▎ WuXi AppTec content team editor
Dementia affects nearly 50 million people worldwide, and there are currently no therapies that can effectively change the course of the disease. Studies suggest that visual impairment may be an important risk factor for dementia, and cataracts affect most older adults at risk of dementia.
Cataracts are the leading cause of blindness worldwide, affecting more than 35 million people worldwide and causing about 20 million people to lose sight. Visual function is so important for the elderly, so will interventions to preserve vision, such as cataract surgery, change the risk of dementia?
A recent study published in JAMA Internal Medicine found that cataract surgery was associated with a nearly 30 percent lower risk of dementia.
Screenshot source: JAMA Internal Medicine
The observational study included a total of 3,038 participants with an average age of 74.4 years who were diagnosed with cataracts or glaucoma but did not develop dementia. Investigators were followed up every 2 years until the patient developed dementia.
The researchers assessed participants' cognitive abilities based on cognitive ability screening, with scores ranging from 0 to 100 points. Participants with scores below 85 received further neurological tests. The primary outcome was the incidence of dementia, as defined in the Diagnostic and Statistical Manual of Mental Disorders (Fourth Edition).
After an average follow-up of 7.8 years, 853 participants were found to have developed dementia, of whom 709 had Alzheimer's disease, and about half of the participants (45%) underwent cataract surgery.
After adjusting for years of schooling, smoking history, and stratification by APOE e genotype (Alzheimer's disease risk-related gene), sex, and age at the time of cataract diagnosis. The researchers found that participants who had undergone surgery on any one eye had a reduced risk of developing dementia for any cause by about 30 percent for at least 10 years after surgery compared to participants who had not undergone cataract surgery (RR= 0.71, P
After adjusting for multiple potential confounding factors (such as eye surgery within two years of dementia diagnosis, etc.), the researchers still found similar results. And cataract surgery has also been linked to reducing the risk of Alzheimer's disease.
However, receiving glaucoma surgery (which does not restore vision) was not significantly associated with the risk of developing dementia compared with cataract surgery.
In addition, the researchers also found that when considering the relationship between cataract surgery, education, smoking history, sex and APOE genotype and risk of developing dementia, the only factor that was more protective than cataract surgery was not to carry the APOE e4 allele (a high-risk gene for Alzheimer's disease).
Image credit: 123RF
Dr Cecilia SLee, lead author of the study and an associate professor of ophthalmology at the University of Washington School of Medicine, said: "The study adjusted for some confounding factors and still found a strong association between cataract surgery and the risk of developing dementia. ”
The researchers analyzed the mechanisms underlying cataract surgery associated with a reduced risk of dementia. First, after cataract surgery, people may get higher quality sensory input, which may be beneficial for reducing the risk of dementia. Second, cataract surgery can reactivate cells that feel blue light, and while people get more blue light, it may also help regulate sleep cycles and cognitive function. Finally, visual impairment can lead to psychosocial difficulties, withdrawal from social interactions, and decreased activity or exercise, all of which may be associated with cognitive decline.
The research team said the study also had limitations, such as only evaluating participants' first cataract surgeries, so it was uncertain whether subsequent surgeries affected the risk of developing dementia.
The paper concludes that the findings suggest that cataract surgery has a significant correlation with a lower risk of dementia in adults aged ≥65. The results have important implications for the care of older adults and, to a large extent, may improve the quality of life for individuals and their families. The results also provide strong evidence, insights and potential treatments for further study of the association of dementia with other retinal diseases such as age-related macular degeneration to slow or prevent age-related dementia.