It’s not quite what scientists expected – the width of blood vessels in the eye, at the back of the retina, may indicate brain health risks, such as dementia and alzheimers years before they actually set in according to a new study published in Psychological Science.

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It is already well known that young people who score very low at IQ tests are at a higher risk for poorer health and shorter lifespan which can’t be explained only by other factors. Psychological scientist Idan Shalev of Duke University and colleagues have tried to find out if there is a any connection between IQ score (I really prefer this term to intelligence in this case) and brain health.

To do this, they turned to opthalmology – the branch of medicine that deals with the eye. They used a technique called digital retinal imaging, which is relatively new and completely noninvasive.

“Digital retinal imaging is a tool that is being used today mainly by eye doctors to study diseases of the eye,” Shalev notes. “But our initial findings indicate that it may be a useful investigative tool for psychological scientists who want to study the link between intelligence and health across the lifespan.”

Basically, you can get a pretty good idea of what happens in the blood vessels in the brain by looking at the blood vessels in the retina – it’s the next best thing. Retinal blood vessels share similar size, structure, and function with blood vessels in the brain. Their results were rather intriguing.

Having wider retinal venules was linked with lower IQ scores at age 38, even after researchers eliminated all the other likely causes, like health, lifestyle, and environmental risk factors that might have played a role.

People who had wider retinal venules had noticeable cognitive deficits, scoring lower on numerous tests of neuropsychological functioning, verbal comprehention, memory, and many more. But what was even more surprising, is that people who had wider blood vessels at age 38 also had lower IQ in childhood, a full 25 years earlier.

“It’s remarkable that venular caliber in the eye is related, however modestly, to mental test scores of individuals in their 30s, and even to IQ scores in childhood,” the researchers observe.

They believe that there is not really a distinct mechanism between retinal vessels and cognitive functioning, but is rather connected to oxygenation of the brain.

“Increasing knowledge about retinal vessels may enable scientists to develop better diagnosis and treatments to increase the levels of oxygen into the brain and by that, to prevent age-related worsening of cognitive abilities,” they conclude.