Signs of damage in the microvasculature of the eye are linked to subsequent cognitive decline, a large prospective study shows.
Using fundus photography, which takes images of the interior surface of the eye, including the retina, investigators at Johns Hopkins Center on Aging and Health in Baltimore, Maryland, found retinopathy was associated with faster cognitive decline over a 20-year period vs no retinopathy.
“One of the reasons we’re so excited about our study is that we think these changes in the very small blood vessels we see in the eye probably mirror the very small blood vessel changes that are going on in the brain,” first author, Jennifer A. Deal, PhD, told Medscape Medical News.
“This lets us get a deeper look at the brain [than we can now] with our standard brain imaging, like MRI, that doesn’t allow us to see blood vessels this small,” she added.
The study was published online February 28 in Neurology.
Accelerated Cognitive Decline
Previous research used fundus photography to examine the relationship between vascular changes in the eyes and cognitive decline. However, the investigators note, these studies are few in number and had limited follow-up, and many were cross-sectional (ie, the participants’ eyes and cognition were assessed simultaneously).
“We can learn a lot from those studies, but we don’t know which came first,” said Deal.
For the current study, investigators used data from the Atherosclerosis Risk in Communities study to determine whether retinal signs were associated with 20-year cognitive decline.
Baseline eye examinations (1993-1995) were conducted in 12,317 participants with an average age of 60 years, and cognition was assessed at three different time points (1990-1992, 1996-1998, and 2011-2013).
They found 365 participants had mild retinopathy, 256 had moderate-to-severe eye damage, and most — 11,692 participants — had no signs of retinopathy.
In the group with moderate-to-severe retinopathy, neuropsychological test scores dropped 1.22 standard deviations (SDs) over two decades of follow-up.
At the same time, those with healthy eyes experienced a decline of 0.91 SD. Even when researchers took into account the participants who missed some of the periodic cognitive assessments, the difference between these two groups was 0.57 SD.
“We came into the study really expecting to see a strong association. We already had information on the relationship between blood vessels in the eye and blood vessels in the brain,” Deal said.
The research also builds on previous findings reported in a subset of the same cohort with a shorter follow-up (Neurology. 2009;73:862-868).
The fundal examination is routine, noninvasive, and easy to administer, Deal said, and clinicians already use it to screen for eye diseases and adverse effects of other conditions, including diabetes and hypertension.
“However, in terms of being sensitive enough to predict cognitive decline…I don’t think we’re quite there with this test,” she added. “So it would be premature to say we could predict cognitive decline based on this test.”
In the meantime, neurologists who detect microvascular damage in patients without diabetes, high blood pressure, or other relevant conditions might consider the need for tighter control of vascular risk factors, Deal said.
She added that newer technology, such as optical coherence tomography, could prove more sensitive for predicting cognitive decline based on the same microvascular changes in the future, but more research is necessary.
Assessment was performed in only one eye of each participant, a limitation of the study. The research is ongoing, with the investigators continuing to follow the study population over time.
A Window to the Brain?
Commenting on the findings for Medscape Medical News, Christina E. Hugenschmidt, PhD, from Wake Forest University in Winston-Salem, North Carolina, said the longitudinal nature of the study contributes to the literature.
“The literature on this idea goes back a few years. The idea is that the vessels in the eyes come from the same blood vessels in the brain at the embryonic stage of development, which is actually pretty cool,” said Hugenschmidt.
“It’s a lot easier to get pictures of the vessels in the eye than the vessels in the brain. So it makes sense that…we might be able to learn about brain health by looking at eye vessels.”
The research adds to the literature by looking at a large number of people over a long span of time, she added.
“The long follow-up period allows you to see how risk plays out during the time when people are most likely to experience dementia and cognitive decline. Seeing eye vessel damage at 60 is actually relatively young. This is reflected in the relatively small numbers of people it affected,” Hugenschmidt said.
“A second point is that while having eye vessel disease increases your risk of developing cognitive decline, not having eye disease does not mean you are free of vascular risk to your brain. Regardless of eye disease, people should take care of their cardiovascular health in order to support their brain health,” she added.
The National Heart, Lung, and Blood Institute and the National Institutes of Health supported the study. Deal and Hugenschmidt have disclosed no relevant financial relationships.
Neurology . Published online February 28, 2018. Abstract
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