Dec. 22—Adults who have undergone cataract surgery have a lower chance of developing dementia, according to a Seattle-based study published this month.
The findings could lead to a better understanding of connections between eye and brain health. The Adult Changes in Thought study is a long-standing, observational study at Kaiser Permanente Washington of more than 5,000 participants over age 65.
Based on data over time of more than 3,000 study participants, older adults who underwent cataract surgery had nearly 30% lower risk of developing dementia from any cause compared with those who didn't. This lowered risk persisted for at least a decade after surgery.
Cataract surgery was associated with lower risk of Alzheimer's disease dementia specifically, said the study that was reported Dec. 6 in JAMA Internal Medicine.
Lead researcher Dr. Cecilia Lee, associate professor and Klorfine Family Endowed Chair in ophthalmology at the University of Washington School of Medicine, said in a UW article that the observational study adjusted for potential variables, yet still yielded a strong association.
"This kind of evidence is as good as it gets in epidemiology," Lee said in the UW report. "This is really exciting because no other medical intervention has shown such a strong association with lessening dementia risk in older individuals."
The mechanisms by which cataract surgery and lessened dementia risk are associated weren't determined in this study, a news release said. Researchers hypothesize that people might be getting higher-quality sensory input after cataract surgery, which might have a beneficial effect in reducing the risk of dementia.
"These results are consistent with the notion that sensory input to the brain is important to brain health," said co-author Dr. Eric B. Larson, a principal investigator of the ACT study and senior investigator at Kaiser Permanente Washington Health Research Institute.
Lee said another hypothesis is that 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."
The study's results highlight a strong case for more research on the eye-brain connection in dementia. Previous studies by Lee's group at UW have shown a strong link between other retinal diseases, such as age-related macular degeneration, and the development of Alzheimer's disease and dementia.
Participants with macular degeneration or other retinal degenerative diseases are more likely to develop dementia. Further understanding the connection between the aging eye and brain may offer insights and potential therapies to slow or prevent age-related dementia.
Researchers tracked participants diagnosed with a cataract or glaucoma but who didn't have dementia at the time they volunteered for the study. Participants also didn't have cataract surgery at the time of enrollment. They are evaluated every two years for cognitive abilities based on the Cognitive Abilities Screening Instrument.
Among the study's limitations, researchers said only the first cataract surgery was evaluated, so researchers don't know if subsequent surgeries would impact dementia risk. Also, a majority of the study population was white, so it's unclear if the effect would be seen in all racial populations.
In a Seattle Times article, however, Lee said she'd like to understand better the role that race and ethnicity might play in future results.