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Does hearing loss cause dementia?

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Does hearing loss cause dementia?

Over recent years more and more media coverage has been seen talking about the link between hearing loss and dementia. Some hearing aid providers even promote their devices based on this media coverage.

Understandably, this can provoke fear or anxiety that if you don’t get hearing aids, you will end up with dementia.

But what does the research say, and why is there an increased focus on this link in recent times?

Dementia statistics

What is dementia?

Before we begin, it’s good to understand what dementia is and isn’t. Dementia is not a specific disease, but several diseases can cause dementia, including Alzheimer’s – the most common cause of progressive dementia.

Dementia is a general term describing symptoms affecting brain function, including your memory, ability to think, and the ability for social interaction.

You may be surprised and horrified to know that end-stage dementia is one of the leading causes of death in the Australian population.

According to Dementia Australia, in 2021, an estimated 472,000 Australians are living with dementia. By 2028 that number is expected to increase to 590,000 and over 1 million by 2058.

Dementia in Australia

  • The second leading cause of death in Australia
  • Leading cause of death for women
  • The third leading cause of death for men
  • 250 people per day diagnosed with dementia
  • 3 in 10 over 85 have dementia
  • 1 in 10 over 60 have dementia
  • 36 people per day die of dementia as the underlying cause
  • In 2018 the cost of dementia to Australia was $15 billion and increasing
  • 52% of aged care residents have dementia

Dementia around the world

  • Dementia affects almost 50 million people worldwide, which is predicted to increase to 131.5 million people by 2050
  • Every three seconds someone in the world develops dementia
  • Two out of three people globally believe there is little or no understanding of dementia in their countries
  • The total estimated worldwide costs of dementia were US$818 billion in 2015
  • If dementia were a country, it would be the world’s 18th largest economy

What are the early symptoms of dementia?

Dementia symptoms start subtly and can be hard to spot initially. Keep an eye out for the signs below to recognise dementia as early as possible.

  • Progressive and frequent memory loss, especially related to recent events
  • Signs of confusion increasing over time
  • Personality or behavioural changes
  • A reduction in the ability to focus or concentrate
  • Apathy, withdrawal or depression
  • Loss of ability to perform everyday tasks.

Keep in mind that displaying some or all these symptoms may not necessarily indicate dementia, but it is best to investigate and identify the causes as early as possible.

What causes dementia?

Since dementia is not a specific disease, the symptoms of dementia can be caused by several different disorders, the most common of which is Alzheimer’s disease.

Other causes include:

  • Vascular dementia
  • Parkinson’s disease. Dementia is common in people with this condition.
  • Dementia with Lewy bodies
  • Frontotemporal dementia
  • Severe head injury
  • Huntington’s disease
  • Leukoencephalopathies
  • Creutzfeldt-Jakob disease
  • Some cases of multiple sclerosis (MS) or amyotrophic lateral sclerosis (ALS).
  • Multiple-system atrophy
  • Infections such as late-stage syphilis
  • Inherited dementia

It’s important to remember there are several causes of dementia, and depending on the cause, some symptoms may be reversible.

dementia statistics 2

The link between hearing loss and dementia

Looking at the causes above, we don’t see ‘hearing loss’ listed explicitly as a cause of dementia. So how has hearing loss been connected to dementia, and why are some organisations touting hearing loss treatment as a preventative measure for dementia?

While a tenuous link between hearing loss and dementia was suggested as far back as the late 1980s, it was a 2020 report in The Lancet that really put the link in the spotlight.

The document Dementia prevention, intervention, and care: 2020 report of the Lancet Commission highlighted 12 things (risk factors) that people could modify that might prevent or delay up to 40% of dementias.

One of those things was encouraging hearing aid use for hearing loss and reducing hearing loss by avoiding excessive noise exposure.

This key message was reported by media organisations worldwide and picked up and amplified by hearing aid manufacturers and resellers.

Before we go any further, it is important to understand that this risk factor was just one of many that could potentially reduce the likelihood of developing dementia over time. The researchers also identified at what life-stage risks should be addressed to have the most significant impact on dementia outcomes.

These modifiable risk factors and life-stages are:

  • Attain a high level of education (Early Life)
  • Treat hearing impairment (Midlife)
  • Minimise diabetes (Later life)
  • Treat hypertension (Midlife)
  • Prevent head injury (Midlife
  • Reduce midlife obesity (Midlife)
  • Avoid excessive alcohol (Midlife)
  • Stop smoking (Later life)
  • Reduce air pollution (Later life)
  • Maintain frequent exercise (Later life)
  • Reduce the occurrence of depression (Later life)
  • Maintain regular social contact (Later life)

While treating hearing impairment is just one of the 12 modifiable risk factors, it was ranked as the highest modifiable risk out of the 12 at 8%. The next closest was smoking at 5%.

