By Salynn Boyles
WebMD Health News
Reviewed by Laura J. Martin, MD
Older people with hearing deficits were more likely than those with normal hearing to develop problems with memory and thinking over the course of the study.
On average, the study participants with hearing issues had significant mental impairments three years earlier than those without them.
Untreated Hearing Loss Common
About two-thirds of adults over the age of 70 have some degree of hearing loss.
And the number of people with dementia is projected to double over the next two decades as the population ages.
The researchers now hope to study whether hearing aids can slow mental decline in the elderly.
Otologist and epidemiologist Frank R. Lin, MD, PhD, led the study. He says only about 15% of people who need hearing aids get them. Lin is an assistant professor at the Johns Hopkins University School of Medicine in Baltimore.
"Our findings emphasize just how important it is for physicians to discuss hearing with their patients and to be proactive in addressing any hearing declines over time," he says.
The investigation included close to 2,000 men and women in their 70s and 80s who took part in an aging and health study that began in the late 1990s.
Hearing was tested in year five of the study, and the men and women underwent a series of tests over the next six years to assess declines in memory and thinking.
The men and women with hearing loss showed evidence of these declines 30% to 40% faster than the people with normal hearing. And those people with more hearing loss had steeper declines in mental function.
The study was published online in the journal JAMA Internal Medicine.
Social Isolation, Brain Overload May Explain Link
While it did not address how age-related hearing loss may worsen problems with memory or thinking, Lin says there are several theories.
One theory is that the social isolation common among people with untreated hearing loss leads to mental decline. Previous research has identified loneliness as a risk factor for such decline, he says.
Another theory is the idea that the working memory is limited with respect to the amount of information it can hold and the operations it can perform.
"The job of the inner ear is to take in sounds and encode them with accurate fidelity before the signal goes to the brain for decoding, but with hearing loss the brain has a very hard time doing that," Lin says. "If the brain constantly has to expend more resources to decode sound, this may come at a cognitive cost."
Neurologist and Alzheimer's researcher Marc L. Gordon, MD, calls the research compelling, but he says more studies are needed to confirm that hearing loss has a direct impact on mental decline and to understand the reasons for the link.
He adds that the study emphasizes the importance of addressing not just hearing loss but also vision loss in the elderly.
"This reinforces the notion that evaluating and treating these sensory impairments may be even more important for an aging person's overall well-being than we have known," he says.
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