Long-term smokers who switched to vaping were halfway towards achieving the vascular health of a non-smoker within a month, a study has found.
Those who ditched cigarettes and vaped instead saw their blood vessel function increase by around 1.5 percentage points within four weeks compared to those who continued smoking.
The researchers said they did not know whether this benefit would be sustained, with more research needed into the long-term implications of vaping.
But they said if this improvement was sustained into the long-term, those who switched would have at least a 13% reduced risk of cardiovascular events, such as heart attacks.
The VESUVIUS study recruited 114 adult UK smokers who had smoked at least 15 cigarettes a day for at least two years and were free from established cardiovascular disease.
Forty patients continued smoking tobacco cigarettes, 37 switched to e-cigarettes with nicotine and 37 switched to e-cigarettes without.
The researchers measured changes in blood vessel function – the earliest detectable change to cardiovascular health – through a test known as flow mediated dilation (FMD).
This measures how far a blood vessel opens and they used another test to measure the stiffness of the blood vessels.
It is crucial to emphasise that e-cigarettes are not safe, just less harmful than tobacco cigarettes when it comes to vascular health.
Overall, the groups who gave up for e-cigarettes experienced a 1.49 percentage point improvement in their vascular function compared to those who continued smoking.
Separate meta-analysis has shown that for every 1% improvement in vascular health, 13% fewer cardiovascular events occur over the long-term.
A healthy non-smoker can expect an average FMD score of 7.7%, the authors said.
Chronic smokers who switched to vaping with nicotine saw their FMD increase by about a fifth from 5.5% to 6.7% at the end of the month.
This means that, within a month, the new vapers were around halfway towards achieving the FMD of a healthy non-smoker.
The authors cautioned that it was not clear whether FMD would continue to improve at the same rate or for how long.
Earlier this week cardiologists said action must be taken to prevent an entire generation becoming addicted to nicotine, as they published separate research suggesting vaping could damage the brain, heart, blood vessels and lungs.
They said there is a “paucity of evidence” to support claims that e-cigarettes are a “healthy” alternative to smoking or that they help people quit.
This contrasts to advice from Public Health England (PHE), which stands by its claim that e-cigarettes are 95% less harmful than smoking.
Jacob George, professor of cardiovascular medicine and therapeutics, who led the study, said conflicting safety advice from public health bodies across the world has led to confusion for the public and policymakers.
But he would not comment on whether PHE’s 2015 estimate was premature or backed up by evidence.
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 devices 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.”
According to Government statistics, approximately 6% of Britain’s adult population use a vaporiser.
Dual use of tobacco and e-cigarettes is making it more challenging for researchers to tease out which effects are due to what, Prof George added.
Prof Jeremy Pearson, associate medical director at the British Heart Foundation, which funded the study, said moving towards a world with no e-cigarettes was a “secondary consideration” compared to stopping people smoking.
He said: “The crunch is that is what this study shows is a change in function, so that you change the ability of the vessel to dilate, but what long-term smoking does may have actually changed the structure of the vessel so however much you stop smoking, it will never get back to normal because it’s changed permanently. We don’t know from this study.”
The findings are published in the Journal of the American College of Cardiology.