Hearing Loss and Cognitive Disorders
Hearing loss doesn’t just affect a person’s ability to hear: an extensive library of evidence also suggests that it can have a profoundly negative impact on cognitive function.
Our brains, it appears, work on a “use it or lose it” basis. We need the stimulation of our senses to keep certain brain regions active. If those senses are interrupted for whatever reason, the brain becomes less active, we develop fewer neural connections, and certain parts begin to lose function.
Hearing is a particularly important sense for brain stimulation. Just the act of engaging in conversation with another person recruits multiple parts of the brain, helping older adults to build their cognitive reserve and buffer against degenerative neurological disorders, like Alzheimer’s.
The evidence for the connection between hearing loss and cognitive decline
Hearing loss and cognitive decline may appear to be separate conditions, but there is now substantial evidence of a close link between the two. A meta-analysis which pooled the results of eleven studies on the connection in 2018, found that cognitive decline was strongly associated with deteriorating hearing function in older adults. Those with moderate hearing loss had a 29 percent greater chance of suffering from cognitive decline at the six-year follow-up, while those with severe hearing loss had a 321 percent greater chance of developing impairment.
Dementia and other cognitive disorders develop well before symptoms become apparent. Like so many diseases of aging, cognitive disorders often take decades before pathology emerges. Because it’s currently impossible to reverse the damage done by these diseases, most medical practitioners recommend that people take steps today to reduce their risk.
Current research focuses mostly on the vascular changes that lead to dementia and other conditions that produce cognitive impairment. Data suggests, however, that around 35 percent of all cognitive decline is lifestyle-related. Drinking, smoking, getting too little exercise, and eating a poor diet can all contribute to a person’s risk of developing a cognitive disorder. Hearing loss is also a factor, accounting for more the 9 percent of the total risk.
How hearing loss impacts the brain
When auditory signals enter the brain, they interact with it in several ways. Not only do they stimulate the unconsciously-active auditory cortex - the part of the brain which creates the experience of sound - but also other vital areas, such as the memory centers. People remember the sounds that they hear and what others say to them.
Thanks to better imaging technology, researchers can now peer into the brain and see what parts of the brain are affected by hearing loss, besides the auditory cortex. What they’ve found is that hearing loss appears to result in a generalized decline in activity across the brain and an accelerated loss of brain volume.
Why does this happen? Part of the answer appears to lie in social isolation: people with hearing loss tend not to want to interact with others as much as those with normal hearing. This isolation, in turn, prevents a person from using brain regions activated on social occasions.
The effects of hearing loss can be insidious. A person may start by skipping just one or two social occasions a month, but over time, miss more and more. Before long, their social life has evaporated, all because of their hearing loss.
So far, there isn’t conclusive evidence that interventions, such as wearing a hearing aid, help people to avoid cognitive decline despite the “observational” data we have so far strongly suggests a connection. What’s needed is a test that randomizes people into wearing hearing aids or not and then follows them over time to see who gets dementia and who doesn’t. No such study has been done.
A new study on the horizon
The good news is that The Cochlear Study says that it is currently surveying more than 850 adults with mild hearing loss to compare those who wear hearing aids with those who don’t. Results will arrive in 2022.
So what do we know so far? The evidence we have suggests that there is a link between hearing loss and cognitive disorders, and we are likely to get data soon, which shows that hearing aids are protective. In the meantime, there are plenty of benefits of choosing to use hearing aids, besides preventing cognitive decline, including improvements in your quality of life and managing tinnitus.