By Alan Mozes
Difficulty recognizing words in loud settings is a common concern for older people, and new research suggests the problem may involve more than hearing loss, but rather age-related structural changes in the brain.
"We found that a small portion of the brain’s auditory cortex is closely related to word recognition, and that structural change in the volume of this area is associated with recognition problems in older patients," says study author Kelly C. Harris, an assistant professor in the department of otolaryngology head and neck surgery at the Medical University of South Carolina.
The National Institute on Aging estimates that about one-third of Americans between the ages of 65 and 74 experience hearing loss—a number that rises to 50% among people 85 and older.
To gauge the role that age-related brain changes might play in hearing loss, the study authors conducted hearing exercises while using MRI to scan the brains of 18 younger adults between the ages of 19 and 39, and 18 older adults between the ages of 61 and 79.
While undergoing the scans, all the participants were tested on their ability to identify certain words, with some words filtered to reduce intelligibility. The researchers found that in "challenging listening conditions," the older adults were generally much worse at recognizing words than younger adults.
Even after accounting for the loss of high-frequency hearing that typically accompanies old age, the researchers found that the poorer performance among the older adults was linked to a reduction in the size of small portions of the auditory cortex, a section of gray matter in the brain that controls hearing.
This could ultimately explain how and why some hearing problems worsen with age.
Harris suggested that, with further research, the findings might improve rehabilitation efforts to help older people cope with particular hearing difficulties.
"Hearing aids don’t help all older adults," she says. "They can improve audibility for many, but there are additional problems going on at the level of the brain that need to be addressed."
Robert D. Frisina, a professor of otolaryngology, biomedical engineering, and neurobiology and anatomy at the University of Rochester in New York, called the new research "a very promising and pioneering study."
"The idea that the brain plays a role in hearing loss as we age is not new," he says. "There are past indications of that. But this is the first study I’ve heard of to explore this idea in a new way by use imaging in humans, and that’s exciting and provides this finding with some sizzle. And locating evidence of the problem in the gray matter part of the brain—where neural processing goes on, as opposed to the white matter which is the communication zone, so to speak—is also pretty new and important."
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(SOURCES: Kelly C. Harris, PhD, assistant professor, otolaryngology head and neck surgery, Medical University of South Carolina, Charleston; Robert D. Frisina, PhD, professor, otolaryngology, biomedical engineering, and neurobiology and anatomy, University of Rochester, NY.; Feb. 15, 2009, Midwinter Meeting of the Association for Research in Otolaryngology, Baltimore)