New research, published in the journal Psychological Science, suggests that the width of blood vessels in the retina may be a good indicator of brain health and IQ.

Researchers, led by psychological scientist Idan Shalev of Duke University, set out to determine how IQ is related to overall brain health. In particular, whether it is in any way associated with the health system of blood vessels that provide the brain with essential nutrients and oxygen.

Through the means of a new, non-invasive method called digital retinal imaging, the researchers got a good look at the small blood vessels in the retina and were able to identify the link between IQ and vascular health.

The blood vessels located in the retina have a similar size, structure and function of those in the brain. Therefore, by observing the retinal blood vessels the researchers determined brain health.

Using data gathered from a longitudinal investigation of health and behavior, which included a total of 1,000 people born between April 1972 and March 1973, the research team made a surprising discovery.

Even after accounting for various different risk factors, they found that people with wide retinal venules, on average, scored lower on IQ tests at the age of 38, compared to those with small venules.

The participants who had wide retinal venules tended to score lower on a number of cognitive measures such as: memory, verbal comprehension, executive function, and perceptual reasoning.

In addition, adults at the age of 38 with wide venules had a lower IQ when they were kids as well, the scientists said that 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.”

This suggests that the association between vascular health and IQ may begin years before any signs of dementia, or age-related declines in brain functioning, begin to appear.

Shalev said:

“Digital retinal imaging is a tool that is being used today mainly by eye doctors to study diseases of the eye. 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.”

While the study didn’t identify specific mechanisms responsible for the relationship between IQ and retinal vessels, the investigators believe that it is probably due to oxygen supply to the brain.

The researchers concluded:

“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.”

Interestingly, a previous study published in the journal Brain, Behavior, and Evolution, revealed that estimating the intelligence of various animal species may be as simple measuring overall brain size. Suggesting that brain size predicts intelligence too.

Written by Joseph Nordqvist