- In recent years, scientists have explored how hearing loss may influence dementia risk.
- A new study has found that those with hearing loss who don’t wear hearing aids are significantly more likely to face dementia.
- The exact link between hearing loss and dementia is still unclear, and research is ongoing.
It’s estimated at least 7 million US adults over 65 have some form of dementia. This figure is anticipated to increase to almost 12 million within 20 years.
Various factors are thought to increase an individual’s risk of developing dementia — including hearing loss.
In a new study published in The Lancet Public Health, researchers in China have further explored the relationship between dementia and hearing loss, along with approaches to help protect against disease onset.
They found that those with hearing loss who did not use hearing aids had a significantly higher risk of dementia than those who did wear such devices.
The potential risk of not using hearing aids
To explore how hearing aids may impact dementia, the researchers analyzed data relating to almost 438,000 UK individuals.
Information was retrieved from the UK Biobank, a database comprising in-depth health and genetic data of almost half a million people.
Of those analyzed, one-quarter (111,822) experienced hearing loss — and, among this group, just 13,092 individuals (12%) wore a hearing aid.
After reviewing the data, the researchers discovered that those with hearing loss who did not use hearing aids had a 42% greater chance of developing all-cause dementia.
Meanwhile, no increased risk was found for those with hearing loss who did wear hearing aids.
This was somewhat unexpected, stated Dr. Fan Jiang from the Centre for Health Management and Policy Research at Shandong University, China, and lead author of the study.
“What surprised me is that those who used hearing aids were as likely to get diagnosed with dementia as someone who had perfect hearing,” he told Healthline.
The researchers arrived at these outcomes even after accounting for other factors that can contribute to dementia. Fan revealed they “also conducted extensive sensitivity and interaction analysis to test the robustness of our findings.”
The findings from the new research are significant, said Fan.
“Our study provides the best evidence to date to suggest that hearing aids could be a minimally invasive, cost-effective treatment to mitigate the potential impact of hearing loss on dementia.”
How hearing loss and dementia are linked
Previous research has affirmed the link between dementia and hearing loss. But exactly how are the two associated?
Unfortunately, “the precise link is still unclear,” said Dr. Adam Kaufman, an otolaryngologist at the University of Maryland Medical Center and assistant professor at the University of Maryland School of Medicine, Department of Otorhinolaryngology-Head & Neck Surgery.
However, research is ongoing, and scientists and doctors have several hypotheses.
1. Sensory deprivation
The first is that hearing loss leads to sensory deprivation, which has large-scale impacts.
For instance, Kaufman told Healthline, this includes “structural changes within brain regions like the hippocampus.” The hippocampus is crucial in memory and learning.
“These structural changes can reduce cognitive reserve and, by extension, lead to a decrease in dementia resiliency,” he said.
Auditory stimulation is vital, agreed Dr. Anna Nordvig, a neurologist and assistant professor of neurology at the Memory Disorders Clinic at NewYork-Presbyterian/Weill Cornell Medicine.
“Full hearing capacity increases the range of input into the brain’s superior temporal lobe — and the temporal lobe is the memory hub,” she shared with Healthline.
“Variety is said to be the spice of life, [and] auditory variety is a necessary spice for the active brain.”
2. Cognitive pathways
It’s thought neurons and pathways related to hearing and cognition could be related.
One explanation “proposes an interaction between altered brain activity in the medial temporal lobe during difficult listening and the organic pathology of Alzheimer’s causing alterations in the brain,” said Dr. Oliver Y. Chin, an otolaryngologist at Houston ENT & Allergy.
When neurons and pathways relating to hearing aren’t stimulated, our cognitive abilities may be impacted.
“If you’re not stimulating central neurons in the auditory pathway, then [you’re not] getting the peripheral stimulus to keep those neurons healthy for cognition,” said Dr. Courtney Voelker, a board-certified neurotologist and director of the Adult & Pediatric Cochlear Implant Program at Pacific Neuroscience Institute at Providence Saint John’s Health Center.
She explained that cells can ‘atrophy’ (die) when unused. Brain cell death has been linked to dementia onset and symptom acceleration.
3. Cognitive load
The final theory relates to the brain being ‘overworked’ by hearing loss.
