January 10, 2022
Cataracts, which cause gradual clouding of the normally clear lens of the eye, are a common cause of blurry vision in older adults. Now a new study reports that having cataract surgery to correct impaired vision is associated with a nearly 30 percent lower risk of developing Alzheimer’s disease and other forms of dementia.
The findings add to growing evidence that intact vision, like intact hearing, is critical to keeping the brain in good health as we age. If the brain has to work extra hard to see or hear, it can take a toll on cognitive function.
The study, from researchers at the University of Washington in Seattle, looked at 3,038 older men and women with cataracts or glaucoma, another other eye disease that can lead to vision loss. All were part of the large and ongoing Adult Changes in Thought Study. None had serious memory problems at the study’s start.
During an average of eight years of follow-up, 853 of people in the study developed Alzheimer’s disease or other forms of dementia. About half had cataract surgery.
The researchers considered various factors that can affect dementia risk, including overall health and other medical conditions, years of schooling and smoking history. Those who had cataract surgery were significantly less likely to develop dementia than those who didn’t have cataract surgery, and the decreased risk persisted for at least a decade after surgery.
“This kind of evidence is as good as it gets in epidemiology,” said Dr. Cecilia Lee, a professor of ophthalmology at the University of Washington and the study’s lead researcher. “This is really exciting because no other medical intervention has shown such a strong association with lessening dementia risk in older individuals.” The findings were published in JAMA Internal Medicine.
The researchers speculate that by improving vision, cataract surgery improves visual input to the brain. Other studies have shown, for example, that other diseases that impair vision, such as age-related macular degeneration, are tied to an increased risk of Alzheimer’s disease.
In addition, people with cataracts who have corrective surgery are better able to see, read, do crossword puzzles, go to plays and concerts, drive and engage with friends, family and the world. Increased social stimulation or engaging in cognitively stimulating activities, numerous studies have shown, may help guard against dementia.
Dr. Lee said another hypothesis is that cataracts cause yellowing of the lens, which blocks light in the blue spectrum from entering the eyes and brain. After cataract surgery, people are getting more blue light. “Some special cells in the retina are associated with cognition and regulate sleep cycles, and these cells respond well to blue light,” she said, “Cataracts specifically block blue light, and cataract surgery could reactivate those cells.”
Experts suggest that everyone have regular vision checks, at least every two years, or more often if you have medical conditions like diabetes or glaucoma that can lead to vision loss. People with Alzheimer’s, too, can benefit from regular vision and hearing checks, to help maintain visual and aural stimulation to the brain.
By ALZinfo.org, The Alzheimer’s Information Site. Reviewed by Marc Flajolet, Ph.D., Fisher Center for Alzheimer’s Research Foundation at The Rockefeller University.
Source: Cecilia S. Lee, MD, MS; Laura E. Gibbons, PhD; Aaron Y. Lee, MD; et al “Association Between Cataract Extraction and Development of Dementia.” JAMA Internal Medicine, December 6, 2021