Dementia affects nearly 50 million people worldwide, and no effective treatments exist.1 Efforts to reduce risk or delay dementia onset are increasingly important, as noted in the recent 2020 Lancet Commission report.1 Twenty percent of adults older than 65 years in the United States experience significant sensory impairment, such as vision or hearing loss, even with correction.2 Addressing sensory loss that affects a substantial portion of older adults may be a potentially modifiable risk factor for dementia in late life.1,3 Because sensory impairments and dementia are both strongly associated with aging,4 more knowledge about the association between sensory impairment and dementia may have important implications for individual and global public health, particularly if interventions to improve sensory function reduce dementia risk.
Visual impairment is an important dementia risk.5,6 Cataract is a leading cause of blindness worldwide, affecting more than 35 million people globally and causing blindness in approximately 20 million.7 Cataract affects most older adults at risk of dementia. However, there are conflicting results regarding the association between cataract extraction and cognitive impairment or dementia.8-10
We hypothesized that older adults with cataract who undergo cataract extraction may have a lower risk of developing dementia compared with participants who do not undergo cataract surgery or participants who undergo other eye procedures that do not restore vision, such as glaucoma surgery. Previous studies exploring this association have been limited by small sample sizes, cross-sectional designs, and varying qualities of dementia assessment.11,12 More importantly, these studies have failed to account for healthy patient bias (ie, when surgery is more likely in healthier individuals with the same cataract severity).
To the best of our knowledge, no study has compared associations between cataract extraction and dementia with other ophthalmic surgical procedures. To address the potential of healthy patient bias, we included glaucoma surgery in our analyses. We used extensive data from the Adult Changes in Thought (ACT) study to address these questions. We examined whether cataract extraction was associated with a lower risk of dementia, and we used the same modeling approach to examine whether glaucoma surgery was associated with a lower risk of dementia.
Findings In this cohort study assessing 3038 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.
This prospective, longitudinal cohort study analyzed 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 years of age 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 3038 participants). Data used in the analyses were collected from 1994 through September 30, 2018, and all data were analyzed from April 6, 2019, to September 15, 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, 3038 participants were included (mean [SD] age at first cataract diagnosis, 74.4 (6.2) years; 1800 women (59%) and 1238 men (41%); and 2752 (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.
Introduction
Dementia affects nearly 50 million people worldwide, and no effective treatments exist.1 Efforts to reduce risk or delay dementia onset are increasingly important, as noted in the recent 2020 Lancet Commission report.1 Twenty percent of adults older than 65 years in the United States experience significant sensory impairment, such as vision or hearing loss, even with correction.2 Addressing sensory loss that affects a substantial portion of older adults may be a potentially modifiable risk factor for dementia in late life.1,3 Because sensory impairments and dementia are both strongly associated with aging,4 more knowledge about the association between sensory impairment and dementia may have important implications for individual and global public health, particularly if interventions to improve sensory function reduce dementia risk.
Visual impairment is an important dementia risk.5,6 Cataract is a leading cause of blindness worldwide, affecting more than 35 million people globally and causing blindness in approximately 20 million.7 Cataract affects most older adults at risk of dementia. However, there are conflicting results regarding the association between cataract extraction and cognitive impairment or dementia.8-10
We hypothesized that older adults with cataract who undergo cataract extraction may have a lower risk of developing dementia compared with participants who do not undergo cataract surgery or participants who undergo other eye procedures that do not restore vision, such as glaucoma surgery. Previous studies exploring this association have been limited by small sample sizes, cross-sectional designs, and varying qualities of dementia assessment.11,12 More importantly, these studies have failed to account for healthy patient bias (ie, when surgery is more likely in healthier individuals with the same cataract severity).
To the best of our knowledge, no study has compared associations between cataract extraction and dementia with other ophthalmic surgical procedures. To address the potential of healthy patient bias, we included glaucoma surgery in our analyses. We used extensive data from the Adult Changes in Thought (ACT) study to address these questions. We examined whether cataract extraction was associated with a lower risk of dementia, and we used the same modeling approach to examine whether glaucoma surgery was associated with a lower risk of dementia.
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