Smokers in their twenties are biologically two decades older than they should be, according to the first study of its kind.
Researchers now warn the ‘fascinating evidence’ proves the notoriously bad habit accelerates the ageing process.
The human body has two different ages – chronological and biological. The latter refers to how old a person seems.
Scientists analysed blood samples from tens of thousands of volunteers to assess how smoking can affect biological ageing.
They predicted the majority of smokers under the age of 30 to actually be aged between 31 and 40 – or 41 to 50.
On the other hand, the ages of 62 per cent of the non-smokers were calculated accurately, the researchers discovered.
The same trend was found for 31 to 40-year-olds, in which the ages of almost half of the smokers were predicted to be 41 to 50.
Older smokers did not show such effects – possibly because those most affected had already died, the researchers said.
The research was carried out by Baltimore-based artificial intelligence solutions company Insilico Medicine.
The results were carried out based on the blood profiles of 149,000 adults, of which 33 per cent (49,000) reported being smokers.
Smokers and non-smokers were matched for age, sex and geography of residence.
The researchers combined an age-prediction model using a technique called deep learning and various biochemical markers among the participants.
These included levels of blood sugar, fasting glucose, iron stores and urea, a waste product excreted in urine.
The findings, published in Scientific Reports, showed that females smokers were worse off than males, in terms of their biological age.
Study author Dr Polina Mamoshina said: ‘Compared with non-smokers, smokers showed an accelerated rate of ageing through to age 55 years regardless of sex.’
‘The contribution of tobacco smoking as an external factor of ageing may eventually be masked by the… deleterious nature of the ageing process.
‘Alternatively, the people most affected by smoking may have died at an earlier age and thus were be excluded from the old-age smoking group.’
Previous research has shown biological age is more useful than using a date of birth for predicting when a person will die.
Her team say the analysis of blood tests could soon replace traditional self-reporting methods used to evaluate the effects on ageing of other lifestyle choices such as diet, exercise and alcohol consumption.
Insilico Medicine uses artificial intelligence, or computer learning, to research ageing and drug development to ‘extend healthy longevity’.
Dr Mamoshina said: ‘We applied artificial intelligence to prove that smoking significantly increases your biological age.
‘I am pleased to be part of the research study, which provides fascinating scientific evidence that smoking is likely to accelerate ageing.’
In the UK there are an estimated 9.4 million current smokers, roughly 19 per cent of the population, and 38 million in the US.
It is the biggest cause of death and illness in Britain, claiming more than 120,000 lives each year through associated disease.