Hearing loss is now known to be a potentially preventable cause of dementia, and research is building the case for hearing aids as one of the stronger tools to protect against it. One study from Johns Hopkins, for example, followed more than 600 adults for 12 years and found that mild hearing loss doubled the risk of dementia. Moderate hearing loss triples someone’s risk of dementia, and severe hearing loss increases the risk fivefold.
For the millions of adults with hearing loss and the estimated 150 million worldwide who will be affected by dementia by 2050, disentangling the link between hearing loss and dementia becomes imperative.
Dementia is a general term for a person’s inability to think, communicate and remember things clearly, affecting their mood, personality and behaviour. There are various causes, but the most common disease that leads to dementia is Alzheimer’s. The risk of dementia also increases with age, as does the risk of hearing loss.
About a third of older adults have hearing loss, so when hearing aids became available over the counter last fall, many medical and public health experts celebrated. Not only are OTC hearing aids generally less expensive, but fewer appointments and easier access mean more people will maintain oral language, a bridge to communication and cognition – our ability to think.
“Language and cognition are two different processes, but they are highly interdependent,” Brooke Hatfield, associate director of speech-language pathology health services at the American Speech-Language-Hearing Association, said in an email. “Language serves as an internal framework for reasoning, problem solving, memory, and other thinking skills.”
Here’s what we know about hearing loss, hearing aids and cognition.
Hearing loss and dementia
According to the Cochlear Center for Hearing and Public Health, a branch of the Johns Hopkins Bloomberg School of Public Health, hearing loss accounts for the largest number of “potentially preventable” cases of dementia. This compares with other factors that may influence dementia risk, such as high blood pressure and lower education, the latter of which may be due to socioeconomic challenges and other factors.
Researchers believe that hearing loss has this effect because of the way it stops sound from entering the brain. If someone has difficulty hearing, their brain will have to work harder to understand sound, potentially speeding up the aging process in the brain and limiting the way a person can think and remember things, according to a fact sheet from the Cochlear Center.
Losing the ability to hear the people around you also limits your communication and connection with them, which can lead to social isolation—an existing public health problem among older and older adults. Social isolation has been found to be associated with an approximately 50% increased risk of dementia and other health problems, according to the US Centers for Disease Control and Prevention.
Taken together, the different theories about hearing loss and dementia can also be a chicken-or-the-egg scenario, according to Hatfield. She pointed to research that suggests hearing loss is a marker of changes in the brain that are already underway, as opposed to changes that come from hearing loss.
Not everyone who has hearing loss develops it over time, however, and the risk of dementia does not appear to be the same for people with lifelong deafness. According to the UK-based charity Social Care Institute for Excellence, people born deaf who use sign language to communicate do not appear to have an increased risk of dementia compared to the general population.
But Hatfield adds that there is some concern about diagnosing dementia in patients who are deaf because of the limitations of the tests, as well as the provider’s lack of experience working with people in the deaf community. But there may still be a “protective factor” to staying engaged in communication and avoiding social isolation when it comes to dementia risk.
“The relationship with dementia and hearing loss seems to be related to having a history of hearing that changes and so the brain changes in response, rather than being related to the act of hearing itself,” Hatfield added.
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Can hearing aids protect against dementia?
The available research says yes.
A study published last month in The Lancet found that people with hearing loss who also use hearing aids I was not have an increased risk of dementia compared to people without hearing loss. Researchers in the study used data from the UK Biobank to look at the health records and dementia diagnoses of a large group of adults aged 40 to 69 from England, Scotland and Wales.
If the “causal relationship” is established through more research, the study authors wrote, hearing aids would “represent a minimally invasive, cost-effective intervention for mitigating all or at least some of the effect of hearing loss on dementia.”
A large systematic review from February also adds to the evidence that hearing aids for people who need them can help prevent the risk of cognitive decline. The review looked at studies of hearing aid use in people with hearing loss, finding that the use of “hearing restoration devices” was associated with a 19% reduction in the dangers of long-term cognitive decline.
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How quickly can a hearing aid help?
The average time someone waits to receive treatment for hearing loss – which in many cases is a hearing aid – is seven to nine years. But like other medical conditions, the sooner someone with hearing loss seeks treatment, the better the outcome, according to Bria Collins, associate director of audiology practices at ASHA.
“The longer someone who communicates through spoken language waits to seek treatment, the more difficult it can be to adjust to hearing speech and environmental sounds again,” Collins said in an email. Think of hearing and language as a muscle we need to exercise, like a runner who runs a few miles each week, she explains. If a runner takes a long break from exercise, she “will not be at the level of athletic performance she was at when her muscles/endurance were used to exercise.”
How long it takes for someone to regain language or performance after getting a hearing aid varies, Collins says. For example, there is evidence that the brain adjusts to having a hearing aid after about four weeks. And while many people feel relief from “listening fatigue” almost immediately in situations where they are watching TV or having a private conversation, they will usually need more time to adjust to more “challenging” listening environments, that require more discernment, such as restaurants, bars or a busy family gathering.
It also depends on how long someone has been deaf and the severity of their hearing loss – going from being very hard of hearing to being thrown into a world full of sound can be jarring for some patients. That’s why audiologists can gradually adjust patients’ hearing aids, Collins explains, so patients aren’t overwhelmed. (This is one known downside to over-the-counter hearing aids and how they can fall short compared to prescription hearing aids that are fitted by a professional.)
“In short, there is no specific amount of time that the brain needs to adapt to reinforcement,” she said. “There is a lot of individual variability.”
Read more: 5 signs you should get tested for hearing loss