All potential complications of diabetes are scary — from reduced sensation in your feet and legs to impaired vision or kidney function. But one possible outcome that many people fear the most is cognitive dysfunction. No one wants to lose control of their body, but for many people, the idea that their mind might not work as well is even scarier.
So finding ways to predict cognitive decline in people with diabetes could be welcome to many people, especially if it were followed by interventions that might help people avoid cognitive changes. Unfortunately, predicting this decline isn’t always easy, and cognitive exams take considerable time and expense — and can have varying results depending on how you’re feeling that day, and other factors that may affect your results.
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But according to a new study, there may be a way to help predict cognitive decline in people with diabetes by administering a test that many people need and receive already — noninvasive retinal imaging scans of your eye.
Abnormalities in scan predict cognitive changes
The study, published in the Journal of Clinical Endocrinology & Metabolism, included 129 participants with type 1 diabetes who had the condition for at least 50 years. At a university hospital setting, participants went through a complete cognitive testing regimen, which included measures of psychomotor speed, immediate memory and delayed memory. Participants also underwent two different kinds of eye scans, optical coherence tomography (OCT) and OCT angiography (OCTA). These tests measured neural retinal layer thicknesses, as well as blood vessel density for both superficial and deep retinal capillary plexus (SCP and DCP).
Researchers found that decreased blood vessel density — as measured by both SCP and DCP — in the eyes was associated with worse delayed memory, as well as worse psychomotor speed involving using their dominant hand to complete tasks. Thinning of the retinal outer nuclear layer was associated with worse psychomotor speed in tests involving participants’ dominant hand as well as their nondominant hand. Thinning of the eye’s outer plexiform layer — a dense network of neuronal synapses — was associated with delayed memory in cognitive tests.
These findings, the researchers wrote, suggest that noninvasive retinal imaging scans — both OCT and OCTA — could be a useful way to screen people with diabetes, especially type 1, for cognitive dysfunction. This screening could then be followed up with a cognitive assessment, and measures to help slow or prevent further cognitive decline could be put in place or ramped up, if needed.
What explains the connection between eyes and brain?
At first glance, the connection between eye damage due to diabetes and cognitive decline may not seem obvious — but considering how close your eyes are to your brain, it shouldn’t be surprising that the two are connected. Diabetes can damage tiny blood vessels in your eyes, leading to retinal damage (diabetic retinopathy), and blood vessel damage could also affect your brain’s blood supply — as well as, potentially, blood vessels in the brain itself.
In explaining this connection, the researchers write that “Changes in multiple metabolic and hormonal factors induced by diabetes likely contribute to the abnormalities in the retina,” along with cardiovascular disease and changes to the central nervous system. Because cognitive dysfunction is associated with both diabetic retinopathy and cardiovascular disease, “abnormalities of the large vessels and capillaries are likely involved in cognitive deficits related to aging people with a chronic duration of type 1 diabetes.”
Right now, there aren’t any recommendations for cognitive screening tied to the results of eye imaging tests in people with diabetes. But as this study demonstrates, it may be time to put screening recommendations in place, at least for people with type 1 diabetes. More studies are needed to find out if the same connection between retinal damage and reduced cognitive function applies to people with type 2 diabetes.
“These findings suggest that noninvasive retinal imaging using OCT and OCTA may provide readily accessible, reproducible and noninvasive surrogate markers to evaluate cognitive dysfunction in people with type 1 diabetes,” the researchers conclude. “Furthermore, these markers may be relevant across the spectrum of retinopathy severity.”
Want to learn more about maintaining cognitive health with diabetes? Read “Nine Tips to Keep Your Memory With Diabetes,” “Keeping Your Brain Strong With Diabetes” and “Memory Fitness: How to Get It, How to Keep It.”