Hearing loss may be linked to dementia

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Dementia, the loss of brain function that happens as a result of specific diseases, is a major health concern facing millions of Americans.

Now, a new study has revealed a link between dementia and hearing loss.

Dementia covers a wide range of diseases that cause mental decline, with Alzheimer's disase accounting for 60 to 80 percent of cases, according to the Alzheimer's Association. About 5.4 million Americans are affected by Alzheimer's alone, and it is the sixth-leading cause of death in the U.S. -- a disease that cannot be prevented, cured or even slowed.

Rates of dementia-related diseases are estimated to double every 20 years because the global population is aging, according to the authors of the new research.

For the study, which was published online on Jan. 21 in JAMA Internal Medicine, researchers looked at 1,984 adults in their 70s and 80s who had no impaired memory or thinking at the beginning of the study. The majority -- 1,162 -- did have some hearing loss.

After a six year follow-up, 609 men and women eventually showed signs of mental impairment when asked to take a standard test for memory, concentration and language.

Seniors who had hearing problems were 24 percent more likely to develop mental decline in the study. On average, researchers believed that people with hearing impairment would take 7.7 years to develop mental impairment, whereas people with normal hearing would take 10.9 years.

Study author Dr. Frank Lin, an otologist and assistant professor at the Johns Hopkins University School of Medicine in Baltimore, told USA Today that he believes social isolation caused by hearing loss in addition to any underlying brain damage that may have caused both hearing loss and mental decline may explain the findings.

"It could also be that if you're constantly having to expend more (mental) energy decoding what you hear, then it comes at a cost,'' Lin said. "Hearing loss doesn't directly contribute to dementia, but leads to cognitive load on the brain."

Dr. Eric Karran, director of research at the nonprofit Alzheimer's Research UK however, pointed out to the BBC, that the connection between hearing loss and cognitive decline was still unknown. The two problems were linked, but the study did not show that one caused the other.

"Many people find their hearing becomes worse as they get older, and age is also the biggest risk factor for dementia," he said. "Understanding whether the two are directly linked could give important insight into the condition, but more research will be needed to fully answer this question."