Hearing & Brain Health
This isn't anything new!
We have known about the link between hearing and cognition for more than three decades. In the last five years or so, the connection between the two has received significant media attention and is often referenced in hearing aid advertisements.
I'm going to break down what we know about the link between hearing loss and cognitive loss and, more importantly, what we know about how the relationship actually works.
Much of the recent thinking about hearing health and cognitive health stems from research studies led by
Dr. Frank Lin at Johns Hopkins University; the facts below are based on Lin's studies.
Here's what we know...
Compared to age-matched people with normal hearing:
24%
People with hearing loss tend to have poorer cognitive function
They have a 24% increased risk of cognitive impairment.
2×
People with hearing loss are more likely to have a diagnosis of dementia
The risk of dementia increases with the severity of the loss, though even a mild loss doubles the risk.
3 yrs
The cognitive abilities of people with hearing loss deteriorate faster
They develop cognitive issues an average of three years sooner.
What explains this?
While the relationship is complex and there are undoubtedly common causal factors (e.g. age-associated factors likely affect both auditory and cognitive mechanisms), there are three key ways in which we think hearing affects cognition.
Hearing loss could affect cognition directly by causing permanent changes to the brain due to reduced auditory stimulation of neural pathways.
- Neuro-imaging studies show that hearing loss is associated with significant reductions in brain volume.
- Hearing loss is associated with increased rates of atrophy in the temporal lobe and reduced activity in the auditory pathways.
When a hearing loss is present, greater cognitive resources are dedicated to auditory processing / effortful listening:
- If too much of a person's "cognitive budget" is spent on listening and straining to hear, less cognitive resources are available for other cognitive processes, such as memory, reasoning, etc.
- Neuro-imaging studies find increased compensatory neural activity in the prefrontal lobe of hearing loss sufferers, suggesting the brain is working harder to overcome hearing loss.
Communication difficulties caused by untreated hearing loss can lead to social withdrawal and isolation.
- If a person stops doing the activities they used to do (going to church, playing bridge, socializing with friends and family, etc.) because these activities are too difficult to navigate with hearing loss, this isolation may accelerate cognitive decline.
- Studies show social isolation is associated with reduced cognitive performance and increased risk of dementia.
What's the Recommendation?
Back in 2017 a large meta-analysis published in The Lancet medical journal defined hearing loss as a "modifiable risk factor" for dementia and suggested that the management of hearing loss could contribute to the prevention or delay of dementia.
- Hearing loss, due to its prevalence, was found to have the highest contribution of all modifiable risk factors (9%).
- As a result, addressing hearing loss is the single most important recommended mid-life lifestyle change to prevent dementia.
How might treating hearing loss help?
While there is currently no hard evidence that wearing hearing instruments can ameliorate cognitive decline or delay the onset of dementia, hearing aids:
- increase auditory stimulation and keep auditory neural pathways active (it's like exercise for the auditory cortex);
- reduce the "cognitive load" or listening effort needed to compensate for a hearing loss, which frees up more cognitive resources for processing what is being said and encoding it to memory;
- improve communication and promote social interaction and engagement, which can reduce social isolation.
💡 In addition, it is well-documented that the treatment of hearing loss with hearing instruments increases quality-of-life and well-being!
At the end of the day...
There are many good reasons to address hearing difficulties and here are a few to add to the list:
- We know definitively that hearing health is related to cognitive health and hearing loss is related to cognitive decline;
-
Management of hearing loss is now recommended as a potentially preventative measure against dementia;
- Hearing health is a key component of healthy aging.
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