Saliva swab could predict if you'll die within the year - would you be brave enough to take the test?

It's the only thing in life that's guaranteed.

But knowing when you're going to die remains somewhat of a mystery.

Now, experts could be one step closer to a 'date of death' test after discovering a simple cheek swab can accurately estimate your risk of dying within the next year by analysing changes to DNA.

A team from Tally Health — a biotechnology company based in New York — have developed an epigenetic clock called CheekAge which is able to work out biological age from easy-to-collect cheek cells.

Rather than a person's actual age, this analyses how old cells are. Biological age can be affected by things like genetics, stress, sleep, nutrition and smoking, and can be higher or lower than a person's actual age.

The scientists tested their method to see how well it predicted mortality from any cause in 1,513 women and men, born in 1921 and 1936 and who were followed throughout their lives.

Analysis revealed that changes to DNA were significantly linked with mortality.

Participants in the highest CheekAge group were 148 per cent more likely to die that year compared to those in the lowest group.

Their method was even more accurate than other epigenetic clocks which analysed blood, the team said.

Their findings were all retrospective, meaning their method was tested on participants who had already passed away.

Future research could involve testing the method on people who are still alive, to see whether it can accurately predict when they will die.

Writing in the journal Frontiers in Aging the team said: 'This implies that a simple, non-invasive cheek swab can be a valuable alternative for studying and tracking the biology of aging.'

However, other experts cautioned that this method cannot be used to predict the day or even year that someone will pass away.

Adele Murrell, Professor of Epigenetics at the University of Bath, said she sees no evidence that the CheekAge clock will be able to forecast the day or even year that someone will die.

Changes to DNA are theoretically reversible, she explained, meaning the method would only be useful for warning people they may be heading for an early demise.

'Given these changes are as a result of lifestyle choices — smoking, weight gain, poor diet and lack of fitness - combined with underlying disease — cancer, obesity, diabetes - all factors that are evident without epigenetic testing, it's not yet clear whether patients will be more likely to change their lifestyle choices when confronted with the epigenetic clock data than when their GP warns them to do so,' she added.

Meanwhile Dusko Ilic, Professor of Stem Cell Sciences at King's College London, said: 'In reality, such clocks provide probabilistic risk assessments rather than concrete predictions.

'Emphasizing mortality in this context may potentially cause unnecessary anxiety and foster a fatalistic mindset in some people, rather than promoting actionable insights into healthspan and well-being.

'A more nuanced approach would be to frame CheekAge as a tool for assessing biological age and associated health risks, encouraging interventions aimed at extending healthy ageing rather than focusing on mortality.'