The use of electronic cigarettes has been linked to successful attempts to quit smoking.
The finding, published in The BMJ today, goes against concerns e-cigarettes undermine motivation and quit attempts.
The observational study estimates the use of e-cigarettes last year may have resulted in an additional 18,000 long-term ex-smokers in England.
“Although these numbers are relatively small, they are clinically significant because of the huge health gains from stopping smoking,” the authors said.
They point out a 40-year-old smoker who quits can expect to gain nine life years, compared with continuing smokers.
Nevertheless, as with any observational study, firm conclusions about cause and effect could not be drawn, they said.
The researchers from University College London assessed data from the Smoking Toolkit Study which involves household surveys of individuals aged 16 and older in England.
They found a positive association between changes in the prevalence of e-cigarette use in England and the success rates of quit attempts.
However, e-cigarette use in quit attempts was negatively associated with the use of nicotine replacement therapy on prescription.
The authors suggest that patients using e-cigarettes may have tried nicotine replacement therapy already but that more research would be needed to confirm this.
Anti-smoking lobby, ASH Ireland, welcomed the study on e-cigarettes that provided additional information on the "possible use and potential" of the devices.
However, chairman of ASH Ireland Dr Patrick Doorley said as e-cigarettes were still new to the market it was not possible to decide on the 'risk versus benefit' that might apply in the medium to longer term.
ASH Ireland is keeping the e-cigarette market and related studies under continuing review.
Dr Doorley said e-cigarettes were commonly regarded as being safer than smoking tobacco products but there were some concerns regarding their safety, not least the unknown long-term health effects of using the product.
“ASH Ireland urges caution when using e-cigarettes until more information becomes available and there is more stringent regulation,” he stressed.
“We acknowledge that many people are now turning to e-cigarettes to help them quit smoking. It is important that these smokers are aware that even those authorities who recommend e-cigarettes acknowledge that they may cause harm and that nicotine replacement products available in pharmacies have been shown to be effective and safe.”
ASH Ireland advises those who choose to use e-cigarettes do so solely with the intention of quitting smoking completely as the single best thing smokers can do to improve their health is to give up smoking entirely.
Dr Doorley urged people wanting to quit to contact the National Quitline at www.quit.ie or 1800 201203.
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