New Indicators for Alzheimer Disease May Be Found in the Eye

Age-related macular degeneration (AMD), diabetic retinopathy (DR), and glaucoma, may be early warning signs that an individual is at risk for developing Alzheimer disease or dementia, according to the results of a new study.

Recently published in Alzheimer’s and Dementia, the study was spurred by a chance meeting between Cecilia S. Lee, MD, MS, assistant professor of Ophthalmology and director of Clinical Trials at the University of Washington, Paul Crane, MD, MPH, professor at the University of Washington, and Eric Larson, MD, MPH, executive director of Kaiser Permanente Washington Health Research Institute. Lee learned of Crane and Larson’s Adult Changes in Thought study, through which the team has been collecting longitudinal data from thousands of patients since 1994 that they hope will yield insights into how to treat and prevent dementia.

Lee, an ophthalmologist who specializes in big data research, used their data set to see if diseases that affect the eyes might be associated with dementia. Some previous studies have suggested an association based on shared characteristics such as progressive neurodegeneration and microvascular insults.

“Any health care providers who provide care for aging patients may be interested in our study results,” Lee told MD Magazine^®. “Health care providers may decide to refer patients to neurologists when they are suspicious of cognitive dysfunction and [patients] have any of these 3 eye conditions.”

Lee and her team reviewed the data of 3877 patients who were over the age of 65 at the start of the study. A total of 90% of the patients were white and had at least a high school degree; 792 of the patients went on to develop Alzheimer disease.

The investigators followed the participants for an average of 8 years each. After controlling for other risk factors such as smoking, age, sex, education, and APOE genotype, they found that diagnoses of glaucoma, AMD, and DR were associated with the risk of developing Alzheimer disease. Cataracts, however, were not. The exclusion of cataracts is especially important because it suggests that the association was not solely because the diseases are all age-related.

The increase in risk for Alzheimer disease ranged from 20% to 67% depending on the diagnosis and its timing. Patients with established glaucoma did not have an increased risk of Alzheimer disease, but those who had been recently diagnosed were at a 46% higher risk than patients without glaucoma at all. AMD patients who had been recently diagnosed showed a 20% increase in Alzheimer disease risk (though this was not significant); however, those with established AMD had a 50% greater risk than their healthy counterparts.

Patients with DR had the highest increases in risk with a 50% increase for those with established DR, and a 67% increase for those with recently-diagnosed DR.

“We have already received several messages of enthusiasm. Our study points out a new exciting area of Alzheimer's research and finding the relationship between the aging eye and the aging brain may lead to new screening methods and better therapies for Alzheimer's disease,” says Lee.

Next, she and her team are exploring the eyes for definitive biomarkers that point to Alzheimer disease and provide clues to understanding this association.

The study, "Associations between recent and established ophthalmic conditions and risk of Alzheimer's disease," is an article in press in Alzheimer’s and Dementia.

Even more resources pertaining to Alzheimer’s disease and dementia can be found on MD Magazine's new sister site, NeurologyLive.