Two of the studies compared e-cigarettes with nicotine patches and found that they were equally effective at reducing smoking.
Although many smokers want to quit, few successfully give up in the long term. Nicotine patches and gum are standard aids for smoking cessation, but recently, e-cigarettes have significantly overtaken these products in popularity among smokers.
However, this trend has concerned some researchers, who have reported mixed results as to whether e-cigarettes promote or reduce smoking behaviors.
In May, Medical News Today reported on an article published in the journal Annals of Allergy, Asthma and Immunology that found e-cigarettes do not reduce use of conventional cigarettes.
However, in the same month, researchers from University College London (UCL) in the UK published findings from their study of e-cigarettes in the journal Addiction. The UCL team surveyed more than 5,800 smokers and found that those attempting to quit were 60% more likely to succeed if they used e-cigarettes, compared with those who used traditional nicotine replacement therapies.
The Cochrane review is based on two randomized trials and 11 observational studies conducted by researchers in the UK and New Zealand. The randomized trials analyzed information from 662 current smokers on their use of e-cigarettes and reduction of cigarette smoking.
The researchers found that about 9% of smokers who used e-cigarettes were able to stop smoking for up to 1 year. Among smokers who used nicotine-free e-cigarettes, about 4% stopped smoking for 1 year.
When the researchers looked at smokers who had reduced the number of cigarettes they smoked without giving up completely, they found that 36% of e-cigarette users halved the number of cigarettes they smoked, as did 28% of participants who were given placebo e-cigarettes.
Two of the studies compared e-cigarettes with nicotine patches and found that they were equally effective at reducing smoking. No serious side effects from e-cigarettes were observed during the studies.
Limited sample size means further studies are required
However, the authors admit that the number of participants in the studies was limited.
"Although our confidence in the effects of electronic cigarettes as smoking cessation interventions is limited because of the small number of trials, the results are encouraging," says Peter Hajek, one of the authors.
"Both trials used electronic cigarettes with low nicotine delivery and it is likely that more recent products are more effective as previous research suggests that higher and faster nicotine delivery facilitates treatment effects," adds Hajek. "Several ongoing studies will help to answer the question more fully."
David Tovey, editor-in-chief at Cochrane, explains why this is an important study:
"This review provides a timely reminder of the challenges faced by smokers who find it hard to stop smoking. The results so far need to be strengthened with further comparisons between electronic cigarettes and other traditional ways of stopping smoking such as chewing gum and patches, and evidence on long-term safety."