An analysis of e-cigarette uptake across 27 European countries published in Tobacco Control finds that they are mostly used by current smokers or would-be quitters - approximately 29 million people.

E-cigarettes are battery operated devices, which are designed to provide a similar nicotine hit and sensory sensation to conventional cigarettes but without the harmful carcinogens produced by burning and inhaling cigarette smoke. They are promoted as a smoking cessation, much like nicotine patches. Critics insist that since the tobacco industry has invested in the emerging market, they must bad. Conspiracy theories always go that if a corporation is not buying a product in order to bury it and protect their business they are buying it in order to replace their business. More speculative are claims that e-cigarettes are a gateway to nicotine addiction or that all of the billions levied against tobacco companies in order to demonize smokers will be undone by e-cigarettes.

In a bid to gauge perceptions of e-cigarettes and their use across Europe, the researchers analyzed data from the 2012 Eurobarometer 385 survey, involving more than 26,500 adults from 27 countries within the European Union. The sample from each country was proportional to its population size and density.

Respondents were asked if they had ever tried e-cigarettes, and how often; whether they had ever heard of them; and whether they thought they were harmful or not to health.

Current smokers were additionally asked if they had attempted to give up smoking during the previous 12 months, and whether they had used e-cigarettes to do this. And they were asked what factors influenced their choice of cigarette brand.

The results showed that e-cigarette users were more likely to be younger - between 15 and 24 - current smokers of up to 20 cigarettes a day, and to have made at least one attempt to stub out their habit over the past year.

Age was the strongest predictor of e-cigarette use, with under 25s more than three times as likely to have tried an e-cigarette as those aged 55 and above.

And would-be quitters over the past year were twice as likely to have tried an e-cigarette as those who had not tried to quit.

Extrapolating the figures to the EU population as a whole in 2012 indicates that 29.3 million adults across the 27 countries have tried e-cigarettes, say the researchers.

Other findings:

• One in five smokers (20.3%); around one in 20 (4.4%) ex-smokers; and one in 100 (1.1%) non-smokers had tried e-cigarettes. Of these, almost one in 10 (9%) were regular users

• Use was more common among those smoking 6-10+ conventional cigarettes a day than among those smoking five or fewer

• 3.74% of all current smokers had used e-cigarettes as a smoking cessation aid

• e-cigarette experimentation among smokers ranged from just under 8% in Slovakia to just over 36% in Denmark

• Factors associated with cigarette brand choice did not influence e-cigarette brand choice

• Four out of 10 respondents thought e-cigarettes were harmful; almost a third were unsure

"Stressing the fact that age was the strongest determinant of e-cigarette use throughout EU, our study's implications are strategically important for European policy makers," write the authors.

"On the one hand, quitting tobacco use at an earlier age would substantially benefit individuals and public health. However, the renormalisation of smoking or 'vaping' in this context, or maintained nicotine addiction, may significantly hinder efforts to stop tobacco use," they conclude.