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Getting older is hard.
Not only do your clothes go out of fashion and slang stops making sense,
but you could also lose your hearing and even experience cognitive decline.
And as it turns out, those two things might be related.
The hearing loss and cognitive stuff, that is.
Several studies show that there’s a link between hearing loss and dementia,
though scientists are still working to understand exactly what’s causing it.
While that sounds like it doesn’t bode well for the majority of elderly people
who experience some extent of hearing loss, this may be good news.
Because, while we don’t have a cure for dementia right now,
we do have treatments for hearing loss, so if hearing loss is a
contributor to dementia, we can do something to prevent it.
Now the term “hearing loss” refers to a process that happens to people who had
average hearing earlier in life, and experienced a decline in hearing as they aged.
This can come from all sorts of sources, like loud sounds
damaging your hearing cells, genetics making you more susceptible to
that sound damage, age-related brain cell deterioration,
and insufficient energy for hearing cells to function.
As it turns out, about two-thirds of adults
over 70 years old in the US experience hearing loss.
And that’s a lot of people!
And the extent of their hearing loss isn’t the same, either.
As with most things in life, hearing falls somewhere on a spectrum.
To get a measurement of the extent of someone’s hearing loss,
they can either fill out a questionnaire or take a hearing test.
The hearing test plays sounds at different intensities to
identify the range of sounds that the person can hear.
If the test results show that they can’t consistently hear sounds
softer than 25 decibels, then they’re considered to have
clinical hearing loss, although the exact cutoff can vary.
So everyone has a different cutoff volume where you can
no longer consistently hear sounds.
It’s called your pure-tone average, or PTA score.
The higher your score, the more severe your hearing loss.
If your PTA score is high enough for a formal hearing loss diagnosis,
then you might have the option to wear hearing aids to
increase the range of sounds you can detect,
making hearing aids an effective treatment for a common problem.
The trouble is, only 14% of the people who need them actually wear hearing aids.
Many people never even see a specialist for hearing loss,
thinking that cranking up their TV volume is just
another trivial part of getting older, just like a penchant for hard candies.
But we’re starting to learn that age-related hearing loss,
when untreated, could increase your risk for developing dementia.
A 2011 study from Johns Hopkins University found that
the risk of dementia was increased in people with age-related hearing loss.
Participants with average hearing had lower risk than those with mild hearing loss,
who had lower risk than participants with moderate hearing loss,
who had lower risk than those with severe hearing loss.
So that would suggest that the worse your hearing gets,
the greater your risk of dementia becomes.
And that’s not all.
A 2019 study out of Columbia and George Washington University
found that this effect isn’t limited to the most extreme cases of hearing loss.
The participants in this study that didn’t meet the clinical threshold for hearing loss
still showed cognitive declines compared to people without any hearing loss.
On average, participants with PTA scores between 1 and 10
scored higher on cognitive tests than participants with scores of 11 to 20.
So even a 10 decibel loss was significantly associated
with cognitive impairment across a variety of tests.
What’s more surprising is that this association is even stronger for participants
with PTA scores between 1 and 25 compared to those with scores above 25.
All this might be a sign that doctors should reconsider that clinical hearing loss
cutoff of 25 decibels so they could detect
and treat more subtle hearing loss that also affects your cognition.
That said, we probably can’t go update all the medical textbooks
with a new cutoff until we identify what a better threshold even would be.
And we still need more data to say that hearing loss
causes dementia in the first place.
What we’ve described so far are associations between hearing loss and dementia,
but it’s not clear if the hearing loss is actually causing the cognitive declines.
It could be a link in the chain that leads to dementia, though.
That 2011 paper pointed out that people who experience hearing loss
have to put more of their mental resources toward hearing,
which may leave fewer resources for things like memory.
On top of that, people experiencing hearing loss may be socially isolated
because communication becomes more difficult.
And there’s data linking social isolation with dementia.
So hearing loss could indirectly lead to dementia
by preventing communication and social interactions.
Or hearing loss and dementia could both be symptoms of some
other widespread problem like vascular disease.
Which would mean that hearing loss could be a red flag that dementia is brewing.
And there’s data to back up this red flag idea.
The 2011 study showed that people who developed dementia lost about
double the decibels of hearing per year compared to those who didn’t develop it.
But whether or not hearing loss causes those cognitive declines,
the big question is if there’s anything we can do about it.
If hearing loss is in some way responsible for people developing dementia,
then treating the hearing loss should prevent it,
which is where hearing aids come in.
But early research into this prevention technique wasn’t terribly promising,
showing no association between self-reported hearing aid use and dementia.
But those researchers didn’t design their experiment around hearing aids.
The 2011 study didn’t include any data on how often participants
wore their hearing aids, what kinds of devices they used,
or even if the participants were using the right device for their diagnosis.
And some scientists think it could take years for the effect of hearing aids to kick in.
So if people who just started wearing hearing aids were mixed in with people
who have been wearing them for years, the results would be harder to interpret.
So at that point there was a lot left to be understood
about the role of hearing aids in cognitive decline.
And, good news, other studies were already under way!
In 2018, a study that followed up with participants over 25 years concluded that
people who wore hearing aids were at lower risk of dementia.
Now, that study was based on how well the participants thought they could hear,
rather than performance in hearing tests.
And while that metric is correlated with hearing test outcomes,
it’s not quite as empirical as tests that define their exact decibel loss.
So the perfect experiment hasn’t been conducted yet.
But none of the studies conducted so far say that
using hearing aids is worse than not using them.
And dementia still isn’t reversible, so if hearing loss is causing dementia,
raising the hearing loss threshold and
actually implementing the treatments available could change lives.
It’s a testament to modern medical research that
we’re starting to figure out this relationship.
And you heard it here first.
If you’re still watching at the end of this video,
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