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Key findings

Where appropriate, key findings have been rated according to the strength of evidence supporting it, as follows:
A Multiple well-designed, randomized clinical trials yielded a consistent pattern of findings.
B Some evidence from randomized clinical trials but the scientific support was not optimal.
C Limited evidence indicative of a possible effect but not sufficient to support a recommendation.

These ‘strength of evidence’ ratings relate primarily to cessation efficacy and safety studies. Currently there are only a few studies on the efficacy of e-cigarettes for smoking cessation that can be evaluated in this way. Other study designs and research methods are used by scientists to investigate a wide range of questions about e-cigarettes and their use.

A further point to note is that, to date, very few studies on e-cigarettes have been undertaken outside Europe, North America and Australasia. Knowledge about awareness, use and other aspects of these products and their users is very limited for much of the world.

Contents of e-cigarette cartridges, refill fluids and vapor

  1. There is a growing but still limited body of information on the composition of the contents of e-cigarette cartridges, refill fluid and vapor generated by the devices. The evidence suggests wide variation in composition of contents and vapor but to date, no studies indicate evidence that e-cigarettes expose users to concentrations of toxins sufficient to cause harm or no harm. Primary refill fluid ingredients are generally propylene glycol (PG), glycerin and nicotine.
    commentary and supporting evidence

Ability to deliver nicotine

  1. Some e-cigarettes do not contain nicotine, but most do, or are capable of delivering nicotine (this applies to products that have refillable containers for the liquid). Studies of product contents and vapor, and absorption of nicotine into the bloodstream indicate wide variability across products; and factors such as the experience of the user and puffing techniques employed also play an important role in nicotine delivery, such that some users can achieve similar levels of nicotine to those found in tobacco smokers.
    2 commentary and supporting evidence

Effects on user health

  1. There has been little research on the health consequences of e-cigarette use. Currently there is no evidence that short-term e-cigarette use poses serious risks to health; evidence is lacking on long-term effects.
    3 commentary and supporting evidence

‘Second-hand’ exposure to vapor

  1. E-cigarette vapor exposes people sharing a room with an e-cigarette user to contaminants, including nicotine, particulates and hydrocarbons. Variation in product contents, designs and emissions suggests that some produce little toxicant exposure, whereas others may pose greater risks. However, the risks to health appear likely to be far lower than from indoor exposure to tobacco smoke.
    3 commentary and supporting evidence

Efficacy in relieving tobacco withdrawal symptoms

  1. Strong evidence exists that e-cigarette use suppresses nicotine withdrawal symptoms, although it is possible this may be a conditioned rather than a pharmacological effect. However, products that deliver physiologically active doses of nicotine would be expected to suppress withdrawal by both pharmacological and non-pharmacological mechanisms.
    2 commentary and supporting evidence

Efficacy in smoking cessation

  1. There is evidence from case reports, user surveys and two randomized controlled trials that e-cigarettes may help some people to quit smoking, but the trials have been limited by product unreliability and lack of adequate statistical power on which to base a more robust assessment of cessation efficacy.
    2 commentary and supporting evidence

Harm reduction

  1. E-cigarettes have considerable potential to provide an alternative to combusted tobacco use for people who are unable to completely give up tobacco or failed with medicinal nicotine, and thus promise a far safer way of delivering nicotine. However, it is possible they could increase harm if they delay cessation in people who use them just to manage situations where they cannot smoke or who perceive that they are reducing harm by smoking fewer cigarettes. Some commentators have expressed concerns about the potential for e-cigarettes to become a gateway product for non-smokers into long-term nicotine dependence or to take up cigarette smoking, and the possibility involvement of the tobacco industry might undermine tobacco control efforts; however, there is limited evidence to date to support these concerns.
    3 commentary and supporting evidence


  1. Summary
    commentary and supporting evidence logo
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