We've known for several years that hearing loss is linked to dementia and decline in memory and thinking skills, but we don't yet understand why they are connected. A new study from Johns Hopkins University in Baltimore may provide an explanation: Older adults with hearing problems appear to have a greater rate of brain shrinkage as they age.
Researchers used information from the ongoing Baltimore Longitudinal Study of Aging to study 126 adults ages 56 to 86 who had yearly MRI brain scans for up to a decade. Fifty-one showed some degree of hearing loss, mostly mild to moderate; these people might have trouble hearing in a restaurant, for example. The researchers found that the brains of those with impaired hearing shrank faster than the brains of those with normal hearing, and that the atrophy was concentrated in the parts of the brain related to hearing.
Frank Lin, M.D., assistant professor of otolaryngology and epidemiology and lead author of the study, says this research lends credence to the theory that "hearing loss is leading to changes in the brain structure or function." It's possible that in the same way a muscle becomes weak if we don't use it, the part of the brain involved with hearing - as well as speech processing and memory - also begins to atrophy.
Lin says the current theory is that hearing impairment doesn't directly cause dementia but that it may exacerbate problems in brain function. "It serves as another hit on the system, which could lead to an earlier expression of dementia," he says. The crucial question, of course, is whether correcting the hearing with a hearing aid will prevent this accelerated brain shrinkage. Lin is planning a large study to research just that question, but results won't be in for several years. For now, though, he recommends correcting hearing problems if at all possible.
"If you want to address hearing loss well, you want to do it sooner rather than later," he says, adding that if hearing loss is potentially causing negative changes in the brain, it's better to treat it before these structural changes take place.
The study was published online Jan. 9 in the journal NeuroImage.
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