Cataract removed in older people might provide them with more than just improved vision, according to research published in JAMA Internal Medicine.
The study, by a team from the University of Washington, the Swedish Medical Centre (Seattle) and the Kaiser Permanente Washington Health Research Institute, suggests they are 30% less likely to develop dementia, including Alzheimerʼs disease, than are people with cataracts who do not have the surgery.
Dementia affects nearly 50m people worldwide, and no effective treatment exists. At least 20% of adults older than 65 in the United States experience significant sensory impairment, such as vision or hearing loss, even with correction.
The key, the researchers say, may be the restoration of vision that comes with cataract surgery. The finding stems from data on 3,038 people 65 and older who were dementia-free at the start of the study and were tracked for nearly 10 years after their decision on eye surgery.
Everyone who ages can get cataracts. Surgery can help remove them.
The researchers said visual impairment has been identified as a dementia risk factor, in part because it can lead to social isolation and decreased cognitive stimulation. But by restoring vision, they wrote, cataract surgery may help delay or prevent the development of dementia.
Glaucoma can lead to blindness. Researchers foresee changing that.
In comparison, they found found no differences in risk for dementia among people who did or did not have glaucoma surgery, which does not restore vision. Glaucoma is a condition that attacks the optic nerve. A cataract is a cloudy area that can develop in the lens of the eye, almost always caused by normal changes in the eye that come with age. Proteins in the lens tend to break down and clump together, according to the National Eye Institute, creating the cloudy area. This can lead to such symptoms as blurred vision, sensitivity to light and difficulty seeing at night.
What you should know about cataract surgery
The only treatment is surgery to remove the clouded lens and replace it with an artificial lens (called an intraocular lens), which restores vision. More than 24m US residents have cataracts, according to the American Academy of Ophthalmology, and nearly half of people who are 80 either have cataracts or have had surgery to remove them.
Cataract is a leading cause of blindness worldwide, affecting more than 35m million people globally and causing blindness in approximately 20m.
Study details
Association Between Cataract Extraction and Development of Dementia
Cecilia Lee, Laura Gibbons, Aaron Lee, Ryan Yanagihara, Marian Blazes, Michael Lee, Susan McCurry, James Bowen, Wayne McCormick, Paul Crane, Eric Larson.
Published in JAMA Internal Medicine on 6 December 2021
Key Points
Question Is cataract extraction associated with reduced risk of developing dementia?
Findings In this cohort study assessing 3,038 adults 65 years of age or older with cataract enrolled in the Adult Changes in Thought study, participants who underwent cataract extraction had lower risk of developing dementia than those who did not have cataract surgery after controlling for numerous additional risks. In comparison, risk of dementia did not differ between participants who did or did not undergo glaucoma surgery, which does not restore vision.
Meaning This study suggests that cataract extraction is associated with lower risk of developing dementia among older adults.
Abstract
Importance
Visual function is important for older adults. Interventions to preserve vision, such as cataract extraction, may modify dementia risk.
Objective
To determine whether cataract extraction is associated with reduced risk of dementia among older adults.
Design, Setting, and Participants
This prospective, longitudinal cohort study analysed data from the Adult Changes in Thought study, an ongoing, population-based cohort of randomly selected, cognitively normal members of Kaiser Permanente Washington. Study participants were 65 or older and dementia free at enrollment and were followed up biennially until incident dementia (all-cause, Alzheimer disease, or Alzheimer disease and related dementia). Only participants who had a diagnosis of cataract or glaucoma before enrollment or during follow-up were included in the analyses (ie, a total of 3,038 participants). Data used in the analyses were collected from 1994 until 30 September 2018, and all data were analysed from 6 April 2019 to 15 September 2021.
Exposures
The primary exposure of interest was cataract extraction. Data on diagnosis of cataract or glaucoma and exposure to surgery were extracted from electronic medical records. Extensive lists of dementia-related risk factors and health-related variables were obtained from study visit data and electronic medical records.
Main Outcomes and Measures
The primary outcome was dementia as defined by Diagnostic and Statistical Manual of Mental Disorders (Fourth Edition) criteria. Multivariate Cox proportional hazards regression analyses were conducted with the primary outcome. To address potential healthy patient bias, weighted marginal structural models incorporating the probability of surgery were used and the association of dementia with glaucoma surgery, which does not restore vision, was evaluated.
Results
In total, 3,038 participants were included (mean [SD] age at first cataract diagnosis, 74.4 (6.2) years; 1,800 women (59%) and 1,238 men (41%); and 2,752 (91%) self-reported white race). Based on 23, 554 person-years of follow-up, cataract extraction was associated with significantly reduced risk (hazard ratio, 0.71; 95% CI, 0.62-0.83; P < .001) of dementia compared with participants without surgery after controlling for years of education, self-reported white race, and smoking history and stratifying by apolipoprotein E genotype, sex, and age group at cataract diagnosis. Similar results were obtained in marginal structural models after adjusting for an extensive list of potential confounders. Glaucoma surgery did not have a significant association with dementia risk (hazard ratio, 1.08; 95% CI, 0.75-1.56; P = .68). Similar results were found with the development of Alzheimer disease dementia.
Conclusions and Relevance
This cohort study found that cataract extraction was significantly associated with lower risk of dementia development. If validated in future studies, cataract surgery may have clinical relevance in older adults at risk of developing dementia.
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