The thickness of the retina can predict a decline in brain power, an eye test study has proved.
Scientists found that people with thin retinas were twice as likely to perform poorly in subtle tests on everyday memory, reaction time and reasoning.
When tested again three years later, these people were also twice as likely to have suffered mental decline.
Separate research building on the breakthrough findings shows the changes can be tracked to predict full-blown dementia nearly a decade later.
Experts hope drugs or lifestyle changes, such as quitting booze and smoking, could slow or even halt onset of the disease in those identified as at risk.
Prof Paul Foster, lead study author, said: “We now know we need to find people at the earliest stages before the brain is irreparably damaged.
“The hope is that either a drug or lifestyle advice can stop this.
“The combination of the two studies showing the increased risk I think does put it beyond doubt. There is unquestionably a link between changes in the retina and changes in people’s mental state.”
Researchers at University College London and Moorfields Eye Hospital used UK Biobank data on OCT scans, which measure the thickness of a layer of neurons on the retina.
The landmark study looked at 32,000 apparently healthy people aged 40 to 69 who had undergone the eye test, available at NHS opticians.
Prof Foster, a world-leading eye specialist, said: “This is even before pre-dementia. It is very mild cognitive impairment like forgetting the number of your local takeaway.
“Things that in the past they would’ve been able to dredge up from their memory. It’s about one in 20 who struggles a bit more with that kind of recall.”
The second paper, published by the Erasmus Medical Centre in Rotterdam, Netherlands, followed 5,000 people with an average age of 69. Over eight years, 86 developed dementia. Those with a thin retina were 44% more likely to do so.
UCL’s paper could revolutionise treatment of the devastating disease, which affects 850,000 Britons. This is expected to increase to one million by 2025.
Initial findings from Prof Foster’s study were presented at a medical conference two years ago, but the project suffered a setback when a lead study author quit.
Researchers have confirmed the findings, which have been peer-reviewed.
Both studies were published in the same edition of Jama Neurology journal. It comes after 99% of trials globally from 2002 to 2012 for potential Alzheimer’s treatments failed.
The UCL team is working out the precise thickness of retina that indicates risk is high enough for patients to be given a diagnosis of pre-dementia.
Prof Foster added: “They will constantly be thinking, ‘When is it going to start?’.
“We need to find a threshold within the measures we have to indicate, if not certain, a very high probability of dementia… before we can identify people who need to modify their lifestyle or take drugs.”
- Women who had their first period at age 16 were a third more likely to develop dementia than those who began puberty at the average age of 13, a US study of 15,000 women aged 40 to 55 found.
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