Age-related macular degeneration (AMD), cataract, and diabetes-related eye disease (DRED) are independently associated with an increased risk for dementia, new data published online in the British Journal of Ophthalmology suggest.
The authors, led by Xianwen Shang, MPH, PhD, with the Department of Ophthalmology, Guangdong Eye Institute, Guangzhou, Guangdong, China, analyzed data on 112,364 adults aged 55 to 73 years who were enrolled in the UK Biobank study.
Participants were assessed between 2006 and 2010 at baseline and were followed until early 2021. During the 1,263,513 person-years of follow-up, 2304 cases of dementia were recorded.
The risk for dementia was 26% higher among those with AMD, 11% higher among those with cataract, and 61% higher among those with DRED compared with people who did not have ophthalmic conditions at the beginning of the study,
Risk for dementia was higher if people had both ophthalmic and systemic conditions — diabetes, heart disease, stroke or depression — than if they had only an ophthalmic or systemic condition, the researchers found.
People who had at least two ophthalmic conditions were at higher risk for dementia than were those with one ophthalmic condition. People who had at least two ophthalmic and at least two systemic conditions were almost three times more likely to develop dementia, the authors state.
Shang told Medscape Medical News that the results have implications for screening practices.
"Our findings suggest that it may be better to do screening among middle-aged or older adults (40–73 years old) with one or more [conditions] of obesity, hypertension, diabetes, cardiovascular disease, or depression," he said.
Shang said their previous research suggested that younger age at diagnosis of systemic conditions was associated with a higher risk for dementia.
"Thus, information on the age at diagnosis of ophthalmic conditions and the important systemic conditions would be useful for detection or prediction of dementia," he said.
The data showed that glaucoma was not an independent risk factor for dementia, a finding consistent with studies from Europe and the United States, the authors write. Glaucoma can increase the risk for vascular dementia but not Alzheimer's disease, their analyses indicate.
Shang said previous studies have demonstrated that cataract surgery may help alleviate the risk for dementia associated with cataract, but much less is known about whether the treatment of AMD or glaucoma can help prevent or delay the development of dementia.
"The improvement or maintenance of vision is critical to obtain information and prevent cognitive decline," he said. "Also, social activity and treatment of important systemic diseases among those with ophthalmic conditions are important for the prevention of dementia."
Cecelia Lee, MD, an ophthalmologist who studies the relationship between eye diseases and dementia at the University of Washington, in Seattle, Washington, told Medscape Medical News that she was glad to see that the results from Shang's team were similar to those her research and others' have shown, especially because the study had a large number of participants.
Awareness Among Physicians
She said this study should not cause alarm among people who have these common eye diseases but rather prompt additional questions by clinicians during eye appointments and in primary care.
More evidence is coming out that ophthalmic health may be very important in older adults who are at risk of developing dementia or Alzheimer's disease, Lee said. She urged screening for treatable eye conditions.
The reasons for the association are not well understood, Lee said, but primary care doctors, geriatricians, and neurologists should be aware that "the health of the retina may be a link to the health of the brain." Likewise, ophthalmologists should be alert to patients who may need referral to a neurologist.
The authors point out that ophthalmic conditions and dementia share several common factors.
Ophthalmic conditions are associated with well-known risk factors of dementia, including diabetes, stroke, heart disease, hypertension, and depression. Other risk factors for ophthalmic conditions as well as dementia are older age, low levels of education, smoking, and physical inactivity.
Poor vision, the authors note, "may result in reduced activation in central sensory pathways, which is associated a higher risk of cognitive load and brain structure damage."
The authors and Lee have disclosed no relevant financial relationships..
Br J Ophthalmol. Published online September 13, 2021. Full text
Marcia Frellick is a freelance journalist based in Chicago. She has previously written for the Chicago Tribune and Nurse.com and was an editor at the Chicago Sun-Times, the Cincinnati Enquirer, and the St. Cloud (Minnesota) Times. Follow her on Twitter at @mfrellick.
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Image 1: Xianwen Shang, MD
Image 2: Cecelia Lee, MD
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Cite this: Common Eye Diseases Linked to Higher Risk for Dementia - Medscape - Sep 17, 2021.