From: Duke University
Department of Psychology & Neuroscience,
Institute for Genome Sciences & Policy
2020 West Main Street, Suite 201
Durham, North Carolina 27708
TITLE: Retinal Vessel Caliber and Lifelong Neuropsychological Functioning
An international research team from the USA, UK, Singapore and New Zealand reports that the size of the blood vessels in the back of the eye can indicate the health of the brain of people approaching midlife (age 38 years), years before age-related declines in brain functioning.
PUBLICATION SOURCE: Psychological Science, advance online publication date, May 2013.
- Young people who score low on IQ tests, tend to be at higher risk for diseases in later life, and even tend to die younger.
- One plausible explanation for this link is that intelligence tests assess brain health.
- Digital retinal imaging is a relatively new and non-invasive method to visualize the small blood vessels in the retina, at the back of the eye. The small vessels in the eye may reflect the conditions of the vessels inside the brain because both eye and brain vessels share similar size, structure and function. Thus, retinal imaging can provide a window to study the health of the brain in living humans.
- We studied the link between retinal vessel width and intelligence tests scores in the representative Dunedin birth cohort of 1000 New Zealanders born in 1972-73, and followed for 38 years with repeated assessments.
- Using a digital fundus camera, which can photograph the interior surface of the eye, we were able to assess the size of the small blood-vessels in the retina, namely, the arterioles and venules (the small branches of the arteries and veins). We also administered intelligence tests in childhood and adulthood.
- We found that study members who presented with wider venules had poorer intelligence tests scores at midlife (age 38 years). This finding held up independently of potential factors that may explain this link, such as low socio-economic status, smoking, or diabetes.
- Moreover, wider venules in the eye were linked with lower childhood IQ that had been tested 25 years earlier.
WHY ARE THESE FINDINGS IMPORTANT?
Previous studies have shown that the blood-vessels in the eye can indicate risk for diseases related to the vessels in the brain, such as stroke and dementia. But these previous studies were conducted on elderly people.
We showed that the small blood-vessels in the eye can indicate the health of the brain of individuals in their 30s, and even the health of the brain in childhood, many years before the late-life onset of age-related brain diseases.
Digital retinal imaging is a tool that is being used today mainly by eye doctors to study diseases of the eye. Our initial findings indicate that retinal imaging may be a useful investigative tool for psychological science to study the link between intelligence and health across the lifespan.
Digital retinal imaging: Photographs of the blood vessels in the retina were taken with a fundus camera. Using computerized software, we measure the retinal vessel diameters of the six largest arterioles and six largest venules in the retina (see figure below). Retinal photographs were assessed at the Singapore Eye Research Institute.
Neuropsychological Functioning: Intelligence tests were administered in childhood at ages 7, 9, 11, and 13 years and again in adulthood at age 38 years. In addition to the IQ test, we also administered various tests to evaluate mental control, memory and motor function.
Participants were 1037 members of the Dunedin Multidisciplinary Health and Development Study which follows all children born between April 1972 and March 1973 in Dunedin, New Zealand. This birth cohort’s families represent the full range of socioeconomic status and health in the general population. Follow-ups have been carried out at ages 3, 5, 7, 9, 11, 13, 15, 18, 21, 26, 32 and most recently at age 38, when 95% of the living cohort members took part.
Figure: An Illustration of the assessment of retinal vessel width.
(1) Duke University, Durham, NC, USA.
(2) MRC Social, Genetic, and Developmental Psychiatry Centre, King’s College London, Institute of Psychiatry, UK.
(3) Singapore Eye Research Institute, Singapore National Eye Center, Singapore.
(4) National University of Singapore, Singapore.
(5) Dunedin School of Medicine, University of Otago, New Zealand.
The study protocol was approved by the institutional ethical review boards of the participating universities. Study members gave informed consent before participating.
MAIN FUNDING SOURCES:
1. The U.S. National Institute on Aging
2. The U.K. Medical Research Council
3. The U.S. National Institute of Child Health and Human Development
4. The U.S. National Institute on Drug Abuse
5. Jacobs Foundation
6. The New Zealand Health Research Council