The width of blood vessels in the retina, located at the
back of the eye, may indicate brain health years before the onset of dementia
and other deficits, according to a new study published in Psychological Science, a journal of the Association for
Research shows that younger people who score low on intelligence
tests, such as IQ, tend to be at higher risk for poorer health and shorter
lifespan, but factors like socioeconomic status and health behaviours don’t
fully account for the relationship. Psychological scientist 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.
How the study was
To investigate the potential link between intelligence and
brain health, the researchers borrowed a technology from a somewhat unexpected
Shalev and colleagues used digital retinal imaging, a
relatively new and non-invasive method, to gain a window onto 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 the Dunedin Multidisciplinary Health and Development Study, a longitudinal
investigation of health and behaviour in over 1000 people born between April
1972 and March 1973 in Dunedin, New Zealand.
The results were intriguing.
Having wider retinal venules 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.
What the findings
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.
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 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.”
The current study doesn’t address the specific mechanisms
that drive the relationship between retinal vessels and cognitive functioning,
but the researchers surmise that it may have to do with oxygen supply to the
“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.