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Am Fam Physician. 2016;93(3):178-179

Clinical Question

Are electronic cigarettes safe and effective in helping smokers to quit or reduce their smoking?

Evidence-Based Answer

Electronic cigarettes with nicotine increase smoking cessation rates compared with placebo, with effectiveness similar to that of nicotine patches. In addition, more patients using electronic cigarettes with nicotine were able to halve their use of cigarettes than those using placebo electronic cigarettes or nicotine patches. Long-term safety is unknown. (Strength of Recommendation: B, based on inconsistent or limited-quality patient-oriented evidence.)

Practice Pointers

Electronic cigarettes have steadily increased in popularity as an alternative to conventional tobacco cigarettes, and 21% of American smokers report having tried them.1 Although their long-term safety and health effects are not known, the most common reason given for using electronic cigarettes has been to quit or reduce cigarette smoking.2,3 Although not marketed as smoking cessation devices and therefore not regulated by the U.S. Food and Drug Administration, electronic cigarettes are widely used for this purpose.1

This Cochrane review combined data from two randomized controlled trials (RCTs) totaling 957 participants. The first of the RCTs randomized 657 smokers into three groups receiving 16-mg nicotine electronic cigarettes, 21-mg nicotine patches, or placebo electronic cigarettes. The study assessed smoking cessation rates at six months, which were confirmed by exhaled carbon monoxide levels. Between the nicotine electronic cigarette and placebo electronic cigarette groups, there were no statistically significant differences in rates of smoking cessation (7.3% vs. 4.1%; P = not significant). The second trial randomized 300 patients to receive electronic cigarettes containing 7.2 mg of nicotine for 12 weeks; 7.2 mg of nicotine for six weeks followed by 5.2 mg of nicotine for six weeks; or no nicotine for 12 weeks. No statistically significant difference in smoking cessation rates among the groups was found at six and 12 months. The overall quality of the data was considered low because of the small number of trials.

When the results from the two included studies were combined, the authors concluded that electronic cigarettes containing nicotine are more effective than placebo for smoking cessation, with an absolute cessation rate of 9% compared with 4% for placebo (relative risk for quitting = 2.29; 95% confidence interval, 1.05 to 4.96). Further, the authors concluded that participants using nicotine electronic cigarettes were able to cut their cigarette use in half more often than participants using placebo electronic cigarettes (relative risk = 1.31; 95% confidence interval, 1.02 to 1.68).

Clinical trial data did not reveal any immediate severe adverse effects with use of electronic cigarettes. Cohort studies identified in the review revealed some cytotoxic effects as well as short-term increased airway resistance with use of electronic cigarettes. Throat irritation did not seem to abate over time. The clinical significance of these effects, as well as the long-term health effects of using electronic cigarettes, is still unknown.

In a recent recommendation statement, the U.S. Preventive Services Task Force found insufficient evidence to recommend the use of electronic cigarettes for smoking cessation.4 Although smokers should be supported in any attempt to quit, the American Heart Association does not recommend the use of electronic cigarettes as a primary smoking cessation aid. Further, it recommends that electronic cigarette users set a quit date rather than use them indefinitely.5 Clinicians giving advice to their patients seeking to quit smoking with the aid of electronic cigarettes should bear in mind the current large knowledge gaps regarding these devices, in particular their long-term safety.

The practice recommendations in this activity are available at

These are summaries of reviews from the Cochrane Library.

This series is coordinated by Corey D. Fogleman, MD, assistant medical editor.

A collection of Cochrane for Clinicians published in AFP is available at

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