“For people with hearing loss, the brain is working ‘overtime’, if you will, trying to hear and make sense of what is being said,” explained Dr. Jim Jackson, professor of medicine at Vanderbilt Medical Center and author of Clearing the Fog: From Surviving to Thriving with Long Covid – A Practical Guide.
As a result, he told Healthline, there aren’t enough resources to go around and “other cognitive systems suffer.”
The delay between hearing loss and dementia
Age-related hearing loss can begin in a person’s 40s, yet most dementia diagnoses occur in those aged 65 and over. If the two are related, how can this large ‘time gap’ be accounted for?
A key area that needs to be explored to help explain this, said Voelker, is linked to neuron atrophy, especially those used in hearing.
“Over the years, if these neurons become unhealthy in the brain, that may be linked to cognitive decline,” she stated — “and that’s probably not an overnight process.”
Jackson agreed the delay is likely a result of an accumulative process.
“It may be [that] hearing loss must be of a certain severity before it starts to increase the risk of cognitive decline, and this threshold isn’t typically met until old age,” he said.
What causes hearing loss?
There are three types of hearing loss, each having different causes, said Dr. Ana Kim, an otolaryngologist and associate professor of Otolaryngology-Head & Neck Surgery at Columbia University Irving Medical Center.
- Conductive hearing loss. “This is caused by any anomaly involving the outer (external auditory canal) and middle ear (ear drum, middle ear space, and hearing ossicles) that interfere with sound conduction to the inner ear (cochlea),” she told Healthline.
- Sensorineural hearing loss. “This is [caused by] nerve loss, affecting the cochlear hair cells or the hearing nerve,” Kim shared.
- Mixed hearing loss. This form involves components of both conductive and sensorineural hearing loss.
Whether dementia causes hearing loss “remains hotly debated,” Kim noted. But how might dementia impact hearing loss?
“If dementia results in compromised higher-order cognitive function, then hearing loss can result,” she explained.
“While the ears pick up sound and act as the initial entry portal, the brain is ultimately in charge of eliminating background and unnecessary signals so that speech and words are clear and meaningful.”
The use of hearing aids
A large number of those with hearing loss do not wear hearing aids. But why?
“The most common reason is that the patient is unsatisfied with the quality of sound they are receiving,” revealed Kaufman.
However, he noted that a trained audiologist could adjust the aid to meet the patient’s needs. For those who find hearing aids aren’t ‘enough’, cochlear implants are another option.
Another issue, explained Chin, is that “hearing aids are costly.” While some start at around $900, others can exceed $6,000 in price.
Two further reasons are related to social stigmas. For instance, “hearing loss is more associated with becoming older, and [people] don’t want to admit that,” Voelker said.
Many people think of hearing aids as unattractive and large, so avoid wearing them.
“But hearing aids have come quite a way,” Voelker shared. “We even have ones that sit completely in the ear, and you don’t see them.”
Kaufman added that social trends might help change attitudes towards hearing aids.
“The ubiquity of young people wearing devices in their ears, like AirPods, may be starting to break down the stigma of wearing things in your ear.”
Preventing hearing loss
For some, gradual hearing loss is genetic and unavoidable. However, whether you’re predisposed or not, it’s essential to be aware of environmental contributors.
To help reduce your risk of hearing loss, Voelker suggested wearing protective devices (such as earplugs) in loud places like concerts, places of worship, and even restaurants.
Not sure if somewhere is considered too noisy?
“You can download free decibel reader apps that tell you when noise is hazardous,” she revealed.
Be mindful of the sound level from devices such as earpods and TVs, said Kaufman. “These devices should be loud enough that you aren’t straining to hear them, but not so loud that you can hear them when you are not in their direct presence.”
Finally, said Chin, be aware of underlying health factors associated with hearing loss, “such as diabetes, hypertension, and hyperlipidemia.”
If you’re worried about your hearing, Chin recommended visiting your doctor. If necessary, they may refer you to an audiologist for testing or an otolaryngologist who can check for structural damage in the ear.
“We have treatments that are successful,” Voelker stated. “It’s just a case of getting the word out to patients to be proactive.”
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