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Electronic cigarettes containing nicotine can double smokers' rates of quitting at one year, compared to e-cigarettes without nicotine (placebo), according to a new small meta-analysis published in the Cochrane Database of Systematic Reviews.
The rates of smoking cessation using nicotine-containing e-cigarettes (9%) were roughly comparable to that seen with other forms of nicotine replacement therapy in past trials. The 1-year rates of smoking abstinence using placebo e-cigarettes (4%) were likewise comparable to past trials using placebo.
E-cigarettes with nicotine also helped non-quitting smokers cut back on real cigarettes. Among the smokers who could not quit, 36% of those using nicotine e-cigarettes cut their smoking by half; 28% of those using placebo e-cigarettes cut cigarette smoking in half.
The evidence was limited, including only two trials of 662 current smokers. This reflects both the relative novelty of electronic cigarettes and the dearth of serious research in this area. Authors concluded,
There is evidence from two trials that electronic cigarettes help smokers to stop smoking long-term compared with placebo e-cigarettes. However, the small number of trials, low event rates and wide confidence intervals around the estimates mean that our confidence in the result is rated 'low' by GRADE standards.
Research on e-cigarettes is lacking partially due to the U.S. government's adversarial approach to e-cigarettes. This is compounded by the multitude of products available and near absence of regulation, resulting in wide inconsistency between products.
As a result, little is known about e-cigarettes' efficacy or safety. For example, the amount of nicotine absorbed by a typical e-cigarette user is unknown.
If the quit rates seen in these trials reflect reality, electronic cigarettes would be as effective as existing forms of nicotine replacement therapy, such as patches, gum, lozenges, and nasal spray. Varenicline (Chantix) holds the smoking cessation aid record for efficacy, with a 33% 1-year quit rate in multiple trials.
But the real challenge for smokers is not just quitting, but staying quit. In one of the few studies that followed smokers for more than one year, more than 1/3 of recently-quit smokers relapsed within a few years of quitting. Whether they quit cold turkey or using nicotine replacement made no difference to their long-term relapse rate. (Electronic cigarettes were not tested in that 2006 trial.)
No serious adverse effects caused by e-cigarette use were reported in either study in the meta-analysis, which had only short-term follow-up.
McRobbie H, et al. Electronic cigarettes for smoking cessation and reduction. Cochrane Database of Systematic Reviews 2014, Issue 12. Art. No.: CD010216. DOI: 10.1002/14651858.CD010216.pub2.