A team of U.S. researchers has found evidence that cataract surgery can be linked to a lower risk of developing dementia, specifically Alzheimer’s disease, in older adults.
The observational study, based on data from more than 3,000 participants over the age of 65, found that those who underwent cataract surgery had a nearly 30 per cent lower risk of developing dementia from any cause compared with those who did not.
Cataract surgery was also associated with lower risk of Alzheimer’s disease specifically.
The results, reported Dec. 6 in JAMA Internal Medicine, suggest that this lowered risk persisted for at least a decade after undergoing surgery.
“This kind of evidence is as good as it gets in epidemiology,” lead researcher Dr. Cecilia Lee said in a press release. “This is really exciting because no other medical intervention has shown such a strong association with lessening dementia risk in older individuals.”
Data for the study was supplied by the Adult Changes in Thought (ACT) study – a long-standing, Seattle-based observational study at Kaiser Permanente Washington, consisting of more than 5,000 participants older than 65.
Researchers tracked participants diagnosed with a cataract or glaucoma who did not have dementia or had not undergone cataract surgery at the time they volunteered for the study. The participants were evaluated every two years for cognitive abilities.
Out of 3,038 participants, 853 subjects developed dementia over a seven-year follow up period – 709 of which were diagnosed as Alzheimer’s. Approximately half of the participants had cataract surgery.
Although the study did not draw a direct link between cataract surgery and a lessened dementia risk, researchers hypothesize that those who underwent surgery may have gotten higher quality sensory input thanks to their improved vision.
“These results are consistent with the notion that sensory input to the brain is important to brain health,” co-author Dr. Eric B. Larson said in a press release.
Another hypothesis is that the eye gets more blue light after cataract surgery.
“Some special cells in the retina are associated with cognition and regulate sleep cycles, and these cells respond well to blue light,” Lee said, “Cataracts specifically block blue light, and cataract surgery could reactivate those cells.”
The researchers adjusted for an extensive list of factors including health-related confounders, including assumptions that participants who underwent cataract surgery might have been healthier and at lower dementia risk to begin with, but still found strong associations when these factors were accounted for.
Eye surgeries performed in the two years prior to dementia diagnosis were ruled out due to the possibility that people with cognitive decline may have been less conscious of vision issues.
Even with this group excluded, the researchers found lower risks of dementia associated with cataract surgery.
Previous research into dementia risks have yielded similar results.
A 2020 study from researchers at the University of Michigan found that the use of hearing aids can be associated with a reduced risk of dementia. The study found that older people who received hearing aids within three years of a hearing loss diagnosis had lower rates of dementia, depression and even falls, than those who didn’t get hearing aids.
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