Can electronic cigarettes help people stop smoking or reduce the amount they smoke, and are they safe to use for this purpose?
Electronic cigarettes (EC) are electronic devices that produce a smoke-like aerosol (commonly referred to as vapour) that the user inhales. This vapour typically contains nicotine without most of the toxins smokers inhale with cigarette smoke. ECs have become popular with smokers who want to reduce the risks of smoking. This review aimed to find out whether ECs help smokers stop or cut down on their smoking, and whether it is safe to use ECs to do this.
We searched for trials published up to July 2014 and found 13 that help answer these questions. Two of the trials compared ECs with and without nicotine. These studies were judged to be at low risk of bias. They were conducted in New Zealand and Italy, and measured whether people had quit smoking for at least six months. In one study, people wanted to quit smoking, but in the other study, they did not. The trial in people who wanted to quit smoking also compared ECs to nicotine patches. The rest of the studies did not put people into treatment groups so could not directly compare ECs with something else. These studies can tell us less about how ECs might help with quitting smoking or with cutting down.
Combined results from two studies, involving over 600 people, showed that using an EC containing nicotine increased the chances of stopping smoking long-term compared to using an EC without nicotine. Using an EC with nicotine also helped more smokers reduce the amount they smoked by at least half compared to using an EC without nicotine. We could not determine if EC was better than a nicotine patch in helping people stop smoking because the number of participants in the study was low. More studies are needed to evaluate this effect. This study showed that people who used EC were more likely to cut down the amount they smoked by at least half than people using a patch. The other studies were of lower quality, but they supported these findings. There was no evidence that using EC at the same time as using regular cigarettes made people less likely to quit smoking. None of the studies found that smokers who used EC short-term (for 2 years or less) had an increased health risk compared to smokers who did not use EC.
Quality of the evidence
The quality of the evidence overall is low because it is based on only a small number of studies. More studies of EC are needed. Some are already underway.
Citation: McRobbie H, Bullen C, Hartmann-Boyce J, Hajek P. Electronic cigarettes for smoking cessation and reduction. Cochrane Database of Systematic Reviews 2014, Issue 12. Art. No.: CD010216. DOI: 10.1002/14651858.CD010216.pub2