Age is just a number, goes the popular saying. Scientists in the U.S., however, believe we are focusing on the wrong number.
They claim that rather than gauging the state of our health based on our age in calendar years, we should be measuring our inflammatory age.
The scientists, from Stanford University and the Buck Institute for Research on Aging, have now developed a blood test to measure inflammatory age (or iAge), a measure of chronic inflammation — and say that checking it regularly could provide an early warning of inflammation-related conditions from heart disease to dementia.
This would give us the time to take measures to improve our health, from lifestyle changes to taking medication.
As Dr Nazish Sayed, an assistant professor of vascular surgery at Stanford, explains: 'We are all going to age and we are all going to die — the only difference is how well we age,' he says.
'The goal is a healthier old age — to prevent some of the ill health associated with ageing and make ageing more graceful.'
US scientists have now developed a blood test to measure inflammatory age, or iAge, and say checking it could provide an early warning of inflammation-related conditions (stock image)
His research, reported in the journal Nature Aging, is based on the understanding that chronic inflammation plays a key role in disease.
We are all familiar with acute inflammation — the fever, swelling and pain that plays a vital role in the healing of wounds and in fighting off infections, which typically lasts only days.
Chronic inflammation, by contrast, is a lingering, low-level inflammation that can, over time, damage our cells and organs and is linked to many diseases, including type 2 diabetes and cancer.
Levels of inflammation increase as we get older, likely due to ageing cells releasing inflammation-fuelling molecules. It can also be worsened by factors such as smoking, obesity, pollution and stress.
The damage caused is often so gradual that we are unaware of it for years, until we start to develop symptoms such as high blood pressure.
To develop the test to measure this 'hidden' inflammation, the researchers analysed blood samples from more than 1,000 people for levels of 50 cytokines, immune system proteins, known to be involved in inflammation.
Combining the results of the blood test with details about the participant's age and health revealed a cytokine 'signature' associated with ill health.
The researchers used this to calculate a person's iAge — their biological age based on their levels of inflammation.
For example, if someone who is 45 has an iAge of 65, their body is 20 years older than it should be, due to the damaging effects of inflammation.
A further experiment supported the claim that our inflammatory age is a better marker of health than our chronological age.
Using blood samples, they calculated the iAge of 37 people from one area of Italy.
Half of the participants were aged between 50 and 79 and in normal health for their age, while the others were in such good health that they had lived to 100 or more.
Levels of inflammation increase as we get older and can also be worsened by factors such as smoking, obesity, pollution and stress (stock image)
The centenarians, on average, had an iAge 40 years lower than their actual age. In contrast, most of the younger group had an iAge that was higher than their chronological age.
Some of the individual results were even more striking.
'We have one outlier, a super-healthy 105-year-old man who has an immune system of a 25-year-old,' says one of the researchers, immunologist Dr David Furman.
The scientists also showed that a person's iAge can be used to predict who is most at risk of becoming frail and so potentially need help with washing, dressing and other everyday tasks.
Furthermore, they were able to pick out those likely to develop a heart condition called left ventricular hypertrophy that raises the risk of heart failure (where the heart struggles to pump blood around the body).
Arne Akbar, a professor of immunology at University College London and president of the British Society for Immunology, told Good Health that iAge is a 'sophisticated way' of measuring age-related rises in inflammation.
However, he adds: 'There are other ways to measure increased inflammation during ageing, such as measuring levels of C-reactive protein [a compound that is a marker of inflammation and can be measured with a simple blood test].
'This raises the question of how sophisticated the measurement of inflammation should be to predict health — and which is easiest and cheapest.'
The new test is several years away from widespread use, however Dr Sayed envisions it being done annually alongside other regular health checks, such as cholesterol tests.
Those with a high iAge could then try to lower their levels of inflammation. This may be through exercising more or changing their diet — both of which can dampen chronic inflammation. Or it may be that new iAge-lowering medicines are developed.
The research showed a cytokine called CXCL9 to be particularly strongly linked to iAge, suggesting a new drug that lowers this could help keep the body healthy for longer.
Dr Alan Cohen, a biologist researching biological ageing at Sherbrooke University in Canada, warns however that the workings of the immune system are so intricate that a drug which tinkers with one part of it could have unintended consequences.
He adds: 'Ageing is multi-dimensional; there is no single thing that is ever going to tell you perfectly what your biological age is.'
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