Electronic cigarettes containing nicotine are more effective in helping smokers quit than gum or patches, according to scientists.
But the researchers have said more evidence is needed on the potential long-term harm of using e-cigarettes.
In a newly updated review published in the Cochrane Library, the team looked at three studies involving 1,498 people that compared e-cigarettes with nicotine replacement therapy, such as patches or gum.
The results showed that more people gave up smoking if they used e-cigarettes containing nicotine than if they used another form of nicotine replacement.
In a statement, the team said: “If six people in 100 quit by using nicotine replacement therapy, 10 people in 100 would quit by using electronic cigarettes containing nicotine.
“This means an additional four people in 100 could potentially quit smoking with nicotine-containing electronic cigarettes.”
Similar results were seen in another three studies that compared nicotine-containing e-cigarettes with those that did not contain nicotine, the researchers added.
Meanwhile, evidence from four studies also showed that more people who used nicotine-containing e-cigarettes gave up smoking than those who received only behavioural support or no support.
The review authors said they did not detect any clear evidence of serious harms from nicotine e-cigarettes but added that evidence about serious harms is uncertain.
They said this is because the overall number of studies was small and serious health problems were very rare in both users and non-users of nicotine e-cigarettes.
Jamie Hartmann-Boyce, from the Cochrane Tobacco Addiction Group, who is the lead author of this updated Cochrane Review, said: “The randomised evidence on smoking cessation has increased since the last version of the review and there is now evidence that electronic cigarettes with nicotine are likely to increase the chances of quitting successfully compared to nicotine gum or patches.
“Electronic cigarettes are an evolving technology.
“Modern electronic cigarette products have better nicotine delivery than the early devices that were tested in the trials we found, and more studies are needed to confirm whether quit rates are affected by the type of electronic cigarettes being used.
“While there is currently no clear evidence of any serious side-effects, there is considerable uncertainty about the harms of electronic cigarettes and longer-term data are needed.
“Scientific consensus holds that electronic cigarettes are considerably less harmful than traditional cigarettes, but not risk-free.”
Commenting on the findings, John Britton, emeritus professor of respiratory medicine at the University of Nottingham, who was not involved in the research, said: “This comprehensive review of all data on the efficacy of electronic cigarettes in helping people to quit provides definitive confirmation that electronic cigarettes offer smokers an effective means of quitting, and perhaps even more so than some licensed stop smoking medicines.
“It therefore endorses the UK policy of promoting electronic cigarettes as a consumer product that can help smokers quit smoking completely, and supports the recommendation of electronic cigarettes in the NHS.
“Questions over their long-term safety will not be resolved until these products have been in use for many years, but all the available evidence indicates that any long-term adverse effects are likely to be far smaller than those of smoking tobacco.”
The updated Cochrane Review now includes 50 studies, an increase of 35 studies since it was last published in 2016.
Its findings come as public health charity Action on Smoking and Health (ASH) published survey figures suggesting the percentage of adults in Great Britain using e-cigarettes fell from 7.1% in 2019 to 6.3%, or around 3.2 million people, in 2020.
The charity argues that “unfounded concerns” about health risks from e-cigarettes could mean smokers are not benefitting from switching to them.
ASH chief executive Deborah Arnott said: “About a third of smokers have never even tried an e-cigarette and less than 20% are currently using one.
“If many more smokers could be encouraged to give e-cigarettes a go, the latest evidence indicates that many more might successfully quit.
“Health professionals have an important role to play. They can give smokers the confidence to try an e-cigarette, by letting them know that they can help them manage cravings and that they are a much safer alternative than continuing to smoke.”