"Smokers can improve the health of their hearts within weeks of switching to e-cigarettes, the largest trial of its kind shows," BBC News reports.
The number of people using e-cigarettes, or vaping, has grown rapidly over the past decade and they have helped many people to give up smoking cigarettes. However, as e-cigarettes have only been available for a relatively short time, we're still building evidence on their health effects – both positive and negative.
In this new Scottish study researchers recruited 115 smokers, about two-thirds of whom were willing to switch to e-cigarettes while a third continued to smoke.
After a month researchers found the arteries of those who switched to e-cigarettes were now better at widening (dilating) when there was an increased blood flow. This ability of the arteries to remain pliable and respond to changes in blood flow is known as vascular function. Poor vascular function is a risk factor for cardiovascular diseases, such as a heart attack.
So this study may indicate these people switching to e-cigarettes had a decreased risk of developing heart disease or stroke. However, the study cannot prove this as it only looked at a very small sample of people and followed them for a very short time.
Also, the effect is very unlikely to result from e-cigarettes themselves: it's an effect of stopping smoking. While we're still gathering evidence on the effects and potential harms of e-cigarettes, there are many other well-established stop smoking treatments.
Read more about getting help to stop smoking.
Where did the story come from?
This study was conducted by researchers from the University of Dundee and funded by the British Heart Foundation. The study was published in the peer reviewed Journal of the American College of Cardiology, and is freely available to access online.
BBC News reports that switching to e-cigarettes improves the health of smokers' hearts within weeks. This is not strictly correct. While vascular function in the main artery in the arm may be a marker for cardiovascular risk, this does not prove a direct improvement in heart health.
What kind of research was this?
This Scottish study involved comparing the results of a randomised controlled trial (RCT) with a comparison control cohort group. In the trial, smokers willing to quit were randomised to e-cigarettes with and without nicotine. The comparison cohort involved smokers unwilling to quit who continued to smoke tobacco cigarettes.
An RCT involving everyone in the study group would have been a more effective method of assessing the effectiveness of an intervention. However, for obvious ethical reasons, this was not possible, as people could not be randomised to an intervention known to be harmful (smoking tobacco).
Therefore, we cannot say any vascular changes are a direct effect of e-cigarettes as other differences between the participants in each group could be having an influence.
What did the research involve?
The study recruited 145 smokers aged over 18 years, who had smoked at least 15 cigarettes daily for the past 2 years, and who were free from existing cardiovascular disease or diabetes. Those willing to quit were randomised to e-cigarettes containing nicotine or no nicotine. Those unwilling to quit continued their usual smoking habit and agreed not to use e-cigarettes alongside during the 4-week trial period.
The main outcome of interest was change in dilation (widening) of the brachial artery in the arm. These measurements were taken at recruitment and after the 4-week trial. The researchers also looked at heart rate and blood levels of cholesterol and inflammatory markers.
114 of the 145 recruited participants (79%) completed follow-up: 40 in the smoking group and 37 in each of the e-cigarette groups.
What were the basic results?
In both e-cigarette groups there was increased dilation of the arm artery in response to increased blood flow (flow-mediated dilation).
The improvement tended to be greater for women than men. They also noticed a bigger improvement among those with the greatest decrease in exhaled carbon monoxide levels (that is, the best compliance with e-cigarettes and no continued tobacco use).
There was no difference in blood markers between groups. For heart rate, they found that any changes were mainly influenced by how much participants had smoked to start with (e.g. heart rate increased for e-cigarette users who had previously been light smokers, and decreased for the heavier smokers).
How did the researchers interpret the results?
The researchers conclude: "Tobacco smokers, particularly females, demonstrate significant improvement in vascular health within 1 month of switching to e-cigarettes. Switching from tobacco smoking to e-cigarettes may be considered a harms reduction measure."
The use of e-cigarettes has grown rapidly over the past decade. Evidence has shown they can decrease cigarette smoking rates, and they're understood to be considerably less harmful than smoking cigarettes. However, as they have only been around for a relatively short period of time, we're still gathering information on their direct health effects – both positive and negative.
This study finds that quitting smoking and moving to e-cigarettes showed improved vascular function within 1 month. Vascular function is understood to be a marker of whether a person may be at risk of developing heart and vascular disease. Therefore, this clearly seems to be a positive effect. However, there are a few points to bear in mind.
First, this small, short-term study is not able to provide evidence that people switching to e-cigarettes would definitely be at reduced risk of having a heart attack or stroke – however plausible this may seem. You would need to look at much larger groups of people, follow them for longer, look at changes in vascular function and other risk markers over time and, ultimately, actual disease outcomes.
As people clearly cannot be randomised to continue smoking or not, we do not know whether there may be other health and lifestyle differences between those using e-cigarettes or tobacco that could also be influencing vascular function. For example, diet and exercise levels and alcohol intake.
Also, this obviously does not mean that e-cigarettes have some special ability to improve vascular function: any direct effects would simply result from stopping tobacco smoking. The same may be seen if people quit using other methods, like nicotine patches.
What we do know for certain is that tobacco smoking is harmful to health in many ways, increasing risk not only of cardiovascular disease but also many cancers and other chronic diseases. Stopping smoking is the important thing – however you achieve it.
There are many well-established and effective smoking cessation methods. We're still building evidence on e-cigarettes. The National Institute for Health and Care Excellence (NICE) currently advises that "the evidence suggests that e-cigarettes are substantially less harmful to health than smoking but are not risk-free. The evidence in this area is still developing, including evidence on the long-term health impact".
Analysis by Bazian
Edited by NHS Website
Links to the headlines
BBC News, 16 November 2019
Links to the science
Journal of the American College of Cardiology. Published online November 15 2019