More than 5,000 participants over 65 participated in the Adult Changes in Thought study. The new study was based on longitudinal data of 3,038 ACT study participants.
“This kind of evidence is as good as it gets in epidemiology,” lead researcher Dr. Cecilia S Lee, associate professor and Klorfine Family Endowed Chair in ophthalmology at the University of Washington School of Medicine, 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.”
The study followed participants who were diagnosed with a cataract or glaucoma, but who didn’t have dementia when they volunteered to participate.
Every two years, participants were evaluated for cognitive abilities based on the Cognitive Abilities Screening Instrument. Scores range from 0-100; those who score under 85 undergo further neurological tests.
In the follow-up period, 853 subjects developed dementia; 709 cases of Alzheimer’s disease occurred. More than 1,000 participants — or 45% — had cataract surgery.
When evaluating dementia risk, researchers found that participants who had cataract surgery in either eye were around 30% less likely to develop any form of dementia for at least a decade following the procedure.
Scientists have been unable to pinpoint why such a link exists.
Some hypothesize that after cataract surgery, people may be getting higher quality sensory input. It could be a benefit in decreasing dementia risk.
“These results are consistent with the notion that sensory input to the brain is important to brain health,” said coauthor Dr. Eric B. Larson, a principal investigator of the ACT study. He is a senior investigator at Kaiser Permanente Washington Health Research Institute.
Another hypothesis is that more blue light gets to the eyes following cataracts 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.”
Limitations of the study included that only the first cataract surgery was analyzed. Researchers don’t know if subsequent surgeries impacted the risk of dementia. Another limitation was that the population was majority white. Whether the effect would be observed in all populations is unclear.
“Innovative research like Dr. Lee’s is helping to uncover how age-related changes in our senses contribute to dementia,” said Dr. Howard Fillit, founding executive director and chief science officer of the Alzheimer’s Drug Discovery Foundation.
ADDF is a nonprofit aimed at accelerating the discovery and development of drugs to treat and prevent Alzheimer’s and related dementias.
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