If all risks were modified or eliminated, it could reduce the risk of dementia by 40%.

dementia statistics

What does research about dementia and hearing loss actually say?

Research has come to light that is strong enough for the writers of the Lancet report to include hearing loss as one of the risks for dementia. And what was once a tenuous link appears to be getting stronger and stronger.

A recent study of over 382,000 participants in Korea found that for those over 65 with severe or profound hearing loss, the likelihood of getting dementia increased by 1.3 times.

Their results showed that for those under 65, with severe or profound hearing loss, the risk was greater at 1.6 to almost two times the likelihood of developing dementia.

In a review and analysis of research studies related to the link between dementia and hearing loss carried out in 2018, researchers found “age-related hearing loss was significantly associated with decline in all main cognitive domains and with increased risk for cognitive impairment and incident dementia.”

The researchers analysed 36 different studies and over 20,000 unique participants and found the studies confirmed that age-related hearing loss is a possible modifiable risk factor for cognitive decline.

Another study in the UK published in 2021 looked at the association between speech-in-noise (SiN) hearing impairment and the increased risk of incident dementia.

This study was an interesting deviation from other research as studies have previously focused on pure-tone audiometry for measuring hearing loss associated with dementia. People who suffer from a speech-in-noise impairment may present as normal hearing when tested using just pure-tone tests.

The study looked at over 82,000 dementia-free patients 60 years or older. Over 11 years, researchers followed these participants and, by the end of the study, concluded that out of the 1,285 participants who developed dementia, 61% had an increased risk of dementia due to SiN hearing loss.

They stated: “SiN hearing impairment is independently associated with incident dementia, providing further evidence for hearing impairment as a potential modifiable dementia risk factor.”

These are just a few of the studies highlighting the association between untreated hearing loss and the incidence of dementia. A quick Google search for scholarly articles on “hearing loss and dementia” brings up over 157,000 results, with over 6,200 of those being made available in 2021 alone.

Correlation vs Causation

We do have to be careful with this kind of research, of course. While there certainly appears to be a correlation between hearing loss and dementia, some researchers point out that we still don’t know if correlation equals causation in this case. Even the Lancet report was hesitant, stating only that: “Hearing loss might result in cognitive decline through reduced cognitive stimulation.”

While it is much harder to prove causality in human subjects, some research has been conducted in animal subjects that shows a relationship between induction of hearing loss and cognitive decline. However, the researchers were not willing to state that the hearing loss was the sole cause of the cognitive decline or enough to trigger an ongoing degenerative process such as Alzheimer’s.

What do we know?

We know it appears from studies that there is a stronger and stronger correlation between hearing loss and dementia. Some studies show that this correlation is more substantial depending on the severity of the hearing loss and the age at which the hearing loss presented itself.

We also know that, along with treating hearing loss, other modifiable risks, like social interaction and depression, can also be affected by hearing loss. It has long been established by studies of people suffering from hearing loss that untreated hearing loss can lead to greater social isolation and depression.

So in effect, this means that by diagnosing and treating hearing loss early, we can effectively help modify three of the risk behaviours listed in the Lancet report. These three risk factors alone accounted for 16% of the 40% increased risk attributed to the 12 risk factors identified above.

Hearing aids and dementia

Here’s what we also know thanks to the Lancet report mentioned previously:

  • A 25-year study of 3,777 people aged 65 years or older found increased dementia incidence in those with self-reported hearing problems except in those using hearing aids.
  • Another study found hearing loss was only associated with worse cognition in those not using hearing aids.
  • A survey of 2040 people older than 50 years, tested every two years for 18 years, found immediate and delayed recall deteriorated less after initiation of hearing aid use, adjusting for other risk factors.
  • Hearing aid use was the largest factor protecting from decline.

The Lancet researchers stated that the long follow-up times in these prospective studies suggest hearing aid use is protective, rather than the possibility that those developing dementia are less likely to use hearing aids.

What would we recommend?

It seems to us that there is enough evidence now available that shows the benefit treating hearing loss can have in relation to the risk factors of dementia.

Add to that the benefit better hearing can give to the overall quality of life and the case is even clearer. We would encourage anyone to seek testing and treatment for hearing loss the moment they (or their family members) realise that their hearing is not as good as it has been.

The Australian Government provides free testing and quality hearing devices to eligible pensioners through their Hearing Services Program. The program is delivered through thousands of audiologists throughout the country so you can find one you trust close to you.

If you suspect you have hearing loss, get yourself tested today.

 

Main image by pch.vector

 

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