When someone asks for words to be repeated, the common perception is that their struggle to understand is due to hearing loss. And while that might be the case in some instances, a new study has revealed that the difficulty often lies in the aging brain, and can sometimes occur in cases where no hearing loss exists.

In the new study, published in the Journal of Neurophysiology, researchers from the University of Maryland set out to discover why older adults often have difficulty following speech amidst background noise.

In the study, 32 English-speaking subjects who had normal hearing were divided into groups based on age. The group of young adults, with an average age of 22, and the group of older adults, who averaged age 65, were given tests to measure their speech comprehension. They were also given tests to measure both mid-brain and cortical activity. The tests measured the subjects’ ability to understand speech both in quiet settings and settings with background noise.

What the researchers discovered was that the older subjects had more difficulty processing speech, whether in a quiet setting or amid background noise. Electroencephalograms and magnetocephalograms, used to measure mid-brain and cortical activity respectively, also revealed neural deficits in the older study participants. So what does this mean? It means that essentially, as we age, our brain’s ability to process and understand speech declines. The decline is unrelated to age-related hearing loss and can occur even in the presence of no hearing loss at all.

“Often we will hear an older person say, ‘I can hear you, I just can’t understand you,'” Samira Anderson, assistant professor at the University of Maryland Department of Hearing and Speech Sciences, tells Science Daily. “This research gives us new insight into why that is the case.”

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