Our eyes and ears are windows into the brain, and changes in vision and hearing can be some of the earliest indicators of cognitive decline—potentially pointing to more-serious problems.
Vision and Dementia
A recent study, published in Scientific Reports, found that a reduction of visual sensitivity “can predict dementia twelve years before it is diagnosed.”Researchers from Loughborough University in the UK studied 8,623 healthy adults in Norfolk, England, following up with them for many years. By the end of the study, 537 participants had developed dementia, giving researchers insights into what may have caused the disease.
At the beginning of the study, participants did a visual sensitivity test. They looked at a screen with a field of moving dots and were asked to press a button when a triangle appeared. Those who would later develop dementia were much slower to see the triangle than those who didn’t.
The researchers set out to figure out why.
They suspect that changes in visual sensitivity may be early indicators of cognitive decline because the vision centers of the brain may be affected by the amyloid plaques associated with Alzheimer’s—and that these areas are affected first—before the parts of the brain related to memory, which only become damaged as the disease progresses. The implication is that vision tests could predict these early changes before memory tests could.
The authors say that another early sign of Alzheimer’s is a loss in eye movements, or “inhibitory control.” This loss means that distracting stimuli tend to hold more of our attention, making focusing a challenge. Those with Alzheimer’s have issues with their ability to ignore these distracting stimuli, which has implications for things such as driving and the risk of accidents, which the authors say they are also investigating.
Doctors working with dementia patients can sometimes sense dementia in patients upon meeting them because they often seem lost and don’t scan their environment or the faces of those to whom they are speaking. This lack of information gathering would make it more difficult for them to remember where they had been and who they had been talking to, and it explains why they may not recognize the same people the next time they meet.
Hearing and Dementia
Hearing also affects dementia development and progression. Research has shown that hearing loss doesn’t just make you more likely to develop dementia—it may be a cause of the disease.1. When hearing is impaired, the brain works harder to hear, diverting resources from other areas of the brain—such as thinking and memory.
3. Hearing loss causes many people to avoid social situations because engaging is difficult. These social interactions are vital to keeping the brain active, especially as we age.
Scientists also wondered if treating hearing loss with hearing aids could reduce the risk of developing the disease.
The study analyzed 2,413 people from the National Health and Aging Trend Study, using a nationwide sample of people older than 65 who receive Medicaid—about half of whom are older than 80.
Researchers found a clear association between severe hearing loss and dementia, finding that dementia was 61 percent more prevalent in people with moderate to severe hearing loss than in those with normal hearing.
They found that people who used hearing aids fared better than those who didn’t. In the group of 853 individuals with moderate to severe hearing loss, those who used hearing aids had a 32 percent lower incidence of dementia.
“This study refines what we’ve observed about the link between hearing loss and dementia, and builds support for public health action to improve hearing care access,” Alison Huang, the study’s lead author, said in the Johns Hopkins article. Ms. Huang holds a doctorate in mental health and is a senior research associate in the Department of Epidemiology at the Bloomberg School and the Cochlear Center for Hearing and Public Health.
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