Retinal health linked to dementia risk, study shows

A new study led by the University of Otago has found a link between our eye health and dementia, with researchers discovering the blood vessels at the back of the eye — called retinal microvasculature — can show early signs someone is at risk of developing dementia.

According to Dementia Australia CEO Professor Tanya Buchanan, dementia is the second leading cause of death for all Australians and is on track to become the country’s biggest cause of death within the next five years. Treatments for Alzheimer’s and some other forms of dementia are considered most effective if they’re started early in the disease course, but current testing methods make this difficult — 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.

Published in the Journal of Alzheimer’s Disease, the Otago-led study used data from eye scans from the Dunedin Multidisciplinary Health and Development Study’s age 45 assessment. Serving as co-lead author was Otago’s Dr Ashleigh Barrett-Young, who said it is thought that many of the disease processes in Alzheimer’s are reflected in the retina — which is directly connected to the brain — making it a good target as a biomarker to identify people at risk of developing dementia.

The eye 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. According to Barrett-Young, 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,” she said.

Barrett-Young said 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.

In the meantime, Buchanan said that looking after our brain health can make a big difference to reducing or delaying the risk of developing dementia, as demonstrated in the ‘Maintain Your Brain’ clinical trial which confirmed that some of the modifiable risk factors for dementia resulted in better cognition in older adults over a three-year period.

According to the Lancet Commission on dementia, there are 14 modifiable risk factors which, if addressed effectively, could reduce dementia incidence globally by 45%. These include smoking, obesity, physical inactivity, hearing loss, high cholesterol and depression.

“It is vital that all Australians understand the importance of maintaining brain health throughout our lives,” Buchanan said.

“It is never too early or too late to reduce your dementia risk.”

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