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New England Journal of Medicine: The Health Effects of Electronic Cigarettes

Chitra Dinakar, M.D., and George T. O'Connor, M.D.


Electronic cigarettes (e-cigarettes), also known as electronic nicotine-delivery systems, are devices that produce an aerosol by heating a liquid that contains a solvent (vegetable glycerin, propylene glycol, or a mixture of these), one or more flavorings, and nicotine, although the nicotine may be omitted. The evaporation of the liquid at the heating element is followed by rapid cooling to form an aerosol. This process is fundamentally different from the combustion of tobacco, and consequently the composition of the aerosol from e-cigarettes and the smoke from tobacco is quite different. E-cigarette aerosol is directly inhaled (or “vaped”) by the user through a mouthpiece. Each device includes a battery, a reservoir that contains the liquid, and a vaporization chamber with heating element. The design of the e-cigarette was originally based on the design of conventional cigarettes but has since evolved, with later-generation devices permitting users to refill a single device with different liquids and to customize the heating element.

The inhalation of aerosol from a nicotine-containing e-cigarette leads to peak serum nicotine concentration within 5 minutes. This rapidity of systemic delivery, combined with a method of use that is the same as that used for conventional cigarettes (i.e., oral inhalation), results in an experience for the user that is closer to cigarette smoking than the forms of nicotine-replacement therapy that have been approved by the Food and Drug Administration (FDA). In 2014, there were an estimated 466 brands and 7764 unique flavors of e-cigarette products; this heterogeneity complicates research on potential health effects. The scientific, regulatory, and lay communities have been impassioned but divided in their responses to e-cigarettes, with some advocating their use on the basis of “harm reduction” as compared with tobacco smoking, and others championing the so-called precautionary principle, which is based on a philosophy that avoids adoption of a new product when the long-term effects of that product are unknown.




In 2010, a total of 1.8% of U.S. adults reported having used an e-cigarette at some time, a rate that rose to 13.0% by 2013; reports of “current use” increased from 0.3% to 6.8% during this period. Although tobacco smokers were among those most likely to be current users of e-cigarettes, a third of current e-cigarette users had never smoked tobacco or were former tobacco smokers. A survey of 4444 college students from eight colleges in North Carolina showed that e-cigarette use was not motivated by the desire to stop smoking cigarettes. A U.S. population survey indicated that adults with mental health conditions such as anxiety disorders and depression were more likely to use e-cigarettes than adults without those conditions.

Of particular concern regarding public health has been the increasing experimentation with and use of e-cigarettes among persons younger than 18 years of age. In 2013, an estimated 263,000 middle-school and high-school students who had never smoked a conventional cigarette reported having used e-cigarettes. In this age group, e-cigarette use continues to increase, with 16% of high-school students in 2015 reporting any use within the preceding 30 days, whereas conventional cigarette smoking declined through 2014 and then remained unchanged in 2015. Recent data suggest that e-cigarette use by youths of high-school age may be associated with an increased risk of subsequent tobacco smoking. A limitation of these reports is the variability in the definitions of “current” use of e-cigarettes and the potential misclassification of regular use and infrequent experimentation.

The reasons for the increasing use of e-cigarettes by minors (persons between 12 and 17 years of age) may include robust marketing and advertising campaigns that showcase celebrities, popular activities, evocative images, and appealing flavors, such as cotton candy. E-cigarettes are marketed on the Internet and social media outlets and are increasingly advertised on television and radio and in shopping malls and print media. In the United States, the exposure of minors to television advertisements for e-cigarettes increased 256% between 2011 and 2013, with as many as 24 million minors exposed to these advertisements in 2013. National survey data suggest an association between exposure to e-cigarette advertising and the use of these products among students in middle school and high school.

Although the sale of e-cigarettes is prohibited in some countries, it is legal in most, including the United States, where the FDA recently finalized rules for the regulation of e-cigarettes as a tobacco product. The U.S. market for e-cigarettes is now estimated to be worth $1.5 billion, a number that is projected to grow by 24.2% per year through 2018. Global sales are predicted to reach $10 billion by 2017.


Read the full article via The New England Journal of Medicine.