THEY can be seen standing outside every major office, enveloped in clouds of sweet-smelling vapour as they grab their dose of nicotine in their coffee and lunch breaks.

Now, a major study has found that cigarette smokers who switch to vaping could significantly improve their vascular health.

The report from the University of Dundee’s School of Medicine came after a two-year trial and found that smokers who transitioned to e-cigarettes showed a significant improvement in their circulatory health within four weeks.

Women experienced greater gains than men, but all those who switched achieved a greater improvement compared to those who continued to use real cigarettes alongside the vaporisers.

The British Heart Foundation-commissioned study, named Vesuvius, is thought to be the largest undertaken to date in determining the impact of e-cigarettes on heart health.

Its findings are published in the Journal of the American College of Cardiology.

Jacob George, professor of Cardiovascular Medicine and Therapeutics at Dundee and the trial’s chief investigator, said that while e-cigarettes were found to be less harmful, the devices may still carry health risks. He said: “It is crucial to emphasise that e-cigarettes are not safe, just less harmful than tobacco cigarettes when it comes to vascular health ... They should not be seen as harmless for non-smokers or young people to try.

“However, for chronic tobacco smokers there were significant improvements in vascular function within a month of switching from a tobacco cigarette to an e-cigarette.

“To put into context, each percentage point improvement in vascular function results in a 13% reduction in cardiovascular event rates such as heart attack.

“By switching from cigarettes to e-cigarettes we found an average percentage point improvement of 1.5 within just one month.

“This represents a significant improvement in vascular health.

“We also found that, in the short term at least, regardless of whether the e-cigarette does or does not contain nicotine, a person will see vascular health improvements compared to smoking a traditional cigarette.

“The longer-term impact of nicotine requires further study and follow-up.”

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George said that women benefitted significantly more than men by switching from tobacco and his team were still looking into the reasons for this.

Vesuvius recruited 114 long-term smokers who had smoked at least 15 per day for at least two years and split them into three groups – those who continued with tobacco, those who switched to e-cigarettes with nicotine and those on nicotine-free e-cigarettes.

According to UK Government figures, around 6% of Britain’s adult population use a vaporiser, though previously the impact of the devices on vascular health have been unclear.

Professor Jeremy Pearson, associate medical director at the British Heart Foundation, said: “Just because e-cigarettes may be less harmful than tobacco doesn’t mean they are completely safe.

“We know they contain significantly fewer of the harmful chemicals, which can cause diseases related to smoking, but we still don’t know the long term impact on the heart and circulation, or other aspects of health.”

Public Health Minister, Joe FitzPatrick, added: “While research shows that switching to e-cigarettes can lead to vascular health benefits for chronic tobacco smokers, access to e-cigarettes needs to be controlled carefully – they are simply not products for children or non-smokers.”