Scientists claim simple blood test could predict future dementia risk

Blood Tests

A team of scientists at King's College London believe they may have identified a 'molecular signature of ageing' which could be used to predict whether or not individuals will later go on to develop Alzheimer's.

The study, published in the journal Genome Biology, analysed blood and tissue samples from 15 healthy young and 15 healthy older individuals. Information contained in the ribonucleic acid, or RNA, a genetic messenger that assists deoxyribonucleic acid, or DNA, to follow through on our genetic blueprint, was then compared to corresponding sample data of hundreds of people collected for several previous studies.

Samples taken from the healthy older people were used to identify a sequence of 150 different markers of healthy ageing to identify an optimum healthy RNA signature for a 65-year-old person. This was then compared to information relating to samples taken from people with an Alzheimer's diagnosis, which indicated how the tissue of those with the degenerative condition differed from the tissue of healthy individuals.

The team discovered that 'biological ages' were found to differ in some cases by as much as two decades – demonstrating that actual age in years is not always reflective of the biological ageing process, and could go some way towards explaining why some people develop dementia at a relatively young age.

Professor James Timmons, of King’s College London, who led the research says: "We use birth year, or chronological age, to judge everything from insurance premiums to whether you get a medical procedure or not.

"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."

Dr Doug Brown, Director of Research, Alzheimer’s Society, says: "With further development this research could help in our quest to find new treatments for the condition, by identifying people who are more likely to develop Alzheimer’s disease so that they can participate in clinical trials.

"People shouldn’t take these findings to mean that most cases of Alzheimer’s are inherited as this is not true. The markers identified in this study are affected by the complex interaction between genetic and environmental factors and we’ll need further research to fully understand what they are telling us about the disease process."

'Early detection critical'

Dr Tara Spires-Jones, Reader and Chancellor’s Fellow, Centre for Cognitive and Neural Systems, University of Edinburgh, says: "This is one of a number of recent studies aiming to develop a blood test capable of detecting the early stages of dementia. This is important because early detection will be critical to effective treatments for dementia."

"While this study looks promising, it is worth noting that it is not yet a fool proof blood test for dementia. While an improvement over many studies, it appears from the data that people with dementia would not always be different from controls on this test. There will also need to be further validation from independent groups."

'Complexities of the human body'

Dr Eric Karran, Director of Research, Alzheimer’s Research UK, says of the findings: "Advances in genetic technologies over the past decades are now allowing scientists to profile the complexities of the human body in more detail than ever before. One of the biggest questions in human biology is how we age, and how this process impacts our wider health and risk for conditions like Alzheimer’s. This study suggests a way to measure a person’s ‘biological age’ and could reveal insights into the ageing process and why some people are more susceptible to age-related health conditions. The ‘biological age’ measured by this test did not seem to be altered by important health parameters such as blood pressure, which we know can be risk factors for dementia. It will be important to determine how the ‘biological age’ score interacts with known population genetic risk factors for diseases like Alzheimer’s. Much of the data in the study represents a snapshot in time, and it will be important to explore further how a person’s biological age score correlates with their health and survival in later life."

"There is much interest in developing a blood test for diseases like Alzheimer’s but such a test would need rigorously validating to show it was accurate and sensitive before it could be used in the clinic. Furthermore, tests that confirm actual pathological changes in the brain will continue to be used for confirming or ruling out clinical diagnoses. This study will need to be repeated and validated in a larger group of people to know whether it could be a useful clinical test for Alzheimer’s or how it could improve current research practices. With an increasingly ageing population in the UK and around the world, it’s important to invest in research in this area to help understand and improve health today and for future generations."

It is hoped the research, which was funded by the Medical Research Council, may help to identify individuals at an early stage - those with low scores but no dementia symptoms - who may wish to volunteer for clinical trials as part of the development of preventative treatments.

Doctor and Couple Talking

Ethical concerns

However, this scenario is unlikely to happen for some time as experts say any tests would first be subject to vigorous appraisal relating to accuracy and reliability before it could be used in practice. In addition, the ethical considerations of introducing such a test, including the emotional and practical implications for those diagnosed with accelerated biological ageing along with an indication of increased risk of developing the degenerative condition could prove to be a barrier to widespread application.

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