If you’ve been putting off cataract surgery or taking your time ordering a new pair of glasses, here’s a reason to reconsider: Fixing your vision may help stave off dementia and Alzheimer’s disease, the most common form of dementia.
Researchers in recent years have uncovered a strong correlation between vision impairment and dementia. While the studies haven’t proved that vision problems cause dementia, or vice versa, they do show that treating a vision problem is linked with a lower risk of developing problems with memory and thinking skills over time.
“This is key because it’s a late-life factor that we can potentially do something about,” says Jennifer Deal, a public health researcher who studies dementia and cognitive decline at Johns Hopkins Bloomberg School of Public Health.
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With Alzheimer’s drugs so far making little progress in beating back the disease, many public health officials have turned their focus to addressing what the Centers for Disease Control and Prevention (CDC) calls “modifiable risk factors” that could help prevent cognitive decline from happening in the first place.
The latest research has prompted some experts to make the case that untreated vision loss deserves more attention as a modifiable risk factor for dementia.
More than 1 out of every 10 Americans age 65 and older have vision impairment, according to the CDC. As many as 70 to 80 percent of those cases are easily correctable by getting the right eyeglasses or with cataract surgery, experts say.
“There’s a lot of potential opportunity here,” says Willa Brenowitz, an epidemiologist at the University of California, San Francisco. “Compared to a lot of other risk factors, [vision loss] is understudied, and older adults tend to have under-corrected vision or they are waiting to get their cataract surgery. Treating their vision loss could improve their quality of life, and that may in turn prevent dementia or slow the decline.”
Studies link vision loss to dementia
The idea of a sensory deficit contributing to dementia risk isn’t new. Hearing loss, which has long been linked to cognitive problems, is the largest modifiable risk factor for dementia, according to a 2020 Lancet Commission report. It’s estimated to account for about 9 percent of dementia cases, according to the report.
It’s only in more recent years that researchers have discovered vision loss may have a similar association.
In 2021, several different large-scale analyses of observational studies — where researchers observe individuals but don’t give treatment or try to affect the outcome — found that older adults with impaired vision were at increased risk of eventually developing cognitive problems. One review, published in the journal Ophthalmology, found that people with eyesight problems were 66 percent more likely to have cognitive impairment, and 109 percent more likely to have dementia, compared to those with no vision issues. A similar analysis found those odds to be 35 and 47 percent higher, respectively.
Meanwhile, a study published in JAMA Internal Medicine in December 2021 offered potential support for the idea that treating a vision problem could prevent cognitive decline. The study followed two groups of people age 65-plus with cataracts who did not have dementia. It found that those who had surgery to remove their cataracts were 30 percent less likely to be diagnosed with dementia in later years than those who didn’t have the surgery. (Note: The researchers adjusted for other factors that could impact the results, such as level of education, race and smoking history.)
Possible reasons for the link
Researchers aren’t sure exactly how or why vision and cognitive health are related, but they believe it’s likely the same mechanism that links hearing loss to dementia.
One possibility is that the disease process degrading your eyesight is also harming your cognition, says Joshua Ehrlich, M.D., an ophthalmologist and population health researcher at the University of Michigan Kellogg Eye Center.
“The eye is an extension of the brain. It’s neural tissue,” he explains. “If you have neural degeneration happening, then it stands to reason the eye might be affected as well as the brain.”
Another theory has to do with “cognitive load.” Because vision loss makes day-to-day tasks such as paying bills or reading a recipe more challenging, the brain has to work harder, potentially taking capacity away from other thinking and memory tasks, says Heather Whitson, M.D., director of the Duke Center for the Study of Aging and Human Development and a professor at the Duke University School of Medicine.
Others speculate that a lack of sensory input — whether visual or auditory — causes parts of the brain to shrink or atrophy.
Finally, it’s possible that vision loss doesn’t cause direct changes in the brain but does make it harder to socialize, be physically active and engage in cognitively meaningful activities such as going to the theater, attending a sporting event or reading a book.
“Vision loss creates social isolation and has all of these other effects on your quality of life,” Brenowitz says. “You’re isolated; you’re not as physically active. Those factors are all potential causes of dementia, so that would be a more indirect pathway.”
Vision loss isn’t a “normal” part of aging
Whatever the reason for the link between cognition and vision, experts emphasize that having eyesight problems does not mean you’re doomed to get dementia.
“It’s an elevated risk, not a certainty,” Whitson says. “The good news here is, this is an entirely modifiable thing.”
In a recent analysis published in JAMA Neurology, Ehrlich and his coauthors studied 2018 data from the Health and Retirement Study and found that about 1.8 percent of dementia cases could have been prevented by better eye care.
That means over 100,000 Americans could potentially preserve their brain health through simple interventions like glasses or cataract surgery, Ehrlich says.
Even if you have a disease like glaucoma or macular degeneration that doesn’t have an easy fix, treatments can slow down the progress of the disease, he adds.
“Vision loss is not normal, even in later life,” Ehrlich says. “If you’re experiencing changes in your vision, or if it’s not as sharp as it’s supposed to be, get your eyes checked. It’s important for your vision health — and it could be important for your cognitive health.”
Michelle Crouch is a contributing writer who has covered health and personal finance for some of the nation’s top consumer publications. Her work has appeared in Reader’s Digest, Real Simple, Prevention, The Washington Post and The New York Times.