New research suggests the width of blood vessels in the retina may provide an early warning sign for brain health years before the onset of dementia and other deficits.
Experts have found that younger people who score low on intelligence tests, such as IQ, tend to be at higher risk for poorer health and shorter lifespan. Factors such as socioeconomic status and health behaviors fail to totally explain the relationship.
Psychological scientist Dr. Idan Shalev of Duke University and colleagues wondered whether intelligence might serve as a marker indicating the health of the brain, and specifically the health of the system of blood vessels that provides oxygen and nutrients to the brain.
In a study published in Psychological Science, a journal of the Association for Psychological Science, Shalev and colleagues used digital retinal imaging to determine vascular conditions in the brain by looking at the small blood vessels of the retina, located at the back of the eye.
Retinal blood vessels share similar size, structure, and function with blood vessels in the brain and can provide a way of examining brain health in living humans.
The researchers examined data from participants taking part in a New Zealand longitudinal investigation of health and behavior in over 1,000 people born between April 1972 and March 1973 in Dunedin, New Zealand.
Researchers were intrigued by the findings.
Having wider retinal venules, the small blood vessels that transfers blood from the capillaries to the veins, was linked with lower IQ scores at age 38, even after the researchers accounted for various health, lifestyle, and environmental risk factors that might have played a role.
Individuals who had wider retinal venules showed evidence of general cognitive deficits, with lower scores on numerous measures of neurospsychological functioning, including verbal comprehension, perceptual reasoning, working memory and executive function.
Surprisingly, the data revealed that people who had wider venules 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 said.
The findings suggest that the processes linking vascular health and cognitive functioning begin much earlier than previously assumed, years before the onset of dementia and other age-related declines in brain functioning.
“Digital retinal imaging is a tool that is being used today mainly by eye doctors to study diseases of the eye,” Shalev said. “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.”
The current study doesn’t address the factors that influence the relationship between retinal vessels and cognitive functioning, but the researchers surmise that it may have to do with oxygen supply to 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 concluded.