In an observational study, a group of researchers took over 3,000 adults aged 65 and above and discovered an otherwise unknown link between cataract surgery and a reduced risk of developing dementia, which includes Alzheimer’s disease.
The researchers explain that the study results found a connection between sensory impairments like vision loss with a higher risk for dementia. They also believe that there is a link between blue light and developing dementia.
With over 55 million people suffering from dementia worldwide, which is a syndrome that is highly associated with a decline in particular cognitive functions like language, comprehension, and memory.
The most common type of Alzheimer’s is dementia, which accounts for 60-80% of all people diagnosed with dementia. For many years, experts and scientists have completed tons of research, looking into the causes of Alzheimer’s, but until now the reason has been out of reach.
A group from the University of Washington School of Medicine in Seattle claim that they discovered a link between a lowered risk of developing dementia in older individuals – Alzheimer’s included – and cataract surgery.
What the study authors think is that this is due to the heightened sensory input and increased exposure to blue light that happens after cataract surgery that could help explain this link. The hope is that this newfound information can help lead scientists to potential new therapies that can either slow down or possibly prevent age-related forms of dementia.
You can check out the results of this observational study where it was published, in the journal of Jama Internal Medicine.
What Is A Cataract?
A cataract is a common condition normally found in older adults when the proteins in the naturally clear lens of the eye end up breaking down, causing the eye to become “cloudy” looking. When this occurs, vision ends up becoming foggy and objects tend to appear either less colorful or blurry, or both. While most cataract issues normally start off small, if left untreated, over time they tend to become quite large and can impair one’s vision, making it hard to read, drive or do other every day tasks.
According to the World Health Organization (WHO), there is an estimated 94 million people all over the world that are living with cataracts.
The most common cause of cataracts is aging, although there are other risk factors such as diabetes, smoking, previous eye injuries, and excessive sun exposure throughout one’s life that may actually increase the risk of developing cataracts later on in life.
Currently, the only way to remove a cataract is via cataract surgery, a procedure that involves an eye surgeon surgically removing the eye’s natural lens and replacing it with an intraocular lens (IOL), which is an artificial lens.
The Aging Brain and the Aging Eye
Lead researcher and associate professor and Klorfine Family Endowed Chair in ophthalmology at the University of Washington School of Medicine, Dr. Cecilia S. Lee, spoke with Medical News Today about the research they were doing.
She shared that in previous research, associations were found between several eye diseases like diabetic retinopathy and age-related macular degeneration (AMD) with an increased risk of dementia and Alzheimer’s disease.
According to Dr. Lee, “A cataract is a natural aging process of the eye and effects the majority of older adults who are at risk for dementia.”
She added,“Sensory loss, including vision and hearing, is of interest to the research community as a possible modifiable risk factor for dementia. Because cataract surgery improves visual function, we hypothesized that older people who undergo cataract surgery might have a decreased risk of developing Alzheimer’s disease and dementia.”
Dr. Lee and her team took data from over 3,000 participants and analyzed it for their ongoing Adult Changes in Thought Study.
The participants in the Adult Changes in Thought Study enrolled when they were 65 years old or older, and they didn’t have dementia. The research team followed up with them ever two years until they began showing symptoms of dementia or when Alzheimer’s disease symptoms began to show.
The company, Kaiser Permanente Washington, managed to collect data for the study between the years 1994 to 2018, which they analyzed between 2019 to 2021. They only included patients that had been given a diagnosis of cataract or glaucoma before enrollment or during their follow-ups.
The researchers took information from the participants’ medical records about their cataract surgeries, they found that from the 3,038 participants in the study, 853 developed dementia, which included 709 with Alzheimer’s disease. In addition, 1,382 of the participants – which is equal to around 45% of the total – had undergone cataract surgery.
While doing further research into the participants that had cataract surgery, Dr. Lee and her team found that there was an ‘almost 30% less risk of developing dementia after their surgery.’ Moreover, the research team also reported that there was no dementia risk for those that underwent glaucoma surgery.
Future Dementia Research and Eye Health
As for the director of scientific programs and outreach for the Alzheimer’s Association, Dr. Claire Sexton, who was not involved with the study, she told MNT what she considered the most important finding, explaining “We’ve seen in previous research that sensory impairments, such as vison loss, are associated with a higher risk for dementia. But this research tells us that improving vision – in this case, extracting cataracts – may reduce risk of dementia.”
She continued, “There is a strong message here for doctors that they need to assess and treat sensory impairment in their patients who are older adults and those with Alzheimer’s disease and other dementias.”
“Assessment of sensory function should also play a role in assessing cognitive changes and diagnosing Alzheimer’s. People with sensory impairments such as vision or hearing loss should track them and discuss them with their doctor. Family members can play an important role in paying attention to sensory changes and encouraging assessment and follow up,” she added.
As for Dr. Lee, her hope is that the results of this study will help doctors understand the importance of eye health especially for older patients that could be at a higher risk for dementia.
She shared, “To date, there are few known measures, other than certain lifestyle factors, such as diet and exercise, that are thought to be preventive against dementia.”
She also said,“Older adults who are experiencing symptoms of cataracts, such as night driving difficulty or seeing halos around bright lights are to be evaluated by ophthalmologists […] who specialize in eye surgeries. If ophthalmologists recommend someone undergoes cataract surgery and the patient is on the fence about proceeding, our study results suggest that cataract surgery would not hurt, and there may be an added benefit.”
How About the Role of Blue Light?
When it comes to blue light, cataracts block it. But after surgery, more blue light can actually enter the eye. As for the study authors, this could possibly play a role in lessening the risk of developing dementia.
For Dr. Lee, she shared that there are special cells in the retina, which are called intrinsically photosensitive retinal ganglion cells (ipRGCs), which tend to be much more sensitive to blue light stimuli, which help regulate one’s circadian cycles.
She explained, “Degeneration and altered function of these cells has been shown to be associated with cognition and Alzheimer’s disease,” she added. “Because cataract surgery restores the passage of blue light through the lens and to the ipRGCs, it may enable the reactivation of those cells in a way that is protective against cognitive decline.”
Moreover, she also said that the retina could possibly give a non-invasive way to help diagnose Alzheimer’s disease and other forms of dementia even before the clinical symptoms of the disease develop.
She said, “Sensitive retinal biomarkers of preclinical Alzheimer’s disease would be very useful for clinical trials of potential treatment approaches.”
She added, “We are currently conducting research where we collect a number of non-invasive, highly sensitive retinal imaging in people with and without cognitive problems and use artificial intelligence (AI) techniques to interpret and analyze the data. Our ultimate goal in the future is to develop AI algorithms that can identify features in the eye that can predict someone’s risks of developing dementia, such as Alzheimer’s disease.”
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