Hearing loss isn’t just an inconvenience—it could be harmful for your brain, too.
A new study from Johns Hopkins University and the National Institute on Aging shows that people with hearing loss have accelerated brain tissue loss. This is in addition to a higher risk of poor physical and mental health, dementia, falls, and hospitalizations.
Frank Lin, Ph.D., an assistant professor at Johns Hopkins, evaluated data from the ongoing Baltimore Longitudinal Study of Aging to compare brain alterations that occurred over time in adults with normal hearing and those with an impaired sense. His research was published in Neuroimage.
According to the American Speech-Language-Hearing Association, more than 30 percent of people over the age of 65 have some type of hearing loss, and 14 percent of people between 45 and 64 do as well. Close to 8 million people between the ages of 18 and 44 have hearing loss.
How Does Hearing Loss Change the Brain?
Studies in the past have linked hearing loss to structural differences in human and animal brains. They’ve found that brains are sometimes smaller in people and animals with poor hearing.
In the Baltimore Longitudinal Study of Aging, 126 participants undergo yearly magnetic resonance imaging (MRI) to track brain changes for up to a decade. They also have physical exams and hearing tests.
When the study period began in 1994, 75 participants had normal hearing, and 51 had impaired hearing that included at least a 25-decibel loss. Lin found that people with hearing loss at the start of the study had quicker rates of brain atrophy than those with normal hearing.
The scientists say that people with diminished hearing lost more than an additional cubic centimeter of brain tissue each year compared to those with normal hearing. People with hearing loss also experienced more shrinkage in the superior, middle, and inferior temporal gyri—parts of the brain that process sound and speech.
Lin wasn’t surprised by that; in fact, he said it may be a result of an “impoverished” auditory cortex, which could shrink due to lack of stimulation. But those parts don’t work alone; they also play roles in memory and sensory integration. And they have been shown to be linked with the early phases of dementia and Alzheimer's disease.
“Our results suggest that hearing loss could be another 'hit' on the brain in many ways,” Lin said. He urges people not to ignore possible hearing loss. If hearing loss is contributing to the differences the scientists saw on the MRI scans, it should be treated before structural brain changes occur.
Eric Smouha, M.D., an associate professor of otolaryngology at the Icahn School of Medicine at Mount Sinai in New York City, said that the new study offers more evidence that hearing loss contributes to dementia.
Time for a Hearing Test?
The American Speech-Language-Hearing Association recommends that adults be screened for hearing loss at least every decade through age 50 and at three-year intervals thereafter. A hearing test takes about 30 minutes and measures hearing sensitivity to pure tones and speech.
A first visit to an audiologist will include questions about your medical history and an ear exam with an instrument called an otoscope. The doctor will then put you through various tests that involve listening and signaling when the audiologist says to.
If you suspect hearing loss, Smouha says, you should go for audiometric testing right away and get a hearing aid if significant loss is detected.
“The study makes a good case for the concept of disuse atrophy…use it or lose it,” Smouha said.
Eric W. Healy, Ph.D., a professor of speech and hearing at Ohio State University, thinks it’s a good idea to have a screening if you think you might have some hearing loss—even the tiniest bit.
“It's not uncommon to believe that you have a ‘problem’ with your hearing,” Healy said. “It’s simple to test, and many people who believe that they have an issue actually don't.”
If you are routinely exposed to loud noises or music, go in for a hearing screening, he said.
“A test done early can serve as a baseline for future comparison,” Healy said. “There's little reason not to.”