Hearing Loss and Dementia: Are They Connected?
Age-related hearing loss can impact so many aspects of life, from participating in conversations to enjoying entertainment to maintaining one’s balance. But, say experts, difficulty hearing may also play a role in cognitive decline—a term that encompasses dementia, a group of progressive, irreversible conditions that cause memory disorders, personality changes and impaired reasoning.
This represents a significant risk for America’s aging population, given that one in three adults between the age of 65 and 74 have hearing loss, according to The National Institute on Deafness and Other Communication Disorders (NIDCD. To keep you informed, here is the important news that experts shared with Hearing Tracker.
The Hearing-Loss Link
One critical study was published in February of 2019 by University of California San Diego researchers; it reviewed the presence of hearing impairment and cognitive decline in 1,164 people for at least 20 years. Adult subjects who did not wear hearing aids were first assessed between 1992 and 1996 for their cognitive function and hearing; they were evaluated up to five more times over the years. At the end of the study, 49.8 percent had mild hearing loss and 16.8 percent had moderate to severe hearing loss.
Participants with age-related hearing loss experienced cognitive decline at a faster rate – up to around seven years sooner – than those with normal hearing, says co-author Dr. Linda McEvoy, professor at UC San Diego's Center for Life Course and Vulnerable Population Research. “People with mild hearing loss were showing a steeper decline [than those without hearing loss], and those with more severe hearing loss were showing [a] more severe decline,” she told Hearing Tracker. “Having a deficit of seven years would mean that someone at age 80 was performing as if they were 87 years old.”
Dr. McEvoy’s study is not the only one to reveal that age-related hearing loss is a risk factor for dementia. For example, a recent report in the Lancet Commission, an international science journal, corroborated this learning. It showed “the largest attributable risk for dementia is hearing loss, and that makes it the largest modifiable risk factor of any others,” explains Dr. Nicholas Reed, assistant professor in the Departments of Epidemiology at the Johns Hopkins University Bloomberg School of Public Health and Otolaryngology-Head and Neck Surgery at the university’s School of Medicine. To show the full extent of this impact, he adds, “If you eliminated all hearing loss in the world, you would eliminate eight percent of dementia in the world.”
Broadening Our View of Dementia
While hearing loss is considered a risk factor for dementia, researchers are also hunting to see what other forces might increase a hearing-impaired person’s chance of developing this kind of cognitive decline. For instance, the interplay of age-related hearing loss, depression and dementia was the focus of a study published in September 2020 and led by Dr. Katharine Brewster, Late-Life Neuropsychiatry T32 Research Fellow at New York’s Columbia University College of Physicians and Surgeons.
“We think the combination of hearing loss and depression puts you at an even higher risk of developing cognitive decline,” Dr. Brewster told Hearing Tracker. She and her team uncovered one especially unexpected finding: Treated, rather than untreated, hearing loss was associated with increased risk for depression and dementia. According to Dr. Brewster, this surprising news show the importance of continued research to understand the connection between hearing loss and cognitive decline.
Another correlation to note: People with dual sensory loss may be at a still higher risk of developing dementia. “Older adults with both hearing and visual impairments have a higher risk of dementia than those with either impairment or no sensory impairments at all,” was a key finding in a July 2020 study led by Phillip Hwang, a University of Washington doctoral candidate in epidemiology. Like with Dr. McEvoy’s findings of the relationship between the level of hearing loss and cognitive decline, Hwang found that “those with a greater severity of hearing and vision impairments were associated with increased risk of severity” of dementia.
Answering the “But Why?” Questions
While there are no hard answers about the connection between hearing loss and dementia, there are hypotheses. Hearing loss could lead to loss of brain cells, specifically neurons, said Dr. Frank Lin, the Director of the Cochlear Center for Hearing and Public Health at Johns Hopkins Medicine, in a JHM article. “Brain scans show us that hearing loss may contribute to a faster rate of atrophy in the brain,” Lin explained. “Hearing loss also contributes to social isolation. You may not want to be with people as much, and when you are you may not engage in conversation as much. These factors may contribute to dementia.”
The Importance of Intervention
While it is unclear whether age-related hearing loss actually causes dementia, early intervention plays a role in optimizing the patient’s life. According to the Center for Disease Control, wearing hearing aids can help manage and slow hearing loss down – a sentiment that all the experts who talked to Hearing Tracker echoed.
“We've seen that even after only six months to a year of hearing aid use, some of these changes in your brain associated with hearing loss can be mitigated and erased,” Dr. Brewster explained.
If research does later indicate that hearing loss contributes to dementia, Hwang said that taking action will be even more crucial. “Early intervention and management of these conditions,” he’s said, “can potentially have an important impact on reducing the risk of dementia in older adults.”