IF scientists could disentangle your DNA to predict your life expectancy, would you want to know?

That conundrum is fast becoming a reality after scientists at Edinburgh University's Usher Institute devised a scoring system which links genetic variations to the likelihood of a person living longer or dying earlier.

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The results are based on an analysis of 500,000 DNA samples from individuals of European ancestry in the UK, Europe and United States, alongside records of their parents’ lifespan.

HeraldScotland: Dr Peter JoshiDr Peter Joshi

Although the majority of people share roughly the same life expectancy based on their DNA profile, there are extremes at either end of the genetic spectrum creating what is known as a 'Bell Curve'.

This means that the top 10 per cent of the population might expect to live up to five years longer than those who score in the lowest 10%, based on their DNA alone.

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The findings are part of ongoing research by Dr Peter Joshi, an actuary and AXA Fellow at the Usher Institute, who has previously led studies involving samples from 150,000 and 300,000 people.

Dr Joshi said: "The way statistics work, you have a clearer lens the more people you have in the sample. This time we showed that a gene that affects which blood type you are - A or B or O - affects how long you live. Another gene, insulin-like growth factor, appears to affect how you age.

"So two people might have different copies of the same gene and one of those people might have the copy that means, all other things being equal, that they might live slightly longer. When we say 'slightly', we're talking maybe a quarter of a year for the average person with the beneficial variant.

"But the overall shape of our findings are that the main way that genetics seems to affect how long you live is through susceptibility to heart disease. If you're carrying variants that protect you from heart disease, they seem to be the things that make the biggest difference."

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The team did not discover significant genetic patterns which pointed to an increased risk of death from cancer, however. Dr Joshi said they believed this is probably because these disease are the result of rarer genetic differences, or more commonly triggered by lifestyle and environmental factors.

Dr Joshi said the research could eventually be used as a public health tool because individuals with a high genetic 'risk score' could be identified early and encouraged to mitigate it by living healthier lives.

He said: "There's inevitably a lot of chance involved whatever your genes and whatever your lifestyle, so that group of people by having a better diet and exercise would on average certainly be able to counteract those effects.

"We certainly see some quite interesting stuff from some of our collaborators where they've looked at genetic risk scores for heart disease and shown that if your BMI is normal, then the score isn't the same prognostic. But if you've got a high BMI then you very quickly move into a significant danger zone.

"So if you knew you had a genetic susceptibility, it would very much tell you that perhaps by reducing my BMI to a normal level it can make a big difference."

Dr Joshi stressed that in the current strict legislative climate we are a "long way away" from a situation where genetic tests could be used as a basis for calculating health or life insurance, adding that the accuracy of DNA forecasts is not yet "powerful enough to excite insurers".

He added that he had purchased genetic testing kits as a Christmas gift for himself and his wife to trace their ancestry - but would also use it to pick apart their DNA.

Asked whether he felt nervous about what he might discover, Dr Joshi said: "I think knowledge is power. The one thing is that the test is likely to tell you about you susceptibility to Alzheimer's disease - and at the moment there's not that much to be done about that.

"So you're giving yourself a piece of information that you might argue is just a fact, but it's a fact that might worry you and that worry is not likely to be very productive in that there's not much you can do about it."