http://fivethirtyeight.com/features...e-dont-know-if-e-cigs-lead-kids-to-real-cigs/
"If you followed the news this week, you might think that teens who try electronic cigarettes are bound to take up Marlboros too. Yep, e-cigarettes are a gateway to smoking, read a news story published by the Fred Hutchinson Cancer Research Center. Teens who vape appear more likely to smoke was the headline at Reuters, and CBS Boston ran a story titled E-Cigarette Smoking Gateway To The Real Thing, Study Finds.
This is what happens when 16 people are made to represent an entire population.
Those headlines were reporting on a study published Tuesday in the journal JAMA Pediatrics in which researchers asked volunteers ages 16 to 26 a series of questions on two occasions, a year apart.
On the first survey, 694 people answered definitely no when asked the following: If one of your friends offered you a cigarette, would you try it? and Do you think you will smoke a cigarette sometime in the next year? The researchers deemed these respondents nonsusceptible. Importantly, some of these respondents said they had used e-cigarettes.
A year later, those same 694 participants were surveyed again, and this time, 37.5 percent of the original e-cigarette users said that theyd gone on to smoke traditional cigarettes. Thats a big percentage considering they werent supposed to be susceptible, especially when you consider that only 9.6 percent of the respondents who hadnt tried e-cigs before that first survey had taken up smoking during the same time period.
The buzziest finding: Compared with people who hadnt used e-cigarettes before the first survey, those who had were about eight times1 as likely to progress to trying a tobacco cigarette by the time of the second survey.
Those startling numbers an 8x multiplier and 37.5 percent conversion rate were the kind that made their way into the journals press release and the news stories. And as press releases go so goes overhyped journalism. If only the numbers were worthy of the headlines.
To understand why theyre not, lets look at where that big 37.5 percent number comes from. All those nonsusceptibles who said they had tried e-cigarettes on the first survey? There were only 16 of them (2.3 percent of 694). And a grand total of six of those 16 people started smoking during the one-year period between the first and second surveys. Voila, six out of 16 makes 37.5 percent its a big number that comes from a small number, which makes it a dubious one.
So because six people started smoking, news reports alleged that e-cigs were a gateway to analog cigs. The study could have just as easily been framed another way: Ten times as many people who hadnt vaped became smokers as those whod used e-cigarettes. (Sixty-five of the 678 nonsusceptibles who had never vaped eventually took a puff of a traditional cigarette.)
The studys lead author, Brian Primack, a professor at the University of Pittsburgh School of Medicine, told me that given the statistical significance of the results, its OK to draw conclusions. In medicine, he said, scientists often base an entire finding on a small group. Well find that seven people had a heart attack in this group and only four had a heart attack in this group, and based on that, we will forever say that you should take Lipitor, he said. He wasnt expecting the small sample in this study to yield statistically significant results, but after analyzing the data in numerous ways, it was all just very consistent, Primack said. We think we really are getting a signal here. If the peer reviewers had decided they couldnt base their conclusions on 16 people, then thats their prerogative, Primack said, but the paper was accepted by the journal."
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