Smokers were 28% less likely to stop using conventional cigarettes if they used e-cigarettes, researchers found.
E-cigarettes (electronic cigarettes) have stirred up much debate since they were first introduced to the US in 2007, with numerous studies questioning the safety of the devices and their effectiveness in helping smokers quit.
Some studies claim e-cigarettes do help people quit conventional smoking; a 2014 Cochrane review, for example, claims the devices are just as effective as nicotine patches.
Based on such findings and results from other studies claiming e-cigarettes are significantly safer than tobacco products, the British National Health Service (NHS) recently approved a brand of e-cigarette called e-Voke - developed by British American Tobacco - as a smoking cessation aid.
This means doctors in the UK could soon prescribe the device to patients who want to quit smoking.
But despite such advances, many health experts across the globe - including many from the US - are not convinced that e-cigarettes are effective in helping smokers quit; last year, the US Preventive Services Task Force (USPSTF) concluded that there is insufficient evidence to suggest the devices should be recommended for this purpose.
This latest study not only supports such a conclusion, but it also warns that the use of e-cigarettes could actually lower the chance of a smoker quitting conventional cigarettes.
"As currently being used, e-cigarettes are associated with significantly less quitting among smokers," says first author Dr. Sara Kalkhoran, who was a clinical fellow of the University of California-San Francisco (UCSF) at the time of research.
E-cigarette users 28% less likely to quit smoking
To reach their findings, Dr. Kalkhoran - now at Harvard Medical School in Boston, MA - and colleagues conducted a systematic review and meta-analysis of 38 studies looking at the link between e-cigarette use and smoking cessation among smokers as young as 15 years old.
According to the researchers, this is the largest study to date to quantify whether e-cigarettes help smokers stop conventional smoking.
The team identified 20 studies that included control groups of smokers who did not use e-cigarettes, and the studies included smokers who did want to quit and those who did not.
Compared with smokers who did not use e-cigarettes, the researchers found that those who did were 28% less likely to quit conventional smoking, even after accounting for other possible confounding factors, such as previous attempts to quit and level of nicotine dependence.
Commenting on the findings, coauthor Stanton A. Glantz, PhD, professor of medicine and director of the Center for Tobacco Research and Education at UCSF, says:
"The irony is that quitting smoking is one of the main reasons both adults and kids use e-cigarettes, but the overall effect is less, not more, quitting.
While there is no question that a puff on an e-cigarette is less dangerous than a puff on a conventional cigarette, the most dangerous thing about e-cigarettes is that they keep people smoking conventional cigarettes."
"E-cigarettes should not be recommended as effective smoking cessation aids until there is evidence that, as promoted and used, they assist smoking cessation," adds Dr. Kalkhoran.
E-cigarette regulation could boost quit-smoking potential
In the US, e-cigarettes are not currently regulated by the Food and Drug Administration (FDA), which the study authors say could be hampering their potential as a smoking cessation aid.
They note that including the devices in smoke-free laws and policies could stop people from using e-cigarettes as a substitute for conventional cigarettes, which could increase the devices' potential to be a help rather than a hindrance.
"The way e-cigarettes are available on the market - for use by anyone and for any purpose - creates a disconnect between the provision of e-cigarettes for cessation as part of a monitored clinical trial and the availability of e-cigarettes for use by the general population," the researchers add.
Not only is the effectiveness of e-cigarettes for smoking cessation being questioned, but numerous studies have challenged the safety of the devices.
Last month, a study reported by Medical News Today associated e-cigarettes with cancer-related cell damage, while an earlier study found flavored e-cigarettes contain chemicals linked to respiratory disease.