Scientists have developed a blood test to estimate how quickly someone is ageing. They believe it could be used to predict a person’s risk of developing Alzheimer’s disease as well as the “youthfulness” of donated organs for transplant operations.
The test measures the vitality of certain genes which the researchers believe is an accurate indication of a person’s “biological age”, which may be younger or older than their actual chronological age.
A study has shown that the test can distinguish between healthy individuals and patients with Alzheimer’s and so might also be used it to identify people in the early stages of the brain disease who have not yet developed symptoms, scientists said.
The “ageing test” could also be used on organs donated for transplant operations to assess their biological age and hence the risk of them failing once they have been transferred into a recipient, said James Timmons, professor of precision medicine at King’s College London.
“We use birth year, or chronological age, to judge everything from insurance premiums to whether you get a medical procedure or not. Most people accept that all 60-year-olds are not the same, but there has been no reliable test for underlying biological age,” Professor Timmons said.
“Our discovery provides the first robust molecular ‘signature’ of biological age in humans and should be able to transform the way that age is used to make medical decisions. This includes identifying those more likely to be at risk of Alzheimer’s, as catching those at early risk is key to evaluating potential treatments,” Professor Timmons said.
Alzheimer's disease mainly affects people over the age of 65
“There was a very strong difference between people with mild cognitive impairment and [healthy people], so it seems as if it could be developed into a test, particularly when combined with relevant clinical variables. However most likely it represents a way to spot 'at risk' people and guide them toward clinical trials for prevention,” he said.
In addition to the possibility of applying the test to dementia, the researcher hope to develop it as a way of assessing the suitability of organs donated for transplant operations from elderly donors.
“For kidney transplantation, older organs are being used more and more, and the older the donor the more likely the transplantation will fail and it would be valuable to know the biological age of the organ before using it,” Professor Timmons said.
It may also be possible to use the test to screen elderly people who have a young biological age so that they could be considered for organ donation if they die of other causes, such as traffic accidents, he said.
The research, published in the on-line journal Genome Biology, analysed the activity levels of a panel of key genes of healthy 65-year-old subjects by measuring the levels of RNA - a close cousin of DNA - in their blood. The seven Alzheimer's risk factors
The scientists used this information on gene activity as a marker of biological ageing. They then studied the RNA of healthy 70-year-olds and analysed their health records over two decades and found that a high gene-activity score was associated with better cognitive health and kidney function across a 12-year period - both predict the risk of an early death.
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An important finding from the research was that this gene activity was the same in the brain and the blood for people with Alzheimer’s disease, giving scientists a way of quickly and easily diagnosing what is happening in the brain just by looking at a blood sample.
“This is the first blood test of its kind and has shown that the same set of molecules are regulated in both the blood and the brain regions associated with dementia, and it can help contribute to a dementia diagnosis,” Professor Timmons said.
“This is very novel. It suggests we can use the gene-signature to better understand Alzheimer’s disease and also as a screen for looking at drugs in human cells - an early step in drug discovery,” he said.
