How well are you ageing?

An international group of researchers has found a set of genes associated with ‘healthy ageing’ in 65-year-olds.

The scientists say their study, published in the journal Genome Biology, provides the first practical and accurate test for the rate at which individual bodies are ageing. It could thus lead to numerous insights in research, with ‘age’ being a critical factor in almost every area of medicine.

“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,” said lead author Professor James Timmons, from the Division of Genetics and Molecular Medicine at King’s College London. “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.”

The seven-year study, taking place at King’s College London, Karolinska Institutet in Sweden and Duke University in the USA, used RNA profiling to measure and compare gene expression in thousands of human tissue samples. Rather than looking for genes associated with disease or longevity, the researchers discovered that the ‘activation’ of 150 genes in the blood, brain and muscle tissue were a hallmark of good health at 65 years of age. From this, they were able to create a reproducible formula for ‘healthy ageing’ and use this to tell how well a person is ageing when compared to others born in the same year.

The researchers used their ‘healthy age gene score’ to compare the RNA profiles of several 70-year-old subjects. Despite all subjects being born within a year of each other, their RNA demonstrated a very wide distribution in healthy age gene score, varying over a four-fold range. This variation was shown to link to long-term health, cognitive health and renal function. In particular, patients diagnosed with Alzheimer’s disease had an altered healthy ageing RNA signature in their blood and, therefore, a lower healthy age gene score, suggesting significant association with the disease.

The correlation between a low score and cognitive decline implies that the molecular test could translate into a simple blood test to predict those most at risk of Alzheimer’s disease or other forms of dementia and age-related diseases. Given that early intervention is important in Alzheimer’s, the score could even be integrated to help decide which middle-aged subjects could be offered entry into a preventative clinical trial many years before the clinical expression of Alzheimer’s.

“This is the first blood test of its kind that 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 also provides strong evidence that dementia in humans could be called a type of ‘accelerated ageing’ or ‘failure to activate the healthy ageing program’.”

Additionally, the molecular test could enable more suitable donor matching for older organ transplants. It could also provide a more efficient way of determining if an animal model of ageing is suitable to evaluate the effectiveness of anti-ageing treatments.

Interestingly, a person’s healthy age gene score was not found to correlate with lifestyle-associated conditions, such as heart disease and diabetes. It is therefore likely to represent a unique rate of ageing largely independent of a person’s lifestyle choices. Furthermore, the study does not provide insight into how to improve a person’s score and thus alter their biological age.

“We now need to find out more about why these vast differences in ageing occur, with the hope that the test could be used to reduce the risk of developing diseases associated with age,” Professor Timmons said.

Image credit: ©iStockphoto.com/Colin McKie