Perspective:

The following are 10 points to remember about electronic cigarettes (e-cigarettes):

1. Smoking-related diseases contribute to the death of >480,000 North Americans each year, creating a heavy economic burden on both the Canadian and US health care systems. An estimated 52.9 million people (or 18.0% of adults ≥18 years of age) in North America currently smoke cigarettes.

2. Use of e-cigarettes has dramatically increased over the past 10 years. They are sold directly to consumers and are designed to mimic the look and feel of conventional cigarettes, creating a smoke-free vapor (with or without nicotine) that is inhaled by the user. Most brands are marketed as lower-cost, tobacco-free alternatives to conventional cigarettes that are not subject to regular smoking laws and thus can be used in typically nonsmoking areas. Although the US Food and Drug Administration (FDA) permits e-cigarettes to be sold under the auspices of tobacco products rather than as drugs or devices, it does not permit e-cigarettes to be marketed for therapeutic purposes such as smoking cessation.

3. E-cigarettes are typically composed of three parts: a plastic tube, an electronic heating component, and a cartridge containing a liquid solution of propylene glycol, with or without nicotine. When a sensor in the device detects airflow, the heating component in contact with the cartridge is activated, vaporizing the solution and producing a smoke-like aerosol that is subsequently inhaled. Because no combustion occurs, the inhalation of nicotine through an e-cigarette is believed to be a safer alternative to cigarette smoking by eliminating the inhalation of harmful compounds, including tar and carbon monoxide.

4. However, many smokers are using e-cigarettes when attempting to quit smoking. A survey of >10,000 adults reported that, of US smokers motivated to quit within the next 6 months, almost half had tried e-cigarettes. Thus, many may be using e-cigarettes in place of nicotine replacement products, which have been demonstrated to be efficacious in assisting smokers to quit.

5. The authors conducted a systematic review using PubMed. Randomized controlled trials (RCTs) and uncontrolled experimental studies involving e-cigarettes, including studies published in English or French language reports, were included.

6. A total of 169 publications were identified, of which seven studies were included. Study sizes ranged from 14 to 657 subjects, and treatment durations ranged from 1 day to 52 weeks. Only one RCT examined the efficacy of an e-cigarette for smoking cessation among current smokers motivated to quit. Among the remaining six experimental studies, two randomized studies were conducted in current smokers (no information on motivation to quit), one randomized study among smokers not motivated to quit, and three nonrandomized studies among smokers not motivated to quit. Quality assessment was performed for four studies. The three nonrandomized studies were not evaluated with Cochrane criteria because they were uncontrolled and therefore of relatively poor quality. Not surprisingly, studies had a high risk of bias for allocation concealment and blinding. Overall, however, the risk of bias was low in other domains.

7. Some studies have demonstrated that e-cigarettes may assist smokers in reducing or quitting traditional cigarettes. One RCT from New Zealand among 657 current smokers compared e-cigarettes (16 mg nicotine cartridge), or placebo e-cigarettes, to nicotine patches (21 mg nicotine per day) for a 12-week study period. At 6 months, biochemically validated continuous abstinence was reported in 7.3% of nicotine e-cigarette users, 5.8% of patch users, and 4.1% of placebo e-cigarette users. The study was underpowered to assess the superiority of e-cigarettes relative to the nicotine patch. The authors concluded that e-cigarettes, with or without nicotine, were modestly effective at helping smokers to quit. Another study conducted of 12 months, examined smoking reduction and abstinence among 300 smokers not motivated to quit. Results showed a reduction in daily cigarette smoking and exhaled carbon monoxide levels at each study visit across all three groups (p < 0.001 vs. baseline), with no differences between groups. The authors concluded that e-cigarette use can cause the persistent modification of smoking behavior among smokers not intending to quit, resulting in important smoking reduction and abstinence.

8. Although the FDA issued a warning in 2009 in response to detectable levels of carcinogens found in e-cigarette cartridges, these levels are similar to those found in approved nicotine replacement products, including the nicotine patch. Adverse events reported in the included studies, typically consisting of throat and mouth irritation, cough, and nausea, were relatively minor and often were found to be self-resolving in studies with both short- and long-term (52-week) follow-up.

9. The current available evidence suggests that e-cigarettes are less harmful than tobacco cigarettes. However, e-cigarettes remain unregulated, and product contents may vary drastically between devices and manufacturer brands.

10. The authors concluded that current available evidence on the risks and benefits of e-cigarette use is limited. Large RCTs are needed to definitively establish their potential for smoking cessation.