Hearing Loss & The Risk Of Dementia

Dementia is the fourth leading cause of death in the US and Europe1.

A fact that most people are unaware of.

When considering major preventable diseases, we focus most of our attention on cardiovascular disease and cancer.

Additionally, most people are unaware that 40% of dementia cases are preventable and attributed to modifiable risk factors2.

Thankfully with a focus on optimising cardiovascular risk factors, the risk of dementia also decreases.

But there are other factors that are not related to cardiovascular disease that also play a role in dementia risk.

Hearing loss is one of them.

Reduced hearing is an underappreciated modifiable risk factor for dementia3.

More than 60% of adults over 70 years of age have some degree of hearing loss4.

What might be more concerning, however, is that by 45 years of age, 26% are impacted by some degree of hearing loss5.

With an average lifespan of close to 80 years, that is multiple decades of reduced hearing ability.

And we know that it takes its toll.

Those with hearing loss are 42% less likely to report a high quality of life compared to those without hearing loss6.

Reduced hearing loss has been associated with a range of adverse outcomes, including:

• Reduced social and emotional interactions

• Loneliness

• Isolation

• A decline in social activities7

Those with reduced hearing are often reluctant to seek help and can struggle for years without assistance8.

Hearing loss has also been linked to greater amounts of vascular disease9.

In addition to the near-term reductions in quality of life, hearing loss has also been linked to the earlier onset of dementia.

Some studies suggest a relative increase of 90% compared to those without hearing impairment10.

Hearing loss accounts for just over 20% of the modifiable risk factors for dementia11.

It is very clear that hearing loss is common in both young and old and is associated with a reduction in quality of life metrics, vascular disease and also dementia.

What can be done?

Multiple studies have investigated the use of hearing aids to reduce the likelihood of dementia.

Some of these studies showed benefits, while others did not.

However, when all of these studies are pooled together in what is called a meta-analysis, the results would seem to favour a reduction in dementia with the use of hearing aids compared to those without hearing correction.

Looking at the data in aggregate, there is a 19% reduction in the incidence of any cause of dementia12.

 

Importantly, these studies were adjusted for the potential confounders of age, sex, level of education, socio-economic status and other comorbidities such as high blood pressure.

The benefit of hearing aids also extended to conversion from mild cognitive impairment to dementia.

In those with documented cognitive impairment, the use of hearing aids resulted in improved cognitive scores, but the benefit was modest.

Quality of life improvements

In addition to the potential reductions in dementia onset with hearing aids, several quality-of-life metrics have been shown to improve.

These include:

• Less anxiety

• Less depression

• Improved quality of life

• Less emotional & social consequences

The question of, why?

Although it is clear that reduced hearing ability is associated with higher rates of dementia, the question remains as to why this is so.

Initial theories proposed a common link between the onset of dementia and hearing loss, but results of the hearing aid studies would tend to refute this hypothesis as correcting the hearing loss in isolation would be unlikely to improve the processes driving the dementia.

Cognitive Load Hypothesis. 

Those with a hearing impairment that is not corrected tend to have worse recall abilities and worse secondary task performance13.

The rationale is that when hearing ability is reduced, a greater cognitive effort must be made to overcome this loss in function.

Consequently, capacity that would typically have been devoted to higher-order tasks such as executive function and memory encoding is reduced.

Over time, this reduced allocation may have the downstream effect of resulting in lower cognitive function and, ultimately, dementia.

The use of hearing aids might theoretically free up cognitive ability for higher-order task functions in the brain.

Sensory Deficit Hypothesis. 

Uncorrected hearing loss is associated with atrophy and reduced brain volumes in areas of the brain involved in hearing function, particularly the right temporal lobe.

Prolonged reductions in activity and the resultant atrophy that follows may explain why those with hearing loss are at risk of future cognitive decline.

Very much a ‘use it or lose it’ phenomenon.

Social Isolation.

Multiple studies have demonstrated that those with hearing loss are at higher risk of social isolation.

Those with reduced hearing abilities often find it more challenging to interact socially and can withdraw from social encounters over time.

Social isolation is an important driver of dementia, and its impact is often under appreciated14.

The factors driving the relationship between impaired hearing and dementia are likely to be multifactorial.

But what is essential for now is that we recognise the link and consider hearing augmentation sooner rather than later.

While hearing assessments are commonplace for those over 65 years of age, I would argue that we should consider more routine screening in much younger adults, given its prevalence.

The relationship between hearing loss, quality of life and dementia is clear, and for once, we have a straightforward and non-invasive method of addressing it.

I hope this message is loud and clear.

Because if it’s not?

Then you know what to do.