Eye health linked to dementia risk

A new University of Otago – Ōtākou Whakaihu Waka study has found a link between our eye health and dementia.

Dunedin Multidisciplinary Health and Development Study researchers discovered the blood vessels at the back of the eye – called retinal microvasculature – can show early signs someone is at risk of developing dementia.

Co-lead author Dr Ashleigh Barrett-Young, of the Department of Psychology, says the findings link to previous work by members of the research team, “putting together pieces of a puzzle” when it comes to recognising early signs of dementia.

The findings are too premature to be applied in the real world yet, but research is continuing around the world.

“Treatments for Alzheimer's and some other forms of dementia may be most effective if they’re started early in the disease course.”

Knowing who would benefit from early treatment is crucial, but difficult to do with current testing methods, which she hopes will improve in the future.

Cognitive tests aren’t sensitive enough in the early stages and a person may not be experiencing any decline yet, while other tests, like MRI and PET scanning, are expensive and not widely available.

“In our study, we looked at the retina which is directly connected to the brain,” she says.

“It’s thought that many of the disease processes in Alzheimer's are reflected in the retina, making it a good target as a biomarker to identify people at risk of developing dementia.”

The study was co-led by Dr Aaron Reuben, of the University of Virginia, showcasing one of Otago’s many collaborations with universities around the world.

Published in the Journal of Alzheimer's Disease, researchers used data from eye scans from the Dunedin Study’s age 45 assessment.

It is New Zealand’s longest-running longitudinal study and is considered the world’s most detailed study of human health and development.

The scans reveal narrower arterioles (the small blood vessels that carry blood away from the heart) and wider venules (the smallest veins which receive blood from capillaries), and thinner retinal nerve fibre layers (which carry visual signals from the retina to the brain) were associated with greater dementia risk.

Dr Barrett-Young says this was somewhat unexpected.

“I was surprised that venules were associated with so many different domains of Alzheimer's disease – that suggests that it might be a particularly useful target for assessing dementia risk.”

Despite the findings, she reminds people not to panic.

“This research is still in an early stage, and we can’t predict your future looking at an eye scan,” she says.

“Hopefully, one day we’ll be able to use AI methods on eye scans to give you an indication of your brain health, but we’re not there yet.”