Nearly 50 million people in the world suffer from dementia, the term for the chronic decline in mental abilities — such as thinking, remembering and reasoning — that affects many as they age. About 5.7 million cases are in the United States, and it’s a number that is expected to rise.
Another prevalent chronic condition is hearing loss, which affects more than 9 million Americans over the age of 65 and 10 million Americans ages 45 to 64.
Research over the years has shown a strong link between hearing loss and dementia. Seniors with hearing loss are significantly more likely to develop dementia over time than those who don’t lose their hearing, according to studies by Johns Hopkins and National Institute on Aging researchers.
While there’s no evidence that hearing loss causes dementia, having hearing loss can increase the risk of developing dementia by up to five times, according to Dr. Bethany Tucker, an audiologist with Colonial Center for Hearing in Williamsburg, Va. The risk increases with the severity of hearing loss.
We don’t know if one causes the other, and we certainly cannot say that if you have hearing loss you will get dementia,” Tucker says.
Nevertheless, studies show the link exists.
Research shows that the link may have something to do with the way the brain works. If hearing loss is present, straining to hear may overwhelm the brain, requiring more mental energy just to hear normal conversations. That could mean less energy to devote to memory, understanding and other cognitive functions. Brain activity changes.
“When we hear something, even just a sound, the temporal lobes are active,” Tucker says. “If there is hearing loss present, those temporal lobes are not getting activated the way that they should be.”
The temporal lobes are the area of the brain where hearing is processed. They are also involved in vision, sensory input, language, emotion, comprehension — and in housing memories. If areas of the brain aren’t being activated the way they should be, they shrink.
“Everything is connected; our body works as a system. If one area — one of our main senses — starts to decline, there’s certainly going to be repercussions in other areas,” Tucker explains. “When dementia is present, it is very important to have the person’s hearing tested. We need to diagnose the hearing loss, properly fit that loss with hearing aids and provide the stimulation to the brain again. By aiding that loss, those areas of the brain will be stimulated again and, hopefully, reactivate.”
A 2015 study by Dr. Isabelle Mosnier, a researcher at Assistance Publique-Hopitaux de Paris, showed a definite link between aiding hearing loss and cognitive function. Nearly 100 people over age 65 with deafness in at least one ear were fitted with a cochlear implant, which stimulates the auditory nerve with electricity. After a year, 80 percent showed cognitive improvement. They also reported less depression — a symptom that is common in those with dementia and hearing loss.
While having hearing loss doesn’t automatically mean someone will develop dementia, research does indicate that doing something to minimize hearing loss could prevent or delay the onset of dementia — or perhaps lessen the severity. As it stands now, one out of every six women and one out of every 10 men living past the age of 55 will develop a form of dementia, including Alzheimer’s disease.
The bottom line? Having hearing loss addressed as soon as it starts is important.
“A lot of people ignore hearing loss because it’s such a slow and insidious process as we age,” says Dr. Frank Lin, the leader of the Johns Hopkins studies who is still researching the issue. “Even if people feel as if they are not affected, we’re showing that it may well be a more serious problem.”
Ways hearing loss may lead to dementia
- The constant effort to hear may stress the brain to the point that less energy is given to functions such as memory and understanding.
- Certain parts of the brain that affect hearing can shrink when they don’t get enough stimulation.
- Being hard of hearing often leads to social isolation, which is a risk factor for cognitive decline and depression — another common risk associated with hearing loss.
- On-going research points to a possible common physiological pathway, such as high blood pressure, that contributes to both hearing loss and dementia.
