Subtle hearing loss while young changes brain function, study finds

The future health of your brain is probably not one of the things that cross your mind while you turn up the volume on your headphones or dance next to a speaker at a concert, but maybe it should be. A recent study carried out by The Ohio State University has revealed that young people with mild, sometimes unnoticeable hearing loss are putting an additional burden on their brains that usually wouldn’t be seen until late-middle age. Lead researcher Yune Lee, an assistant professor of speech and hearing science at Ohio State, said, “Hearing loss, even minor deficits, can take a toll in young people – they’re using cognitive resources that could be preserved until much later in life. Most concerning, this early hearing loss could pave the way for dementia.”

About the study

The study was published in the online neuroscience journal eNeuro. It can be read in its entirety here. What Lee and his research team originally set out to study had nothing to do with hearing loss–or so they thought. They wanted to take a closer look at brain activity and speech recognition – specifically, the cognitive changes that occur when one is trying to comprehend more difficult sentences. For the study, Lee and other researchers recruited 35 participants, all healthy men and women between the ages of 18 and 41 years old. They then played sentences of varying difficulty for the participants, while using functional magnetic resonance imaging (fMRI) technology to measure and map brain activity. The participants heard sentences in sets of four, with subtle differences and increasing grammatical complexity from one sentence to the next: Kings with three black horses that appreciate queens are good Kings that appreciate queens with three black horses are good Kings with three black horses that queens appreciate are good Kings that queens appreciate with three black horses are good They had to answer questions about each sentence to indicate comprehension, such as “What is the gender of the agent who is doing the appreciating?” Researchers were only expecting to see activity and changes in the left hemisphere of the brain as participants deciphered these sentences. But a different type of brain activity was observed in those subtle with hearing loss.

A surprising discovery

What the research team observed altered the course of the study, and the findings have the potential to change the way we think about mild hearing loss acquired in youth. Prior to the fMRI tests, the researchers checked participants’ hearing to ensure there weren’t any problems that would change the results of the study. Although some of the young people had minor hearing loss, nothing was considered serious enough to exclude them from the study. But as the fMRI results revealed, those with subtle hearing decline displayed an increased cognitive demand in the act of deciphering speech. In other words, their brains had to work harder than those with normal hearing, using a different part of the brain–specifically the right frontal cortex–to compensate for the hearing loss. This area is outside of the normal language network in young, healthy people, who typically do all of their language processing in the left hemisphere of the brain.

The implications

It’s important to note that many of the participants who exhibited this increased cognitive burden in understanding speech had very mild hearing loss, so mild that they described their hearing as “normal”. We often think of noise-induced hearing loss as being the result of exposure to industrial noise or explosive sounds, but it listening to loud music at an entertainment venue or on a personal music player poses a risk that is just as real. Researcher Lee commented on this hearing loss-cognitive health connection: “Previous research shows that people with mild hearing loss are twice as likely to have dementia. And those with moderate to severe hearing loss have three to five times the risk,” he said. Noise-induced hearing loss from routine exposures such as listening to music can be very subtle and hard to detect, but it may have serious repercussions later in life. The key, Lee says, is for young people to take their hearing health seriously now.

Visit Us at Orange County Physicians’ Hearing Services

It is now known that there are consequences of hearing loss that go beyond simply misunderstanding words; the effort needed to correctly perceive speech comes at the cost of cognitive resources, and this additional burden on the brain could greatly increase the risk of dementia later in life. To schedule a hearing test, contact us at Orange County Physicians’ Hearing Services today.