A new study has uncovered a link between hearing loss and mild cognitive impairment, which is often a precursor to Alzheimer’s. Previous studies have shown a link, but this study pinpoints what kind of hearing loss is linked to dementia—and what is not.
Scientists in the south of Italy looked at 1,604 people with an average age of 75. Of those people, 26 percent had what is called peripheral age-related hearing loss, which is caused by problems in how the inner ear and hearing nerves function. Twelve percent had central age-related hearing loss, which stems from problems with the brain’s ability to process noise—in other words, they can hear, but they can’t understand.
When the researchers looked at what kind of hearing loss overlapped with mild cognitive impairment, people with central hearing loss were twice as likely to have mild cognitive impairment as people who had no hearing loss. Amongst people with central hearing loss, 75 percent had mild cognitive impairment. But people with peripheral hearing loss were no more likely to have memory problems than those who had no hearing issues.
The study highlights the fact that hearing loss isn’t always a problem with being able to hear; sometimes, it’s the brain’s ability to process the noise that is malfunctioning.
“These preliminary results suggest that central hearing loss may share the same progressive loss of functioning in brain cells that occurs in cognitive decline, rather than the sensory deprivation that happens with peripheral hearing loss,” said study author Rodolfo Sardone, a researcher at The University of Bari Aldo Moro. “It’s a problem with perception. Tests of hearing perception should be given to people who are older than 65 and also to people with cognitive impairment.”
The authors also conducted studies on verbal comprehension, noting that people who had trouble understanding speech had lower scores on memory tests.
Hearing loss is one of the most common disabilities in elderly people, affecting about one-third of people over age 65. This study doesn’t prove that hearing loss causes memory loss, but it does show an association between the two. Study authors hope that it might one day be a way to figure out who is most at risk for dementia, since hearing loss has been shown to be a risk factor for dementia, and mild cognitive impairment patients often go on to develop dementia.
This study is part of the Great Age Study, a population-based study based in Italy. It will be released at the American Academy of Neurology’s annual meeting in April.