It was already known that hearing problems could lead to dementia. But how exactly does this happen? Scientists from China have finally found the answer.
Hearing problems are not just a daily discomfort that reduces quality of life, leads to social isolation, and can even cause depression. It has been proven: the worse a person hears, the greater their chances of developing dementia.
Presbycusis — the common form of age-related hearing loss — complicates speech recognition. As a result, the brain stops receiving clear sound signals, and the areas responsible for processing information begin to atrophy, while memory becomes increasingly weaker.
But how exactly is hearing loss related to dementia? What mechanisms underlie this? For a long time, science could not provide an explanation. Chinese scientists took on the challenge of solving this mystery.
Researchers from Tianjin University and Shandong Provincial Hospital discovered a neurobiological link between presbycusis and cognitive impairments. It turned out that four areas of the brain — the shell and the fusiform gyrus (involved in sound and speech processing), as well as the precuneus and the medial superior frontal gyrus (necessary for memory and decision-making) — become less connected to the brain's functional networks in older adults who have hearing problems.
In their study, the authors assessed cognitive abilities, as well as hearing thresholds and speech recognition thresholds in 55 volunteers with presbycusis and 55 healthy controls. Using magnetic resonance imaging, they examined the neural activity of key brain areas at rest, as well as the volume of gray matter.
"In the group of patients with presbycusis, neural activity changed significantly, and gray matter atrophied. These changes are associated with increased hearing thresholds and reaction times, as well as lower scores on cognitive assessment tests," the study published in the journal eNeuro states.
"It turned out that the brain is constantly straining to decipher muffled speech, which leads to overexertion," comments Dr. Ana Baranova, a biological sciences expert. "Constant activity, it turns out, does not contribute to the overall health of the brain areas working to exhaustion. Overworked regions shrink in volume, which pushes a person with hearing loss into the arms of old man Alzheimer's."
Therefore, the use of hearing aids can officially be considered one of the preventive measures against dementia, just like wearing glasses. The medical journal JAMA Ophthalmology reports: the brains of people with poor vision who do not correct it receive less information, which can lead to the development of dementia.
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