer looked dazzlingly bright.

Then he started to notice a buzzing sound in his ears – and everything changed. By his mid-40s, Beethoven was almost totally deaf. He imagined rather than heard what his compositions sounded like, sitting at the piano with a pencil in his mouth, touching the other end of the piano to feel the vibration of the note. So, the Moonlight Sonata was composed.

In recent years, hearing loss is now recognised as a major public health issue, linked to mental health, heart health and risk of dementia. For many, hearing loss happens due to the wear and tear of old age.

The good news is that there are ways to restore hearing to those who are losing it. There are also promising new-generation drug therapies being developed for a condition that up to now has had none.

While we may not all be musical virtuosos, maintaining our hearing is essential to healthy ageing. When sounds of 20 to 25 decibels, such as rustling leaves, a ticking watch or a whisper from a few feet away, are no longer detectable, this is considered to qualify as a diagnosis of hearing loss.

What causes hearing loss?

There are three conditions that can cause a loss of hearing:

A blockage in the ear can be due to ear wax or infection, impairs sound waves from reaching the inner ear. This ‘conductive’ hearing loss can be fixed.

More complex is sensorineural hearing loss (SNHL) due to damage to the inner ear, either the bones in the inner ear or the nerve pathways from ear to brain. A range of factors, including advancing age, genes, underlying disease, noise damage or medicines that are toxic to the inner ear, notably antibiotics called aminoglycosides, can damage the neural pathways and impair hearing.

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The third possibility is auditory neuropathy spectrum disorder (ANSD) where the ability of the brain to process sound is faulty. Both sensorineural hearing loss and auditory neuropathy spectrum disorder can be improved with technology or therapy but are irreversible.

About one in five of the global population, over 1.5 billion people, have some form of hearing loss, including about half of people over 65 years, according to the WHO World Report on Hearing (2021). With each decade of life, the risk of hearing loss doubles – by the age of 70, about two-thirds of people report some level of hearing loss, according to a paper in the Journal of Gerontology (2011).

The WHO predicts that by 2050, a quarter of the world’s population of 10 billion will have some level of hearing loss, with 700 million sufficiently hard of hearing to need a hearing aid, cochlear implant or other intervention such as lip-reading or sign language.

Hearing loss and other health issues

With a global epidemic of loneliness already in place, the implications for rising levels of hearing loss in communities are huge, including potential for further social isolation, lowered self-esteem, inability to work and persistent tiredness.

A review in the Association of Psychological Science Journal (2015) found that social isolation for any reason increased the risk of death from any cause by over a third. A recent review in Applied Sciences (2026) found that many of the known risk factors for cardiovascular disease – including obesity, type 2 diabetes, imbalance in blood lipids and high blood sugar are also risk factors for hearing loss.

Researchers at the National University Health System in Singapore have found that people with hearing loss have a 38% higher risk of cardiovascular disease. One Chinese study found that those with severe hearing loss had a 78% increased risk of stroke.

The evidence suggests that hearing loss is a consequence of the same problems that increase the risk of cardiovascular disease by damaging small blood vessels in the inner ear, aligned with oxidative stress and inflammation – although the exact mechanisms are yet to be elucidated.

Hearing loss is also linked to increased risk of falls, depression and dementia. A landmark report in the Lancet (2024) identified hearing loss as one of 14 risk factors for dementia, with increased risk ranging from 28% to 139%.

A recent paper in Ageing Research Reviews (2024) found that for each 10 decibels of hearing loss, risk of dementia increased by as much as 16%.

The reasons for the links between hearing loss and dementia are still debated. Possibilities include the links between hearing loss and social isolation, loneliness and depression; the overloading of the brain by the burden of processing sounds; or that hearing loss is another symptom of dementia that occurs before cognitive deficits.

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Future therapies for hearing loss

More promising is the future availability of drugs that prevent or even reverse hearing loss. In April, the US Food and Drug Administration approved a treatment for a rare form of congenital deafness called DFNBO. It is causing excitement as the first biological treatment for hearing loss.

It offers hope to researchers looking to fix hearing loss in later life that has a genetic basis, while researchers in Australia are working on gene therapy to improve the performance of cochlear implants.

Another approach involves using stem cells to stimulate the neurons that link the cochlea in the inner ear to the auditory nerve. The degeneration of these neurons is a leading cause of sensorineural hearing loss – the stem cells can coax the neurons to regenerate. A clinical trial of this therapy is currently underway, delivered simultaneously with a cochlear implant.

Thirdly, clinical trials are underway to find a chemical compound that protects the part of the inner ear that breaks down in age-related hearing loss. Previous trials of these drugs have failed, but researchers are hopeful that there is potential to find a drug that will get over the line.

Healthy diet to protect hearing

While we wait for new treatments to hit the market, there is evidence that a healthy diet can protect hearing. Foods rich in antioxidants, folate, omega-3 fatty acids and magnesium have all been advised to offer protection of the inner ear. A recent paper in the Journal of Prevention of Alzheimer’s Disease (2025) reported eating healthily is linked to reduced hearing loss as well as cognitive impairment.

The question that many people will ask is: if I get my hearing corrected, will that reduce my risk of developing dementia? The answer is not clear-cut. The world’s first clinical trial, published in the Lancet in 2023 to investigate whether hearing devices delayed the onset of dementia, did not find a significant difference overall.

But for a subgroup who were more susceptible to dementia because of age, education level, income, smoking status and underlying health conditions, hearing aids substantially reduced dementia risk.

While experts continue to argue over the degree to which using a hearing aid protects against onset of dementia, there are other very good reasons to wear one.

Whether you are a musical virtuoso or a sixty-plus individual just trying to manage your day-to-day life and enjoy the company of family and friends, making sure your hearing is as good as it can be will help you to hear the rustling leaves, the whisper in the wind and almost every other aspect of your day.

Dr Catherine Conlon is a public health doctor in Cork.

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