A new study has found a troubling link between hearing loss and dementia: Hearing specialists from Johns Hopkins report that hearing-impaired adults between the ages of 75 and 84 were more likely to experience cognitive and memory problems than those in the same age range with normal hearing. In fact, those study participants who had hearing problems experienced cognitive decline 30 to 40 percent faster than those with normal hearing.
"[People have thought] hearing loss in older adults is an inconsequential part of getting older," said Frank Lin, senior study investigator and an otologist and epidemiologist at Johns Hopkins. "But hearing loss has very real consequences and could lead to cognitive decline."
Hearing loss affects an estimated 27 million Americans age 50 and up, but only 15 percent of those sufferers use hearing aids, according to a press release on the study.
The study's close to 2,000 participants were in good health when the study first began in 2001 -- researchers excluded those people who could have experienced hearing loss due to other causes. Hearing and brain cognition tests were administered over six years. Researchers found that the level of brain functioning was directly related to hearing loss, with those suffering from hearing loss dealing with "significant cognitive impairment" 3.2 years sooner than those whose hearing remained at normal levels.
But just how are hearing loss and cognitive impairment connected?
"Your inner ear has to take in a complex sound and convert it into a signal that goes into the brain," Lin explained. "When we say that people have hearing loss, it means the inner ear is no longer as good at encoding those signals with accuracy and fidelity. So the brain gets a very garbled message -- you can hear what's being said but you can't quite make it out. It takes a little more effort to hear what that person said."
As a result, "the brain has to rededicate sources to help with hearing and sound processing," Lin said. "That comes at the loss of something else."
And that something else appears to be brain functioning. MRIs have shown the prefrontal cortex being activated in those experiencing hearing loss to help auditory processing, taking away from the part of the brain focused on "working memory."
"Secondly as we develop hearing loss, we withdraw socially," Lin continued. "You're less likely to go out and you may be less likely to be engaged in conversation. One of the major risk factors for dementia" is social isolation.
While it's good to take hearing loss prevention into consideration, it isn't quite clear that preventing hearing loss means cutting down the risk of dementia, Lin said.
"We just don't know yet," he said. "Next month we're submitting a large grant to the National Institutes of Health for a clinical trial."