Cataract surgery linked with lessened dementia risk
Date:
December 6, 2021
Source:
University of Washington School of Medicine/UW Medicine
Summary:
Based on the longitudinal data of over 3,000 study participants,
researchers found that subjects who underwent cataract surgery
had nearly 30% lower risk of developing dementia from any cause
compared with those who did not. This lowered risk persisted for at
least a decade after surgery. Cataract surgery was also associated
with lower risk of Alzheimer disease dementia specifically.
FULL STORY ========================================================================== Cataracts affect most older adults at risk for dementia, and now
researchers are finding strong evidence that cataract surgery is
associated with a lower risk of developing dementia.
==========================================================================
The Adult Changes in Thought (ACT) study is a long-standing, Seattle-based observational study at Kaiser Permanente Washington of more than 5,000 participants older than 65. Based on the longitudinal data of over
3,000 ACT study participants, researchers have now found that subjects
who underwent cataract surgery had nearly 30% lower risk of developing
dementia from any cause compared with those who did not. This lowered
risk persisted for at least a decade after surgery. Cataract surgery
was also associated with lower risk of Alzheimer disease dementia
specifically. The results were reported Dec. 6 in JAMA Internal Medicine.
Lead researcher Dr. Cecilia S Lee, associate professor and Klorfine
Family Endowed Chair in ophthalmology at the University of Washington
School of Medicine, said the observational study adjusted for a number
of potential confounders, yet still yielded a strong association.
"This kind of evidence is as good as it gets in epidemiology," Lee
said. "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 was not determined in this study. Researchers hypothesize that people may 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 results highlight a strong case
for further research on the eye-brain connection in dementia. Previous
studies by Lee's group at the UW have shown a strong link between other
retinal diseases, such as age-related macular degeneration, and the
development of Alzheimer disease and dementia. Subjects with macular degeneration or other retinal degenerative diseases are more likely
to develop dementia, In the current study, subjects undergoing vision- improving cataract surgery had lower risk of developing dementia. Further understanding the connection between the aging eye and brain may offer
insights and potential therapies to slow or prevent age-related dementia.
The study: Researchers tracked participants diagnosed with a cataract or glaucoma but who did not have dementia at the time they volunteered for
the study. Participants also did not have cataract surgery at the time
of enrollment. Participants are evaluated every two years for cognitive abilities based on the Cognitive Abilities Screening Instrument, which
scores in a range from 0-100. Participants with scores less than 85
undergo further neurological tests.
During follow-up of 3,038 participants (an average of 7.8 years per
person), 853 subjects developed dementia, with 709 cases of Alzheimer
disease.
Approximately half of the participants (1,382 individuals or 45%) had
cataract surgery. Analysis for risk of developing dementia showed that
subjects who had undergone cataract surgery in either eye were about 30%
less likely to develop any form of dementia for at least 10 years after
their surgery.
========================================================================== Analysis was adjusted for an extensive list of factors including
health-related confounders. Cataract surgery could appear to have a
protective effect due to a healthy patient bias, where participants
who underwent cataract surgery might have been healthier and at lower
dementia risk. Researchers performed analyses to account for several
types of potential bias, but still found strong associations when these
factors were accounted for.
Researchers excluded eye surgeries in the two years prior to dementia
diagnosis to rule out the possibility that people with cognitive decline
prior to dementia diagnosis may have been less conscious of vision issues,
and thus less likely to have undergone cataract surgery. Even with this
group excluded, the researchers found lower risks of dementia associated
with cataract surgery.
As another control, participants were also evaluated for a possible link between another type of eye surgery (glaucoma surgery) and dementia. In
this case, no association was found.
Strengths of study: This was a community-based, prospective cohort
study with more than 23,000 person-years of follow up. More than 98%
of the ACT cohort were seen at least once by eye care clinicians, with
an average of 27 encounters. Dementia diagnoses were made by a panel of
experts using research criteria. The possibility of healthy patient bias
and potential confounders were thoroughly investigated.
Limitations of study: Results could be explained by unmeasured or
residual confounding factors, like any observational study. There
could be coding errors for cataract diagnosis. Only the participant's
first cataract surgery was evaluated so researchers don't know whether subsequent surgeries impacted dementia risk. The majority of the study population was White, and it is unclear if the effect would be observed
in all populations.
"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), a nonprofit dedicated solely to
accelerate the discovery and development of drugs to treat and prevent Alzheimer's disease and related dementias.
As part of its Diagnostics Accelerator research initiative, the ADDF
is also supporting Dr. Lee's work to develop new diagnostic tools for Alzheimer's that use non-invasive imaging of the retina and artificial intelligence.
The study was funded by NIH grants NIH/NEI K23EY029246, NIH/NIA R01
AG060942, NIH/NIA P50 AG05136, NIH/NIA U01AG006781, NIH/NIA U19 AG066567, Alzheimer's Drug Discovery Foundation Diagnostics Accelerator Award,
Latham Vision Innovation Award, and an unrestricted grant from Research
to Prevent Blindness.
========================================================================== Story Source: Materials provided by University_of_Washington_School_of_Medicine/UW_Medicine.
Note: Content may be edited for style and length.
========================================================================== Journal Reference:
1. Cecilia S. Lee, Laura E. Gibbons, Aaron Y. Lee, Ryan T. Yanagihara,
Marian S. Blazes, Michael L. Lee, Susan M. McCurry, James D. Bowen,
Wayne C. McCormick, Paul K. Crane, Eric B. Larson. Association
Between Cataract Extraction and Development of Dementia. JAMA
Internal Medicine, 2021; DOI: 10.1001/jamainternmed.2021.6990 ==========================================================================
Link to news story:
https://www.sciencedaily.com/releases/2021/12/211206113004.htm
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